Understanding the Role of 2D Nature on the Junction Properties in WS2 Layers; Effect of AFM Tip Induced Loading Force on Spatially Varying Contact

Abstract In the present study, AFM metal tip induced loading force dependent electrical transport behaviour of WS2 domains synthesized using chemical vapour deposition technique has been investigated. Raman spectroscopy, optical microscopy and atomic force microscopy (AFM) techniques have been employed to characterize the synthesized two-dimensional (2D) domains. The local nanoscale I-V measurements have been carried out as a function of loading force (53 – 300 nN) using conductive atomic force microscopy to probe the interface formed between AFM tip (Pt coated) and 2D domains of WS2 layers. An interesting phenomena of decreasing junction current with increasing loading force obtained at the centre of single layer WS2 sample is opposed by an increasing junction current at the edges of domain. Loading force induced spatially varying, compressive and tensile strain resulting in charge polarization causing an opposite flow of majority electron carriers away and towards the tip-WS2 domain has been explained as the possible mechanism for the applied opposing uniaxial strains. This study reports the influence of single layer nature of WS2 constituting polar edges and wrinkle terminations on electronic properties of metal-semiconductor contacts. These results are crucial for understanding the junction properties and application of 2D material based devices in next-generation electronics.