Tunable and anisotropic photoresponse of layered Re0.2Sn0.8Se2 ternary alloy

Abstract

In order to produce high-performance optoelectronic devices, alloy engineering has been exploited in ternary transition metal dichalcogenides. In the present study, we demonstrated the effect of rhenium incorporation on the structural and electrical response in SnSe2 layered crystals grown by direct vapour transport technique. Elemental conformation was characterized by EDAX. The powder X-ray diffraction shows the hexagonal phase and high crystallinity of grown compounds, which is also confirmed by the TEM SAED pattern. Perfectly hexagonal shaped microcrystals are shown in SEM surface micrograph. Raman spectra indicate the redshift in the vibrational mode peaks of SnSe2 with the rhenium doping. Current-time characteristic was measured to study to the effect of alloy engineering on the photoresponse ability of the grown compound. Among all, Re0.2Sn0.8Se2 ternary alloy shows the enhanced photoresponse under polychromatic illumination, showing the suppression of deep-level defect states after incorporation of Re in SnSe2 lattice structure. These materials have a layered structure and exhibit the anisotropic conductivity. Hence the anisotropic photodetection characteristics of Re0.2Sn0.8Se2 ternary alloy based photodetectors are further studied in detail. Photocurrent and photo responsivity are higher along the symmetric contacts, whereas along the asymmetric contacts both the quantities are lower in magnitude because the photogenerated carriers have to cross the perpendicular resistance of is layers stacked together by the weak Vander Waal's forces. Increasing the bias voltage enhances the photoresponsivity from 5.141 mAW−1 to 67.231 mAW−1 and photodetectivity 0.971 to 3.452 × 109 Jones. Anisotropic photoresponse was also studied under the monochromatic light. Results provide the significant understanding of tunable and layered structure dependent anisotropic photoresponse ability of TMDC materials.