基于IDT/ZnO/AlN/Diamond结构的混合SAW/BAW压力敏感元件特性研究

利用有限元方法分析了基于IDT/ZnO/AlN/Diamond不同结构混合SAW/BAW器件的声学特性,包括层状薄膜结构、ZnO薄膜刻蚀结构和填充结构。结果表明,当h_(ZnO)/λ=0.3、h_(AlN)/λ=0.5,且ZnO被完全刻蚀(d/h_(ZnO)=1)时,刻蚀结构混合SAW/BAW(准西沙瓦波)的机电耦合系数(K^(2))取得最大值6.54%,比层状结构(d/h_(ZnO)=0)提升了近一倍。刻蚀结构中,SiO_(2)和Diamond填充物的引入不仅提高了准西沙瓦波的K_(2),而且改善了其压力传感特性。当d/h_(ZnO)=1时,SiO_(2)和Diamond填充结构准西沙瓦波的压力频移分别为81.2 kHz/MPa和207.4 kHz/MPa,比刻蚀结构分别提高了58.7%和300%;同时,Diamond填充物的引入使准西沙瓦波的频率压力系数(PCF)达到最大值297×10^(-6)/MPa,比d/h_(ZnO)=0时提高了约30%。由此可知,通过引入不同的填充物可以开发不同的功能传感器,在压力、温度和气敏等传感领域将具有极大的应用前景。

一种新型环形上DBR刻蚀微结构VCSEL及其空心光束

设计了带有质子注入高阻区的刻蚀微结构面发射半导体激光器结构,使得从出光口到上DBR形成环形波导,进而直接产生空心激光束输出。使用FDTD软件计算了刻蚀微结构VCSEL的光场分布,得到的环形模式图样在不同模式数目下都能保持空心光束的特性。制备了室温下激射波长为848 nm的微结构VCSEL,并测试其输出特性。阈值电流为0.27 A,峰值功率最高可达170 mW。不同电流下的近场图都显示出非常明显的空心环形光斑,远场光强分布曲线也符合空心光束的特性。该新型VCSEL技术为空心光束甚至阵列器件的发展提供了一种新的方法。

一种悬臂梁厚度可控的制作方法

针对湿法腐蚀加速度计悬臂梁时出现的梁厚度不均匀性问题，采取项层硅可定制的SOI材料制作出梁厚度均匀性一致的器件；采用干法刻蚀工艺减小结构开窗面积提高了产量。针对干法刻蚀中出现的负载效应和footing效应对结构层的厚度和形貌的影响问题，采用硅岛填充方式来减小负载效应；通过试验摸索了一组工艺参数，最大化减弱了footing效应，保证了器件厚度的均匀性，同时也提高了产量。

基于绝缘体上硅材料的25通道200 GHz的阵列波导光栅（英文）

报道了基于绝缘体上硅材料的25通道、信道间隔200 GHz的阵列波导光栅,分别优化了输入波导/输出波导/阵列波导间的最小间距(Δx_i/Δx_o/d),及其自由传播区和阵列波导之间边界结构(W_2/L_2/L_3).实验结果表明,该阵列波导光栅的插入损耗为5～7 dB,串扰为13～15 dB,该阵列波导光栅的性能得到有效提升.同时也提出了减小插损与串扰的进一步优化方案.

Effect of KOH treatment on structural and photovoltaic properties of ZnO nanorod arrays

ZnO nanorod arrays （NRs） were synthesized on the fluorine-doped SnO2 transparent conductive glass （FTO） by a simple chemical bath deposition （CBD） method combined with alkali-etched method in potassium hydroxide （KOH） solution. X-ray diffraction （XRD）, scanning electron microscopy （SEM） and current-voltage （I-V） curve were used to characterize the structure, morphologies and optoelectronic properties. The results demonstrated that ZnO NRs had wurtzite structures, the morphologies and photovoltaic properties of ZnO NRs were closely related to the concentration of KOH and etching time, well-aligned and uniformly distributed ZnO NRs were obtained after etching with 0.1 mol/L KOH for 1 h. ZnO NRs treated by KOH had been proved to have superior photovoltaic properties compared with high density ZnO NRs. When using ZnO NRs etched with 0.1 mol/L KOH for 1 h as the anode of solar cell, the conversion efficiency, short circuit current and open circuit voltage, compared with the unetched ZnO NRs, increased by 0.71%, 2.79 mA and 0.03 V, respectively.

