Photoconduction Properties in Tungsten Disulfide Nanostructures

Abstract

We reported the photoconduction properties of tungsten disulfide (WS₂) nanoflakes obtained by the mechanical exfoliation method. The photocurrent measurements were carried out using a 532 nm laser source with different illumination powers. The results reveal a linear dependence of photocurrent on the excitation power, and the photoresponsivity shows an independent behavior at higher light intensities (400-4000 Wm^-2). The WS₂ photodetector exhibits superior performance with responsivity in the range of 36-73 AW^-1 and a normalized gain in the range of 3.5-7.3 10^-6 cm²V^-1 at a lower bias voltage of 1 V. The admirable photoresponse at different light intensities suggests that WS₂ nanostructures are of potential as a building block for novel optoelectronic device applications.

Keywords: nanoflake; normalized gain; photoconductivity; photodetector; responsivity; tungsten disulfide.

Figure 1

Structural characterization of CVT-grown WS₂ bulk crystal. (a) X-ray diffraction pattern and (b) Raman spectrum.

Figure 2

(a) AFM height profile of a WS₂ nanoflake with a thickness of 155 nm; inset shows the AFM image of the respective device. (b) i_d−V curve of a typical WS₂ nanoflake with a thickness of 230 nm; inset shows SEM image of the WS₂ nanoflake device of thickness 155 nm.

Figure 3

Photocurrent response of a WS₂ nanoflake under laser illumination of a wavelength of 532 nm. The photocurrent is measured as a function of time under various powers at a fixed bias voltage of 1 V. The ON/OFF denotes the laser light condition.

Figure 4

The dependence of (a) photocurrent and (b) responsivity on incident light intensities from 80 to 4000 Wm⁻². The photocurrent data points were fitted using linear function.

Figure 5

Variation of (a) gain and (b) normalized gain of a WS₂ nanoflake photodetector with a variation of light intensity from 80 to 4000 Wm⁻².