技术领域Technical field
本发明属于光学显微镜领域，具体涉及一种光力信号解调方法和光致力显微镜。The invention belongs to the field of optical microscopes, and specifically relates to an optical force signal demodulation method and an optical force microscope.
背景技术Background technique
能够看清楚更小更细微的物体是人类孜孜以求的目标，显微镜是最好的工具。但是当对材料和器件的检测要求进入纳米尺度，由于受到光学衍射极限的物理限制，传统光学显微镜难以胜任。近场光学显微镜的出现和发展不仅突破了光学衍射极限，而且实现了超衍射分辨率的光学成像，为科学家们在纳米尺度上认识光与物质的相互作用提供了重要工具。近场光学显微镜根据其原理不同，大致分为两类：一类是利用纳米光学天线或光纤波导直接收集和探测近场光场信号，比如散射型扫描近场光学显微镜、孔径型扫描近场光学显微镜等；另一类是通过探测光学近场产生的光力作用，实现超分辨的近场成像。相比于直接探测光场的近场光学显微镜，探测光力作用的近场显微镜具有更高的空间分辨率、更宽的光谱适用范围、更加简单的光路系统、不受探测器制约等诸多优势。Being able to see smaller and more subtle objects clearly is a goal that humans strive for, and a microscope is the best tool. However, when the detection requirements for materials and devices enter the nanometer scale, traditional optical microscopes are unable to perform due to the physical limitations of the optical diffraction limit. The emergence and development of near-field optical microscopes not only break through the optical diffraction limit, but also achieve optical imaging with super-diffraction resolution, providing scientists with an important tool to understand the interaction between light and matter at the nanometer scale. Near-field optical microscopes can be roughly divided into two categories according to their different principles: one is to use nano-optical antennas or fiber optic waveguides to directly collect and detect near-field light field signals, such as scattering-type scanning near-field optical microscopes and aperture-type scanning near-field optical microscopes. Microscopes, etc.; the other is to achieve super-resolution near-field imaging by detecting the light force generated by the optical near-field. Compared with near-field optical microscopes that directly detect light fields, near-field microscopes that detect the effects of light force have many advantages such as higher spatial resolution, wider spectral application range, simpler optical path systems, and are not restricted by detectors. .
现有的探测光力作用的近场显微镜主要包括光热诱导显微镜和光诱导力显微镜，现有的光热诱导显微镜的缺点为：(1)AFM针尖与样品存在硬接触，在对样品进行扫描时，样品容易被针尖损伤且针尖容易受到污染和磨损；(2)工作波长主要在红外光波段，应用范围有限；(3)样品厚度有限制，厚度在100nm左右的样品较易探测，样品过厚或过薄会导致信噪比过低；(4)由于AFM探针与样品直接接触，因此，容易受外界环境振动干扰，从而导致信号中噪声较大，提取有用信号困难；(5)光热诱导显微镜进行检测的空间分辨率较低，红外波段的空间分辨率一般为50纳米-100纳米；(6)由于使用棱镜，激发光需要从斜下方45°左右入射，因此光热诱导显微镜难以与倒置显微镜集成使用；现有的光诱导力显微镜的缺点为：(1)光诱导偶极交互力极其微弱，这对探测系统的灵敏度提出了挑战；(2)由于采用抛物面镜从侧面激发，激发光角度调节复杂，系统不易与现有显微镜系统集成使用；(3)光力诱导显微镜进行检测的空间分辨率较低，红外波段的空间分辨率一般为30纳米左右，(4)对探针的本身的机械结构、制备工艺和所使用的材料特性均有较高的要求。Existing near-field microscopes that detect the effects of light force mainly include photothermal induction microscopes and photoinduced force microscopes. The shortcomings of the existing photothermal induction microscopes are: (1) There is hard contact between the AFM tip and the sample. When scanning the sample, , the sample is easily damaged by the needle tip and the needle tip is susceptible to contamination and wear; (2) the working wavelength is mainly in the infrared light band, and the application range is limited; (3) the sample thickness is limited, samples with a thickness of about 100nm are easier to detect, and the sample is too thick Or being too thin will result in a low signal-to-noise ratio; (4) Since the AFM probe is in direct contact with the sample, it is easily disturbed by external environmental vibrations, resulting in greater noise in the signal and difficulty in extracting useful signals; (5) Photothermal The spatial resolution of detection under induction microscope is low, and the spatial resolution in the infrared band is generally 50 nanometers to 100 nanometers; (6) Due to the use of prisms, the excitation light needs to be incident from about 45° obliquely below, so it is difficult to use photothermal induction microscope with The inverted microscope is integrated and used; the shortcomings of the existing light-induced force microscope are: (1) the light-induced dipole interaction force is extremely weak, which poses a challenge to the sensitivity of the detection system; (2) due to the use of parabolic mirrors to excite from the side, the excitation The adjustment of the light angle is complicated, and the system is not easy to be integrated with existing microscope systems; (3) The spatial resolution of light force-induced microscopy for detection is low, and the spatial resolution of the infrared band is generally about 30 nanometers. (4) The sensitivity of the probe The mechanical structure, preparation process and material properties used all have high requirements.
发明内容Contents of the invention
本发明旨在至少在一定程度上解决相关技术中的技术问题之一。为此，本发明的目的在于提出一种光力信号解调方法和光致力探测显微镜。由此，显著提高了样品的原位成像的便捷性，显著提高了探针的振动电信号的探测灵敏度，显著增加了样品扫描分辨率。The present invention aims to solve one of the technical problems in the related art, at least to a certain extent. To this end, the purpose of the present invention is to propose a photoforce signal demodulation method and a photoforce detection microscope. As a result, the convenience of in-situ imaging of the sample is significantly improved, the detection sensitivity of the probe's vibrational electrical signal is significantly improved, and the sample scanning resolution is significantly increased.
在本发明的一个方面，本发明提出了一种光力信号解调方法。在本发明的实施例中，所述光力信号解调方法包括：In one aspect of the invention, the invention proposes an optical signal demodulation method. In an embodiment of the present invention, the optical signal demodulation method includes:
将探针的振动电信号分别同时输入至第一图锁相放大器和第二图锁相放大器，所述第一图锁相放大器的参考信号频率为所述探针的悬臂受迫振动信号频率，所述第二图锁相放大器的参考信号频率为所述悬臂受迫振动信号频率和激发光的重复频率的之和或之差；The vibration electrical signal of the probe is simultaneously input to the lock-in amplifier in the first figure and the lock-in amplifier in the second figure respectively, and the reference signal frequency of the lock-in amplifier in the first figure is the forced vibration signal frequency of the cantilever of the probe, The reference signal frequency of the lock-in amplifier in the second figure is the sum or difference of the cantilever forced vibration signal frequency and the repetition frequency of the excitation light;
采用所述第一图锁相放大器对所述探针的振动电信号进行解调得到样品的高度信号，采用所述第二图锁相放大器对所述探针的振动电信号进行解调得到样品的光力信号。The lock-in amplifier of the first figure is used to demodulate the vibration electrical signal of the probe to obtain the height signal of the sample, and the lock-in amplifier of the second figure is used to demodulate the vibration electrical signal of the probe to obtain the sample. light signal.
根据本发明实施例的光力信号解调方法，本申请的方法将第一图锁相放大器的参考信号频率设置为探针的悬臂受迫振动信号频率且将第二图锁相放大器的参考信号频率设置悬臂受迫振动信号频率和激发光的重复频率的之和或之差，可以通过单次扫描实现样品的原位高度成像和光力成像，可以同时提供样品的多维度信息，由此，显著提高了样品的原位成像的便捷性，显著提高了探针的振动电信号的探测灵敏度，显著增加了样品扫描分辨率。According to the optical signal demodulation method of the embodiment of the present invention, the method of the present application sets the reference signal frequency of the lock-in amplifier in the first figure to the cantilever forced vibration signal frequency of the probe and sets the reference signal of the lock-in amplifier in the second figure The frequency setting is the sum or difference of the frequency of the forced vibration signal of the cantilever and the repetition frequency of the excitation light. In-situ height imaging and optical force imaging of the sample can be achieved through a single scan, and multi-dimensional information of the sample can be provided at the same time. Therefore, significantly It improves the convenience of in-situ imaging of samples, significantly improves the detection sensitivity of the probe's vibrational electrical signals, and significantly increases the sample scanning resolution.
