Photosensor Device Based on Few‐Layered WS₂ Films

Abstract

Few‐layered films of WS2, synthesized by chemical vapor deposition on quartz, are successfully used as light sensors. The film samples are structurally characterized by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and high‐resolution transmission electron microscopy. The produced samples consist of few layered sheets possessing up to 10 layers. UV–visible absorbance spectra reveals absorption peaks at energies of 1.95 and 2.33 eV, consistent with the A and B excitons characteristic of WS2. Current–voltage (I–V) and photoresponse measurements carried out at room temperature are performed by connecting the WS2 layered material with Au/Ti contacts. The photocurrent measurements are carried out using five different laser lines ranging between 457 and 647 nm. The results indicate that the electrical response strongly depends on the photon energy from the excitation lasers. In addition, it is found that the photocurrent varies non‐linearly with the incident power, and the generated photocurrent in the WS2 samples varies as a squared root of the incident power. The excellent response of few‐layered WS2 to detect different photon wavelengths, over a wide range of intensities, makes it a strong candidate for constructing novel optoelectronic devices.

Optoelectronic Devices Based on Atomically Thin Transition Metal Dichalcogenides

“…The same device structure has also been used in conjunction with other 2D semiconductors, such as GaSe, GaTe, In 2 Se 3 , black phosphorus and several others [46][47][48][49][50][51][52]. Wavelength-dependent studies have shown that the photocurrent follows the TMD absorption spectrum.…”

Heterostructures of transition metal dichalcogenides

“…Indeed, similar lattice parameters allow the creation of a variety of TMDC heterostructures with very few structural defects [26]. However, despite their technological relevance [27] and various results from first principles calculations [28][29][30], the properties that can be expected from such systems are still under debate. In particular, the nature of the band gap (direct versus indirect) of the MoSe 2 -WSe 2 and MoTe 2 -WTe 2 heterostructures is not settled [31].…”

Mechanisms of Photoconductivity in Atomically Thin MoS2

“…Although graphene offers the possibility of photodetection over an unrivaled wavelength range [3][4][5] and with ultra-high bandwidth 5,6 , its photoresponsivity is limited by the vanishing bandgap and picosecond carrier lifetime. Recently, TMDs have attracted much interest for photodetection applications [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] , due to their potential for achieving very high responsivities. Broadly speaking, two groups of TMD-based photodetectors have been investigated: (i) vertically stacked heterostructure devices, where a few-layer TMD semiconductor is sandwiched between graphene or transparent metal electrodes 11,12 , and (ii) lateral metal-TMD-metal detectors [13][14][15][16][17][18][19][20][21][22][23][24] , whose device structure resembles that of field-effect transistors [27][28][29] (FETs).…”