Au修饰薄膜CdSe电极的界面动力学行为的研究

研究了Au修饰的薄膜CdSe电极在多硫溶液中的瞬态光电流行为,测量了界面异相电荷转移,表面电荷复合及光腐蚀反应速度常数K_F,K_R及K_c。结合了光电子能谱(XPS)及扫描电镜(SEM)表面分析,对三种不同Au量修饰的薄膜CdSe电极进行界面动力学行为的分析。     

电活性分子L-B膜修饰CdSe薄膜电极的光电化学研究

用电活性分子——硬脂酸二茂铁酯L-B膜修饰了薄膜CdSe电极,在单色光650nm光照下用循环伏安法研究修饰的薄膜电极的光电化学性能。研究结果指出经多层L-B膜修饰后,薄膜CdSe电极的,I-V性能和光稳定性都有明显改善。用界面能级关系讨论了硬脂酸二茂铁酯L-B膜在光照的CdSe薄膜/Fe(CN)_6~(4-)溶液界面起传递电荷的中介作用,加速了界面的电荷转移。     

多晶n-CdSe电极在K_4Fe(CN)_6-EDTA溶液中稳定性的研究

旋转环盘电极(RRDE)研究表明,多晶n-CdSe电极表面经金属离子溶液处理,提高溶液的pH及增加溶液中还原剂K_4Fe(CN)_6的浓度均使该电极在K_4Fe(CN)_6-FDTA体系中的稳定因子S提高。用Au、Ru、Pt及Pb等离子溶液处理电极表面时,S值增大。Ru离子处理使S增大几乎可达1。从X射线荧光光谱和Mott-Schottky关系图分析证明,处理后的CdSe多晶电极表面沉积了一层金属薄层。本文对电极表面沉积的金属薄层、溶液pH等的影响、稳定因子S提高的原因也作了初步讨论。     

薄膜CdSe及CdSexTe1—x电极的光电子能谱研究

用X射线光电子能谱(XPS)研究了不同含氧气氛中烧结的薄膜CdSe及Cdse_xTe_(1-x)电极表面,以及薄膜与Ti底基之间的界面。研究中发现,二种薄膜电极的表面形成了CdO,SeO_2及TeO_2氧化物,与薄膜接触的Ti底基表面上形成了TiO_2。用俄歇电子能谱(AES)对在电极表面及Ti表面所生成的氧化层分别进行了深度分析。结果表明,各种氧化物形成的程度有很大的不同,氧化层厚度也存在差异。对影响薄膜电极的光电性能的因素进行了讨论。     

表面粗糙度对X70碳钢在HNO_3溶液中阳极溶解行为的影响

采用动电位极化和恒电位极化技术研究了表面粗糙度对X70碳钢在0.5 mol/L HNO_3溶液中的阳极溶解行为产生的影响。X70碳钢在0.5 mol/L HNO3溶液中发生阳极溶解时有电流振荡现象出现,振荡是由电极表面膜的周期性生成和溶解导致的。通过分析不同表面粗糙度时的电流振荡,得出结论:表面比较粗糙时,电极难以钝化,阳极溶解比较剧烈;相反,表面非常光滑时,电极容易钝化,阳极溶解比较轻微。     

表面沉积钯层的n型硅光阳极特性的研究

测量了n-si电极的光电流-电位特性曲线,从光腐蚀的角度研究了用恒电位脉冲法沉积钯对单晶n-si光响应的作用。讨论了光电流密度随Pd层沉积量的变化规律,测定了n-si/Pd电极的光极化特性曲线、光谱响应曲线及在强碱溶液中的稳定曲线。     

电沉积Cu2xIn2—2xSe2薄膜的光电化学研究

用电沉积法制得Ｃｕ２ｘＩｎ２－２ｘＳｅ２（铜铟硒）（０＜ｘ＜１）薄膜＾［１］并用ＥＤＡＸ对其组成进行分析。对薄膜电极的光电化学性能、光谱响应、能隙与ｘ的依赖关系进行了研究。借助于现场微区扫描光电流谱观察了热处理、薄膜厚度、光极化对薄膜电极的光电性能影响。研究了Ｐｂ（ＮＯ３）２有效的浸渍对簿膜光电性能的影响。     

TiO2-Pt/Mm（Ni3.4Mn0.4Al0.3Co0.7）电极的可助光充电

1～8 nm的Pt微粒通过光催化分解法沉积在20～50 nm的TiO₂微粒表面,然后把所制备的TiO₂-Pt纳米微粒修饰到富La的贮氢合金电极的表面,形成可助光充电的TiO₂-Pt/Mm（Ni_3.4Mn_0.4Al_0.3Co_0.7）电极（TPM电极）,研究了TPM电极的光电化学、可助光充电行为。结果表明：微小的电流对TPM电极的光充电效应有较强的辅助作用。当TPM电极只被光照时,放出的电量较小;而在光照的同时加上一个微弱的电流,可显著改善其光充电性能。通过交流阻抗谱和循环伏安实验研究了其光充电机理。     

