Nonvolatile electrical switching of optical and valleytronic properties of interlayer excitons

Long-lived interlayer excitons (IXs) in van der Waals heterostructures (HSs) stacked by monolayer transition metal dichalcogenides (TMDs) carry valley-polarized...     

Novel linear and nonlinear optical properties of electromagnetically induced transparency systems

We describe some interesting linear and nonlinear optical properties of three-level electromagnetically induced transparency (EIT) systems, such as absorption reduction, sharp dispersion change, and enhanced Kerr nonlinearity. These novel optical properties are very useful in enhancing efficient nonlinear optical processes, which can find applications in optoelectronic devices. We present some experiments done in our group in the past few years with three-level atomic systems, especially more recent experiments with EIT medium inside an optical cavity.     

Investigations on electrical and optical properties of samarium chloride coordinated urea-thiourea semi-organic complex

ABSTRACT

Samarium chloride coordinated urea-thiourea semi-organic complex was prepared at room temperature by slow evaporation technique. The complexes were prepared with high degree of crystallinity. The unit cell parameters determined by powder X-ray diffraction reveals the complex to be having orthorhombic system with P_nma space group. The dielectric measurements were made by impedance spectroscopy and various dielectric parameters were studied as a function of temperature and frequency. The ac conductivity is governed by Arrhenius type behaviour and universal power law. In optical analysis, the transmittance characteristics of complexes were studied in ultra-violet and visible region of electromagnetic spectrum.     

Effect of a hydrogen ratio in electrical and optical properties of hydrogenated Al-doped ZnO films

This study examined the effect of the hydrogen ratio on the electrical and optical properties of hydrogenated Al-doped zinc oxide (AZO) thin films deposited by rf magnetron sputtering using a ceramic target (98 wt% ZnO, 2 wt% Al₂O₃). Various AZO films on glass were prepared by changing the H₂/(Ar?+?H₂) ratio at room temperature. The AZO/H films showed a lower resistivity and a higher carrier concentration and mobility than the AZO films. However, the resistivity and mobility of the AZO/H films increased and decreased with increasing H₂ flow ratio, respectively. As a result, the AZO/H films grown with 2% H₂ addition showed excellent electrical properties with a resistivity of 4.98?×?10⁴ Ωcm. The UV-measurements showed that the optical transmission of the AZO/H films was >85% in the visible range with a wide optical band gap. In addition, the effect of H₂ flow ratio on the structure and composition of hydrogenated AZO thin films have also been studied.     

Integrating optical and electrical engineering courses

The expansion in the fields of optical engineering and optoelectronics has made it essential to introduce optical engineering concepts into undergraduate courses and curricula. Because of limits on the number of course requirements for the B.S. degree, it is not clear how these topics should be introduced without replacing some of the traditional requirements. This paper demonstrates how optical engineering concepts can be easily presented as an integral part of electrical engineering subjects, with a minimal amount of replacement, while enhancing the depth and understanding of both fields. Courses such as linear signals and systems, electricity and magnetism, and electronics which traditionally represent the core requirements of the undergraduate electrical engineering curriculum contain subjects that have direct correlations with optical engineering concepts. The major changes that are needed are the creation of textbooks that contain concepts and examples in areas of both optical and electrical engineering and some relearning and familiarization on the part of instructors. This approach allows for a fresh look at courses being offered in electrical engineering, while providing the necessary background in optical engineering for students     

一种新型光电电压互感器

提出了一种用于高压测量的新型光学电压互感器.该互感器由形变测量单元、光电转换电路及供电单元3个部分组成.利用压电晶体的逆压电效应,在高压作用下,压电晶体产生交替形变,并通过光杠杆方法来测量压电晶体的交替形变.详细介绍了形变检测原理.为了实现互感器结构的紧凑化,提出了基于平行板的多反射光臂的结构,以达到互感器所需求的精度.该光臂的长度仅依赖于平行板的高度和入射光束的水平角度,和平行板之间的相对距离无关,简化了互感器的安装和设计.此外,对光电信号的处理进行设计,依据所设计的光电信号处理电路可以实现0.1级(500 kV)的互感器精度.     

