Effect of Mo Growth Duration on Rapid Thermally Processed Metal Chalcogenide Thin Films for IR Detection

Abstract

Two-dimensional (2D) materials have emerged as transformative candidates for next-generation electronic and optoelectronic devices. Among those, molybdenum ditelluride (MoTe2 ) stands out for its ideal bandgap, making it highly suitable for infrared (IR) detection applications. In particular, p-MoTe2 /n-Si heterojunctions hold significant promise for photodetector technologies. This study focuses on the synthesis of MoTe2 thin films via a rapid thermal processing (RTP) technique, with a systematic variation in the molybdenum (Mo) deposition duration using a sputtering system prior to the thermal evaporation of tellurium (Te). Mo thin films are sputtered onto Si substrates, followed by Te evaporation, and the Mo/Te-coated substrates are processed in an RTP furnace at a growth temperature of 600 °C and growth duration of 10 min, under a base pressure of 2 torr and an argon gas flow of 160 sccm. The Mo deposition time is varied from 0.5 to 5 minutes to examine its impact on the structural, optical, and electrical properties of the MoTe2 thin films. The Mo growth duration was systematically varied from 0.5 to 5 minutes. X-ray diffraction (XRD) analysis revealed distinct peaks at 2θ = 12.8° , 25.5° , 39.2° , and 53.2° , corresponding to the (002), (004), (006), and (008) planes of the hexagonal 2H-MoTe₂ structure. Raman spectroscopy further confirmed the characteristic vibrational modes of MoTe2 , with prominent peaks observed at ~119 cm⁻1 and ~172 cm⁻1, attributed to the in-plane E1g and out-of-plane A1g modes, respectively. Additionally, the E1 2g mode (~232 cm⁻1) and B1 2g mode (~287 cm⁻1) were clearly identified. Atomic force microscopy (AFM) analysis had shown an increase in root mean square (RMS) surface roughness with higher growth temperatures. The optical bandgap of MoTe2 , determined using Tauc plots, was estimated as 0.9 eV for 5 min Mo growth duration. Currentvoltage (I-V) and current-time (I-T) measurements demonstrated optimal device performance at Mo growth duration of 5 minutes, yielding the highest responsivity and detectivity values of 127.37 mA/W and 8.52 × 108 Jones, respectively, under 1060 nm IR illumination