Role of growth temperature on microstructural and electronic properties of rapid thermally grown MoTe2thin film for infrared detection

Abstract

In the field of electronic and optoelectronic applications, two-dimensional materials are found to be promising candidates for futuristic devices. For the detection of infrared (IR) light, MoTe₂possesses an appropriate bandgap for which p-MoTe₂/n-Si heterojunctions are well suited for photodetectors. In this study, a rapid thermal technique is used to grow MoTe₂thin films on silicon (Si) substrates. Molybdenum (Mo) thin films are deposited using a sputtering system on the Si substrate and tellurium (Te) film is deposited on the Mo film by a thermal evaporation technique. The substrates with Mo/Te thin films are kept in a face-to-face manner inside the rapid thermal-processing furnace. The growth is carried out at a base pressure of 2 torr with a flow of 160 sccm of argon gas at different temperatures ranging from 400 °C to 700 °C. The x-ray diffraction peaks appear around 2θ= 12.8°, 25.5°, 39.2°, and 53.2° corresponding to (002), (004), (006), and (008) orientation of a hexagonal 2H-MoTe₂structure. The characteristic Raman peaks of MoTe₂, observed at ∼119 cm^-1and ∼172 cm^-1, correspond to the in-plane E_1gand out-of-plane A_1gmodes of MoTe₂, whereas the prominent peaks of the in-plane E¹_2gmode at ∼234 cm^-1and the out-of-plane B¹_2gmode at ∼289 cm^-1are also observed. Root mean square (RMS) roughness is found to increase with increasing growth temperature. The bandgap of MoTe₂is calculated using a Tauc plot and is found to be 0.90 eV. Electrical characterizations are carried out using current-voltage and current-time measurement, where the maximum responsivity and detectivity are found to be 127.37 mA W^-1and 85.21 × 10⁷Jones for a growth temperature of 600 °C and an IR wavelength illumination of 1060 nm.

Keywords: IR detector; IT; IV; MoTe2 thin film; Raman; XRD.