Weixuan Jing

Surface plasmon enhanced photoluminescence of ZnO nanorods by capping reduced graphene oxide sheets.

A hybrid structure of reduced graphene oxide (rGO) sheets/ZnO nanorods was prepared and its photoluminescence intensity ratio between the UV and defect emission was enhanced up to 14 times. By controlling the reduction degree of rGO on the surface of ZnO nanorods, the UV emission was tuned with the introduction of localized surface plasmons resonance of rGO sheets. The suppression of the defect emission was ascribed to the charge transfer and decreased with the distance between the rGO and ZnO nanorods.

Low-temperature remote plasma-enhanced atomic layer deposition of graphene and characterization of its atomic-level structure

Graphene has attracted a great deal of research interest owing to its unique properties and many potential applications. Chemical vapor deposition has shown some potential for the growth of large-scale and uniform graphene films; however, a high temperature (over 800 °C) is usually required for such growth. A whole new method for the synthesis of graphene at low temperatures by means of remote plasma-enhanced atomic layer deposition is developed in this work. Liquid benzene was used as a carbon source. Large graphene sheets with excellent quality were prepared at a growth temperature as low as 400 °C. The atomic structure of the graphene was characterized by means of aberration-corrected transmission electron microscopy. Hexagonal carbon rings and carbon atoms were observed, indicating a highly crystalline structure of the graphene. These results point to a new technique for the growth of high-quality graphene for potential device applications.

Tungsten-rhenium thin film thermocouples for SiC-based ceramic matrix composites

A tungsten-rhenium thin film thermocouple is designed and fabricated, depending on the principle of thermal-electric effect caused by the high temperature. The characteristics of thin film thermocouples in different temperatures are investigated via numerical analysis and analog simulation. The working mechanism and thermo-electric features of the thermocouples are analyzed depending on the simulation results. Then the thin film thermocouples are fabricated and calibrated. The calibration results show that the thin film thermocouples based on the tungsten-rhenium material achieve ideal static characteristics and work well in the practical applications.

Range Analysis of Thermal Stress and Optimal Design for Tungsten-Rhenium Thin Film Thermocouples Based on Ceramic Substrates

A thermal stress range analysis of tungsten-rhenium thin film thermocouples based on ceramic substrates is presented to analyze the falling off and breakage problems caused by the mismatch of the thermal stresses in thin film thermocouples (TFTCs) and substrate, and nano-indentation experiments are done to measure and calculate the film stress to compare with the simulation results. Optimal design and fabrication of tungsten-rhenium TFTCs based on ceramic substrates is reported. Static high temperature tests are carried out, which show the optimization design can effectively reduce the damage caused by the thermal stress mismatch.

Characterization of line edge roughness and line width roughness of nano-scale typical structures

Two kinds of nano-scale typical structures were fabricated for characterizing line edge roughness(LER) and line width roughness(LWR). With Cr and Si3N4 thin films alternately deposited on a silicon substrate and electronic beam lithography employed on a positive resist ZEP520 layer, a nano-scale multiple linewidth standard and a nano-scale grating structure were processed respectively. In regard to the nano-scale multiple linewidth standards, an offline image analysis algorithm of Scanning Electron Microscopy (SEM) image and a random error analysis method were employed to characterize its LER and LWR, including standard deviations 3 σLER and 3 σLWR. With respect to the nano-scale grating structure, sampling and evaluation length, amplitude standard deviation, skewness, kurtosis, auto-correlation function as well as power spectral density function of the nano-scale grating structure were analyzed based on stochastic process analysis to show LER characteristics. Similarly Motif parameters-based analysis also was introduced to get LER characteristics of the nano-scale grating structure.

A Highly Thermostable In2O3/ITO Thin Film Thermocouple Prepared via Screen Printing for High Temperature Measurements

An In2O3/ITO thin film thermocouple was prepared via screen printing. Glass additives were added to improve the sintering process and to increase the density of the In2O3/ITO films. The surface and cross-sectional images indicate that both the grain size and densification of the ITO and In2O3 films increased with the increase in annealing time. The thermoelectric voltage of the In2O3/ITO thermocouple was 53.5 mV at 1270 °C at the hot junction. The average Seebeck coefficient of the thermocouple was calculated as 44.5 μV/°C. The drift rate of the In2O3/ITO thermocouple was 5.44 °C/h at a measuring time of 10 h at 1270 °C.

