Disclosure of Invention
The invention provides a broadband absorbing device based on a phase change material, which is used for solving the defects that a broadband absorber in the prior art is complex in structure, sensitive to angle change and not adjustable in absorption range, realizing a dynamically adjustable broadband absorbing structure based on the phase change material, insensitive to angle, simple in structure and easy to integrate.
The invention provides a broadband absorbing device based on phase change material, comprising:
the broadband absorption cavity structure comprises an anti-reflection layer, a phase change layer and a metal layer, and the broadband absorption cavity structure utilizes the absorption characteristic and the dynamic adjustable characteristic of a phase change material and a semiconductor material with the K value larger than a first preset threshold value to jointly form a broadband absorber to absorb and adjust light;
The anti-reflection layer comprises a plurality of dielectric materials with refractive index gradients, wherein the K value of the dielectric materials is smaller than 1, and the refractive indexes of the dielectric materials are distributed in a gradient manner from top to bottom;
the lithium tantalate single-chip structure is positioned below the broadband absorption cavity structure;
When light rays are emitted to the broadband absorption cavity structure, the broadband absorption cavity structure is used for converting absorbed light energy into heat energy, the lithium tantalate single-chip structure is used for converting the heat energy into electric energy through a pyroelectric effect and outputting current, so that the state of the phase change layer is changed according to the current, and the absorbed light rays are regulated.
According to the broadband absorption device based on the phase change material, the broadband absorption cavity structure comprises a plurality of metal layers, wherein the effective N and K of the metal layers are larger than 1, and the larger the effective N and K are, the better the effective N and K are;
The medium in the anti-reflection layer has refractive index gradient, the refractive index n value has gradient distribution, the K value tends to 0 from top to bottom, and a plurality of dielectric materials with the K value tending to 0 form the anti-reflection layer structure. .
According to the broadband absorption device based on the phase change material, the broadband absorption cavity structure comprises an FP cavity formed by the metal layer and the dielectric layer through the phase change layer, or an FP cavity formed by the phase change layer and the metal layer.
According to the broadband absorption device based on the phase-change material, the broadband absorption cavity structure comprises a reflecting layer, a phase-change layer, a dielectric layer, a first semiconductor material layer, a second semiconductor material layer and a metal layer which are sequentially arranged from top to bottom.
According to the broadband absorbing device based on the phase-change material, the first semiconductor layer is made of materials with N and K values of Ge, si and the like being larger than 1 and mainly used for absorbing light, the second semiconductor layer is made of materials with N values of Cr, W and the like being larger than 1 and K values being smaller, the metal layer is made of materials with conductivity of W, ag and the like and stable in performance, and the layer mainly provides electrode driving and generates heat to drive state change of the phase-change material.
According to the broadband absorption device based on the phase-change material, provided by the invention, the voltage applied to the metal layer is regulated and controlled according to the current, and the crystallization and amorphization ratio of the phase-change material in the phase-change layer is controlled so as to regulate and control the absorption of light.
According to the broadband absorption device based on the phase change material, the thickness of the phase change material used by the phase change layer is less than 1 micron.
According to the broadband absorbing device based on the phase change material, provided by the invention, a plurality of phase change layers are provided, each phase change layer comprises a phase change material layer and electrode layers positioned on two sides of the phase change material layer, and the electrode layers between two adjacent phase change material layers are shared.
According to the broadband absorption device based on the phase change material, the phase change material used by the phase change layer is one or more of GeTe, sbTe, snSb, agSbTe, inSbTe, geSb, GST and other alloys, wherein the percentage of each atom is adjustable, and the K value of the phase change material is larger than 0.5;
The anti-reflection layer is made of low-K-value media such as TIO2, ta2O5, mgF2, znS and the like.