Chemical etching process of copper electrode for bioelectrical impedance technology

In order to obtain bioelectrical impedance electrodes with high stability, the chemical etching process was used to fabricate the copper electrode with a series of surface microstructures. By changing the etching processing parameters, some comparison experiments were performed to reveal the influence of etching time, etching temperature, etching liquid concentration, and sample sizes on the etching rate and surface microstructures of copper electrode. The result shows that the etching rate is decreased with increasing etching time, and is increased with increasing etching temperature. Moreover, it is found that the sample size has little influence on the etching rate. After choosing the reasonable etching liquid composition （formulation 3）, the copper electrode with many surface microstructures can be obtained by chemical etching process at room temperature for 20 rain. In addition, using the alternating current impedance test of electrode-electrode for 24 h, the copper electrode with a series of surface microstructures fabricated by the etching process presents a more stable impedance value compared with the electrocardiograph （ECG） electrode, resulting from the reliable surface contact of copper electrode-electrode.

UItrastructural Observation on Rat Spermatozoa Treatedwith Tripchlorolide(T_4) from Tripterygium wilfordii

Adult male rats were treated orally with monomer T_4(Tripchlorolide) isolated from Tripterygium wilfordii, at the dose of 50μg/kg/day,6 days/week for6 weeks.Ultrathin section and freeze etching replica of seminiferous tubules and epididymal spermatozoa were examined with elec-tron microscope. The results showed that the spemiogenesis was inhibited T_4 in seminiferous tu-bules. However,the damage and disruption of the spermatozoa were more serious in the epididymis.Damage of the structure and function ot microtubule and microfilament may be the chief reason for sperm damage. Sperm membrane was also very sensitive to the treatiment of monomer T_4.

Fabrication of Ultra Deep Electrical Isolation Trenches with High Aspect Ratio Using DRIE and Dielectric Refill

A novel technique to fabricate ultra deep high aspect ratio electrical isolation trenches with DRIE and dielectric refill is presented.The relationship between trench profile and DRIE parameters is discussed.By optimizing DRIE parameters and RIE etching the trenches’ opening,the ideal trench profile is obtained to ensure that the trenches are fully refilled without voids.The electrical isolation trenches are 5μm wide and 92μm deep with 0.5μm thick oxide layers on the sidewall as isolation material.The measured I-V result shows that the trench structure has good electrical isolation performance:the average resistance in the range of 0～100V is more than 10 11Ω and no breakdown appears under 100V.This isolation trench structure has been used in fabrication of the bulk integrated micromachined gyroscope,which shows high performance.

Transition of super-hydrophobic states of droplet on rough surface

Twelve samples with periodic array square pillars microstructure were prepared on the silicon wafer by plasma etching techniques, on which space b of the square pillars increased from 5 to 60 μm. In order to study the effect ofb on the wettability of the rough surface, the effects of apparent contact angle （CA） and sliding angle （a） of the droplet on the rough surface were measured with the contact angle meter. The results show that the experimental values of CA well agree with the classical wetting theory and a decreases with the increase of b. Two drop shapes exist on the samples＇ surface, corresponding to the Cassie state and the Wenzel state respectively. The contact state in which a drop would settle depends typically on the size of b. On the role of gravitation, the irreversible transition of a drop from Cassie state to Wenzel state should occur at a certain space of the square pillars. Since the transition has implications on the application of super-hydrophobic rough surfaces, theoretically, the prediction of wetting state transition on square pillar array micro-structured surfaces provides an intuitionistic guidance for the design of steady superhydrophobic surfaces.

