NiO/TiO_2纳米管阵列异质结电极的制备及光电化学性能

采用阳极氧化方法在金属钛表面制备TiO2纳米管阵列,管内径为60～90 nm,壁厚约为15 nm,长度为600 nm,通过化学镀Ni并结合空气中热处理过程,在TiO2表面生长出NiO纳米颗粒层,厚度约为200 nm,颗粒尺寸为20～40 nm,获得异质结型NiO/TiO2纳米管阵列复合电极.结果表明,在100 mW/cm2的辐照下,该光阳极可提高其光电化学特性.在0.65 V偏压时的光电流密度和光电转换效率分别为3.05 mA/cm2和1.41%.

纳米Cu_2O／TiO_2异质结薄膜电极的制备和表征

通过阴极还原在纳米TiO2膜上电沉积Cu2O,获得了p-Cu2O／n-TiO2异质结电极．研究了沉积温度对Cu2O膜厚、纯度和形貌的影响,制备出纯度较高、粒径为40-50nm的Cu2O 薄膜．纳米Cu2O膜在200℃烧结后透光性最好,禁带宽度为2．06eV．光电化学测试表明纳米 p-Cu2O／n-TiO2异质结电极呈现较强的n-型光电流响应并且能够提高光电转换效率．

A monolithic InGaP/GaAs HBT power amplifier for W-CDMA applications

A monolithic microwave integrated circuit （MMIC） power amplifier （PA） is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the power supply and temperature, but also compensates deviations caused by the increase in input power. The bias circuit is a current-mirror configuration, and the feedback circuit helps to maintain bias voltage at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. A shunt capacitor at the base node of the active bias transistor enhances the linearity of the PA. The chip is fabricated in an InGaP/GaAs heterojunction bipolar transistor （HBT） process. Measured results exhibit a 26. 6-dBm output compression point, 33.6% power-added efficiency （PAE） and - 40.2 dBc adjacent channel power ratio （ACPR） for wide-band code division multiple access （W-CDMA） applications.

Ferroelectric polarization-enhanced photocatalytic performance of heterostructured BaTiO_(3)@TiO_(2) via interface engineering

A catalyst of ferroelectric-BaTiO_(3)@photoelectric-TiO_(2) nanohybrids(BaTiO_(3)@TiO_(2))with enhanced photocatalytic activity was synthesized via a hydrolysis precipitation combined with a hydrothermal approach.Compared to pure TiO_(2),pure BaTiO_(3) and BaTiO_(3)/TiO_(2) physical mixture,the heterostructured BaTiO_(3)@TiO_(2) exhibits significantly improved photocatalytic activity and cycling stability in decomposing Rhodamine B(RhB)and the degradation efficiency is 1.7 times higher than pure TiO_(2) and 7.2 times higher than pure BaTiO_(3).These results are mainly attributed to the synergy effect of photoelectric TiO_(2),ferroelectric-BaTiO_(3) and the rationally designed interfacial structure.The mesoporous microstructure of TiO_(2) is of a high specific area and enables excellent photocatalytic activity.The ferroelectric polarization induced built-in electric field in BaTiO_(3) nanoparticles,and the intimate interfacial interactions at the interface of BaTiO_(3) and TiO_(2) are effective in driving the separation and transport of photogenerated charge carriers.This strategy will stimulate the design of heterostructured photocatalysts with outstanding photocatalytic performance via interface engineering.

An effective CdS/Ti-Fe_(2)O_(3)heterojunction photoanode:Analyzing Z-scheme charge-transfer mechanism for enhanced photoelectrochemical water-oxidation activity

Z-scheme photocatalytic system has been regarded as a popular field of research in photoelectrochemical(PEC)water splitting.Among the many obstacles facing a Z-scheme photocatalytic system,the analysis methods of interfacial Z-scheme charge transfer still remain a significant challenge.Hence,in this study,CdS/Ti-Fe_(2)O_(3)heterojunction photoanodes are elaborately designed to explore the charge-transfer behavior in PEC water splitting.In this study,photophysical measurements,including the Kelvin probe measurement,surface photovoltage spectroscopy(SPV),and transient photovoltage spectroscopy(TPV),are used to monitor the migration behavior of photogenerated charges at the interface electric field of CdS/Ti-Fe_(2)O_(3)Z-scheme heterojunction photoanodes.The Kelvin probe and SPV measurements demonstrate that CdS/Ti-Fe_(2)O_(3)interfacial driving force favors the rapid transfer of photoexcited electrons to CdS.The double-beam strategy based on TPV indicates that more electrons of Ti-Fe_(2)O_(3)are combined with the holes of CdS owing to the intensive interface electric field.The results of these measurements successfully prove the Z-scheme migration mechanism of CdS/Ti-Fe_(2)O_(3)photoanodes.Benefiting from the desirable charge transfer at the interface electric field,CdS/Ti-Fe_(2)O_(3)photoanodes exhibit superior photocatalytic oxygen evolution reaction performance compared with that of pure Ti-Fe_(2)O_(3).The photocurrent density of the 25CdS/Ti-Fe_(2)O_(3)photoanode reaches 1.94 mA/cm^(2) at 1.23 V versus reversible hydrogen electrode without excess cocatalyst,and it is two times higher than that of pure Ti-Fe_(2)O_(3)photoanode.Therefore,an outstanding strategy is provided in this study to prove the Z-scheme charge-transfer mechanism of photocatalytic systems in PEC water splitting.

