Friction characteristics of mechanically exfoliated and CVD-grown single-layer MoS_2  

作　　者：Dinh Le Cao KY Bien-Cuong TRAN KHAC Chinh Tam LE Yong Soo KIM Koo-Hyun CHUNG 

机构地区：[1]School of Mechanical Engineering,University of Ulsan [2]Department of Physics and Energy Harvest Storage Research Center,University of Ulsan

出　　处：《Friction》2018年第4期395-406,共12页摩擦（英文版）

基　　金：supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF);funded by the Ministry of Science, ICT and Future Planning (NRF-2017R1A2B4009651)

摘　　要：In this work, the friction characteristics of single-layer MoS2 prepared with chemical vapor deposition （CVD） at three different temperatures were quantitatively investigated and compared to those of single-layer MoS2 prepared using mechanical exfoliation. The surface and crystalline qualities of the MoS2 specimens were characterized using an optical microscope, atomic force microscope （AFM）, and Raman spectroscopy. The surfaces of the MoS2 specimens were generally flat and smooth. However, the Raman data showed that the crystalline qualities of CVD-grown single-layer MoS2 at 800 ℃ and 850 ℃ were relatively similar to those of mechanically exfoliated MoS2 whereas the crystalline quality of the CVD-grown single-layer MoS2 at 900 ℃ was lower. The CVD-grown single-layer MoS2 exhibited higher friction than mechanically exfoliated single-layer MoS2, which might be related to the crystalline imperfections in the CVD-grown MoS2. In addition, the friction of CVD-grown single-layer MoS2 increased as the CVD growth temperature increased. In terms of tribological properties, 800 ℃ was the optimal temperature for the CVD process used in this work. Furthermore, it was observed that the friction at the grain boundary was significantly larger than that at the grain, potentially due to defects at the grain boundary. This result indicates that the temperature used during CVD should be optimized considering the grain size to achieve low friction characteristics. The outcomes of this work will be useful for understanding the intrinsic friction characteristics of single-layer MoS2 and elucidating the feasibility of single-layer MoS2 as protective or lubricant layers for micro- and nano-devices.In this work, the friction characteristics of single-layer MoS_2 prepared with chemical vapor deposition(CVD) at three different temperatures were quantitatively investigated and compared to those of single-layer MoS_2 prepared using mechanical exfoliation. The surface and crystalline qualities of the MoS_2 specimens were characterized using an optical microscope, atomic force microscope(AFM), and Raman spectroscopy. The surfaces of the MoS2 specimens were generally flat and smooth. However, the Raman data showed that the crystalline qualities of CVD-grown single-layer MoS2 at 800 °C and 850 °C were relatively similar to those of mechanically exfoliated MoS2 whereas the crystalline quality of the CVD-grown single-layer MoS_2 at 900 °C was lower. The CVD-grown single-layer MoS_2 exhibited higher friction than mechanically exfoliated single-layer MoS_2, which might be related to the crystalline imperfections in the CVD-grown MoS_2. In addition, the friction of CVD-grown single-layer MoS_2 increased as the CVD growth temperature increased. In terms of tribological properties, 800 °C was the optimal temperature for the CVD process used in this work. Furthermore, it was observed that the friction at the grain boundary was significantly larger than that at the grain, potentially due to defects at the grain boundary. This result indicates that the temperature used during CVD should be optimized considering the grain size to achieve low friction characteristics. The outcomes of this work will be useful for understanding the intrinsic friction characteristics of single-layer MoS2 and elucidating the feasibility of single-layer MoS_2 as protective or lubricant layers for micro- and nano-devices.

关 键 词：atomic force microscope chemical vapor deposition grain boundary FRICTION mechanical exfoliation MoS2 

分 类 号：O484.1[理学—固体物理] TH117.1[理学—物理]