Regulating the hydrothermal synthesis of ZnO nanorods to optimize the performance of spirally hierarchical structure-based glucose sensors

This paper reports the effects of the synthesizing parameters on the surface morphologies of ZnO nanorod-based spirally hierarchical structures and the performance of related spirally hierarchical structure-based glucose sensors. ZnO nanorods were hydrothermally synthesized on Au cylindrical spirals with 3 sets of the synthesizing parameters, and glucose oxidase (GOx) was immobilized on these ZnO nanorods, thus 3 batches of the spirally hierarchical structure-based glucose enzymatic electrodes were fabricated. Geometric, crystalline and electrochemical characterization indicates that of all 3 batches of the spirally hierarchical structures, those fabricated respectively at 25 mM Zn2+ concentration of the growth solution, for 1.5 h the growth duration, and at 0.5 mM Zn2+ concentration of the seed solution all have Gaussian random rough surfaces. This gives rise to the largest surface area of the related spirally hierarchical structure, the most effective GOx immobilization of the corresponding enzymatic electrode, and the optimal performance of the related glucose sensor. The results benefit not only the batch construction but also the standardization of other hierarchical structure-based glucose sensors.

Construction of 3d arrays of cylindrically hierarchical structures with zno nanorods hydrothermally synthesized on optical fiber cores

This paper reports on UV-mediated enhancement in the sensitization of semiconductor quantum dots (QDs) on zinc oxide (ZnO) nanorods, improving the charge transfer efficiency across the QD-ZnO interface. The improvement was primarily due to the reduction in the interfacial resistance achieved via the incorporation of UV light induced surface defects on zinc oxide nanorods.The photoinduced defects were characterized byXPS, FTIR, andwater contact anglemeasurements, which demonstrated an increase in the surface defects (oxygen vacancies) in the ZnO crystal, leading to an increase in the active sites available for the QD attachment. As a proof of concept, a model cadmium telluride (CdTe) QD solar cell was fabricated using the defect engineered ZnO photoelectrodes, which showed ∼10% increase in photovoltage and ∼66% improvement in the photocurrent compared to the defect-free photoelectrodes. The improvement in the photocurrent was mainly attributed to the enhancement in the charge transfer efficiency across the defect rich QD-ZnO interface, which was indicated by the higher quenching of the CdTe QD photoluminescence upon sensitization.This paper reports on UV-mediated enhancement in the sensitization of semiconductor quantum dots (QDs) on zinc oxide (ZnO) nanorods, improving the charge transfer efficiency across the QD-ZnO interface. The improvement was primarily due to the reduction in the interfacial resistance achieved via the incorporation of UV light induced surface defects on zinc oxide nanorods. The photoinduced defects were characterized by XPS, FTIR, and water contact angle measurements, which demonstrated an increase in the surface defects (oxygen vacancies) in the ZnO crystal, leading to an increase in the active sites available for the QD attachment. As a proof of concept, a model cadmium telluride (CdTe) QD solar cell was fabricated using the defect engineered ZnO photoelectrodes, which showed ∼10% increase in photovoltage and ∼66% improvement in the photocurrent compared to the defect-free photoelectrodes. The improvement in the photocurrent was mainly attributed to the enhancement in the charge transfer efficiency across the defect rich QD-ZnO interface, which was indicated by the higher quenching of the CdTe QD photoluminescence upon sensitization.

Agglomeration and dendritic growth of Cu/Ti/Si thin film

Agglomeration and the transformation from random fractal to dendritic growth have been observed during Cu/Ti/Si thin film annealing. The experimental results show that the annealing temperature, film thickness, and substrate thickness influenced the agglomeration and dendritic growth. Multifractal spectrum is used to characterize the surface morphology quantificationally. The shapes of the multifractal spectra are hook-like to the left. Value of Δα increases with the annealing temperature rising, and Δf increases from 500°C to 700°C but reduces from 700°C to 800°C. The dendritic patterns with symmetrical branches are generated in the surfaces when the thin films were annealed at 800°C.

A new kind of thermocouple made of p-type and n-type semi-conductive oxides with giant thermoelectric voltage for high temperature sensing

A new kind of thermocouple consisting of n-type and p-type semi-conductive oxides with a giant thermoelectric voltage is reported. The thermocouple was fabricated from n-type La0.8Sr0.2CrO3 and p-type In2O3 and it exhibits a high thermoelectric voltage of 410.3 mV at 1270 °C, which is the highest value reported for any type of thermocouples to date. This achievement challenges the long-established material selection principles for thermocouples and opens a new way for designing highly sensitive thermal sensors. The thermocouple developed in this work has great potential for practical applications in high temperature sensing in harsh environments.