Design and Fabrication of Novel Dual-Base Negative-Differential-Resistance Heterojunction Bipolar Transistor

Based on planar Si dual-base transistor conception, a novel mesa dual-base heterojunc- tion bipolar transistor ( HBT) is designed and fabricated. Molecule beam extension. selective wet chemical etching, common contact photolithography and metal lift-off technique are adopted in the process. The device has particular and distinct voltage-controlled negative differential resistance (NDR) and photo-controlled NDR. The highest peak-to-vally current rate of the voltage-controlled NDR is larger than 148 and the peak current varies with the increase of collector voltage. The device features high speed and high frequency characteristics derived from HBT and intrinsic bistability and self-latching characteristics due to NDR. A single dual-base HBT can be seen as an integration of NDR device, HBT and photoconductive device. Compared with common HBT.the groove is the key factor producing NDR.

p-Cu_2O/n-TiO_2纳米管复合电极的制备及其光电性能

采用二次阳极氧化法制备结构规整的TiO_2纳米管阵列,进一步采用恒电流电化学沉积Cu_2O制备纳米管阵列异质结复合电极Cu_2O/TiO_2。采用扫描电镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外-可见漫反射光谱(UV-vis DRS)等对样品进行表征。SEM结果表明TiO_2纳米管垂直排列在基底Ti上,管径约为50 nm,管长约为1μm左右,Cu_2O以颗粒状均匀地沉积在TiO_2纳米管阵列上;XRD结果表明TiO_2为锐钛矿晶型,而沉积的Cu_2O为立方型;XPS结果表明Cu_2O/TiO_2中Cu和Ti分别以Cu^(1+)和Ti^(2+)的形式存在;UV-vis DRS结果表明沉积Cu_2O的电极材料的吸光范围由紫外区扩展到紫外-可见区。光电性能测试结果表明:制备的Cu_2O/TiO_2复合电极具有良好的光电分解水的活性,其光电流密度是TiO_2电极的2倍以上。Cu_2O沉积量为5.18×10-7mol时,Cu_2O/TiO_2的光转化效率可达0.41%(0.735 V vs.RHE)。采用焙烧方法改善Cu_2O/TiO_2电极性能,在373 K下空气中焙烧0.5 h,电极的光转化效率可达0.65%(0.759 V vs.RHE)。最后考察了CT-0.1-373和CT-0.1电极的稳定性,经连续100次线性伏安(LSV)扫描,CT-0.1-373的光转化效率为0.64%(0.762 V vs.RHE),而未经焙烧处理的CT-0.1电极,经100次LSV扫描光转化效率值降低至0.38%(0.767 V vs.RHE),结果表明低温焙烧处理不仅可显著提高Cu_2O/TiO_2复合电极的光电活性,也可改善其稳定性。

Heteroepitaxial growth of ZnO nanosheet bands on ZnCo204 submicron rods toward high-performance Li ion battery electrodes

We report the direct synthesis of ZnC0204 and ZnO/ZnC0204 submicron rod arrays grown on Ni foil current collectors via an ammonia-evaporation-induced method by controlling the ratio of Zn to Co. These three-dimensional （3D） hierar- chical self-supported nanostructures are composed of one-dimensional （1D） ZnCo204 rods and two-dimensional （2D） ZnO nanosheet bands perpendicular to the axis of the each ZnCo204 rod. We carefully deal with the heteroepitaxial growth mechanisms of hexagonal ZnO nanosheets from a crystallographic point of view. Furthermore, we demonstrate the ability of these high-surface-area ZnO/ZnCo204 heterostructured rods to enable improved electrolyte permeability and Li ion transfer, thereby enhancing their Li storage capability （-900 mA.h.g-1 at a rate of 45 mA.h.g-1） for Li ion battery electrodes.

CuI-Si Heterojunction Solar Cells with Carbon Nanotube Films as Flexible Top-Contact Electrodes

We report the fabrication of CuI-Si heterojunction solar cells with carbon nanotubes （CNTs） as a transparent electrode. A flexible CNT network was transferred onto tile top of a polycrystalline CuI layer, making a conformal coating with good contact with the underlying CuI. The solar cells showed power conversion efficiencies in the range of 6% to 10.5%, while the efficiency degradation was less than 10% after the device was stored in air for 8 days. Compared with conventional rigid electrodes such as indium tin oxide （ITO） glass, the flexibility of the CNT films ensures better contact with the active layers and removes the need for press-contact electrodes. Degraded cells can recover their original performance by acid doping of the CNT electrode. Our results suggest that CNT films are suitable electrical contacts for rough materials and structures with an uneven surface.