另外，根据本发明上述实施例所述的光力信号解调方法还可以具有如下附加的技术特征：In addition, the optical signal demodulation method according to the above embodiments of the present invention may also have the following additional technical features:
在本发明的一些实施例中，转化得到所述探针的振动电信号的装置包括四象限探测器。In some embodiments of the present invention, the device for converting the vibration electrical signal of the probe includes a four-quadrant detector.
在本发明的一些实施例中，所述第二图锁相放大器的参考信号频率通过所述悬臂受迫振动信号频率和所述激发光的重复频率混频得到。In some embodiments of the present invention, the reference signal frequency of the lock-in amplifier in the second figure is obtained by mixing the cantilever forced vibration signal frequency and the repetition frequency of the excitation light.
在本发明的一些实施例中，对所述悬臂受迫振动信号频率和所述激发光的重复频率进行混频的装置为所述第二图锁相放大器内的混频器。In some embodiments of the present invention, the device for mixing the frequency of the cantilever forced vibration signal and the repetition frequency of the excitation light is a mixer in the lock-in amplifier in the second figure.
在本发明的再一个方面，本发明提出了一种实现上述实施例所述的光力信号解调方法的光致力探测显微镜。在本发明的实施例中，所述光致力探测显微镜包括光学激发系统、控制系统和信号采集系统，所述光学激发系统包括激发光光源、驱动器和探针，所述激发光光源发出的激发光聚焦到样品待检测面，所述探针设置在所述样品的上方且所述探针不和所述样品待检测面接触，所述驱动器用于驱动所述探针发生振动；In yet another aspect of the present invention, the present invention proposes a photoforce detection microscope that implements the photoforce signal demodulation method described in the above embodiment. In an embodiment of the present invention, the photoforce detection microscope includes an optical excitation system, a control system and a signal acquisition system. The optical excitation system includes an excitation light source, a driver and a probe. The excitation light emitted by the excitation light source Focusing on the surface of the sample to be detected, the probe is arranged above the sample and does not contact the surface of the sample to be detected, and the driver is used to drive the probe to vibrate;
所述控制系统用于控制样品进行移动，以使所述激发光照射到样品的所有待检测区域；The control system is used to control the movement of the sample so that the excitation light irradiates all areas to be detected on the sample;
所述信号采集处理系统包括四象限探测器、第一图锁相放大器和第二图锁相放大器，所述四象限探测器用于接收探针的振动信号和将所述振动信号转换为振动电信号，探针的所述振动电信号分别同时经过所述第一图锁相放大器和所述第二图锁相放大器进行解调，以便得到样品的高度信号和光力信号。The signal acquisition and processing system includes a four-quadrant detector, a first-image lock-in amplifier, and a second image lock-in amplifier. The four-quadrant detector is used to receive the vibration signal of the probe and convert the vibration signal into an electrical vibration signal. , the vibration electrical signal of the probe is simultaneously demodulated by the first lock-in amplifier and the second lock-in amplifier, so as to obtain the height signal and optical force signal of the sample.
根据本发明实施例的光致力探测显微镜，相比于光热诱导显微镜，本申请的光致力探测显微镜的优点在于：(1)探针是在轻敲模式下进行工作的，因此可以避免探针和样品待检测面发生直接接触，既解决了扫描中探针容易污染和磨损、样品容易受到探针损伤等问题，又解决了提取探测的有效信号困难的问题；(2)本发明的光致力探测显微镜不是对样品热膨胀进行检测，光致力探测显微镜的工作波长可以覆盖紫外-可见光-红外甚至太赫兹波段，实现了波长应用范围的扩展；(3)由于本发明的光致力探测显微镜不是对样品热膨胀进行检测，因此允许的样品厚度的更宽；(4)通过采用光力信号解调方法，实现了单次扫描即可得到样品的原位高度成像和光力成像，同时提供样品的多维度信息；相比于光诱导力显微镜，本申请的光致力探测显微镜的优点在于：(1)本发明的激发光可以从样品的下方照射在样品的待检测面，通过控制样品待检测面和针尖之间的距离，可以使得针尖受到的作用力处于大范围的引力和斥力交替变化中，从而大幅度提升了光致力探测显微镜的检测信号强度；(2)由于光致力探测显微镜的检测信号强度得到大幅提升，因此可以降低激发光强度，也可以使用电场增强效果较弱的硅针尖进行探测，通过降低激发光强度有利于避免样品受激光损伤，通过采用硅针尖较小的针尖曲率半径可以获得更好的横向空间分辨率；(3)通过采用光力信号解调方法，实现了单次扫描即可得到样品的原位高度成像和光力成像，同时提供样品的多维度信息。According to the photoforce detection microscope according to the embodiment of the present invention, compared with the photothermal induction microscope, the advantages of the photoforce detection microscope of the present application are: (1) The probe works in a tapping mode, so the probe can be avoided Direct contact with the surface of the sample to be detected not only solves the problem of easy contamination and wear of the probe during scanning, and the susceptibility of the sample to damage by the probe, but also solves the problem of difficulty in extracting effective signals for detection; (2) The photoelectric force of the present invention The detection microscope does not detect the thermal expansion of the sample. The working wavelength of the photodetection microscope can cover the ultraviolet-visible light-infrared and even terahertz bands, realizing the expansion of the wavelength application range; (3) Since the photodetection microscope of the present invention does not detect the sample Thermal expansion is detected, so the sample thickness is allowed to be wider; (4) By using the optical force signal demodulation method, the in-situ height imaging and optical force imaging of the sample can be obtained in a single scan, while providing multi-dimensional information of the sample ; Compared with the photoinduced force microscope, the advantages of the photoinduced force detection microscope of the present application are: (1) The excitation light of the present invention can be irradiated from the bottom of the sample to the surface to be detected of the sample, by controlling the relationship between the surface of the sample to be detected and the needle tip The distance between the two can make the force on the tip of the needle be in a wide range of alternating gravitational and repulsive forces, thus greatly improving the detection signal intensity of the photodetection microscope; (2) Because the detection signal intensity of the photodetection microscope has been greatly improved Therefore, the intensity of the excitation light can be reduced, or a silicon tip with a weak electric field enhancement effect can be used for detection. By reducing the intensity of the excitation light, it is helpful to avoid laser damage to the sample. By using a silicon tip with a smaller tip curvature radius, better results can be obtained. The lateral spatial resolution; (3) By using the optical force signal demodulation method, the in-situ height imaging and optical force imaging of the sample can be obtained in a single scan, while providing multi-dimensional information of the sample.
另外，根据本发明上述实施例所述的光致力探测显微镜还可以具有如下附加的技术特征：In addition, the photodetection microscope according to the above embodiments of the present invention may also have the following additional technical features:
在本发明的一些实施例中，还包括：全内反射镜，所述激发光光源发出的激发光通过所述全内反射镜聚焦到所述样品待检测面。In some embodiments of the present invention, the method further includes: a total internal reflection mirror, through which the excitation light emitted by the excitation light source is focused onto the surface of the sample to be detected.
在本发明的一些实施例中，所述激发光光源发出的激发光平行于所述全内反射镜的光轴方向偏心射入全内反射镜。In some embodiments of the present invention, the excitation light emitted by the excitation light source is eccentrically incident on the total internal reflection mirror parallel to the optical axis direction of the total internal reflection mirror.
在本发明的一些实施例中，所述可见光光源发出的可见光平行于所述全内反射镜的光轴方向偏心射入全内反射镜。In some embodiments of the present invention, the visible light emitted by the visible light source is eccentrically incident on the total internal reflection mirror parallel to the optical axis direction of the total internal reflection mirror.
