In-situ Raman analysis of hydrogenation in well-defined ultrathin molybdenum diselenide deposits synthesized through vapor phase deposition.

ABSTRACT: We report on the synthesis, characterization and in-situ Raman spectroscopy analysis of hydrogenation in ultrathin crystalline MoSe2 deposits. We use a controllable vapor phase synthesis method using MoSe2 powder as the only precursor, to fabricate nano- to micro-size few layer thick MoSe2 deposits with tunable number densities on SiO2/Si substrates. We employ this controllable synthesis method to correlate characteristic Raman spectroscopy response of MoSe2 at ca. 242?cm-1 (A1g) and ca. 280?cm-1 (E2g1) with the thickness of the deposits acquired from atomic force microscopy (AFM). We also use this array of well-defined atomically thin MoSe2 deposits to study possible hydrogenation effects on select architectures using in-situ Raman spectroscopy. Interestingly, our analysis indicates that ultrathin MoSe2 deposits with exposed edges show a blue shift of 1-2?cm-1 when exposed to H2 flow at 150-250 sccm for 2-4?hours in a sealed reaction cell. Exposure to Ar flow under same condition reverses the observed shift in the A1g mode of the select MoSe2 deposits. Our measurements provide in-situ evidence for hydrogen adsorption on MoSe2 deposits at room temperature and insight into the possible active sites for hydrogen reactions on layered dichalcogenides at lower dimensions.

SUBMITTER: Santiago PJ 

PROVIDER: S-EPMC7311385 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature