Published: May 30, 2018
Frank W. DelRio, Justin M. Gorham, Koo-hyun Chung, Bien Cuong Tran Khac
Transition metal dichalcogenide two-dimensional materials have attracted significant attention due to their unique optical, mechanical, and electronic properties. For example, molybdenum disulfide (MoS2) exhibits a tunable band gap that strongly depends on the numbers of layers, which makes it an attractive material for optoelectronic applications. In addition, recent reports have shown that laser thinning can be used to engineer an MoS2 monolayer with specific shapes and dimensions. Here, we study laser-thinned MoS2 in both ambient and vacuum conditions via confocal µ-Raman spectroscopy, imaging X-ray photoelectron spectroscopy (i-XPS), and atomic force microscopy (AFM). For low laser powers in ambient environments, there is insufficient energy to oxidize the MoS2, which leads to etching and re-deposition of amorphous MoS2 on the nanosheet as confirmed by AFM. At high powers in ambient, the laser energy and oxygen environment enable both MoS2 nanoparticle formation and nanosheet oxidation as revealed in AFM and i-XPS. At comparable laser power densities in vacuum, MoS2 oxidation is suppressed and the particle density is reduced as compared to ambient. The extent of nanoparticle formation and nanosheet oxidation in each of these regimes is found to be dependent on the number of layers and laser treatment time. Finally, anomalous Raman trends are explained in terms of the physical changes to the MoS2, and Raman spectra are utilized to estimate the temperatures from the laser treatment.
Citation: ACS Applied Materials and Interfaces
Pub Type: Journals
Molybdenum disulfide, X-ray photoelectron spectroscopy, confocal Raman spectroscopy, atomic force microscopy, nanoparticles, laser irradiation
Created May 30, 2018, Updated November 10, 2018