Controlled synthesis of transition metal dichalcogenide thin films for electronic applications

Abstract

Please cite this article in press as: R. Gatensby, et al., Controlled synthesis of transition metal dichalcogenide thin films for electronic applications, Appl. Surf. Sci. (2014) Two dimensional transition metal dichalcogenides (TMDs) are exciting materials for future applications in nanoelectronics, nanophotonics and sensing. In particular, sulfides and selenides of molybdenum (Mo) and tungsten (W) have attracted interest as they possess a band gap, which is important for integration into electronic device structures. However, the low throughput synthesis of high quality TMD thin films has thus far hindered the development of devices, and so a scalable method is required to fully exploit their exceptional properties. Within this work a facile route to the manufacture of devices from MoS 2 and WS 2 , grown by vapour phase sulfurisation of pre-deposited metal layers, is presented. Highly homogenous TMD films are produced over large areas. Fine control over TMD film thickness, down to a few layers, is achieved by modifying the thickness of the pre-deposited metal layer. The films are characterised by Raman spectroscopy, electron microscopy and X-ray photoelectron spectroscopy. The thinnest films exhibit photoluminescence, as predicted for monolayer MoS 2 films, due to confinement in two dimensions. By using shadow mask lithography, films with well-defined geometries were produced and subsequently integrated with standard microprocessing process flows and electrically characterised. In this way, MoS 2 based sensors were produced, displaying sensitivity to NH 3 down to 400 ppb. Our device manufacture is versatile, and is adaptable for future nanoscale (opto-) electronic devices as it is reproducible, cost effective and scalable up to wafer scale.

Rhenium-doped MoS2 films

“…22 Following the inter-diffusion anneal, the sample is exposed to sulfur vapour as described previously. 20 In this low pressure process (20 mTorr), the metal film is alloyed over the course of 30 min at 900 C. After the film is removed from the furnace, the total thickness is 55 nm 6 5 nm, indicating a doubling of the initial thickness, which is comparable to our previous results. Thinner MoS 2 films for HRSTEM were created by sputtering thinner initial layers of Re and Mo (0.1 nm Re and 0.7 nm Mo).…”

“…Essentially, the process consists in the deposition of a thin layer of a transitional metal which is then exposed to chalcogen vapour. We have reported extensively on this process for the formation of intrinsic TMDs of both metal sulphides 20 and metal selenides. 21 The real advantage of this technique is the opportunity to "scale-up".…”

Two-Dimensional Materials for Sensing: Graphene and Beyond

“…Even though atomically thin films of TMDs synthesized by micromechanical cleavage, ultrasonication in organic solvents, aqueous surfactant solutions, or solutions of polymers in solvents, intercalation and exfoliation are well suited for applications in gas sensing [80][81][82][83], catalysis [150], composites [151], energy storage and conversion [152,153], the as prepared TMDs are not compatible with standard microlithography techniques in the nanodevice fabrication process. Gatensby and his co-workers [154] proposed a facile route for fabricating devices from MoS2 and WS2, grown by vapor phase sulfurization of pre-deposited metal layers which allows the production of highly homogenous TMD films over large areas with fine control of thickness from bulk to monolayer. Using shadow mask lithography, well-defined geometries were produced that could be easily integrated with standard micro-processing methods.…”

Controllable Growth of Single Layer MoS2 and Resistance Switching Effect in Polymer/MoS2 Structure

“…The systems for synthesizing MoS 2 have been widely examined in the past few years. Chemical vapor deposition (CVD) approach has been proved as a confident system in synthesizing large area and high quality single layer TMD layer [8][9][10][11][12][13][14][15]. The common technique for growing MoS2 layer was deposition of molybdenum trioxide (MoO 3 ) or Mo on a silicon dioxide (SiO 2 ) substrate and followed by sulfurization by a sulfur vapor at high temperature.…”