Qingchun Zhang

Bio: Qingchun Zhang is an academic researcher from Southwest University of Science and Technology. The author has contributed to research in topics: Algal bloom & Silicon carbide. The author has an hindex of 38, co-authored 217 publications receiving 4277 citations. Previous affiliations of Qingchun Zhang include University of South Carolina & Chinese Academy of Sciences.

Photocatalytic degradation of tetracycline antibiotics using three-dimensional network structure perylene diimide supramolecular organic photocatalyst under visible-light irradiation

Abstract: The occurrence of antibiotics in the ambient environment has raised serious concerns. In this work, the kinetics and mechanism of photocatalytic degradation tetracycline (TC) was investigated using three-dimensional network structure perylene diimide supramolecular organic photocatalyst (3D-PDI). Under visible-light irradiation, 3D-PDI exhibited excellent degradation performance and stability for several tetracycline-based antibiotics (e.g., tetracycline; chlortetracycline; oxytetracycline.). The adsorption and degradation rate of TC by 3D-PDI were 8.21 and 12.7 times higher than that of bulk-PDI. The enhanced adsorption and degradation performance of TC by 3D-PDI were mainly due to the larger specific surface area and π-electron conjugation of 3D network supramolecular system. Superoxide radical ( O2−), hydrogen peroxide (H2O2) and hole (h+) the main reactive species (RSs) for TC degradation. Under the attack of photocatalytic RSs, TC undergoes hydroxylation, demethylation, aromatization, and ring-opening processes, and finally complete mineralization into CO2 and H2O. These results revealed that perylene diimide supramolecular photocatalyst may be efficiently applied for the remediation of tetracycline contaminated natural waters.

SiC Power Devices for Microgrids

Abstract: Microgrids with distributed generation sources are critical for reduction of greenhouse gas emissions and imported energy. However, power converters and circuit breakers built with silicon (Si) switches are too bulky and inefficient to be used in the microgrid system. The development of high-voltage power devices based on silicon carbide (SiC) will be a critical component in building the microgrid with distributed and fluctuating sources of power generation. In this paper, the physics and technology of high-voltage (>10 kV) 4H-SiC power devices, namely MOSFETs and insulated gate bipolar transistors are discussed. A detailed review of the current status and future trends in these devices is given with respect to materials growth, device design, and fabrication processing.

Effect of surface NH3 anneal on the physical and electrical properties of HfO2 films on Ge substrate

Abstract: Metal-oxide-semiconductor capacitors were fabricated on germanium substrates by using metalorganic-chemical-vapor-deposited HfO2 as the dielectric and TaN as the metal gate electrode. It is demonstrated that a surface annealing step in NH3 ambient before the HfO2 deposition could result in significant improvement in both gate leakage current and the equivalent oxide thickness (EOT). It was possible to achieve a capacitor with an EOT of 10.5 A and a leakage current of 5.02×10−5 A/cm2 at 1 V gate bias. X-ray photoelectron spectroscopy analysis indicates the formation of GeON during surface NH3 anneal. The presence of Ge was also detected within the HfO2 films. This may be due to Ge diffusion at the high temperature (∼400 °C) used in the chemical-vapor deposition process.

Alternative surface passivation on germanium for metal-oxide-semiconductor applications with high-k gate dielectric

Abstract: An alternative surface passivation process for high-k Ge metal-oxide-semiconductor (MOS) device has been studied The surface SiH4 annealing was implemented prior to HfO2 deposition X-ray photoelectron spectroscopy analysis results show that the SiH4 surface passivation can greatly prevent the formation of unstable germanium oxide at the surface and suppress the Ge out-diffusion after the HfO2 deposition The electrical measurement shows that an equivalent oxide thickness of 135A and a leakage current of 116×10−5A∕cm2 at 1V gate bias was achieved for TaN∕HfO2∕Ge MOS capacitors with the SiH4 surface treatment

Alternative Plasmonic Materials: Beyond Gold and Silver

Abstract: Materials research plays a vital role in transforming breakthrough scientific ideas into next-generation technology. Similar to the way silicon revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research in plasmonics and metamaterials lacks good material building blocks in order to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, especially metals. There are many materials, other than conventional metallic components such as gold and silver, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2D materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions.

A Survey of Wide Bandgap Power Semiconductor Devices

Abstract: Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Applications of 2D MXenes in energy conversion and storage systems

Abstract: Transition metal carbides and nitrides (MXenes), a family of two-dimensional (2D) inorganic compounds, are materials composed of a few atomic layers of transition metal carbides, nitrides, or carbonitrides. Ti3C2, the first 2D layered MXene, was isolated in 2011. This material, which is a layered bulk material analogous to graphite, was derived from its 3D phase, Ti3AlC2 MAX. Since then, material scientists have either determined or predicted the stable phases of >200 different MXenes based on combinations of various transition metals such as Ti, Mo, V, Cr, and their alloys with C and N. Extensive experimental and theoretical studies have shown their exciting potential for energy conversion and electrochemical storage. To this end, we comprehensively summarize the current advances in MXene research. We begin by reviewing the structure types and morphologies and their fabrication routes. The review then discusses the mechanical, electrical, optical, and electrochemical properties of MXenes. The focus then turns to their exciting potential in energy storage and conversion. Energy storage applications include electrodes in rechargeable lithium- and sodium-ion batteries, lithium-sulfur batteries, and supercapacitors. In terms of energy conversion, photocatalytic fuel production, such as hydrogen evolution from water splitting, and carbon dioxide reduction are presented. The potential of MXenes for the photocatalytic degradation of organic pollutants in water, such as dye waste, is also addressed, along with their promise as catalysts for ammonium synthesis from nitrogen. Finally, their application potential is summarized.

Review of Solid-State Transformer Technologies and Their Application in Power Distribution Systems

Abstract: The solid-state transformer (SST), which has been regarded as one of the 10 most emerging technologies by Massachusetts Institute of Technology (MIT) Technology Review in 2010, has gained increasing importance in the future power distribution system. This paper presents a systematical technology review essential for the development and application of SST in the distribution system. The state-of-the-art technologies of four critical areas are reviewed, including high-voltage power devices, high-power and high-frequency transformers, ac/ac converter topologies, and applications of SST in the distribution system. In addition, future research directions are presented. It is concluded that the SST is an emerging technology for the future distribution system.