Impact of Ar Flow Rates on Micro-Structural Properties of WS2 Thin Film by RF Magnetron Sputtering.

Md Akhtaruzzaman,Md Shahiduzzaman,Kamaruzzaman Sopian,Khan Sobayel Bin Rafiq,Nowshad Amin,Ghulam Muhammad,Mohammad Aminul Islam

doi:10.3390/nano11071635

Abstract

Tungsten disulfide (WS2) thin films were deposited on soda-lime glass (SLG) substrates using radio frequency (RF) magnetron sputtering at different Ar flow rates (3 to 7 sccm). The effect of Ar flow rates on the structural, morphology, and electrical properties of the WS2 thin films was investigated thoroughly. Structural analysis exhibited that all the as-grown films showed the highest peak at (101) plane corresponds to rhombohedral phase. The crystalline size of the film ranged from 11.2 to 35.6 nm, while dislocation density ranged from 7.8 × 1014 to 26.29 × 1015 lines/m2. All these findings indicate that as-grown WS2 films are induced with various degrees of defects, which were visible in the FESEM images. FESEM images also identified the distorted crystallographic structure for all the films except the film deposited at 5 sccm of Ar gas flow rate. EDX analysis found that all the films were having a sulfur deficit and suggested that WS2 thin film bears edge defects in its structure. Further, electrical analysis confirms that tailoring of structural defects in WS2 thin film can be possible by the varying Ar gas flow rates. All these findings articulate that Ar gas flow rate is one of the important process parameters in RF magnetron sputtering that could affect the morphology, electrical properties, and structural properties of WS2 thin film. Finally, the simulation study validates the experimental results and encourages the use of WS2 as a buffer layer of CdTe-based solar cells.

Highlights

Chalcogenides of the first-row transition materials have drawn researchers’interest for their elementary abundance and impressive structural characteristics [1].The characteristic features of these chalcogenides are their well-known two-dimensional structures in which metal and chalcogen are periodically arranged
The objective of this study is to evaluate the micro-structural changes of WS2 thin film that occurred due to the variation in gas flow rate
WS2 thin film was deposited for 30 min on soda-lime glass substrates of 7.5 cm × 2.5 cm × 0.2 cm by radio frequency (RF) magnetron sputtering technique

Summary

Introduction

Chalcogenides of the first-row transition materials have drawn researchers’interest for their elementary abundance and impressive structural characteristics [1].The characteristic features of these chalcogenides are their well-known two-dimensional structures in which metal and chalcogen are periodically arranged. Chalcogenides of the first-row transition materials have drawn researchers’. Interest for their elementary abundance and impressive structural characteristics [1]. The characteristic features of these chalcogenides are their well-known two-dimensional structures in which metal and chalcogen are periodically arranged. Transition-metal dichalcogenides (TMDCs) are commonly known as 2D materials that exhibit hexagonal structure, but their hexagonal structure is not atomic-thin like graphene. The overall efficiency of atomically thin TMDCs based devices depends on a number of factors, including stability, thickness, substratum, contacts, temperature, and surface functionalization of material. Few-layered MX2 (M = Mo, W; X = S, Se) TMDCs exhibit various fascinating properties associated with their reduced thickness [2,3]. TMDCs undergo a layer-dependent transition in their band structure from an indirect to a direct bandgap

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