Abstract
We report on the structural properties and morphology of the quaternary semiconductor AgIn4GaTe8, prepared by direct fusion of stoichiometric mixture of constituent elements. For this, powder X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM) techniques were employed. From the XRD patterns we have identify a tetragonal phase together with a secondary orthorhombic phase. A strain/size analysis of the full-width-half-maximum (FWHM) of the diffraction lines, showed an anisotropic microstructure associated to the presence of microstrains, induced by crystallite size variations combined with crystallite dislocations. The SEM measurements reveal a material with very rough surface and faceted grains. The grain size determined from SEM micrographs was larger than the crystallite size obtained from the XRD data.
Highlights
Ternary and quaternary semiconductors provide a natural way of tuning the desired band gap and flexibility to control other material parameters, by changing the relative composition of the pure elements in the alloy
In a recent work we have shown that polycrystalline Ag(In1-xGax)5Te8 may exhibit a single tetragonal structure for all x values [9], the presence of these two phases in AgIn4GaTe8 is not surprising, since other authors have report that the ternary AgGa5Te8 can crystallize in both tetragonal and orthorhombic structure [8,13]
The unit cell parameters obtained for the tetragonal phase in our sample depart from the values a=6.1503 Å, c=12.329 Å, and c/a=2.0046, reported for single-tetragonal AgIn4GaTe8 [9]
Summary
Ternary and quaternary semiconductors provide a natural way of tuning the desired band gap and flexibility to control other material parameters, by changing the relative composition of the pure elements in the alloy. The most studied of the first class of alloys are Ag(In,Ga)(Te,Se)2 [3,4,5], which crystallize in the non-centrosymmetric chalcopyrite structure This is because these compounds appear as promising candidates for infrared nonlinear optical devices, and solar cells applications [6,7]. Semiconductors of the family I-III5-VI8 with tetragonal or orthorhombic structure depending on the ion of group III, have band gaps suitable for optimum energy conversion solar cells, and thermoelectric properties useful for applications in waste-heat recovery, air conditioning, and refrigeration [8]. It is known that Ag(In,Ga)5Te8 is obtainable because at these concentrations, the constituent elements melt congruently at relatively low temperatures [10] This information is of importance, since the electronic and other physical properties for applications may depend on the growth conditions
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