According to the broadband absorption device based on the phase change material, the thickness of the reflecting layer is smaller than 1 micrometer, the thickness of the phase change layer is smaller than 500nm, the thickness of the first semiconductor material layer is smaller than 200nm and larger than 10nm, the thickness of the second semiconductor material layer is smaller than 500nm and larger than 50nm, the thickness of the metal layer is smaller than 1 micrometer, and the thickness of the lithium tantalate single-crystal chip structure is not limited to 75 micrometers.
According to the broadband absorption device based on the phase change material, the absorbed light energy is converted into heat energy through the broadband absorption cavity structure, the heat energy is converted into electric energy through the pyroelectric effect by the lithium tantalate single-chip structure, the current is output, and the state of the phase change layer is changed according to the current, so that broadband absorption adjustment is realized, the size of an absorption range can be adjusted according to the requirement, the adjustment direction is wide, the angle is insensitive, the structure is simple, the integration is easy, the inherent limitation of the existing structure is overcome, the great technical progress significance is realized, and new possibility is provided for further development of broadband absorption technology.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
A phase change material based broadband absorbing device of the present invention is described below in connection with fig. 1, comprising:
A broadband absorption cavity structure including an anti-reflection layer, a phase change layer 203, and a metal layer 207;
a lithium tantalate single wafer structure 208 located beneath the broadband absorption cavity structure;
When light rays are emitted to the broadband absorption cavity structure, the broadband absorption cavity structure is used for converting absorbed light energy into heat energy, the lithium tantalate single-chip structure is used for converting the heat energy into electric energy through a pyroelectric effect and outputting current, so that the state of the phase change layer is changed according to the current, and the absorbed light rays are regulated.
The phase change layer 203 includes a phase change material, the order of combination of the metal and the phase change material is not limited, and the metal layer 207 may be disposed on both sides of the phase change material. The metal layer not only plays a role of forming an FP (Fabry-Perot) cavity with the phase-change material, but also plays a role of controlling the phase-change of the phase-change material. By applying a voltage to the metal layers on both sides of the phase change material, the crystal structure of the phase change material can be changed, thereby realizing the adjustment of the light absorption ratio of the broadband absorber structure.
The broadband absorption cavity structure mainly comprises an anti-reflection layer, a phase change layer 203 and a metal layer 207, and can achieve the effect of absorbing and adjusting in visible and infrared. The metal layer 207 has a high loss characteristic.
Below the broadband absorber cavity structure is a lithium tantalate single-wafer structure 208, and the absorbed light energy is converted into heat energy and conducted to a pyroelectric material, which converts the heat energy into electric energy through a pyroelectric effect, so that current can be output for use in solar cells and broadband heat radiators.
Through the design, the broadband absorption structure can be adjusted according to actual requirements, the proportion of target light absorption is adjusted, the maximum absorption can be more than ninety percent, and the broadband absorber is insensitive to angles after the absorption range reaches 400nm so as to meet the requirements of the broadband absorber on absorbers for infrared stealth, optical or thermal detection, solar cells, broadband heat radiators and the like.
According to the embodiment, the absorbed light energy is converted into heat energy through the broadband absorption cavity structure, the heat energy is converted into electric energy through the pyroelectric effect by the lithium tantalate single-chip structure, the current is output, and the state of the phase-change layer is changed according to the current, so that broadband absorption adjustment is realized, the size of an absorption range can be adjusted according to the needs, the adjustment direction is wide, the angle is insensitive, the structure is simple, the integration is easy, the inherent limitation of the existing structure is overcome, the great technical progress significance is realized, and new possibility is provided for further development of broadband absorption technology.
Based on the above embodiment, in this embodiment, the extinction coefficient of the metal layer is greater than a first preset threshold, and the refractive index is greater than a second preset threshold;
the medium in the anti-reflection layer has a refractive index gradient and the absorptivity is greater than a third preset threshold.
The broadband absorption cavity structure comprises a plurality of metal layers, wherein the effective N and K of the metal layers are larger than 1, the medium absorptivity in the anti-reflection layer is smaller than 1, the smaller the medium absorptivity is, the better the medium absorptivity is, and finally the medium absorptivity tends to 0.
