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Investigation on MoS2(1-x)Te2x Mixture Alloy Fabricated by Co-sputtering Deposition Y. Hibino1, S. Ishihara1, 4, N. Sawamoto1, T. Ohashi2, K. Matsuura2, H. Machida3, M. Ishikawa3, H. Sudo3, H. Wakabayashi2, and A. Ogura1 1 Meiji University, Kanagawa 214-8571, Japan. 2 Tokyo Institute of Technology, Kanagawa 226-8502, Japan. 3 Gas-Phase Growth Ltd., Tokyo 184-0012, Japan. 4 Research Fellow of the Japan Society for the Promotion of Science, Tokyo 102-0083, Japan. ABSTRACT We report the synthesis of MoS2(1-x)Te2x by co-sputtering deposition and effect of mixture on its bandgap. The deposition was carried out at room temperature, and the sputtering power on individual MoS2 and MoTe2 targets were varied to obtain films with different compositions. Investigation with X-ray photoelectron spectroscopy confirmed the formation of Mo-Te and MoS bonds after post-deposition annealing (PDA), and one of the samples exhibited composition ratio of Mo:S:Te = 1:1.2:0.8 and 1:1.9:0.1 achieving 1:2 ratio of metal to chalcogen. Bandgap of MoS1.2Te0.8 and MoS1.9Te0.1 was evaluated with Tauc plot analysis from the extinction coefficient obtained by spectroscopic ellipsometry measurements. The obtained bandgaps were 1.0 eV and 1.3 eV. The resulting bandgap was lower than that of bulk MoS2 and higher than that of bulk MoTe2 suggesting mixture of both materials was achieved by co-sputtering. INTRODUCTION 2D materials represented by graphene, h-BN, and transition metal dichalcogenides (TMD) are of great interest among the researchers all over the world for its intriguing physical properties and its applications towards various devices due to its superiority to conventional 3-D materials in thin region [1]. When exploited as device materials such as channels in transistors, the bandgap has a great impact on its performance. TMD, unlike pristine graphene, exhibits bandgap which prevents current leakage which, in turn, suppresses excessive power consumption. As well as its favorable properties in terms of use in devices, its physical properties have attracted much attention such as direct to indirect bandgap transition between single-layer and multi-layer [2], the means to tune the bandgap [3-5], ability to store information in the form of valley polarization [6,7], and so on. Alloying TMDs would enable tuning the bandgap and this gives rise to variety of applications in optics and optoelectronics [8,9], as well as opportunities to further understand the physical properties of the material. There have been reports on alloying both the metal (Mo1-xWxS2) [4] and the chalcogen (MoS2(1-x)Se2x ) [5] parts of the material by chemical vapor deposition. The reported alloys exhibit wide range of bandgap. It has been reported that, under simulation not taking the so-called bowing effect[10] into account, the bandgap of single layer MoS2(1-x)Te2x varies approximately between 1.0 eV and 1.8 eV according to the composition. On the other hand, there have not been any reports on TMD alloy fabrication using co-sputtering technique. Sputtering deposition produces