Thin-layer electrochemical studies of the underpotential deposition (UPD) of Bi and Te on cold rolled silver substrate have been performed. The voltammetric analysis of underpotential shift demonstrates that the initial Te UPD on Bi-covered Ag and Bi UPD on Te-covered Ag fitted UPD dynamics mechanism. A thin film of bismuth telluride was formed by alternately depositing Te and Bi via an automated flow deposition system. X-ray diffraction indicated the deposits of Bi2Te3. Energy Dispersive X-ray Detector quantitative analysis gave a 2: 3 stoichiometric ratio of Bi to Te, which was consistent with X-ray Diffraction results. Electron probe microanalysis of the deposits showed a network structure that results from the surface defects of the cold rolled Ag substrate and the lattice mismatch between substrate and deposit.

The process of Sb 2 Te 3 thin film growth on the Pt substrate by electrochemical atomic layer epitaxy (ECALE) was studied. Cyclic voltammetric scanning was performed to analyze the electrochemical behavior of Te and Sb on the Pt substrate. Sb 2 Te 3 film was formed using an automated flow deposition system by alternately depositing Te and Sb atomic layers for 400 circles. The deposited Sb 2 Te 3 films were characterized by XRD, EDX, FTIR and FESEM observation. Sb 2 Te 3 compound structure was confirmed by XRD pattern and agreed well with the results of EDX quantitative analysis and coulometric analysis. FESEM micrographs showed that the deposit was composed of fine nano particles with size of about 20 nm. FESEM image of the cross section showed that the deposited films were very smooth and dense with thickness of about 190 nm. The optical band gap of the deposited Sb 2 Te 3 film was determined as 0.42 eV by FTIR spectroscopy, and it was blue shifted in comparison with that of the bulk Sb 2 Te 3 single crystal due to its nanocrystalline microstructure.

研究了利用电化学原子层外延法（electrochemical atomic layer epitaxy,ECALE）在Pt电极上生长Sb2Te3化合物半导体薄膜热电材料的过程.采用循环伏安扫描分别研究了Te和Sb在Pt衬底上以及在覆盖了一层元素之上的电沉积特性,在此基础上使用自动沉积系统交替电化学沉积了400个Te和Sb原子层.采用XRD,FESEM和FTIR等多种分析测试手段对沉积薄膜的结构、形貌、禁带宽等进行了表征.XRD结果表明,沉积物是Sb2Te3化合物,与EDX定量分析和电量计算结果吻合;FESEM对薄膜表面及断面形貌检测表明沉积颗粒排列紧密、大小均匀,平均粒径约为20nm,薄膜均匀平坦,膜厚约190nm;由于沉积薄膜的纳米结构,FTIR吸收谱出现蓝移,测得Sb2Te3薄膜禁带宽为0.42eV.

The Bi_2Te_3 thin film deposition on Au substrate using electrochemical atomic layer epitaxy(ECALE) is reported in this article.Cyclic voltammograms of Bi and Te on the Au substrate were performed to investigate electrochemical aspects of tellurium and bismuth.200 cycle deposits were formed by using an optimized deposition program.X-ray diffraction,EDX quantitative analysis and FESEM studies of the morphology of substrates and deposits indicated the stoichiometric ratio of Bi to Te is 2∶3;the deposits are Bi_2Te_3,not mixture of Bi and Te;the quality of the deposits are symmetrical,compact and glazed,with a(015) preferred orientation,which suggested an epitaxy growth mechanism of Bi_2Te_3 thin films has taken place.

A nanocrystalline Sb2Te3 VA-VIA group compound thin film was grown via the route of electrochemical atomic layer epitaxy (ECALE) in this work for the first time. The electrochemical behavior of Te and Sb on Pt, Te on Sb-covered Pt, and Sb on Te-covered Pt was studied by methods of cyclic voltammetry, anode potentiodynamic scanning, and coulometry. A steady deposition of the Sb2Te3 compound could be attained after negatively stepped adjusting of the UPD potentials of Sb and Te on Pt in each of the first 40 depositing cycles. The structure of the deposit was proven to be the Sb2Te3 compound by X-ray diffraction. The 2:3 stoichiometric ratio of Sb to Te was verified by EDX quantitative analysis, which is consistent with the result of coulometric analysis. A nanocystalline microstructure was observed for the Sb2Te3 deposits, and the average grain size is about 20 nm. Cross-sectional SEM observation shows an interface layer about 19 nm in thickness sandwiched between the Sb2Te3 nanocrystalline deposit and the Pt substrate surface. The optical band gap of the deposited Sb2Te3 film Was determined as 0.42 eV by FTIR spectroscopy and it is blueshifted in comparison with that of the bulk Sb2Te3 single crystal because of its nanocrystalline microstructure.

The developing status of thermoelectric materials was reviewed and the mechanism for nanostructured thermoelectric materials to enhance the figure of merit was discussed in this paper.A new methord named as electrochemical atomic layer epitaxy(ECALE),which uses underpotentional deposition (UPD) to restrict 3D growth and realize 2D growth,was introduced and discussed for preparation of thin film and superlattice.At last,some vital factors involved in ECALE were pointed out and the developing trends of thermoelectric materials and device were summarized.

Electrochemical atomic layer epitaxy(ECALE)is a combination of two feasible growth techniques, the electrochemical deposition and atomic layer epitaxy.The growth involves the alternating electro-deposition of each component elment of a compound,one monolayer at a time by underpotential deposition that is critical in ECALE.In this paper,the principle and characteristics of ECALE is introduced in detail,and the main factors influencing the ECALE progress are analyzed.Besides,the research progress of ECALE used in preparation of new materials is re- viewed.

The waveplate is a usual but important component in optical system. Generally, λ/2 (or λ/4) waveplate is work at specifically wavelength. If the wavelength of the wave is not match to that of the waveplate, the phase retardation of wave would not π (or π/2). The broadband waveplate which the phase retardation is same in its bandwidth is widely used in spectrum shaping, laser tuning and optical communication. In this paper, an infrared three-stage waveplate is designed with the feature of wide band and high-resolution by the aid of computer simulation. The result of experiment turns to be high consistency with the design. The appropriate wavelength range of the waveplate is 1200～1650 nm. The central wavelength is 1390 nm. The phase retardation for λ/2 complex waveplate is 180.0°±3.6° and 90.0°±3.6° for λ/4 ones.