Anthracene based metal-organic framework showing efficient angle-dependent polarized emission, luminescent thermometry, and photoelectronic response

The development of luminescent metal-organic frameworks (MOFs) has attracted extensive attention due to their applications in photoelectric device, organic light-emitting diodes (OLEDs), anti-counterfeiting, biological imaging and so on. In this...

Tunable Schottky Barrier and Interfacial Electronic Properties in Graphene/ZnSe Heterostructures

With a direct bandgap, two-dimensional (2D) ZnSe is a promising semiconductor material in photoelectric device fields. In this work, based on first-principles methods, we theoretically studied the modulation of the Schottky barrier height (SBH) by applying horizontal and vertical strains on graphene/ZnSe heterojunction. The results show that the inherent electronic properties of graphene and ZnSe monolayers are both well-conserved because of the weak van der Waals (vdW) forces between two sublayers. Under horizontal strain condition, the n(p)-type SBH decreases from 0.56 (1.62) eV to 0.21 (0.78) eV. By changing the interlayer distance in the range of 2.8 Å to 4.4 Å, the n(p)-type SBH decreases (increases) from 0.88 (0.98) eV to 0.21 (1.76) eV. These findings prove the SBH of the heterojunction to be tuned effectively, which is of great significance to optoelectronic devices, especially in graphene/ZnSe-based nano-electronic and optoelectronic devices.

Two-dimensional centrosymmetrical antiferromagnets for spin photogalvanic devices

Spin-dependent photogalvanic effect (PGE) in low-dimensional magnetic systems has recently attracted intensive attention. Based on first-principle transport calculations and symmetry analyses, we propose a robust scheme to generate pure spin current by PGE in centrosymmetric materials with spin polarization antisymmetry. As a demonstration, the idea is successfully applied to a photoelectric device constructed with a zigzag graphene nanoribbon (ZGNR), which has intrinsic antiferromagnetic coupling between the two edges and spin degenerate band structure. It suggests that spin splitting is not a prerequisite for pure spin current generation. More interestingly, by further introducing external transverse electric fields to the two leads to lift the spin degeneracy, the device may behave multifunctionally, capable of producing fully spin-polarized current or pure spin current, depending on whether the fields in the two leads are parallel or antiparallel. Very importantly, our scheme of pure spin current generation with PGE is not limited to ZGNR and can be extended to other two-dimensional (2D) centrosymmetric magnetic materials with spin polarization antisymmetry, suggesting a promising category of 2D platforms for PGE-based pure spin current generation.

Analysis of InGaN Multiple-Quantum-Well Photoelectric Device of Visible Light Communication

The key to achieving high-speed and high-quality visible light communication is to increase the modulation speed of Light-Emitting Diode (LED). Therefore, in this study, the influence of the Composite Mechanism of Carrier (CMC) on the modulation speed of LED is studied by designing different structures of the InGaN Multi-quantum-well (MQW) LED active region. Because the carrier subspace waves function of narrow quantum well LED overlaps more frequently and the electron leakage effect is more significant, the compound rate is faster and the modulation bandwidth is higher. InGaN quantum barrier LED with a content of 1% can increase the weight of radiation recombination, which makes the modulation bandwidth higher than GaN quantum barrier LEDs; when the in content is 5%, electron leakage and Auger recombination have a dominant position. Moreover, because these two compounding mechanisms have a fast compounding rate, the modulation bandwidth is significantly increased. Then the 405 nm laser-excited photoluminescence (PL) is introduced to analyze the carrier dynamics in the LED and obtain the related processes of carrier distribution and transport. The proposed carrier microscopic model can well explain change characteristics of the PL luminescence peak, luminous intensity, and half-height width of InGaN/GaN MQW LED with different excitation wavelengths. At low temperature, the PL peak of the InGaN/GaN quantum well LED redshifts with the increase of temperature, because the weakly bound carrier transfers the obtained energy to the deeply bound energy level of high In content.