Study on the electrical and optical properties of ITO and AZO thin film by oxygen gas flow rate

Transparent conductive oxide (TCO) thin films such as tin doped indium oxide (ITO), zinc doped indium oxide (IZO) and Al doped zinc oxide (AZO) have been widely used as transparent electrode for display. ITO and AZO thin films for display was prepared by the facing targets sputtering (FTS) system. The FTS method is called a plasma-free sputter method because the substrate is located apart from plasma. This system can deposit the thin film with low bombardment by high energetic particles in plasma such as γ-electrons, negative ions and reflected Ar atoms. ITO and AZO thin films were deposited on glass substrate at room temperature with oxygen gas flow rate and input power. And the electrical, structural and optical properties of the thin films were investigated. As a result, the resistivity of ITO, AZO thin film is 6?×?10^?4 Ω cm, 1?×?10^?3 Ω cm, respectively. And the optical transmittance of as-deposited thin films is over 80% at visible range.     

LED光电参数测量系统的设计

本文针对LED生产的实际需求,给出了新型LED光电参数测量系统的软硬件设计方案。该系统主要由工控主机、微型光谱仪、SOC单片机和高精度测量电路构成。通过实验测量表明该系统的测量精度高、测量时间短,同时还具有操作简便等优点。     

Fabrication and electrical properties of PC-PNZT-PVDF-GO composites

The objectives of this research are to fabricate and investigate new smart composites for the sensing and actuation applications in civil engineering. The fabrication and properties of cement-based piezoelectric ceramic composites are emphasized. However, cement-based piezoelectric composites are still difficult to obtain great electrical properties due to the evidence of some pores in the composites. Therefore, a novel approach to effectively improve their polarization of piezoelectric ceramic is to add a semiconductor (graphene oxide) and an insulator (polyvinylidene fluoride) phases between piezoelectric particles by the introduction of a small volume fraction of a third phase. Microstructure of the new composites was investigated using Scanning electron microscope (SEM). Dielectric permittivity and ferroelectric properties were then investigated.     

Investigation of the optical and electrical characteristics of aspark gap

A spark-gap apparatus and a high-speed optoelectronic measurement system were used to examine the optical and electrical characteristics of spark discharges. Parameters studied included the magnitude and polarity of the discharge voltage, gap length, and the impedance of the discharge circuit. Analyses were performed to compare the measured optical signatures as a function of the discharge current. Results of the experimentally measured parameters compare well with theoretically computed values. The work has application in the study of electrostatic discharge (ESD) events     

Effects of substrate temperature on electrical and optical properties ITO films deposited by r.f. magnetron sputtering

Indium tin oxide (ITO) films have been prepared by r.f. magnetron sputtering using powder target. X-ray diffraction analysis indicates that the deposited films were polycrystalline and retained a cubic bixbite structure. The ITO films deposited at low substrate temperature (T _s) exhibit a (411) preferred orientation but the films deposited at high T _s prefer a (111) orientation. The substrate temperature was found to significantly affect the electrical properties. As the T _s was increased, the conductivity of ITO films was improved due to thermally induced crystallization. The lowest resistivity (8.7?×?10^?4 Ω-cm) was obtained from ITO films deposited at 450 °C. However, optical properties of the films were somewhat deteriorated. The infrared (IR) reflectance of the film increases with increasing the substrate temperature.     

Modulation on the electrical and optical properties of Na and Rh co-doped Ruddlesden-Popper layered Ca3Ti2O7

Layered perovskite Ca_2.91Na_0.09Ti_2-xRh_xO₇ (x?=?0.00, 0.02, 0.04, 0.06) were synthesized by a conventional solid-state reaction. Room temperature ferroelectricity has been confirmed. The remanent polarization increases with an increase of Rh content, which is due to a larger oxygen octahedral distortion by Rh doping. The coercive field increases with Rh doping as the pinning effect of oxygen vacancies reduce the mobility of domain wall. Remanent polarization and coercive field are caused by different mechanisms, so it is possible to modulate them independently to meet the requirement of application in ferroelectric field. The concentration of oxygen vacancy increased with Rh doping, leading to the significant increase of leakage current density. The bandgap of samples doped with Rh drastically decrease and the visible light response of the sample was improved by Rh doping due to the formation of impurity energy levels within the band gap.

