No abstract

Position-sensitive-detectors (PSDs) based on lateral photoeffect has been widely used in diverse applications 1-9 , including optical engineering, aerospace and military fields. With increasing demand in long distance, low energy consumption, and weak signal sensing systems, the poor responsivity of conventional PSDs has become a bottleneck limiting its applications, e.g. silicon p-n or p-i-n junctions 2-5 , or other materials and architectures 6-10 . Herein, we present a high performance graphene based PSDs with revolutionary interfacial amplification mechanism. Signal amplification in the order of ~10 4 has been demonstrated by utilizing the ultrahigh mobility of graphene and long lifetime of photo-induced carriers at the interface of SiO 2 /Si. This would improve the detection limit of Si-based PSDs from W to nW level, without sacrificing the spatial resolution and response speed. Such interfacial amplification mechanism is compatible with current Si technology and can be easily extended to other sensing systems 11,12 .

Electrostatic sensing technology is widely utilized in both military and civilian applications, including electrostatic prevention in gas stations and various electronic devices. The high sensitivity of electrostatic sensor is capable to detect not only weak electrostatic charges, but also the weak disturbance of electrostatic field in distant. Here, we present a high-performance graphene-based electrostatic sensor.Combining the ultrahigh mobility of graphene and the long lifetime of carriers in lightly doped SiO 2 /Si substrate, our device achieves a fast response of ~2 s and detection limit of electrostatic potential as low as ~5 V, which is improved by an order of magnitude as compared to commercial product. The proposed device structure opens a promising pathway to high-sensitive electrostatic detection, and also greatly facilitates the development of novel sensors, e.g. portable and flexible electrostatic sensor.

Two-dimensional (2D) 2H-MoTe2 is a promising semiconductor because of its small bandgap, strong absorption, and low thermal conductivity. In this paper, we systematically study the optical and excitonic properties of atomically thin 2H-MoTe2 (1–5 layers). Due to the fact that the optical contrast and Raman spectra of 2H-MoTe2 with different thicknesses exhibit distinctly different behaviors, we establish a quantitative method by using optical images and Raman spectra to directly identify the layers of 2H-MoTe2 thin films. Besides, excitonic states and binding energy in monolayer/bilayer 2H-MoTe2 are measured by temperature-dependent photoluminescence (PL) spectroscopy. At temperature T = 3.3 K, we can observe an exciton emission at ∼ 1.19 eV and trion emission at ∼ 1.16 eV for monolayer 2H-MoTe2. While at room temperature, the exciton emission and trion emission both disappear for their small binding energy. We determine the exciton binding energy to be 185 meV (179 meV), trion binding energy to be 20 meV (18 meV) for the monolayer (bilayer) 2H-MoTe2. The thoroughly studies of the excitonic states in atomically thin 2H-MoTe2 will provide guidance for future practical applications.

Motion tracking has attracted great attention in the fields of real‐time tracking, nanorobotics, and targeted therapy. For achieving more accurate motion tracking, the highly sensitive position‐sensitive detector (PSD) is desirable. Here, we demonstrate a meliorated PSD based on graphene‐Si heterojunction for motion tracking. The position sensitivity of PSD was improved by employing surface engineering of graphene. Through modulating the transport property of graphene, nearly 20‐fold increase of sensitivity was achieved under weak light, and at the same time, the detection limit power was reduced to ~ 2 nW. A motion tracking system was developed based on the improved PSD, and human arm swing was tracked, which demonstrated high sensitivity and real‐time tracking capabilities of the PSD. In addition, the PSD can support up to ~ 10 kHz high‐frequency tracking. This work provides a new strategy for improving the performance of PSD, and promotes the development of two‐dimensional materials in novel optoelectronic devices.image