Strain Induced Phase Transition of WS2 by Local Dewetting of Au/Mica Film upon Annealing

Tomasz Kosmala,Hikmet Sezen,Gaetano Granozzi,Cecilia Mattevi,Luca Gregoratti,Stefano Agnoli,Matteo Amati,Pawel Palczynski

doi:10.3390/surfaces4010001

Abstract

Here, we present a proof-of-concept experiment where phase engineering at the nanoscale of 2D transition metal dichalcogenides (TMDC) flakes (from semiconducting 2H phase to metallic 1T phase) can be achieved by thermal annealing of a TMDC/Au/mica system. The local dewetting of Au particles and resulting tensile strain produced on the TMDC flakes, strongly bound to the Au surface through effective S-Au bonds, can induce a local structural phase transition. An important role is also played by the defects induced by the thermal annealing: when vacancies are present, the threshold strain needed to trigger the phase transition is significantly reduced. Scanning photoelectron microscopy (SPEM) was revealed to be the perfect tool to monitor the described phenomena.

Highlights

Strain Induced Phase Transition of WS2In recent years, 2D transition metal dichalcogenides (TMDCs) [1] have gathered a great deal of interest because of their potential applications in catalysis [2,3], optoelectronic and electronic devices [4,5], and energy conversion systems [6]
W 4fDiscussion and S 2p Scanning photoelectron microscopy (SPEM) maps recorded at room temperature (RT) are shown in Thesemaps images clearly at show thetemperature well‐defined(RT)
Our proof-of-concept experiment demonstrates that phase engineering in TMDCs is possible by manipulation of the strain with spatial resolution

Summary

Introduction

2D transition metal dichalcogenides (TMDCs) [1] have gathered a great deal of interest because of their potential applications in catalysis [2,3], optoelectronic and electronic devices [4,5], and energy conversion systems [6]. The ability of creating conductive and semiconductive heterojunctions within the same material can be clearly exploited for the realization of molecular scale electronic devices with atomically thin 2D layers [9] Given those radically different properties of 2H and 1T, the control at the nanoscale of the crystalline phase of the TMDCs is important to achieve the desired properties in the final devices. Within this context, the strain engineering method [10] represents a suitable route to tailor materials properties by modifying mechanical or structural features. Strain [11,12]

Different structural models of the

Results

S or SO

Conclusions