Vapor-Phase Synthesis of Two-Dimensional Layered Gallium Chalcogenide Crystals

Abstract

There has been rising interest in exploring two dimensional (2D) layered materials for future electronics and optics. Especially, atomically thin 2D materials exhibit new physical properties, compared with their bulk counterparts. Because of these features, 2D materials have the potentials to apply to next generation nanoelectronic devices. However there is a bottleneck for the application, which is a large size 2D material. There has been releasing a number of reports about large area 2D material’s growth, such as graphene, h-BN, TMDCs (MoS2, WSe2, NbSe2, TaS2, etc). However the research of 2D gallium chalcogenide is rarely reported and there is no report about growth of 2D gallium sulfide atomic layer. It is also 2D layered materials and its common formula is MX (M=Ga, X=S, Se, Te). In single layer, X-M-M-X are strongly bonded by covalent forces but each of layers are weakly bonded between neighbor layers by van der Waals forces. Recently, some groups prove that atomic layer Gallium chalcogenides have large band gap and exhibit fast response, high photoresponsivity, external quantum efficiency and good ON/OFF current ratio. So it is promising materials for application in high performance photodetectors, gas sensors and optoelectronic devices. For these applications, we synthesize large area gallium chalcogenide single layer films and various crystals, which have different thickness from few hundred nanometer to single layer, directly on SiO2/Si substrate using vapor phase synthesis. The gallium chalcogenides, synthesized from pure gallium and sulfur or selenium precursors, are characterized using raman spectroscopy and AFM depending on their thickness. From TEM, SEM analysis, we recognize the crystallinity, which shows the uniform single crystalline. Galliuim chalcogenide FET shows n-type semiconductor characteristic in GaS, p-type semiconductor characteristic in GaSe and similar electrical properties reported before. Our synthesis method can be used potentially for the synthesis of other 2D metal monochalcogenides and broaden the building blocks for the fabrication of 2D electronic and optoelectronic devices and provides the possibility of 2D gallium chalcogenide in applications.