在本发明的一些实施例中，所述全内反射镜包括全内反射棱镜和全内反射物镜中的至少一种。In some embodiments of the present invention, the total internal reflection mirror includes at least one of a total internal reflection prism and a total internal reflection objective lens.
在本发明的一些实施例中，所述探针的针尖和所述样品待检测面沿Z方向的距离为1纳米-65纳米，优选为1纳米-10纳米。In some embodiments of the present invention, the distance along the Z direction between the tip of the probe and the surface of the sample to be detected is 1 nm to 65 nm, preferably 1 nm to 10 nm.
在本发明的一些实施例中，倒置显微镜，所述倒置显微镜包括可见光光源和倒置显微镜检测部，所述可见光光源发射的可见光通过所述全内反射镜照射在所述样品待检测面，经由所述样品反射的所述可见光的反射光进入所述倒置显微镜检测部进行检测。In some embodiments of the present invention, the inverted microscope includes a visible light source and an inverted microscope detection part. The visible light emitted by the visible light source is irradiated on the surface of the sample to be detected through the total internal reflection mirror, and passes through the The reflected light of the visible light reflected by the sample enters the detection part of the inverted microscope for detection.
在本发明的一些实施例中，所述光学激发系统还包括滤波器，所述滤波器用于对所述激发光光源发出的所述激发光进行波长选择和强度调制。In some embodiments of the present invention, the optical excitation system further includes a filter, which is used to perform wavelength selection and intensity modulation of the excitation light emitted by the excitation light source.
在本发明的一些实施例中，所述光学激发系统还包括光束整形器，所述光束整形器用于将波长选择和强度调制后的单色光转化为单色基模高斯光束。In some embodiments of the present invention, the optical excitation system further includes a beam shaper, which is used to convert the wavelength-selected and intensity-modulated monochromatic light into a monochromatic fundamental mode Gaussian beam.
在本发明的一些实施例中，所述光学激发系统还包括扩束准直器，所述扩束准直器用于对所述单色基模高斯光束进行扩束准直。In some embodiments of the present invention, the optical excitation system further includes a beam expansion collimator, and the beam expansion collimator is used for beam expansion and collimation of the monochromatic fundamental mode Gaussian beam.
在本发明的一些实施例中，所述控制系统包括样品位移平台和控制器，所述样品设置在所述样品位移平台上，所述控制器用于驱动所述样品位移平台和所述探针进行移动。In some embodiments of the present invention, the control system includes a sample displacement platform and a controller, the sample is arranged on the sample displacement platform, and the controller is used to drive the sample displacement platform and the probe. move.
在本发明的一些实施例中，所述样品位移平台包括压电式样品位移平台和机械式样品位移平台中的至少一种。In some embodiments of the present invention, the sample displacement platform includes at least one of a piezoelectric sample displacement platform and a mechanical sample displacement platform.
在本发明的一些实施例中，所述样品位移平台为纳米精度的样品位移平台。In some embodiments of the present invention, the sample displacement platform is a nanometer-precision sample displacement platform.
在本发明的一些实施例中，所述控制器包括闭环控制器。In some embodiments of the invention, the controller includes a closed loop controller.
在本发明的一些实施例中，所述激发光光源包括宽谱激光器。In some embodiments of the invention, the excitation light source includes a broad spectrum laser.
本发明的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本发明的实践了解到。Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
附图说明Description of the drawings
本发明的上述和/或附加的方面和优点从结合下面附图对实施例的描述中将变得明显和容易理解，其中：The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:
图1是根据本发明一个实施例的光力信号解调方法的示意图；Figure 1 is a schematic diagram of an optical signal demodulation method according to an embodiment of the present invention;
图2是根据本发明一个实施例的光致力探测显微镜的结构示意图；Figure 2 is a schematic structural diagram of a photodetection microscope according to an embodiment of the present invention;
图3是根据本发明一个实施例的控制系统和探针的结构示意图；Figure 3 is a schematic structural diagram of a control system and a probe according to an embodiment of the present invention;
图4是根据本发明实施例1的测试样品的示意图；Figure 4 is a schematic diagram of a test sample according to Embodiment 1 of the present invention;
图5是根据本发明实施例1的样品扫描的高度图；Figure 5 is a height map of a sample scan according to Embodiment 1 of the present invention;
图6是根据本发明实施例1的样品扫描的光力图；Figure 6 is an optical force diagram of a sample scan according to Embodiment 1 of the present invention;
图7是检测图5的横向空间分辨率的检测图。FIG. 7 is a detection chart for detecting the lateral spatial resolution of FIG. 5 .
附图标记：Reference signs:
1-激发光光源；2-探针；3-样品位移平台；4-全内反射镜；5-可见光光源；6-倒置显微镜检测部；7-滤波器；8-光束整形器；9-扩束准直器；10-驱动器；11-四象限探测器；12-第一图锁相放大器；13-第二图锁相放大器；14-控制器；15-探针移动控制器；16-样品位移平台X方向移动控制器；17-样品位移平台Y方向移动控制器；18-h-BN纳米片；19-WS2纳米片；20-硼硅酸盐玻璃衬底。1-Excitation light source; 2-Probe; 3-Sample displacement platform; 4-Total internal reflection mirror; 5-Visible light source; 6-Inverted microscope detection part; 7-Filter; 8-Beam shaper; 9-Expansion Beam collimator; 10-driver; 11-four-quadrant detector; 12-lock-in amplifier in the first picture; 13-lock-in amplifier in the second picture; 14-controller; 15-probe movement controller; 16-sample Displacement platform X-direction movement controller; 17-sample displacement platform Y-direction movement controller; 18-h-BN nanosheet; 19-WS2 nanosheet; 20-borosilicate glass substrate.
具体实施方式Detailed ways
下面详细描述本发明的实施例，所述实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施例是示例性的，旨在用于解释本发明，而不能理解为对本发明的限制。Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and are not to be construed as limiting the present invention.
在本发明的一个方面，本发明提出了一种光力信号解调方法。在本发明的实施例中，参考附图1，上述光力信号解调方法包括：将探针的振动电信号分别同时输入至第一图锁相放大器和第二图锁相放大器，上述第一图锁相放大器的参考信号频率为上述探针的悬臂受迫振动信号频率，上述第二图锁相放大器的参考信号频率为上述悬臂受迫振动信号频率和激发光的重复频率的之和或之差；采用上述第一图锁相放大器对上述探针的振动电信号进行解调得到样品的高度信号，采用上述第二图锁相放大器对上述探针的振动电信号进行解调得到样品的光力信号。需要解释的是：附图1中的f1为探针的悬臂受迫振动信号频率、f2为第二图锁相放大器的参考信号频率、fm为激发光的重复频率。In one aspect of the invention, the invention proposes an optical signal demodulation method. In an embodiment of the present invention, with reference to Figure 1, the above-mentioned optical signal demodulation method includes: simultaneously inputting the vibration electrical signal of the probe to the lock-in amplifier in the first figure and the lock-in amplifier in the second figure respectively, and the above-mentioned first The reference signal frequency of the lock-in amplifier in the figure is the cantilever forced vibration signal frequency of the probe. The reference signal frequency of the lock-in amplifier in the second figure is the sum or the sum of the cantilever forced vibration signal frequency and the repetition frequency of the excitation light. Difference; use the lock-in amplifier in the first figure to demodulate the vibration electrical signal of the probe to obtain the height signal of the sample, and use the lock-in amplifier in the second figure to demodulate the vibration electrical signal of the probe to obtain the light signal of the sample force signal. It should be explained that f1 in Figure 1 is the forced vibration signal frequency of the probe's cantilever, f2 is the reference signal frequency of the lock-in amplifier in the second figure, and fm is the repetition frequency of the excitation light.
