High Photo-response in Conformally Grown Monolayer MoS₂ on Rugged Substrate

Conformal growth of atomic-thick semiconductor layers on patterned substrates can boost up the performance of electronic and optoelectronic devices remarkably. However, conformal growth is a very challenging technological task, since the control of the growth processes requires utmost precision. Herein, we report on conformal growth and characterization of monolayer MoS₂ on planar, micro-rugged, and nano-rugged SiO₂/Si substrates via metal-organic chemical vapor deposition. The continuous and conformal nature of monolayer MoS₂ on the rugged surface was verified by high-resolution transmission electron microscopy. Strain effects were examined by photoluminescence (PL) and Raman spectroscopy. Interestingly, the photo-responsivity (~254.5 mA/W) of as-grown MoS₂ on the nano-rugged substrate was 59 times larger than that of the planar sample (4.3 mA/W) under a small applied bias of 0.1 V. Such enhancement in the photo-responsivity arises from a large active area for light-matter interaction and local strain for PL quenching, where the latter effect is the key factor and unique in the conformally grown monolayer on the nano-rugged surface.