Ti-contacted halide-assisted CVD grown WSe_2 monolayers for high performance photodetectors

摘要

Transition metal dichalcogenides (TMDCs) have received a great deal of attention from the scientific community since the advent of graphene. Tungsten diselenide (2H-WSe_2) has particularly drawn-out attention of researchers because of its broadband spectral detection range. In this work, we have reported a halide assisted chemical vapor deposition (HA-LPCVD) technique for synthesis of large crystallites of 2H-WSe_2 with high crystalline perfection. The average crystallite size of synthesized 2H-WSe2 was in the order of ～20 μm. We have reported device 2H-WSe_2 device fabrication using poly (methyl methacrylate) and electron beam lithography process to define titanium (Ti) metal contacts. A temperature (T) dependent analysis of the electronic transport reported here reveals a T-dependent conduction process existing at the interface of Ti and 2H-WSe_2 and an interfacial barrier height of ～ 0.35 eV was calculated at the thermionic emission regime. From the reported optoelectronic characterization, an on-off ratio (I_(on)/I_(off)) of ～9 was calculated. Furthermore, a responsivity (R) of ～ 242 A/W was calculated for our 2H-WSe_2 based photodetector under broadband light excitation. The reported photodetector figures of merit will open avenues for use of monolayer 2H-WSe_2 with Ti metal contacts for high performance photodetection.