Morphological, Optical, and Electrical Properties of p-Type Nickel Oxide Thin Films by Nonvacuum Deposition

In this study, a p-type 2 at% lithium-doped nickel oxide (abbreviation L2NiO) solution was prepared using Ni(NO3)2·6H2O, and LiNO3·L2NiO thin films were deposited using an atomizer by spraying the L2NiO solution onto a glass substrate. The sprayed specimen was heated at a low temperature (140 °C) and annealed at different high temperatures and times. This method can reduce the evaporation ratio of the L2NiO solution, affording high-order nucleating points on the substrate. The L2NiO thin films were characterized by X-ray diffraction, scanning electron microscopy, UV–visible spectroscopy, and electrical properties. The figure of merit (FOM) for L2NiO thin films was calculated by Haacke’s formula, and the maximum value was found to be 5.3 × 10−6 Ω−1. FOM results revealed that the L2NiO thin films annealed at 600 °C for 3 h exhibited satisfactory optical and electrical characteristics for photoelectric device applications. Finally, a transparent heterojunction diode was successfully prepared using the L2NiO/indium tin oxide (ITO) structure. The current–voltage characteristics revealed that the transparent heterojunction diode exhibited rectifying properties, with a turn-on voltage of 1.04 V, a leakage current of 1.09 × 10−4 A/cm2 (at 1.1 V), and an ideality factor of n = 0.46.

Tunable Photoluminescence of ZnO Nanowire Arrays via Native Defects

Natural ZnO nanomaterials have abundant oxygen vacancies which has great influence on the physical properties. Here, the ZnO nanowire arrays (ZNAs) have been obtained using microwave heating method. These samples' photoluminescence (PL) properties were studied under different annealing conditions. The field emission scanning electron microscope (SEM) image shows that the vertically aligned ZNAs basically have the same morphology after annealing at different times. X-ray diffraction (XRD) spectra demonstrate the best crystallization when the sample was annealed at 400 °C for 2 hours. Photoluminescence pattern indicates that the near-band-edge (NBE) emission is stronger with increasing annealing times, however, the defect-related emission decreases with the annealing times. This result indicates that crystallization of ZnO nanowires can be improved and the defects can decrease by annealing and the crystallization of the sample is wonderful at 400 °C for 2 h annealing. Meanwhile, adjusting photoluminescence characterizes through annealing can provide the basis for application of ZnO in photoelectric device.

Synthesis and characterization of CdS@ZnO nanoribbon@quantum dot and their enhanced visible-light-driven photocatalytic activities

CdS/ZnO nanoribbon/quantum dot was prepared using thermal decomposition method. Size and distribution of ZnO quantum dots on CdS nanobelt were controlled by concentrations of zinc acetate ethanol solution and thermal decomposition temperature. The structure and optical properties of CdS nanobelts and CdS/ZnO heterostructures are studied by XRD, TEM, PL and Raman scattering and UV–Vis absorption spectra. The photocatalytic performances of CdS nanobelts and CdS/ZnO heterostructures are tested by photocatalytic degradation of RhB aqueous solution under visible light irradiation. Compared with that (83.57%) of CdS nanobelts, the degradation rate (88.66%) of RhB using CdS/ZnO heterostructures as catalyst is significantly improved, which suggests better development prospect in photocatalytic technology and photoelectric device.

Back-Side Electron-Bombarded Silicon pin-Strip

Introduction. In recent decades, in the field of photoelectronics, special attention has been paid to the development of semiconductor matrix photodetectors. These detectors have become an effective alternative to existing television receiving systems. Among such devices, linear position-sensitive sensors are used in cases where the rapid registration of changes to the environment is required (for instance, high-speed locators for flying vehicles).Aim. To develop a strip of silicon pin-diodes as part of a hybrid IR-detector for effective registration of photoelectrons with time resolution less than 10 ns, as well as to model the key electro-physical characteristics of the strip.Materials and methods. In the device under development, the registration of photoelectrons is achieved by the presence of a near-surface field using p ++–p junction formed by diffusion of boron into the silicon with resistivity of 3 kΩ · cm. The pulling field is also formed in the space charge region between p ++ - and n ++ -regions. Diffusion of phosphorus was carried out to create the n ++ -region. Numerical calculations of potential distribution, concentration of free charge carriers and currents were carried out using software for 1D- and 2D-modelling (SimWin and TCAD Synopsys).Results. 2D-calculation of charge carrier concentration and potential distribution was performed. The study determined the minimum bias for the complete depletion of the i-layer, including that for longitudinal grooves of various depths. The strip was tested as part of a hybrid photoelectric device by irradiating light pulses from IR LED. When the voltage on the diodes was reached –270 V, the duration of the signal front on all channels was 5…9 ns.Conclusion. For use in IR-hybrid detectors, a strip of 12 silicon pin-diodes was developed with a sensitive element of 24 × 0.2 mm in dimension. The study of pulse characteristics showed that the necessary duration of the front signal on all channels was achieved without thinning thus satisfying the requirements for high-speed position-sensitive sensor of the infrared radiation.