Fabrication and characterization of squama-shape micro/nano multi-scale silicon material

This paper presents the fabrication of squama-shape micro/nano multi-scale structures and the analysis of the interaction among different-scale structures during the fabrication processes. Well-designed microstructures made of inverted pyramids and V-shape grooves are fabricated by KOH wet etching. High-dense high-aspect-ratio (HAR) nanostructures are fabricated atop microstructures by an improved maskless deep reactive ion etching (DRIE) process, with an optimized recipe to form micro/nano dual-scale structures (MNDS). Due to the impact of the profile of microstructures on the shape of nanostructures, dissymmetrical (i.e., squama-shape) nanopillars have been formed on the inclined surfaces of microstructures, while the symmetrical nanopillars are formed on the horizontal surfaces with different formation velocities. Furthermore, the optical properties of MNDS are not sensitive to structural parameters of microstructures, making the sample overcome the lithography limitation of conventional processes for photo-devices. Eventually, three-level structures are fabricated by sputtering a gold thin film on the MNDS, and the profile of MNDS is selective in the deposition of gold particles, which is very useful for practical applications.

Metal-assisted chemical etching of silicon and the behavior of nanoscale silicon materials as Li-ion battery anodes

This review outlines the developments and recent progress in metal-assisted chemical etching of silicon, summarizing a variety of fundamental and innovative processes and etching methods that form a wide range of nanoscale silicon structures. The use of silicon as an anode for Li-ion batteries is also reviewed, where factors such as film thickness, doping, alloying, and their response to reversible lithiation processes are summarized and discussed with respect to battery cell performance. Recent advances in improving the performance of silicon-based anodes in Li-ion batteries are also discussed. The use of a variety of nanostructured silicon structures formed by many different methods as Li-ion battery anodes is outlined, focusing in particular on the influence of mass loading, core-shell structure, conductive additives, and other parameters. The influence of porosity, dopant type, and doping level on the electrochemical response and cell performance of the silicon anodes are detailed based on recent findings. Perspectives on the future of silicon and related materials, and their compositional and structural modifications for energy storage via several electrochemical mechanisms, are also provided.

Etched Optical Fiber Vibration Sensor to Monitor Health Condition of Beam Like Structures

Using a center etched single mode optical fiber, a simple vibration senor is designed to monitor the vibrations of a simply supported beam. The sensor has high linear response to the axial displacement of about 0.8mm with a sensitivity of 32mV/10p, m strain. The sensor is tested for periodic and suddenly released forces, and the results are found to coincide with the theoretical values. This simple design, small in size and low cost sensor may find applications in industry and civil engineering to monitor the vibrations of the beam structures and bridges.

Experiment study on micro-structure on different crystallographic planes of mc-Si etched in alkaline solution

The investigation of multi-crystalline silicon （mc-Si） surface etching technology is a key point in solar cell research. In this paper, mc-Si surface was etched in the common alkaline solution modified by an additive for 20 minutes at 78-80~C. Samples＇ surface morphology was observed by scanning electron microscope （SEM）. It is firstly found that the etched mc-Si surface has the uniform distribution of trap pits although the morphologies of trap pits are slightly different on different crystallographic planes. Si （100） plane was covered with many small Si-mountaln ranges or long V-shape channels arranged in a crisscross pat- tern. For （110） plane and （111） plane, they were full of a lot of triangle pit-traps （or quadrilateral holes） and twisted earthworm trap pits, respectively. The measured reflectance of the sample was 20.5% at wavelength range of 400--900 nm. These results illustrate that alkaline solution modified by an additive can effectively etch out trap pits with a good trapping light effect on mc-Si surfaces. This method should be very valuable for mc-Si solar cells.

Integrated ionic sieving channels from engineering ordered monolayer two-dimensional crystallite structures

Atomically thin solid-state channels enabling selective molecular transport could potentially be used in a variety of separation and energy conversion applications.The density of channels,their height,distance and edge structure are the key factors that dramatically impact the selective transport performance.However,such channels with small constrictions and atomic precision have been limited to proof-ofconcept demonstrations based on microscale two-dimensional(2D)crystal stripes.Here,we report the engineering of highly ordered,scalable monolayer graphene crystallite arrays by chemical vapor deposition(CVD)method with a modified anisotropic etching approach.The size,shape,distance and edge structure of the graphene crystallite arrays in a large area could be delicately controlled through tailoring the synthetic parameters.This array structure can act as pillars to prop up a smooth single-crystal graphene film,and the fabricated integrated angstrom-size(3.4A)channels allow water transport but exclude hydrated ions,demonstrating potential in selective ionic sieving and nanofiltration practice.