根据本发明实施例的光力信号解调方法，本申请的方法将第一图锁相放大器的参考信号频率设置为探针的悬臂受迫振动信号频率且将第二图锁相放大器的参考信号频率设置悬臂受迫振动信号频率和激发光的重复频率的之和或之差，可以通过单次扫描实现样品的原位高度成像和光力成像，可以同时提供样品的多维度信息，由此，显著提高了样品的原位成像的便捷性，显著提高了探针的振动电信号的探测灵敏度，显著增加了样品扫描分辨率。According to the optical signal demodulation method of the embodiment of the present invention, the method of the present application sets the reference signal frequency of the lock-in amplifier in the first figure to the cantilever forced vibration signal frequency of the probe and sets the reference signal of the lock-in amplifier in the second figure The frequency setting is the sum or difference of the frequency of the forced vibration signal of the cantilever and the repetition frequency of the excitation light. In-situ height imaging and optical force imaging of the sample can be achieved through a single scan, and multi-dimensional information of the sample can be provided at the same time. Therefore, significantly It improves the convenience of in-situ imaging of samples, significantly improves the detection sensitivity of the probe's vibrational electrical signals, and significantly increases the sample scanning resolution.
具体地，参考附图1，探针的振动电信号f1&fm分别同时输入至第一图锁相放大器和第二图锁相放大器作为输入信号频率；振荡器1产生探针的悬臂受迫振动信号频率f1，f1作为第一图锁相放大器的参考信号频率；振荡器1产生探针的悬臂受迫振动信号频率f1也可以作为f2的混频信号之一，振荡器产生激发光的重复频率fm作为f2的混频信号之一，由此得到的混频信号f2作为第二图锁相放大器的参考信号频率，由此，通过第一图锁相放大器的输出信号作为维持探针和样品之间距离恒定的反馈信号，从而在扫描过程中产生了样品待检测面高度图，而第二图锁相放大器输出的光力信号在扫描过程中产生了光力图，光力图反映了样品光学吸收系数等重要物性。本发明的光力信号解调方法，可以有效将样品的形貌信息和光学信息用两个不同的频率编码到两个不同的信道中，消除了高度信号和光力信号之间的耦合，实现了样品待检测面高精度的原位测量，通过单次扫描可同时获得高度图和光力图，有利于对照研究样品待检测面高度和光力的关系。相比于现有技术，本发明的光力信号解调方法在激发光功率保持恒定的情况下，可大幅度提升检测到的光力信号强度，在检测到的光力信号强度保持恒定的情况下，可以大幅度降低激发光的功率。Specifically, with reference to Figure 1, the vibration electrical signals f1 & fm of the probe are simultaneously input to the lock-in amplifier in the first figure and the lock-in amplifier in the second figure as the input signal frequency; the oscillator 1 generates the cantilever forced force of the probe. The vibration signal frequency f1 , f1 is used as the reference signal frequency of the lock-in amplifier in the first figure; the oscillator 1 generates the forced vibration signal of the cantilever of the probe. The frequency f1 can also be used as one of the mixing signals of f2 , and the oscillator generates The repetition frequency fm of the excitation light is used as one of the mixing signals of f2 , and the resulting mixing signal f2 is used as the reference signal frequency of the lock-in amplifier in the second figure. Therefore, through the output of the lock-in amplifier in the first figure The signal acts as a feedback signal to maintain a constant distance between the probe and the sample, thereby generating a height map of the sample surface to be detected during the scanning process. In the second picture, the optical force signal output by the lock-in amplifier generates an optical force map during the scanning process. The optical force diagram reflects important physical properties such as the optical absorption coefficient of the sample. The optical signal demodulation method of the present invention can effectively encode the morphological information and optical information of the sample into two different channels using two different frequencies, eliminating the coupling between the height signal and the optical signal, and realizing High-precision in-situ measurement of the surface of the sample to be detected can simultaneously obtain the height map and light force map through a single scan, which is conducive to comparative study of the relationship between the height of the sample to be detected and the light force. Compared with the existing technology, the optical signal demodulation method of the present invention can greatly increase the intensity of the detected optical signal when the excitation light power remains constant. , the power of the excitation light can be greatly reduced.
在本发明的实施例中，转化得到上述探针的振动电信号的装置并不受特殊限定，作为一个优选的方案，转化得到上述探针的振动电信号的装置可以为四象限探测器。In the embodiment of the present invention, the device for converting the vibration electrical signal of the probe is not particularly limited. As a preferred solution, the device for converting the vibration electrical signal of the probe can be a four-quadrant detector.
根据本发明的一个具体实施例，上述第二图锁相放大器的参考信号频率通过上述悬臂受迫振动信号频率和激发光的重复频率混频得到。According to a specific embodiment of the present invention, the reference signal frequency of the lock-in amplifier in the second figure is obtained by mixing the frequency of the forced vibration signal of the cantilever and the repetition frequency of the excitation light.
本发明的实施例中，对上述悬臂受迫振动信号频率和上述激发光的重复频率进行混频的装置并不受特殊限定，作为一个优选的方案，对上述悬臂受迫振动信号频率和上述激发光的重复频率进行混频的装置可以为第二图锁相放大器内的混频器，由此，可以采用第二图锁相放大器本身的混频器得到第二图锁相放大器的参考信号频率，既节省了工作成本又提高了工作效率。In the embodiment of the present invention, the device for mixing the frequency of the forced vibration signal of the cantilever and the repetition frequency of the excitation light is not particularly limited. As a preferred solution, the frequency of the forced vibration signal of the cantilever and the frequency of the excitation light are mixed. The device for mixing the repetition frequency of light can be the mixer in the lock-in amplifier in the second figure. Therefore, the reference signal frequency of the lock-in amplifier in the second figure can be obtained by using the mixer of the lock-in amplifier in the second figure. , which not only saves work costs but also improves work efficiency.
在本发明的再一个方面，本发明提出了一种实现上述实施例所述的光力信号解调方法的光致力探测显微镜。在本发明的实施例中，参考附图2，上述光致力探测显微镜包括光学激发系统、控制系统和信号采集系统，上述光学激发系统包括激发光光源1、驱动器10和探针2，上述激发光光源1发出的激发光聚焦到样品待检测面，上述探针2设置在上述样品的上方且上述探针2不和上述样品待检测面接触，上述驱动器10用于驱动上述探针2发生振动；上述控制系统用于控制样品进行移动，以使上述激发光照射到样品的所有待检测区域；上述信号采集处理系统包括四象限探测器11、第一图锁相放大器12和第二图锁相放大器13，上述四象限探测器11用于接收探针2的振动信号和将上述振动信号转换为振动电信号，探针2的振动电信号分别同时经过上述第一图锁相放大器12和上述第二图锁相放大器13进行解调，以便得到样品的高度信号和光力信号。In yet another aspect of the present invention, the present invention proposes a photoforce detection microscope that implements the photoforce signal demodulation method described in the above embodiment. In the embodiment of the present invention, with reference to Figure 2, the above-mentioned photoforce detection microscope includes an optical excitation system, a control system and a signal acquisition system. The above-mentioned optical excitation system includes an excitation light source 1, a driver 10 and a probe 2. The above-mentioned excitation light The excitation light emitted by the light source 1 is focused on the surface of the sample to be detected. The probe 2 is arranged above the sample and does not contact the surface of the sample to be detected. The driver 10 is used to drive the probe 2 to vibrate; The above-mentioned control system is used to control the movement of the sample so that the above-mentioned excitation light irradiates all the areas to be detected on the sample; the above-mentioned signal acquisition and processing system includes a four-quadrant detector 11, a first picture lock-in amplifier 12 and a second picture lock-in amplifier. 13. The four-quadrant detector 11 is used to receive the vibration signal of the probe 2 and convert the vibration signal into an electrical vibration signal. The electrical vibration signal of the probe 2 passes through the lock-in amplifier 12 in the first figure and the second lock-in amplifier 12 respectively. The lock-in amplifier 13 performs demodulation to obtain the height signal and optical force signal of the sample.