Ti-2Al-1.5Mn合金表面纳米管阵列薄膜的光电化学响应特性研究

采用阳极氧化法在20V条件下氧化3h于TC1(Ti-2Al-1.5Mn)合金表面制备了纳米管阵列薄膜。研究了薄膜的表面形貌及结构,着重考察其作为光电极的开路电位和光生电流响应特性。结果表明,该纳米管膜具有高度有序的纳米管阵列结构,平均管径90nm,管长520nm。经过600℃热处理后,该薄膜电极光电响应速度快,光生电子和空穴的复合少,电子的传输效率高。     

电沉积Cu_（2x）In_（2－2x）Se_2薄膜的光电化学研究

用电沉积法制得Ｃｕ＿（２ｘ）Ｉｎ＿（２－２ｘ）Ｓｅ＿２（铜铟硒）（０＜ｘ＜１）薄膜￣［１］并用ＥＤＡＸ对其组成进行分析．对薄膜电极的光电化学性能、光谱响应、能隙与ｘ的依赖关系进行了研究．借助于现场微区扫描光电流谱观察了热处理、薄膜厚度、光极化对薄膜电极的光电性能影响．研究了Ｐｂ（ＮＯ＿３）＿２有效的浸渍对薄膜光电性能的影响．     

修饰的薄膜CdSe电极／Fe（CN）6^4—溶液界面的电荷转移

本文研究了硬脂酸二茂铁酯L-B膜修饰的薄膜Cdse电极的光诱发界面多相电荷转移过程。通过测量异相电荷转移反应速度常数K_(et),进一步分析了修饰的薄膜CdSe电极光电化学过程的可能反应速度控制步。分析表明界面的电荷转移是反应的速度控制步。薄膜CdSe电极可以通过选择电活性修饰分子和溶液中氧化还原离子来进一步提高和改善其光电化学性能。     

拉氏变换阻抗分析测量CdSe薄膜电极的表面态

在光电化学光能转换的研究中,由于多种因素在半导体/溶液界面形成了各种性质和作用不同的表面态,在界面的电荷和能量转移中起着重要作用,对光电转换性能产生较大的影响。对于多晶半导体——作为具有实用前景和目前深受重视的光电转换材料,由于存在较多的晶格缺陷和晶粒界面,在表面形成了浓度较高的表面态,这些表面态可作为光生电子空穴的复合中心,是造成多晶材料光电转换效率低于单晶材料的主要原因。因此测量和研究半导体/溶液界面的表面态能量分布,性质及作用对研究光电转换过程的机理,特别是对改善多晶半导体的性能都具有直接的重要意义。     

Electrochemical solar cells with polypyrrole-coated CdSe sintered electrodes

A thin layer of polypyrrole was formed on sintered CdSe electrodes. The photoelectrochemical properties of bare CdSe and P-Py/CdSe electrodes were studied in electrolyte with the redox couple [K₃Fe(CN)₆]. The results were explained by assuming that a p-n junction is formed on CdSe electrodes with polypyrrole working as a p-type semiconductor.     

Fabrication and Dielectric Properties of Ba0.63Sr0.37TiO3 Thin Films on SiC Substrates

Ba_0.63Sr_0.37TiO₃ (BST) films were first deposited on SiC substrates with LNO bottom electrodes by magnetron sputtering. The BST/LNO/SiC thin films exhibit high dielectric tunability and low dielectric loss while maintaining excellent temperature coefficient of dielectric constant in the temperature range between 250 and 350 K. We also investigated the effect of film thickness on the dielectric properties. BST(430 nm)/LNO/SiC film has higher tunability (68.09% @700 kV/cm), lower loss tangent (tanδ = 0.00987) and quite a bit higher figure of merit (FOM = 68.99) as compared with that of BST(300 nm)/LNO/SiC film. Our results demonstrate that combining ferroelectric BST films with SiC substrates is very promising for the development of tunable devices over a large temperature range.     

