title: Laser-Induced Particle Adsorption on Atomically Thin MoS2.
abstract: Atomically thin molybdenum disulfide (MoS2) shows great potential for use in nanodevices because of its remarkable electronic, optoelectronic, and mechanical properties. These material properties are often dependent on the thickness or the number of layers, and hence Raman spectroscopy is widely used to characterize the thickness of atomically thin MoS2 due to the sensitivity of the vibrational spectrum to thickness. However, the lasers used in Raman spectroscopy can increase the local surface temperature and eventually damage the upper layers of the MoS2, thereby changing the aforementioned material properties. In this work, the effects of lasers on the topography and material properties of atomically thin MoS2 were systematically investigated using Raman spectroscopy and atomic force microscopy. In detail, friction force microscopy was used to study the friction characteristics of atomically thin MoS2 as a function of laser powers from 0.5 to 20 mW and number of layers from 1 to 3. It was found that particles formed on the top surface of the atomically thin MoS2 due to laser-induced thermal effects. The degree of particle formation increased as the laser power increased, prior to the thinning of the atomically thin MoS2. In addition, the degree of particle formation increased as the number of MoS2 layers increased, which suggests that the thermal behavior of the supported MoS2 may differ depending on the number of layers. The particles likely originated from the atmosphere due to laser-induced heating, but could be eliminated via appropriate laser powers and exposure times, which were determined experimentally. The outcomes of this work indicate that thermal management is crucial in the design of reliable nanoscale devices based on atomically thin MoS2.
authors.affiliation: School of Mechanical Engineering, University of Ulsan , Ulsan 44610, Republic of Korea.
authors.forename: Bien Cuong
authors.initials: BC
authors.lastname: Tran Khac
authors.affiliation: Department of Environmental Engineering, Inha University , Incheon 22212, Republic of Korea.
authors.forename: Ki-Joon
authors.initials: KJ
authors.lastname: Jeon
authors.affiliation: School of Mechanical Engineering, University of Ulsan , Ulsan 44610, Republic of Korea.
authors.forename: Seung Tae
authors.initials: ST
authors.lastname: Choi
authors.affiliation: Department of Physics and Energy Harvest Storage Research Center, University of Ulsan , Ulsan 44610, Republic of Korea.
authors.forename: Yong Soo
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Applied Chemicals and Materials Division, Material Measurement Laboratory, National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
authors.forename: Frank W
authors.initials: FW
authors.lastname: DelRio
authors.affiliation: School of Mechanical Engineering, University of Ulsan , Ulsan 44610, Republic of Korea.
authors.forename: Koo-Hyun
authors.initials: KH
authors.lastname: Chung
keywords: Raman spectroscopy; adsorbates; friction force microscopy; laser power; thermal conductivity