具体地，激发光光源发出的激发光可以对样品的待检测面进行照射，由于光电场的电磁极化效应，导致样品待检测面产生诱导偶极子，设置在样品待检测面上方的探针针尖会产生镜像偶极子，两个偶极子之间存在电磁相互作用力(即偶极交互力)，从而改变了探针悬臂固有的振动状态。当针尖因受到偶极交互力的作用而使探针悬臂的振动状态发生改变时，四象限探测器的光斑位置会发生改变，四象限探测器会收集光斑位置信息并将光斑位置信息转化为相应的振动电信号，振动电信号包含探针悬臂自身固有的振动特性信息和探针悬臂所受到的光力作用信息。最终，由四象限探测器输出的振动电信号分别经过上述第一图锁相放大器和上述第二图锁相放大器进行解调，将第一图锁相放大器的参考信号频率设置为探针的悬臂受迫振动信号频率，将第二图锁相放大器的参考信号频率设置悬臂受迫振动信号频率和激发光的重复频率的之和或之差，由此，可以通过单次扫描实现样品的原位高度成像和光力成像，可以同时提供样品的多维度信息。Specifically, the excitation light emitted by the excitation light source can illuminate the surface of the sample to be detected. Due to the electromagnetic polarization effect of the light electric field, an induced dipole is generated on the surface of the sample to be detected. The probe is arranged above the surface of the sample to be detected. The tip of the needle will produce a mirror dipole, and there is an electromagnetic interaction force (ie, dipole interaction force) between the two dipoles, thus changing the inherent vibration state of the probe cantilever. When the tip of the probe changes the vibration state of the probe cantilever due to the interaction force of the dipole, the spot position of the four-quadrant detector will change. The four-quadrant detector will collect the spot position information and convert the spot position information into the corresponding The vibration electrical signal contains information about the inherent vibration characteristics of the probe cantilever itself and information about the optical force exerted on the probe cantilever. Finally, the vibration electrical signals output by the four-quadrant detector are demodulated by the lock-in amplifier in the first picture and the lock-in amplifier in the second picture respectively, and the reference signal frequency of the lock-in amplifier in the first picture is set to the cantilever of the probe. Forced vibration signal frequency, set the reference signal frequency of the lock-in amplifier in the second picture to the sum or difference of the cantilever forced vibration signal frequency and the repetition frequency of the excitation light. Thus, the in-situ sample can be achieved through a single scan Height imaging and light force imaging can provide multi-dimensional information of the sample at the same time.
根据本发明的一个具体实施例，参考附图2，上述光致力探测显微镜还包括：全内反射镜4，上述激发光光源1发出的激发光通过上述全内反射镜4从样品底部聚焦到上述样品待检测面，由此，激发光光源1发出的激发光既可以通过全内反射镜4聚焦增加高频消逝场分量，又可以消除照射到探针2的透射激发光，从而避免了透射激发光对探针2产生影响，使得后续第二图锁相放大器输出的光力信号全部来源于样品本身，极大地提高了检测精度，同时还有利于光致力探测显微镜与倒置显微镜6集成。According to a specific embodiment of the present invention, with reference to Figure 2, the above-mentioned photoforce detection microscope also includes: a total internal reflection mirror 4. The excitation light emitted by the above-mentioned excitation light source 1 is focused from the bottom of the sample to the above-mentioned surface through the above-mentioned total internal reflection mirror 4. The surface of the sample to be detected, thus, the excitation light emitted by the excitation light source 1 can be focused by the total internal reflection mirror 4 to increase the high-frequency evanescent field component, and can also eliminate the transmitted excitation light irradiating the probe 2, thereby avoiding transmission excitation The light affects the probe 2, so that the optical force signal output by the lock-in amplifier in the second picture all comes from the sample itself, which greatly improves the detection accuracy and is also conducive to the integration of the optical force detection microscope and the inverted microscope 6.
需要解释的是：在使用全内反射镜时，本领域技术人员一般会在全内反射镜和样品之间滴加折射率匹配油，该折射率匹配油的作用是填充全内反射镜跟样品之间的空气间隙，从而减少甚至消除光线在样品下表面的反射，只有当光线到达样品待检测面，才能满足全反射条件，因此，激发光可以直接穿过样品底部在样品的待检测面发生全反射。It should be explained that when using a total internal reflection mirror, those skilled in the art will generally drop refractive index matching oil between the total internal reflection mirror and the sample. The function of the refractive index matching oil is to fill the total internal reflection mirror and the sample. The air gap between them reduces or even eliminates the reflection of light on the lower surface of the sample. Only when the light reaches the surface of the sample to be detected can the total reflection condition be met. Therefore, the excitation light can directly pass through the bottom of the sample and occur on the surface of the sample to be detected. total reflection.
根据本发明的再一个具体实施例，参考附图2，上述激发光光源发出的激发光平行于上述全内反射镜的光轴方向偏心射入全内反射镜，由此，进一步保证了激发光在样品待检测面发生全反射，从而避免了透射激发光对探针2产生影响，进一步保证了后续第二图锁相放大器输出的光力信号全部来源于样品本身，极大地提高了检测精度。According to another specific embodiment of the present invention, with reference to Figure 2, the excitation light emitted by the above-mentioned excitation light source is eccentrically incident on the total internal reflection mirror parallel to the optical axis direction of the above-mentioned total internal reflection mirror, thereby further ensuring that the excitation light Total reflection occurs on the surface of the sample to be detected, thereby avoiding the impact of the transmitted excitation light on the probe 2, further ensuring that the optical signal output by the lock-in amplifier in the second picture is all derived from the sample itself, which greatly improves the detection accuracy.
在本发明的实施例中，上述全内反射镜4并不受特殊限定，只要可以实现激发光光源1发出的激发光通过全内反射镜4在样品的待检测面发生全反射即可，作为一个优选的方案，上述全内反射镜4包括全内反射棱镜和全内反射物镜中的至少一种。In the embodiment of the present invention, the above-mentioned total internal reflection mirror 4 is not particularly limited, as long as the excitation light emitted by the excitation light source 1 can be completely reflected on the surface of the sample to be detected through the total internal reflection mirror 4, as In a preferred solution, the above-mentioned total internal reflection mirror 4 includes at least one of a total internal reflection prism and a total internal reflection objective lens.
根据本发明的又一个具体实施例，参考附图2或3，上述探针2针尖和上述样品待检测面沿Z方向的距离为1纳米-65纳米，优选为1纳米-10纳米，由此，将上述探针2和上述样品待检测面沿Z方向的距离控制在上述范围内，保证了探针的针尖受到的作用力处于大范围的引力和斥力交替变化中，从而进一步提升了光致力探测显微镜的检测信号强度。According to another specific embodiment of the present invention, with reference to Figure 2 or 3, the distance along the Z direction between the tip of the probe 2 and the surface of the sample to be detected is 1 nanometer to 65 nanometers, preferably 1 nanometer to 10 nanometers, so , the distance along the Z direction between the above-mentioned probe 2 and the above-mentioned sample surface to be detected is controlled within the above-mentioned range, ensuring that the force exerted on the tip of the probe is in a wide range of alternating attraction and repulsion, thereby further improving the photodynamic force. The detection signal intensity of the detection microscope.
具体地，当上述激发光光源发出的激发光通过上述全内反射镜聚焦到上述样品待检测面，改变探针悬臂固有的振动状态的作用力可能包括：(1)由于光电场的电磁极化效应，导致样品待检测面产生诱导偶极子，设置在样品待检测面方的探针的针尖会产生镜像偶极子，两个偶极子之间存在电磁相互作用力，电磁相互作用力会改变探针悬臂固有的振动状态；(2)随着激发光照射在样品待检测面产生的热不断积累，可能会引发样品待检测面产生极其微弱的热致形变，由于探针并未与样品直接接触，这种热致形变仅仅被视为对样品和探针之间距离的微扰，由于样品与探针之间的范德瓦耳斯力对距离非常敏感，极小的样品和探针之间距离的变化，可能会引起可探测的范德瓦耳斯力发生改变，从而可能改变了探针悬臂固有的振动状态。Specifically, when the excitation light emitted by the above-mentioned excitation light source is focused onto the above-mentioned sample surface to be detected through the above-mentioned total internal reflection mirror, the force that changes the inherent vibration state of the probe cantilever may include: (1) due to electromagnetic polarization of the optical electric field. The effect causes an induced dipole to be generated on the surface of the sample to be detected. The tip of the probe set on the surface of the sample to be detected will produce a mirror dipole. There is an electromagnetic interaction force between the two dipoles, and the electromagnetic interaction force will Change the inherent vibration state of the probe cantilever; (2) As the heat generated by the excitation light irradiates the surface of the sample to be detected continues to accumulate, it may cause extremely weak thermal deformation of the surface of the sample to be detected, because the probe is not in contact with the sample. In direct contact, this thermally induced deformation is only regarded as a perturbation to the distance between the sample and the probe. Since the van der Waals force between the sample and the probe is very sensitive to distance, extremely small samples and probes Changes in the distance between them may cause changes in the detectable van der Waals forces, which may change the inherent vibration state of the probe cantilever.
