Synthesis and characterization of tungsten disulfide thin films by spray pyrolysis technique for n-WS2/p-Si junction diode application

Abstract

Tungsten disulfide (WS2) thin films were deposited on the glass substrate by varying its temperature from 350 to 500 °C using jet nebulizer spray pyrolysis (JNSP) technique. The WS2 thin films were characterized through various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX), UV–Visible spectroscopy (UV), photoluminescence (PL), Hall measurements and current–voltage (I–V) characteristics. XRD pattern revealed that the prepared WS2 films are polycrystalline in nature with rhombohedral and hexagonal crystal structures. The average crystallite size of WS2 thin films changed from 52.23 to 47.40 nm. SEM images showed the uniform grain size, which is agglomerated at the higher substrate temperature. The presence of elements like W and S was confirmed through EDX spectrum. From UV analysis, the minimum optical band gap and maximum absorption was obtained for the film deposited at 450 °C. The WS2 thin films exhibited an n-type semiconductor nature with the carrier concentration of 1014 cm−3, which was demonstrated through hall measurements. Also, the electrical resistivity of the WS2 films varied from 3.26 × 105 to 1.59 × 107 Ω cm. The p-Si/n-WS2 junction diode was fabricated with various substrate temperature of (350–500 °C). Junction diode parameters like ideality factor (n), barrier height (ϕB) and reverse saturation current (Io) values were calculated and interpreted based on the thermionic emission theory model.