Depletion region

About: Depletion region is a research topic. Over the lifetime, 9393 publications have been published within this topic receiving 145633 citations.

Dissipative particle dynamics simulation of depletion layer and polymer migration in micro- and nanochannels for dilute polymer solutions.

Abstract: The flows of dilute polymer solutions in micro- and nanoscale channels are of both fundamental and practical importance in variety of applications in which the channel gap is of the same order as the size of the suspended particles or macromolecules. In such systems depletion layers are observed near solid-fluid interfaces, even in equilibrium, and the imposition of flow results in further cross-stream migration of the particles. In this work we employ dissipative particle dynamics to study depletion and migration in dilute polymer solutions in channels several times larger than the radius of gyration (Rg) of bead-spring chains. We compare depletion layers for different chain models and levels of chain representation, solvent quality, and relative wall-solvent-polymer interactions. By suitable scaling the simulated depletion layers compare well with the asymptotic lattice theory solution of depletion near a repulsive wall. In Poiseuille flow, polymer migration across the streamlines increases with the Peclet and the Reynolds number until the center-of-mass distribution develops two symmetric off-center peaks which identify the preferred chain positions across the channel. These appear to be governed by the balance of wall-chain repulsive interactions and an off-center driving force of the type known as the Segre-Silberberg effect.

Fabrication and properties of a high-performance chlorine doped graphene quantum dot based photovoltaic detector

Abstract: Functionalized graphene quantum dot (GQD) based materials play an important role in the development of high-performance, low-cost, large-area optoelectronic devices. The progress, however, is impeded by the poor understanding of the physical mechanism for GQDs in these devices. In this paper, chlorine doped GQD (Cl-GQD) based photovoltaic photodetectors have been fabricated using a solution process, and it was found that the presence of Cl-GQDs can significantly enhance the performance of the device. The improved performance of Cl-GQD based devices has been investigated by systematically studying the structural, morphological, optical, electrical, electrochemical and photoelectrical properties. The important photovoltaic detectors parameters such as the saturation current densities (J0), barrier heights (Φb), built-in potentials (Vbi), carrier concentrations (N) and depletion layer widths (Wd) have been calculated and discussed by studying the I–V and C–V characteristics under different illuminations. The frequency dependent capacitance and conductance have also been discussed. The results provide guidance for developing high-performance graphene based optoelectronic devices.

High-Gain InAs Avalanche Photodiodes

Abstract: We report two InAs avalanche photodiode structures with very low background doping in the depletion region. Uniform electric fields and thick depletion regions have been achieved. Excess noise measurements are consistent with k~0 and gain as high as 70 at room temperature is observed. The measured gain-bandwidth product is >; 300 GHz. All measurements are consistent with Monte Carlo simulations.