根据本发明的又一个具体实施例，参考附图2，还包括：倒置显微镜，上述倒置显微镜包括可见光光源5和倒置显微镜检测部6，上述可见光光源5发射的可见光通过上述全内反射镜4照射在上述样品待检测面，经由上述样品待检测面反射的上述可见光反射光进入上述倒置显微镜检测部6进行检测，由此，倒置显微镜6可以实现对样品待检测面的光学显微放大，且激发光可以和倒置显微镜6的显微镜内部光学系统共用光路，从而节约了成本。According to another specific embodiment of the present invention, with reference to Figure 2, it also includes: an inverted microscope. The above-mentioned inverted microscope includes a visible light source 5 and an inverted microscope detection part 6. The visible light emitted by the above-mentioned visible light source 5 is illuminated by the above-mentioned total internal reflection mirror 4. On the surface of the sample to be detected, the visible reflected light reflected by the surface of the sample to be detected enters the detection part 6 of the inverted microscope for detection. Therefore, the inverted microscope 6 can achieve optical microscopic amplification of the surface of the sample to be detected and excite The light can share an optical path with the internal optical system of the microscope of the inverted microscope 6, thereby saving costs.
进一步地，上述可见光光源发出的可见光和激发光光源发出的激发光均平行于上述全内反射镜的光轴方向偏心射入全内反射镜，进一步有利于实现发光可以和倒置显微镜的显微镜内部光学系统共用光路，从而节约了成本。Furthermore, the visible light emitted by the above-mentioned visible light source and the excitation light emitted by the excitation light source are eccentrically ejected into the total internal reflection mirror parallel to the optical axis direction of the above-mentioned total internal reflection mirror, which further facilitates the realization of luminescence and the internal optics of the inverted microscope. The system shares the optical path, thereby saving costs.
根据本发明的又一个具体实施例，上述光学激发系统还包括滤波器7，上述滤波器7用于对上述激发光光源1发出的上述激发光进行波长选择和强度调制，由此，可以通过样品选择对应的激发光的波长和激发光的强度，实现样品待检测面关键物性参数的有效激发，进而提高了光致力探测显微镜的检测效果。According to another specific embodiment of the present invention, the above-mentioned optical excitation system also includes a filter 7. The above-mentioned filter 7 is used for wavelength selection and intensity modulation of the above-mentioned excitation light emitted by the above-mentioned excitation light source 1, whereby the sample can be passed through Select the corresponding wavelength and intensity of the excitation light to achieve effective excitation of key physical parameters of the sample surface to be detected, thereby improving the detection effect of the photodetection microscope.
根据本发明的又一个具体实施例，上述光学激发系统还包括光束整形器8，上述光束整形器8用于将波长选择和强度调制后的单色光转化为单色基模高斯光束，由此，可以将单色光转化为检测需要的单色基模高斯光束，从而得到高质量的激光光斑，提高了光致力探测显微镜的检测效果。According to another specific embodiment of the present invention, the above-mentioned optical excitation system also includes a beam shaper 8. The above-mentioned beam shaper 8 is used to convert the monochromatic light after wavelength selection and intensity modulation into a monochromatic fundamental mode Gaussian beam, whereby , which can convert monochromatic light into the monochromatic basic mode Gaussian beam required for detection, thereby obtaining a high-quality laser spot and improving the detection effect of the photodetection microscope.
根据本发明的又一个具体实施例，上述光学激发系统还包括扩束准直器9，上述扩束准直器9用于对上述单色基模高斯光束进行扩束准直，由此，当激光光束经过扩束准直器9后，可以更好的匹配全内反射镜4的入瞳对于光束直径等参数的要求，进而提高了光致力探测显微镜的检测效果。According to another specific embodiment of the present invention, the above-mentioned optical excitation system also includes a beam expansion collimator 9. The above-mentioned beam expansion collimator 9 is used for beam expansion and collimation of the above-mentioned monochromatic fundamental mode Gaussian beam. Therefore, when After the laser beam passes through the beam expander collimator 9, it can better match the requirements of the entrance pupil of the total internal reflection mirror 4 for beam diameter and other parameters, thereby improving the detection effect of the photodetection microscope.
根据本发明的又一个具体实施例，上述控制系统包括样品位移平台3和控制器14，上述样品设置在上述样品位移平台3上，上述控制器14用于驱动上述样品位移平台3和上述探针2进行移动。According to another specific embodiment of the present invention, the above-mentioned control system includes a sample displacement platform 3 and a controller 14. The above-mentioned sample is arranged on the above-mentioned sample displacement platform 3. The above-mentioned controller 14 is used to drive the above-mentioned sample displacement platform 3 and the above-mentioned probe. 2 to move.
在本发明的实施例中，上述样品位移平台3的种类并不受特殊限定，本领域技术人员可以根据实际情况进行选择，作为一个优选的方案，上述样品位移平台3包括压电式样品位移平台和机械式样品位移平台中的至少一种。In the embodiment of the present invention, the type of the above-mentioned sample displacement platform 3 is not particularly limited. Those skilled in the art can choose according to the actual situation. As a preferred solution, the above-mentioned sample displacement platform 3 includes a piezoelectric sample displacement platform. and at least one of a mechanical sample displacement platform.
根据本发明的又一个具体实施例，上述样品位移平台3为纳米精度的样品位移平台，由此，可以以更小的步进精度更加精准的调节样品位移平台3上的样品移动距离，进而确保实现纳米级别的空间分辨率。According to another specific embodiment of the present invention, the above-mentioned sample displacement platform 3 is a nanometer-precision sample displacement platform. Therefore, the sample movement distance on the sample displacement platform 3 can be adjusted more accurately with smaller step accuracy, thereby ensuring Achieve nanometer-level spatial resolution.
在本发明的实施例中，上述控制器14包括但不限于闭环控制器。In the embodiment of the present invention, the above-mentioned controller 14 includes but is not limited to a closed-loop controller.
根据本发明的又一个具体实施例，上述控制器14包括探针移动控制器15、样品位移平台X方向移动控制器16和样品位移平台Y方向移动控制器17，由于样品的高度具有不均匀性，通过探针移动控制器15可以精准调控探针2和样品待检测面的距离，进而可以更好地对样品进行检测；通过设置样品位移平台X方向移动控制器16和样品位移平台Y方向移动控制器17，可以分别对样品的X方向和Y方向上的移动距离进行精准调控。According to another specific embodiment of the present invention, the above-mentioned controller 14 includes a probe movement controller 15, a sample displacement platform X-direction movement controller 16 and a sample displacement platform Y-direction movement controller 17. Due to the uneven height of the sample, , the distance between the probe 2 and the sample surface to be detected can be accurately controlled through the probe movement controller 15, so that the sample can be better detected; by setting the sample displacement platform X-direction movement controller 16 and the sample displacement platform Y-direction movement The controller 17 can accurately control the moving distance of the sample in the X direction and Y direction respectively.
