Design and Simulation of Improved SOI SiGe Hetero-Junction Bipolar Transistor Architecture with Strain Engineering

In order to improve the electrical and frequency characteristics of SiGe heterojunction bipolar transistors (HBTs), a novel structure of SOI SiGe heterojunction bipolar transistor is designed in this work. Compared with traditional SOI SiGe HBT, the proposed device structure has smaller window widths of emitter and collector areas. Under the act of additional uniaxial stress induced by Si0.85Ge0.15, all the collector region, base region and emitter region are strained, which is beneficial to improve the performance of SiGe HBTs. Employing the SILVACOⓇTCAD tools, the numerical simulation results show that the maximum current gain βmax, the Earley voltage VA are achieved for 1062 and 186 V, respectively, the product of β and VA, i.e., β ×VA, is 1.975 × 105 V and, the peak cutoff frequency fT is 419 GHz when the Ge component in the base has configured to be a trapezoidal distribution. The proposed SOI SiGe HBT architecture has a 52.9% improvement in cutoff frequency fT compared to the conventional SOI SiGe HBTs.

Modelling and Calculation of Silicon Conduction Band Structure and Parameters with Arbitrary Uniaxial Stress

Using the k·p theory, the coupling effect between the Δ1 and Δ2’ bands on the energy band structure of different energy valleys is studied. The analytical model of the energy-dispersion relationship applicable to uniaxial stress for arbitrary crystal plane and orientation as well as different energy valleys is established. For typical crystal orientations, the main parameters of energy band structure such as band edge level, splitting energy, density-of-state (DOS) effective mass and conductivity effective mass are calculated. The calculated results are in good agreement with the data reported in related literature. Finally, the relationship between the DOS effective mass, conductivity effective mass and the change of stress and orientation of different crystal planes is given. The proposed model and calculation results can provide a theoretical reference for the design of nano-electronic devices and TCAD simulation.

Artificial photosynthesis bringing new vigor into plastic wastes

The accumulation of plastic wastes in landfills and the environment threatens our environment and public health,while leading to the loss of potential carbon resources.The urgent necessary lies in developing an energy-saving and environmentally benign approach to upgrade plastic into value-added chemicals.Artificial photosynthesis holds the ability to realize plastic upcycling by using endless solar energy under mild conditions,but remains in the initial stage for plastic upgrading.In this review,we aim to look critically at the photocatalytic conversion of plastic wastes from the perspective of resource reutilization.To begin with,we present the emerging conversion routes for plastic wastes and highlight the advantages of artificial photosynthesis for processing plastic wastes.By parsing photocatalytic plastic conversion process,we demonstrate the currently available routes for processing plastic,including plastic photodegradation,tandem decomposition of plastic and CO_(2) reduction,selective plastic oxidation,as well as photoreforming of plastic.This review concludes with a personal perspective for potential advances and emerging challenges in photocatalytic plastic conversion.

Lignin composite ionic liquid lubricants with excellent anti-corrosion,anti-oxidation,and tribological properties

A new type of lubricating material(BTA-P_(4444)-Lig)was synthesized by combining lignin with tetrabutylphosphorus and benzotriazole.The tribological properties,corrosion resistance,and anti-oxidation properties of BTA-P_(4444)-Lig as a lubricant were investigated.The lubricating material exhibits excellent friction reduction and wear resistance,as well as good thermal stability and excellent oxidation resistance.Mechanistic analysis reveals that the active elements N and P in the lubricating material react with the metal substrate,and the reaction film effectively blocks direct contact between the friction pairs,affording excellent friction reduction and wear resistance.At the same time,the phenolic hydroxyl group in lignin reacts with oxygen free radicals to form a resonance-stable semi-quinone free radical,which interrupts the chain reaction and affords good anti-oxidant activity.

Agricultural Risk Factors Influence Microbial Ecology in Honghu Lake

Agricultural activities, including stock-farming, planting industry, and fish aquaculture,can affect the physicochemical and biological characters of freshwater lakes. However, the effects of pollution producing by agricultural activities on microbial ecosystem of lakes remain unclear.Hence, in this work, we selected Honghu Lake as a typical lake that is influenced by agriculture activities. We collected water and sediment samples from 18 sites, which span a wide range of areas from impacted and less-impacted areas. We performed a geospatial analysis on the composition of microbial communities associated with physicochemical properties and antibiotic pollution of samples. The co-occurrence networks of water and sediment were also built and analyzed. Our results showed that the microbial communities of impacted and less-impacted samples of water were largely driven by the concentrations of TN, TP, NO_3^--N, and NO_2^--N, while those of sediment were affected by the concentrations of Sed-OM and Sed-TN. Antibiotics have also played important roles in shaping these microbial communities: the concentrations of oxytetracycline and tetracycline clearly reflected the variance in taxonomic diversity and predicted functional diversity between impacted and less-impacted sites in water and sediment samples, respectively. Furthermore, for samples from both water and sediment, large differences of network topology structures between impacted and less-impacted were also observed. Our results provide compelling evidence that the microbial community can be used as a sentinel of eutrophication and antibiotics pollution risk associated with agricultural activity; and that proper monitoring of this environment is vital to maintain a sustainable environment in Honghu Lake.