     

Dielectric mixtures: electrical properties and modeling

A review of the current state of understanding of dielectric mixture properties, and approaches to use numerical calculations for their modeling are presented. It is shown that interfacial polarization can yield different non-Debye dielectric responses depending on the properties of the constituents, their concentrations and geometrical arrangements. Future challenges on the subject are also discussed.     

Ni-ZrO_2金属陶瓷的制备及电性能

目前Ｎｉ－ＺｒＯ２金属陶瓷极认为是一种有潜力的固体氧化物燃料电池用负极材料而得到重视。本文通过对ＮｉＯ－ＺｒＯ２复相陶瓷进厅还原处理,制毒了Ｎｉ－ＺｒＯ２,金属陶瓷。测试了复相陶瓷的高温电导率及其在还原过程中的变化情况和最终得到的金属陶瓷的高温电导率,分别探讨了复相陶瓷和金属陶瓷的导电机制。对复相陶瓷还原过程中材料显微结构的变化进行了初步的分析。主要结论如下：（１）复相陶瓷中电导的主要通道是Ｙ－ＺｒＯ２相;（２）复相陶瓷的还原过程可以分为三个阶段,即：化学后应速率控制阶段、扩散控制阶段和Ｎｉ的熔融加剧阶段;（３）金属陶瓷的电导在Ｎｉ含量较低时,田Ｙ－ＺｒＯ２相中Ｖ。（带有＋２价电荷的氧空位）的运动决定;反之,则由Ｎｉ相中的电子电导决定。     

Structural and optical properties of Er-doped AlN

Based on first-principles calculations, we have studied the crystal, electronic structure and optical properties in both wurtzite and zinc blend structure of AlN doped with rare-earth element Er. The calculations indicate that the lattice parameters increase after doping showing the distortion of the crystal structure and its density of states is obviously asymmetric indicating the sample is magnetism. The static dielectric constant ε₁(0) of doped systems are increasing compare with pure AlN and the value of zinc blend structure Al_0.75Er_0.25N is biggest than that of other structures. Dielectric imaginary part ε₂(ω) and absorption coefficient I(ω) both show red shift and the absorption enhance in visible region after doping.     

Study of structural and electrical properties of Ag-starch nanocomposites

ABSTRACT

In the present work, Ag nanoparticles prepared by chemical reduction were used to synthesize Ag-starch nanocomposites. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to ascertain the formation of Ag-starch nanocomposites. Current-voltage (I-V) measurements reveal that the conductivity of starch increases with increasing concentration of Ag nanoparticles. I-V data was further analysed to ascertain the actual conduction mechanism responsible for charge transport in starch and Ag-starch nanocomposites. Poole-Frenkel (PF) emission was found to be dominant conduction mechanism responsible for increased conductivity of Ag-starch nanocomposites.     

Investigation of the effects of milling ceramic targets on the optical and electrical properties of BST thin films deposited by RF sputtering

Abstract

The RF sputtering method was utilized to deposit thin films of Ba_1-xSr_xTiO₃ (BST). The targets utilized in these experiments were prepared from ceramic powders with different particle size. The goal of this work is to examine whether the particle size distribution of the target can affect the properties of the thin films fabricated by the sputtering method. The Atomic Force Microscope (AFM) was used to examine the grain size in the thin films. The composition of the thin films and the bulk materials were examined by Fourier Transform Infrared (FTIR) spectroscopy. The dielectric properties of the thin films were measured and compared to its bulk counterparts. It was found that on lattice matched electrodes of SrRuO₃ on LaAlO₃ substrates, the thin films deposited from ceramic targets manufactured from ball-milled powders had finer grain size than those deposited from targets made from unmilled powders. However, this phenomenon was not observed in the case of polycrystalline films deposited on platinized silicon wafers.