Peculiar spectra and photocurrent oscillation caused by laser interference in WX2(X = S, Se) bubbles

We report the successful synthesis of WX2(X = S, Se) crystals by chemical vapor deposition and fabrication of micron-sized bubbles on the WX(2)crystals via a facile annealing process in Ar atmosphere. The optical and fluorescence images show evident interference oscillating rings in spherical cap-shaped WX(2)bubbles, and such optical interference can cause intensity oscillations in photoluminescence (PL) and Raman mapping images, which are mainly attributed to the local thermal effect. Structure of this bubble profoundly affects the band structure of WX2, such as the appearance of direct bandgap in few-layer WSe(2)bubbles. Similar to the monolayer WS(2)bubble, the deconvoluted PL and Raman peaks of the WSe(2)bubbles exhibit obvious oscillation in normalized integral intensity, position and width as the external pressure decreases. In addition, the photocurrent mapping images of the monolayer WS(2)and bilayer WSe(2)bubble devices unambiguously reveal the photocurrent oscillation phenomenon due to the optical interference enhancement or decrement on the suspended film. Our results open up a novel avenue in optoelectronics by manipulating 2D material bubbles.