Abstract
Transition metal dichalcogenides (TMDCs) have recently been the focus of extensive research activity owing to their fascinating physical properties. As a new member of TMDCs, Mo doped ReSe2 (Mo:ReSe2) is an octahedral structure semiconductor being optically biaxial and highly anisotropic, different from most of hexagonal layered TMDCs with optically uniaxial and relatively high crystal symmetry. We investigated the effects of physisorption of gas molecule on the few-layer Mo:ReSe2 nanosheet based photodetectors. We compared the photoresponse of the as-exfoliated device with annealed device both in air or ammonia (NH3) environment. After annealing at sub-decomposition temperatures, the Mo:ReSe2 photodetectors show a better photoresponsivity (~55.5 A/W) and higher EQE (10893%) in NH3 than in air. By theoretical investigation, we conclude that the physisorption of NH3 molecule on Mo:ReSe2 monolayer can cause the charge transfer between NH3 molecule and Mo:ReSe2 monolayer, increasing the n-type carrier density of Mo:ReSe2 monolayer. The prompt photoswitching, high photoresponsivity and different sensitivity to surrounding environment from the few-layer anisotropic Mo:ReSe2 can be used to design multifunctional optoelectronic and sensing devices.
Highlights
Transition metal dichalcogenides (TMDCs) have recently been the focus of extensive research activity owing to their fascinating physical properties
GaS nanosheet photodetectors made on SiO2/Si substrates or flexible polyethylene terephthalate (PET) substrates exhibit a photoresponsivity at 254 nm of up to 4.2 AW21 and 19.2 AW21, respectively, which far exceeds that of graphene-based devices
In order to understand the experimental results, first-principles calculations are performed to investigate the adsorption of NH3 molecule on the Mo:ReSe2 surface
Summary
Transition metal dichalcogenides (TMDCs) have recently been the focus of extensive research activity owing to their fascinating physical properties. Mo:ReSe2, a new member of TMDCs, is an anisotropic semiconductor crystallized in a distorted layered CdCl2-type octahedral structure of triclinic symmetry, different from most of hexagonal layered TMDCs. A clustering of Re4 diamond units forms along the b-axis within the van der Waals plane in Mo:ReSe2 monolayer, resulting in the crystals being optically biaxial[24]. On account of ‘‘diamond chains’’ clustering structure, Mo:ReSe2 shows in-plane optical and electrical anisotropic response, which may be exploited for fabrication of polarization sensitive photodetectors, photoelectrochemical solar cells and other optoelectronic devices[26,27]. In this communication, we report the few-layer Mo:ReSe2 nanosheets based photodetectors. These few-layer Mo:ReSe2 nanosheets were mechanically exfoliated on SiO2/Si substrates, and were characterized by atomic force microscopy (AFM) and Raman spectra
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