A dynamically adjustable broadband absorber is composed of an anti-reflection layer, a phase change material and an absorptive metal with high refractive index and extinction coefficient.
The anti-reflection layer is composed of a medium with refractive index gradient and high absorptivity, and the regulation is mainly realized by the phase change material in the phase change layer 203. The metal thin film with high refractive index and extinction coefficient and the phase change layer 203 absorb and regulate light with 400nm to 2500 nm.
The phase change material of phase change layer 203 may include the following chalcogenide compounds and alloys thereof, including but not limited to high loss low refractive index characteristic phase change materials such as GST, GSST, IST, geSbTe, agInSbTe, inSbTe, agSbTe, ag2In4Sb76Te17 (AIST), which may enable a wide range of absorption tuning. In addition, the atomic percentages in the above formulas may vary. The phase change material may further comprise at least one dopant, such as C, N. Preferably, the phase change material is chosen GSST, which has large loss in the visible range, small refractive index, and good thermal stability of GSST.
On the basis of the above embodiment, the broadband absorption cavity structure in this embodiment includes an FP cavity formed by the metal layer 207 and the dielectric layer sandwiching the phase change layer 203, or an FP cavity formed by the phase change layer 203 and the metal layer 207.
On the basis of the above embodiment, as shown in fig. 2, the broadband absorption cavity structure in this embodiment includes a first anti-reflection layer 101, a second anti-reflection layer 102, a phase-change layer 103, a dielectric layer 104, a first semiconductor material layer 105, a second semiconductor material layer 106, and a metal layer 107, which are sequentially disposed from top to bottom.
Alternatively, the phase change material of phase change layer 103 is a high loss low refractive index material including, but not limited to GSST, the metal layer is Ag, wherein GSST is an ultra-thin phase change material with strong optical loss.
Below the phase change material is a first semiconductor material layer 105 and a second semiconductor material layer 106, and the first semiconductor material layer 105 and the second semiconductor material layer 106 may be a high extinction coefficient metal, such as Ge and Cr. The phase change material may be surrounded up and down by a dielectric material TIO2.
As shown in fig. 1, the broadband absorbing device based on the phase change material includes a first anti-reflection layer 201, a second anti-reflection layer 202, a phase change layer 203, a dielectric layer 204, a first semiconductor material layer 205, a second semiconductor material layer 206, a metal layer 207 and a lithium tantalate single-chip structure 208, which are sequentially arranged from top to bottom.
On the basis of the above embodiment, the optical loss of the first semiconductor material layer 205 in this embodiment is greater than the fourth preset threshold and the refractive index is greater than the fifth preset threshold;
The optical loss of the second semiconductor material layer 206 is greater than the fourth preset threshold and the refractive index is greater than the fifth preset threshold.
Based on the above embodiments, in this embodiment, the voltage applied to the metal layer 207 is controlled according to the magnitude of the current, so as to control the crystallization and amorphization ratio of the phase change material in the phase change layer 203, so as to regulate the absorption of the light.
The phase change material of the phase change layer 203 may be converted between crystalline and amorphous states under electrical or laser stimulation, thereby changing the transmittance and reflectance of the phase change layer 203. The first anti-reflection layer 201 of the top layer is deposited with a transparent lossless material MgF2, and the second anti-reflection layer 202 is deposited with a TIO2, which together form an anti-reflection layer. The phase change layer 203 may control the crystallization state of the phase change material by applying a voltage across the metal layer 207W.
Specifically, a pulse voltage with medium intensity is applied to W, the W generates heat, the temperature of the phase change material is increased to a temperature interval above the crystallization temperature and below the melting temperature under the action of heat, and the phase lattice is orderly arranged to form a crystalline state at the time, so that the transformation from an amorphous state to a crystalline state is realized.
