Tunable Photoinduced Carrier Transport of a Black Phosphorus Transistor with Extended Stability Using a Light-Sensitized Encapsulated Layer

In this article, we propose a novel approach to demonstrate tunable photoinduced carrier transport of a few-layered black phosphorus (BP) field-effect transistor (FET) with extended air stability using a “light-sensitized ultrathin encapsulated layer”. Titanium suboxide (TiO_x) ultrathin film (approximately 3 nm), which is an amorphous phase of crystalline TiO₂ and can be solution processed, simultaneously exhibits the unique dual functions of passivation and photoinduced doping on a BP FET. The photoinduced electron transfer at TiO_x/BP interfaces provides tunable n-type doping on BP through light illumination. Accordingly, the intrinsic hole-dominated transport of BP can be gradually tuned to the electron-dominated transport at a TiO_x/BP FET using light modulation, with enhanced electron mobility and extended air stability of the device. The novel device structure consisting of a light-sensitized encapsulated layer with controllable and reversible doping through light illumination on BP exhibits great potential for the future development of stable BP-based semiconductor logic devices or optoelectronic devices

Understanding the Interplay between Molecule Orientation and Graphene Using Polarized Raman Spectroscopy

We present a systematic study in investigating the orientation characteristics of pentacene molecules grown on graphene substrates using polarized Raman spectroscopy. The substrate-induced orientation alignment of pentacene can be well distinguished through the polarized Raman spectra. Interestingly, we found that the nature of polycrystalline graphene not only provides efficient route to control molecular orientation, but also acts as an excellent template allowing conjugated molecules to stack accordingly. The relative orientation of the well-aligned pentacene molecules and the nearby graphene domains exhibits several preferred angles due to atomic interactions. This unique feature is further examined and verified by single domain graphene. Furthermore, polarized Raman spectroscopy contains abundant information allowing us to analyze the ordering level of pentacene films with various thicknesses, which provides insightful perspectives of manipulating molecular orientations with graphene and spatial organization between conjugated systems, in a more quantitative manner