Photoemission oscillation in epitaxially grown van der Waals β-In2Se3/WS2 heterobilayer bubbles

Thin films of millimeter-scale continuous monolayer WS2have been grown on SiO2/Si substrate, followed by the de position of β-In2Se3crystals on monolayer WS2to prepare In2Se3/WS2van de Waals heterostructures by a two-step chem ical vapor deposition(CVD) method. After the growth of In2Se3at elevated temperatures, high densities of In2Se3/WS2heterostructure bubbles with monolayer to multilayer β-In2Se3crystals atop are observed. Fluorescence of the resultan β-In2Se3/WS2heterostructure is greatly enhanced in intensity upon the formation of bubbles, which are evidenced by the Newton’s rings in optical image owing to constructive and destructive interference. In photoluminescence(PL) mapping images of monolayer β-In2Se3/monolayer WS2heterobilayer bubble, significant oscillatory behavior of emission intensity is demonstrated due to constructive and destructive interference. However, oscillatory behaviors of peak position are also observed and come from a local heating effect induced by an excitation laser beam. The oscillatory mechanism of PL is fur ther verified by changing the exterior pressure of bubbles placed in a home-made vacuum chamber. In addition, redshifted in peak position and broadening in peak width are observed due to strain effect during decreasing the exterior pressure o bubbles.