A short and strong voltage is applied to W, high heat is generated instantaneously, the temperature of the phase-change material is increased to be higher than the melting temperature, the long-range order of a crystalline state is destroyed, the phase-change material is rapidly cooled to be lower than the crystallization temperature due to the very short pulse falling edge, the phase-change material is fixed in an amorphous state, and the transition from the crystalline state to the amorphous state is realized.
The ratio of light absorption by the narrow band absorption cavity structure is regulated by the transmittance and reflectance changes of the phase change material of the phase change layer 203 when it is transformed between amorphous and crystalline states.
The phase-change layer of the phase-change broadband absorption cavity structure has a large difference in light absorption under different states, and the phase-change material is stable under crystalline and amorphous states, so that the voltage or laser can be removed when the phase-change material is in a stable state, the power consumption of the whole absorption device in the adjusting process is low, and the absorption device is dynamically adjustable.
Based on the above embodiments, the thickness of the phase change material used for the phase change layer 203 in this embodiment is less than 1 micrometer.
The thickness of the phase change material used for the phase change layer 203 is less than 1 micron, and the higher the temperature required for crystallization of the phase change material due to the increase in the thickness of the phase change material, the more suitable the thickness is within 1 micron. The phase change material of phase change layer 203 may be driven with a voltage. When the voltage is driven, the bottom metal W of the narrow-band absorption cavity structure applies voltage to enable the phase change material to change phase.
Based on the above embodiments, in this embodiment, there are a plurality of phase change layers 203, each phase change layer 203 includes a phase change material layer and electrode layers located on two sides of the phase change material layer, and the electrode layers between two adjacent phase change material layers are shared.
Based on the above embodiment, in this embodiment, the first anti-reflection layer 201 is MgF2, the second anti-reflection layer 202 is TIO2, the phase-change layer 203 is GSST, the dielectric layer 204 is TIO2, the first semiconductor material layer 205 is Ge, the second semiconductor material layer 206 is Cr, and the metal layer 207 is W.
The phase change material used by the phase change layer is one of GeTe, sbTe, snSb, agSbTe, inSbTe, geSb and GST alloy, wherein the percentage of each atom is adjustable, and the K value of the phase change material is more than 0.5;
The anti-reflection layer is made of a medium with one K value of TIO2, ta2O5, mgF2 and ZnS smaller than a second preset threshold value;
the first semiconductor material layer is made of a material with one of Ge and Si, wherein the N and K values of the material are both larger than 1;
the second semiconductor material layer is made of a material with one of Cr and W, wherein the N value of the material is larger than 1, and the K value of the material is smaller than a third preset threshold value;
the metal layer is made of a material with stable conductive performance, wherein one of W and Ag.
Based on the above embodiment, in this embodiment, the thickness of the first anti-reflection layer 201 is 90nm, the thickness of the second anti-reflection layer 202 is 50nm, the thickness of the phase-change layer 203 is 8nm, the thickness of the dielectric layer 204 is 36nm, the thickness of the first semiconductor material layer 205 is 25nm, the thickness of the second semiconductor material layer 206 is 200nm, the thickness of the metal layer 207 is 200nm, and the thickness of the lithium tantalate single-chip structure 208 is 75 μm.
Fig. 3 is a schematic diagram of an absorption spectrum of GSST in an amorphous state in fig. 1. Fig. 4 is a schematic diagram of an absorption spectrum of GSST in the crystalline state in fig. 1. The phase change material layer is crystallized from amorphous to partially to completely by applying different voltages to the metal layer 207W. The magnitude of the applied voltage depends on the actual situation, and the absorption ratio of the target light is adjusted according to the actual requirement.
Fig. 5 and 6 show that the absorption angle insensitivity of GSST in amorphous and amorphous states in the phase change material-based broadband absorption device provided by the present invention can reach 70 ° and is completely not much different within the range of 60 °.
It should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that the technical solution described in the above-mentioned embodiments may be modified or some technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiments of the present invention.