Layer-by-Layer Thinning of Mos2 by Thermal Annealing

Nanoscale

Published on 05 July 2013. Downloaded by ECOLE POLYTECHNIC FED DE LAUSANNE on 28/05/2014 16:17:05.

COMMUNICATION

View Article Online

View Journal | View Issue

Layer-by-layer thinning of MoS2 by thermal annealing

Cite this: Nanoscale, 2013, 5, 8904

Xin Lu,a Muhammad Iqbal Bakti Utama,a Jun Zhang,a Yanyuan Zhaoa and Qihua Xiong*ab

Received 16th June 2013 Accepted 2nd July 2013 DOI: 10.1039/c3nr03101b www.rsc.org/nanoscale

By thermal annealing, few-layer MoS2 flakes can be thinned down. In one hour, the upper layer is peeled off due to sublimation. Eventually, monolayer MoS2 is achieved. We have characterized the process by optical contrast, Raman spectroscopy and atomic force microscopy (AFM), and observed a mixture of surfaces of N and N À 1 layers.

Atomically thin layered transition metal dichalcogenides (TMDs) have aroused lots of interest recently, especially molybdenum disulde (MoS2). As a typical TMD, MoS2 possesses special layer-related electronic and optical properties.1 Bulk MoS2 has an indirect gap, which increases gradually as we move towards atomic scale. The indirect gap evolves into a direct one in a monolayer.2 Both single-layer and multilayer MoS2 have been shown to be suitable materials for electronic devices, such as eld effect transistors (FETs), FET-based small signal ampliers, FET-based sensing devices and transistorbased integrated circuits.3–6 Monolayer MoS2 is considered a suitable material for valleytronics,7 since valley polarization has already been demonstrated at low temperature.8,9 Other features have been observed at low temperature, such as an increasing photoluminescence (PL) intensity in few-layer MoS210 and tightly bound trions in monolayer MoS2.11 Due to the direct gap, single-layer MoS2 has a stronger PL than the fewlayer MoS2, even at room temperature.12,13 All the evidence shows monolayer MoS2 to be a suitable candidate for optoelectronics devices,1,12,13 and the optoelectronic application of...