Unveiling the electrical and photo-physical properties of intrinsic n-type 2D WSe<inf>2</inf>for high performance field-effect transistors

Atomically thin semiconducting 2D transition metal dichalcogenides have garnered remarkable attention from the scientific community due to their prodigious contributions in the field of next-generation electronic and optoelectronic devices. In this continuation, we report a facile synthesis protocol of monolayer WSe2 films via the atmospheric-pressure chemical vapor deposition (APCVD) technique using hydrothermally synthesized hexagonal-phase tungsten oxide (h-WO3) nanorods. The as synthesized WSe2 crystal is a monolayer of ∼0.9 nm thickness as confirmed by atomic force microscopy. The confocal Raman and photoluminescence (PL) mapping suggests that the grown monolayer WSe2 triangles have lattice defects at edge sites, with a slight red-shift of ∼2 nm in PL, a blue-shift of ∼2 cm-1 in Raman peak and reduction in both the intensities. Confocal time-resolved PL mapping at edges reveals a fast-decay component of ∼582 ps and a slow-decay component of ∼2.18 ns that also signifies the presence of lattice defects, which serves as localized-states for photon-generated charge excitons. Furthermore, we have also investigated its electrical property by devising field-effect transistors (FETs). The fabricated WSe2 based FET shows intrinsic n-type behavior. WSe2 FET offers an electron mobility (μ) of ∼13.2 cm2 V-1 s-1, current ON/OFF ratio of ∼107 with a subthreshold slope (SS) of ∼397 mV/decade, which is relatable to the other reported works on WSe2 based FETs. In addition, the device exhibits very high on-current of order of ∼150 μA/μm. These results indicate that h-WO3 nanorod assisted APCVD synthesized WSe2 has prospective of being a competitor for next-generation optoelectronic, and valley-tronic devices.