Quantum Multi-body Interactions in Semiconducting WSe_2 and C_(60)-Graphene Hybrids for High-performance Photodetectors

摘要

In this work we will discuss the use of a halide-assisted low-pressure chemical vapor deposition (HA-LPCVD) with NaCl to help facilitate the growth of monolayer WSe2 at low growth temperatures of ~ 750°C, which is lower than the typical temperatures needed with conventional CVD for realizing monolayer (1L) WSe2. Moreover, we experimentally probed the quantum multi-body interactions in 1L WSe_2 ascribed to excitons, trions and other localized states by analyzing the temperature-dependent photoluminescence spectra. A 1L WSe2 based photodetector was fabricated using Al contacts, which shows a high photoresponsivity, and the interface state trap density D_(it) of the Al/WSe2 junction was computed to be extremely low. Hybrids of two-dimensional (2D) graphene with fullerene (C_(60)) molecules were also fabricated using electrophoretic deposition, where the C_(60) clusters are electrically charged upon the application of an external bias in a polar solvent. A low energy shift in the Fermi level E_F ~ 140 meV was calculated for the hybrids. When the hybrid devices were irradiated with a broadband white light source and a tunable laser source (with wavelength λ ranging from ~ 400-1100 nm), a strong photoresponse was evident, in contrast to the bare graphene devices which appeared unresponsive. We will discuss the strong photo-response of the C_(60)-graphene hybrids reported here which we attribute to the doping enhancement arising in the graphene upon the adsorption of C_(60).