Fabrication & characterization of macroporous CdSe nanostructure via colloidal crystal templating with electrodeposition method

Large area ordered arrays of macroporous Cadmium Selenide (CdSe) nanostructure, which possesses high refractive index and negligible absorption in the visible spectrum critical for the realization of photonic band gaps, was prepared via colloidal templating by galvanostatic electrodeposition. This work investigates the effect of electrodeposition parameters on the macroporous CdSe nanostructure. Field Emission Scanning Electron Microscope (FESEM) images showed two and three dimensional porous structures, consisting of interconnected close-packed arrays of pores. For CdSe thin film of thickness less than 1/3 of the diameter of a polystyrene sphere, it showed a monolayer of circular pores. As for film thickness close to the diameter of the sphere, the pores adopted irregular rounded triangular shapes. When the film thickness was more than one layer of the colloidal polystyrene template, the pores were spherical and had the same diameter as the polystyrene spheres. X-ray Diffraction (XRD) showed that the CdSe films prepared had a cubic structure with nanometer grain size, which was smaller than the diameter of the template spheres as well as the diameter of the interconnected channels. A range of 45–70 nm thick CdSe films with > 90% optical transmittance showed that there was negligible absorption at wavelength of 750 nm. In addition, the CdSe thin film exhibited a band gap energy of 2.07 eV, blue-shifted from the characteristic 1.7 eV of CdSe. This blue-shift characteristic of the deposited CdSe film further indicated that it was nanocrystalline which is potentially useful in photonic applications.     

Fabrication & characterization of macroporous CdSe nanostructure via colloidal crystal templating with electrodeposition method

Large area ordered arrays of macroporous Cadmium Selenide (CdSe) nanostructure, which possesses high refractive index and negligible absorption in the visible spectrum critical for the realization of photonic band gaps, was prepared via colloidal templating by galvanostatic electrodeposition. This work investigates the effect of electrodeposition parameters on the macroporous CdSe nanostructure. Field Emission Scanning Electron Microscope (FESEM) images showed two and three dimensional porous structures, consisting of interconnected close-packed arrays of pores. For CdSe thin film of thickness less than 1/3 of the diameter of a polystyrene sphere, it showed a monolayer of circular pores. As for film thickness close to the diameter of the sphere, the pores adopted irregular rounded triangular shapes. When the film thickness was more than one layer of the colloidal polystyrene template, the pores were spherical and had the same diameter as the polystyrene spheres. X-ray Diffraction (XRD) showed that the CdSe films prepared had a cubic structure with nanometer grain size, which was smaller than the diameter of the template spheres as well as the diameter of the interconnected channels. A range of 45–70 nm thick CdSe films with > 90% optical transmittance showed that there was negligible absorption at wavelength of 750 nm. In addition, the CdSe thin film exhibited a band gap energy of 2.07 eV, blue-shifted from the characteristic 1.7 eV of CdSe. This blue-shift characteristic of the deposited CdSe film further indicated that it was nanocrystalline which is potentially useful in photonic applications.     

Improved performance of dense TiO2/CdSe coupled thin films by low temperature process

Dense TiO₂ and TiO₂/CdSe coupled nanocrystalline thin films were synthesized onto ITO coated glass substrate by chemical route at relatively low temperature (≤100 °C). TiO₂ films were nanocrystalline and crystallinity disappears after CdSe deposition as evidenced by X-ray powder diffraction. Surface morphology and physical appearance of films were studied from SEM and actual photo-images, reveals dense nature of TiO₂ (10-12 nm spherical grains, faint violet) and CdSe (80-90 nm spherical grains, deep brown), respectively. Presence of two absorption edges in UV spectra implies existence of separate phases rather than composite formation. TiO₂ film was found to have higher water contact angle (71°) than TiO₂/CdSe (61°) and CdSe (56°). I-V and stability tests of photo-electrochemical cells were performed with TiO₂ and TiO₂/CdSe film electrodes (under light of illumination intensity 80 mW/cm²) in lithium iodide as an electrolyte using two-electrode system.     

Electrodeposition of polycrystalline ZnTe from simple and citrate-complexed acidic aqueous solutions

The cathodic electrodeposition of polycrystalline zinc telluride from aqueous acidic solutions of zinc sulphate and tellurite, under constant or pulsing voltage, is described. Various compositions of the bath were tested with respect to the Zn/Te precursor ratio, including addition of citrate buffer as a complexation agent. Metallic (Ni and Ti) and semiconductor (CdTe and CdSe) electrodes were used as cathode-substrates. The deposits were characterized by XRD, SEM-EDX and FTIR techniques. The formation of compact barrier layers of zinc blend, stoichiometric ZnTe or mixed (Zn,Cd)Te was attained. Pulse plating in a citrate-free bath and constant potential plating from a citrate bath were seen to have the most beneficial effect on the properties of the electrodeposits, as leading to improved microstructure of the ZnTe films, in terms of crystallinity and stoichiometry. Further, the employment of [1 1 1]-oriented CdTe or CdSe substrates featured an epitaxial growth of polycrystalline ZnTe films as well as an improved Zn/Te atomic ratio compared to the metallic substrates.