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| Identifiers | |
|---|---|
3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.031.765 |
| EC Number |
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| |
| |
| Properties | |
| As2Te3 | |
| Molar mass | 532.64 g·mol−1 |
| Structure[1] | |
| Monoclinic | |
| C2/m | |
a = 14.339 Å,b = 4.006 Å,c = 9.873 Å α = 90°, β = 95°, γ = 90° | |
Lattice volume (V) | 564.96 |
Formula units (Z) | 4 |
| Hazards | |
| GHS labelling: | |
  | |
| Danger | |
| H301,H331,H410 | |
| P261,P264,P270,P271,P273,P301+P310,P304+P340,P311,P321,P330,P391,P403+P233,P405,P501 | |
| Related compounds | |
Otheranions | Arsenic trioxide Arsenic trisulfide Arsenic triselenide |
Othercations | Antimony telluride Bismuth telluride |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Arsenic(III) telluride is aninorganic compound with thechemical formulaAs2Te3. It exists in two forms, themonoclinic α phase which transforms under high pressure to a rhombohedral β phase.[2] The compound is asemiconductor, with most current carried byholes.[3] Arsenic telluride has been examined for its use innonlinear optics.[4]
Arsenic(III) telluride is a bulk form[clarification needed] ofgroup 15sesquichalcogenides[clarification needed] which form chains ofAs2Te3 molecules that are eventually[clarification needed] stacked on top of each other and held together by weakVan der Waals forces.[5] This stacking of long branches ofAs2Te3 molecules gives arsenic(III) telluride an amorphous crystalline[clarification needed] structure that can be found in the ɑ-As2Te3 and β-As2Te3 configurations at different pressures. Atambient pressure, ɑ-As2Te3 yields a monoclinic structure with low thermoelectric properties; however, when placed in high pressure environments, ɑ-As2Te3 transforms into the β-As2Te3 configuration that has a rhombohedralR3mspace group with highthermoelectric properties.[6][clarification needed]
As2Te3 is a semiconductor and has been used to study nonlinear optics due to its ability to conduct electrical current; however, at high temperatures when doped with impurities[which?] causes these conductive abilities to transform irreversibly from its traditional semiconductor ability to metal conduction only.[5][7] This irreversible transformation is most likely caused by the doping materials added toAs2Te3 forming impurity clusters which causes an increase inparamagnetic tendency of the complex.[5][clarification needed]
As2Te3 is the least studied amorphouschalcogenide compound, which are a group of semiconductors primarily used innonlinear optics as glasses or lenses to redistribute light.[8] It has not been studied widely due to the difficulty to synthesizeAs2Te3 into amorphous crystalline solids. In order to avoid crystalizing arsenic telluride, it must be quenched quickly after it comes out of the melt.[8] Arsenic telluride andAs2Te3 containing materials are starting to increase in popularity in the field ofnonlinear optics because the amorphous glassesAs2Te3 is exceptional at redistributing the electrical charge density of the light source (typically a laser) when it interacts within the medium.[9] The significance of this redistribution is that it allows for the modification of the laser’s nature to perform a specific function. Some examples of this are the use of lasers in sensors, optical communication systems, as well as changing the color of the laser for equipment and other machinery used in materials research.[6][7]
It has also been discovered in recent studies thatAs2Te3 presents mobility edges, which are edges surrounding a conductive gap,[clarification needed] regardless of temperature allowing for the amorphous structure to conduct electricity at greater rates than expected.[8] Due to this, it can be hypothesized that the mobility edges lie betweendelocalized andlocalized states as well as having a more energetically efficient transition from dark mobility tophotoconductive mobility than other amorphous glasses.[8]
Arsenic(III) telluride, in its doped crystalline form, houses electron carriers that are caused by doping impurities that sit close to the edge due to the relatively free electron density around the edges.[10] These relatively free electrons interact with the impurities causing a decrease in electron density around the edge which causes a “tail” to form. These band tails overlap causing a gap or a hole, similar top-type doping, that can be used for conduction; however, the mobility of the carriers in the lattice decreases significantly near theFermi level of the two tails.[7][10] This indicates that electronic stimuli, usuallyphonon related, is needed to induce hopping of electrons into the gap to cause conduction.[5][10] The need of external phonon stimuli to cause electrical conductivity ofAs2Te3 crystals further supports the effectiveness ofAs2Te3 orAs2Te3 based glasses in the use of nonlinear optics because the light upon entering the lattice causes the electron hopping inducing conduction. Since the electrons are hopping into the conductance gap near the Fermi level, the light is being modified and will exit the lattice in a different form than it entered.[10]