Spatially and Precisely Controlled Large-Scale and Persistent Optical Gating in a TiO -MoS Heterostructure.

Optical gating derived from persistent photodoping is a promising technique that can control the transport behavior of two-dimensional (2D) materials through light modulation. The advantage of photoinduced doping is that the doping can be controlled precisely and spatially by tuning the light intensity and position. As most photoinduced doping methods suffer from a low doping level, persistent, strong photodoping was conducted in this study in TiO -MoS heterostructures under ultraviolet (UV) illumination, which precisely controlled the doping to a high level (1.

Environment-insensitive and gate-controllable photocurrent enabled by bandgap engineering of MoS junctions.

Two-dimensional (2D) materials are composed of atomically thin crystals with an enormous surface-to-volume ratio, and their physical properties can be easily subjected to the change of the chemical environment. Encapsulation with other layered materials, such as hexagonal boron nitride, is a common practice; however, this approach often requires inextricable fabrication processes. Alternatively, it is intriguing to explore methods to control transport properties in the circumstance of no encapsulated layer.

Precisely Controlled Ultrastrong Photoinduced Doping at Graphene-Heterostructures Assisted by Trap-State-Mediated Charge Transfer.

Ultrastrong and precisely controllable n-type photoinduced doping at a graphene/TiOx heterostructure as a result of trap-state-mediated charge transfer is demonstrated, which is much higher than any other reported photodoping techniques. Based on the strong light-matter interactions at the graphene/TiOx heterostructure, precisely controlled photoinduced bandgap opening of a bilayer graphene device is demonstrated.

Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect Transistors.

Recent discoveries of the photoresponse of molybdenum disulfide (MoS2) have shown the considerable potential of these two-dimensional transition metal dichalcogenides for optoelectronic applications. Among the various types of photoresponses of MoS2, persistent photoconductivity (PPC) at different levels has been reported. However, a detailed study of the PPC effect and its mechanism in MoS2 is still not available, despite the importance of this effect on the photoresponse of the material.

Probing substrate influence on graphene by analyzing Raman lineshapes.

We provide a new approach to identify the substrate influence on graphene surface. Distinguishing the substrate influences or the doping effects of charged impurities on graphene can be realized by optically probing the graphene surfaces, included the suspended and supported graphene. In this work, the line scan of Raman spectroscopy was performed across the graphene surface on the ordered square hole.

Surface-enhanced Raman scattering of suspended monolayer graphene.

The interactions between phonons and electrons induced by the dopants or the substrate of graphene in spectroscopic investigation reveal a rich source of interesting physics. Raman spectra and surface-enhanced Raman spectra of supported and suspended monolayer graphenes were measured and analyzed systemically with different approaches. The weak Raman signals are greatly enhanced by the ability of surface-enhanced Raman spectroscopy which has attracted considerable interests.

Observation of strain effect on the suspended graphene by polarized Raman spectroscopy.

We report the strain effect of suspended graphene prepared by micromechanical method. Under a fixed measurement orientation of scattered light, the position of the 2D peaks changes with incident polarization directions. This phenomenon is explained by a proposed mode in which the peak is effectively contributed by an unstrained and two uniaxial-strained sub-areas.

MOS photodetectors based on Au-nanorod doped graphene electrodes.

By using Au-nanorod (Au-NR) doped graphene as a transparent conducting electrode, Si-based metal-oxide-semiconductor (MOS) photodetectors (PDs) exhibit high external quantum efficiency (EQE) and fast response time. It is found that upon adding Au-NRs to the graphene, a significant increase in EQE is observed for both planar and Si-nanotip (Si-NT) MOS PDs. The planar Si-based MOS PDs reveal a notable photoresponse with an EQE of 49% at the peak wavelength of 530 nm under zero bias and an EQE of 66% at the peak wavelength of 600 nm under - 0.