MOCVD of Monolayer MoS 2 using Novel Molybdenum Precursor i-Pr 2 DADMo(CO) 3
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.237
MOCVD of Monolayer MoS2 using Novel Molybdenum Precursor i-Pr2DADMo(CO)3 S. Ishihara1, 4, Y. Hibino1, N. Sawamoto1, H. Machida3, H. Wakabayashi2, and A. Ogura1 1
Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571, Japan.
2
Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8502, Japan.
3
Gas-phase Growth Ltd, #301 Nokodai-Tamakoganei Venture Port, 2-24-16 Naka, Koganei, Tokyo 184-0012, Japan.
4 Research Fellow of the Japan Society for the Promotion of Science, 5-3-1, Kojimachi, Chiyoda-ku, Tokyo, 102-0083, Japan.
ABSTRACT
Metal organic precursor has a sufficiently high vapor pressure at low temperature, contributing high-speed low-temperature MOCVD-MoS2 film formation. We fabricated monolayer MoS2 by 1 step cold-wall MOCVD using di-isopropyl-diazadiene-molybdenum tricarbonyl [i-Pr2DADMo(CO)3] and di-tertiary-butyl disulfide [(t-C4H9)2S2]. These precursors are able to be vaporized using bubbling system and deposited at low temperature. From the XPS investigations, Mo-S bonding peaks were observed and S:Mo ratio was calculated as 2:1, suggesting formation of MoS2. Moreover, molybdenum carbides and nitrogen impurities were not observed which was confirmed by XPS and EDX. From the results of Raman spectroscopy, AFM height distribution, and spectroscopic ellipsometry, it was determined that the film thickness is 0.64 nm which is corresponding to monolayer MoS 2, the lateral grain size is approximately 100 nm, and the bandgap energy is 1.8 eV.
INTRODUCTION Two-dimensional layered molybdenum disulfide has superior device performances even in a thin region [1]. Single-layer (1L) MoS2, in particular, shows novel properties, which are significantly different from bulk MoS2. Accordingly, it is desired to establish a fabrication technique of the high quality MoS2 thin film with superior mass productivity. Various fabrication techniques have been previously introduced, and especially chemical vapor deposition (CVD) can produce high-quality thin film [2]. CVD is mainly classified into two types [3]. The first is regarded as a two-step CVD, in which metal Mo precursor is initially deposited by e-beam evaporation and then sulfurized to form MoS2 [4]. The second is regarded as a one-step CVD, wherein gaseous of Mo and S precursors are simultaneously introduced and react to form
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MoS2 [5]. Among them, 1 step CVD is suitable for fabrication of large grain size MoS 2 thin film. In general, solid powder precursors, such as MoO 3 and elemental S, are mainly used for CVD; however, their low vapor pressure largely limit the reaction rate. Contrastingly, metal organic precursor has a sufficiently high vapor pressure at low temperature, contributing high-speed lo
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