进一步地，当样品待检测面可能出现凹凸不平的区域时，采用探针移动控制器可以精准调控探针和样品待检测面的距离，进而可以更好地对样品进行检测，由于样品待检测面的凹凸不平区域的Z方向变化值极小，因此探针和样品待检测面的距离基本保持不变，从而需要精度较高的探针移动控制器才能更好地实现样品检测。Furthermore, when there may be uneven areas on the surface of the sample to be detected, the probe movement controller can be used to accurately control the distance between the probe and the surface of the sample to be detected, so that the sample can be better detected, because the surface of the sample to be detected is The Z-direction change value of the uneven area is extremely small, so the distance between the probe and the surface to be detected of the sample remains basically unchanged, which requires a high-precision probe movement controller to better achieve sample detection.
在本发明的实施例中，上述激发光光源包括但不限于宽谱激光器。In embodiments of the present invention, the above-mentioned excitation light source includes but is not limited to a broad spectrum laser.
在本发明的实施例中，上述宽谱激光器包括但不限于超连续谱激光器。In embodiments of the present invention, the above-mentioned broad spectrum laser includes but is not limited to supercontinuum laser.
根据本发明实施例的光致力探测显微镜，相比于光热诱导显微镜，本申请的光致力探测显微镜的优点在于：(1)探针是在轻敲模式下进行工作的，因此可以避免探针和样品待检测面发生直接接触，既解决了扫描中探针容易污染和磨损、样品容易受到探针损伤等问题，又解决了提取探测的有效信号困难的问题；(2)本发明的光致力探测显微镜不是对样品热膨胀进行检测，光致力探测显微镜的工作波长可以覆盖紫外-可见光-红外甚至太赫兹波段，实现了波长应用范围的扩展；(3)由于本发明的光致力探测显微镜不是对样品热膨胀进行检测，因此允许的样品厚度的更宽；(4)通过采用光力信号解调方法，实现了单次扫描即可得到样品的原位高度成像和光力成像，同时提供样品的多维度信息；相比于光诱导力显微镜，本申请的光致力探测显微镜的优点在于：(1)本发明的激发光可以从样品的下方照射在样品的待检测面，通过控制样品待检测面和针尖之间的距离，可以使得针尖受到的作用力处于大范围的引力和斥力交替变化中，从而大幅度提升了光致力探测显微镜的检测信号强度；(2)由于光致力探测显微镜的检测信号强度得到大幅提升，因此可以降低激发光强度，也可以使用电场增强效果较弱的硅针尖进行探测，通过降低激发光强度有利于避免样品受激光损伤，通过采用硅针尖较小的针尖曲率半径可以获得更好的横向空间分辨率；(3)通过采用光力信号解调方法，实现了单次扫描即可得到样品的原位高度成像和光力成像，同时提供样品的多维度信息。According to the photoforce detection microscope according to the embodiment of the present invention, compared with the photothermal induction microscope, the advantages of the photoforce detection microscope of the present application are: (1) The probe works in a tapping mode, so the probe can be avoided Direct contact with the surface of the sample to be detected not only solves the problem of easy contamination and wear of the probe during scanning, and the susceptibility of the sample to damage by the probe, but also solves the problem of difficulty in extracting effective signals for detection; (2) The photoelectric force of the present invention The detection microscope does not detect the thermal expansion of the sample. The working wavelength of the photodetection microscope can cover the ultraviolet-visible light-infrared and even terahertz bands, realizing the expansion of the wavelength application range; (3) Since the photodetection microscope of the present invention does not detect the sample Thermal expansion is detected, so the sample thickness is allowed to be wider; (4) By using the optical force signal demodulation method, the in-situ height imaging and optical force imaging of the sample can be obtained in a single scan, while providing multi-dimensional information of the sample ; Compared with the photoinduced force microscope, the advantages of the photoinduced force detection microscope of the present application are: (1) The excitation light of the present invention can be irradiated from the bottom of the sample to the surface to be detected of the sample, by controlling the relationship between the surface of the sample to be detected and the needle tip The distance between the two can make the force on the tip of the needle be in a wide range of alternating gravitational and repulsive forces, thus greatly improving the detection signal intensity of the photodetection microscope; (2) Because the detection signal intensity of the photodetection microscope has been greatly improved Therefore, the intensity of the excitation light can be reduced, or a silicon tip with a weak electric field enhancement effect can be used for detection. By reducing the intensity of the excitation light, it is helpful to avoid laser damage to the sample. By using a silicon tip with a smaller tip curvature radius, better results can be obtained. The lateral spatial resolution; (3) By using the optical force signal demodulation method, the in-situ height imaging and optical force imaging of the sample can be obtained in a single scan, while providing multi-dimensional information of the sample.
在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本发明的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不必须针对的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任一个或多个实施例或示例中以合适的方式结合。此外，在不相互矛盾的情况下，本领域的技术人员可以将本说明书中描述的不同实施例或示例以及不同实施例或示例的特征进行结合和组合。In the description of this specification, reference to the terms "one embodiment," "some embodiments," "an example," "specific examples," or "some examples" or the like means that specific features are described in connection with the embodiment or example. , structures, materials or features are included in at least one embodiment or example of the invention. In this specification, the schematic expressions of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification unless they are inconsistent with each other.
尽管上面已经示出和描述了本发明的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本发明的限制，本领域的普通技术人员在本发明的范围内可以对上述实施例进行变化、修改、替换和变型。Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are illustrative and should not be construed as limitations of the present invention. Those of ordinary skill in the art can make modifications to the above-mentioned embodiments within the scope of the present invention. The embodiments are subject to changes, modifications, substitutions and variations.
实施例1Example 1
本实施例提供一种采用光致力探测显微镜检测物质的方法，其步骤如下：This embodiment provides a method for detecting substances using a photodetection microscope. The steps are as follows:
(1)首先对本实施例的光致力探测显微镜进行介绍：(1) First, the photodetection microscope of this embodiment is introduced:
本实施例所述的光致力探测显微镜包括光学激发系统(激发光光源、驱动器、探针、全内反射镜、滤波器、光束整形器和扩束准直器)、控制系统(压电式样品位移平台、探针移动控制器；样品位移平台X方向移动控制器和样品位移平台Y方向移动控制器)和信号采集处理系统(四象限探测器、第一图锁相放大器(即高度图锁相放大器)和第二图锁相放大器(即光力图锁相放大器))；激发光光源发射的激发光依次通过滤波器、光束整形器和扩束准直器，再平行于全内反射镜的光轴方向偏心射入全内反射物镜，最后在样品的待检测面发生全反射；通过探针移动控制器精准调控探针和样品待检测面的距离，通过设置样品位移平台X方向移动控制器和样品位移平台Y方向移动控制器分别对样品的X方向和Y方向上的移动距离进行精准调控；四象限探测器用于接收探针的振动信号且将所述振动信号转为振动电信号，探针的振动电信号分别同时经过高度图锁相放大器和光力图锁相放大器进行解调，从而得到样品的高度信号和光力信号。The photodetection microscope described in this embodiment includes an optical excitation system (excitation light source, driver, probe, total internal reflection mirror, filter, beam shaper and beam expansion collimator), a control system (piezoelectric sample Displacement platform, probe movement controller; sample displacement platform X-direction movement controller and sample displacement platform Y-direction movement controller) and signal acquisition and processing system (four-quadrant detector, first map lock-in amplifier (i.e. height map lock-in Amplifier) and the second picture lock-in amplifier (i.e. optical force diagram lock-in amplifier)); the excitation light emitted by the excitation light source passes through the filter, beam shaper and beam expansion collimator in sequence, and then is parallel to the light of the total internal reflection mirror The axial direction is eccentrically injected into the total internal reflection objective lens, and finally total reflection occurs on the surface of the sample to be detected; the distance between the probe and the surface of the sample to be detected is accurately controlled by the probe movement controller, and the X-direction movement controller of the sample displacement platform is set by The Y-direction movement controller of the sample displacement platform accurately controls the movement distance of the sample in the X-direction and Y-direction respectively; the four-quadrant detector is used to receive the vibration signal of the probe and convert the vibration signal into an electrical vibration signal. The vibration electrical signals are demodulated by the height map lock-in amplifier and the optical force map lock-in amplifier at the same time, thereby obtaining the height signal and optical force signal of the sample.
具体地，本实施例中的激发光光源为400-700nm波长连续可调谐激光器，功率1mW(633nm波长处)，激光重复频率为1399.6kHz，线偏振光；全内反射镜使用100X，NA＝1.45的复消色差全内反射荧光物镜，使用折射率为1.5(25℃时)的折射率匹配油填充全内反射镜和样品待检测面之间的空隙，所使用的AFM探针是针尖镀金的硅探针，镀金厚度25nm左右，探针一阶共振频率为267.1kHz，二阶共振频率为1666.7kHz，一阶刚度为40N/m；样品位移平台为压电式纳米精度二维平移台，由两个闭环伺服控制器对X方向和Y方向进行精确控制，扫描过程中样品-针尖距离保持恒定由比例-积分-微分(PID)控制器实现，高度图锁相放大器和光力图锁相放大器均为全数字锁相放大器。Specifically, the excitation light source in this embodiment is a continuously tunable laser with a wavelength of 400-700nm, a power of 1mW (at a wavelength of 633nm), a laser repetition frequency of 1399.6kHz, and linearly polarized light; the total internal reflection mirror is 100X, NA=1.45 The apochromatic total internal reflection fluorescence objective lens uses refractive index matching oil with a refractive index of 1.5 (at 25°C) to fill the gap between the total internal reflection mirror and the surface of the sample to be detected. The AFM probe used has a gold-plated tip. The silicon probe has a gold plating thickness of about 25nm. The first-order resonance frequency of the probe is 267.1kHz, the second-order resonance frequency is 1666.7kHz, and the first-order stiffness is 40N/m. The sample displacement platform is a piezoelectric nano-precision two-dimensional translation stage, consisting of Two closed-loop servo controllers precisely control the X and Y directions. The sample-tip distance is kept constant during the scanning process by a proportional-integral-derivative (PID) controller. Both the height map lock-in amplifier and the optical force map lock-in amplifier are Fully digital lock-in amplifier.
(2)具体检测物质的方法步骤为：(2) The specific method steps for detecting substances are:
分别制备厚度近似相同的二硫化钨(WS2)和六方氮化硼(h-BN)多层纳米片若干，纳米片厚度百纳米量级，片径30nm-1000nm不等，将二硫化钨(WS2)和六方氮化硼(h-BN)在酒精分散后充分混合、振荡，用超声波对含有二硫化钨(WS2)和六方氮化硼(h-BN)的酒精溶液进行超声，将混合均匀后的两种纳米片分散液滴加到0.17mm厚度的透明硼硅酸盐玻璃衬底上，70℃加热烘干1小时，得到测试样品如附图4所示，18是混合物中h-BN纳米片，19是混合物中的WS2纳米片，20是硼硅酸盐玻璃衬底。A number of tungsten disulfide (WS2 ) and hexagonal boron nitride (h-BN) multilayer nanosheets with approximately the same thickness were prepared respectively. The nanosheet thickness was in the order of hundreds of nanometers and the sheet diameter ranged from 30nm to 1000nm. The tungsten disulfide ( WS2 ) and hexagonal boron nitride (h-BN) are thoroughly mixed and oscillated after being dispersed in alcohol, and the alcohol solution containing tungsten disulfide (WS2 ) and hexagonal boron nitride (h-BN) is ultrasonicated. The two uniformly mixed nanosheet dispersions were added dropwise to a transparent borosilicate glass substrate with a thickness of 0.17mm, and heated and dried at 70°C for 1 hour to obtain the test sample as shown in Figure 4. 18 is h in the mixture. -BN nanosheets, 19 is the WS2 nanosheets in the mixture, 20 is the borosilicate glass substrate.
对上述样品采用光致力探测显微镜进行逐点成像扫描，扫描范围3.3μm×3.3μm，扫描速度为20毫秒每像素点，探针的针尖和样品待检测面沿Z方向的距离为4nm(即探针发生受迫振动的振幅的60％)，由于WS2和h-BN两种纳米片在633nm波长下吸光度存在明显差异，在633nm单色激光下进行样品扫描成像，高度图如附图5所示，说明h-BN纳米片和WS2纳米片厚度较为均一，无法单纯从高度图上分辨纳米片的类型，需要引入具有材料分辨能力的探测手段，光力图如附图6所示，低亮度区域401为h-BN，高亮度区域402为WS2，该结果与EDS能量色散谱结果吻合，通过对本实施例的光力图的横向空间分辨率进行检测，参考附图7，得到横向空间分辨率大约为15nm，空间分辨率得到大幅提高。The above-mentioned samples were scanned point by point using a photodetection microscope. The scanning range was 3.3 μm × 3.3 μm. The scanning speed was 20 milliseconds per pixel. The distance between the tip of the probe and the surface to be detected of the sample along the Z direction was 4 nm (i.e., the probe 60% of the amplitude of the forced vibration of the needle). Since there is a significant difference in the absorbance of the two nanosheetsWS2 and h-BN at a wavelength of 633nm, the sample was scanned and imaged under a 633nm monochromatic laser. The height map is shown in Figure 5. shows that the thickness of h-BN nanosheets and WS2 nanosheets is relatively uniform, and the type of nanosheets cannot be distinguished simply from the height map. It is necessary to introduce detection methods with material resolution capabilities. The optical force diagram is shown in Figure 6. Low brightness The area 401 is h-BN, and the high-brightness area 402 is WS2 . This result is consistent with the EDS energy dispersion spectrum result. By detecting the lateral spatial resolution of the optical force diagram of this embodiment, and referring to Figure 7, the lateral spatial resolution is obtained At about 15nm, the spatial resolution is greatly improved.
对样品光力图的横向空间分辨率进行检测的方法为：(1)首先找到两种材料的分界线，使样品沿着分界线的法线方向(即附图6中的白色虚线)做线扫描，以扫描的距离作为横轴，光力探测信号(振幅)作为纵轴，绘制光力-距离曲线图；(2)由于两种材料的物性差异，在扫过分界线时曲线会出现具有一定斜率的上升沿或下降沿，测量上升沿或下降沿所需要的距离，此距离即为横向空间分辨率。The method to detect the lateral spatial resolution of the optical force diagram of the sample is: (1) First find the dividing line between the two materials, and make the sample perform a line scan along the normal direction of the dividing line (i.e., the white dotted line in Figure 6) , with the scanning distance as the horizontal axis and the optical force detection signal (amplitude) as the vertical axis, draw the optical force-distance curve; (2) Due to the difference in physical properties of the two materials, the curve will have a certain slope when sweeping the dividing line. On the rising edge or falling edge, measure the distance required for the rising edge or falling edge. This distance is the lateral spatial resolution.
尽管上面已经示出和描述了本发明的实施例，可以理解的是，上述实施例是示例性的，不能理解为对本发明的限制，本领域的普通技术人员在本发明的范围内可以对上述实施例进行变化、修改、替换和变型。Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are illustrative and should not be construed as limitations of the present invention. Those of ordinary skill in the art can make modifications to the above-mentioned embodiments within the scope of the present invention. The embodiments are subject to changes, modifications, substitutions and variations.
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| CN202310539799.0ACN116593739B (en) | 2023-05-12 | 2023-05-12 | Method for demodulating a light signal and light-driven microscope |
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| CN110121644A (en)* | 2016-08-22 | 2019-08-13 | 布鲁克纳米公司 | It is characterized using the infrared light of the sample of oscillation mode |
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| WO2004005844A2 (en)* | 2002-07-04 | 2004-01-15 | University Of Bristol | Scanning probe microscope |
| WO2013003864A1 (en)* | 2011-06-30 | 2013-01-03 | The Regents Of The University Of California | Mechanical detection of raman resonance |
| CN102495238A (en)* | 2011-11-11 | 2012-06-13 | 北京航空航天大学 | Sixth harmonic imaging system based on tapping mode atomic force microscope |
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| CN115104034A (en)* | 2019-12-17 | 2022-09-23 | 分子前景公司 | Resonance-enhanced detection method using scanning probe microscopy and modulation of the frequency range |
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