电沉积Bi2Te3基薄膜的电化学阻抗谱研究

以不锈钢为基底,利用电化学沉积方法制备Bi2Te3基薄膜材料,并采用X射线衍射技术、电子探针微观分析等方法对薄膜进行结构和成分表征,通过电化学阻抗谱技术对不锈钢表面Bi2Te3的电化学沉积机理进行了初步探讨.结果表明Bi-Te和Bi-Te-Se体系具有相似的电化学沉积机理,即Bi3+和2HTeO+或H2SeO3首先被还原为Bi单质和Te或Se单质,然后Bi单质与Te或Se单质反应生成Bi2Te3基化合物,而Bi-Sb-Te体系中,2HTeO+首先被还原为Te单质,生成的Te再与Bi3+和Sb(III)反应生成Bi2Te3基化合物,三种体系的沉积都受电化学极化控制.     

Bismuth sulfide thin films with low resistivity on self-assembled monolayers

Using self-assembled monolayers (SAMs), highly crystalline bismuth sulfide thin films with low electrical resistivity have been prepared from aqueous solution at low temperature (40-70 degrees C). The nucleation and growth process of Bi2S3 thin films was investigated in detail by XPS, AES, SEM, XRD, SAED, and HRTEM. Solution conditions have marked effects on the microstructure, growth rate, and mechanism of Bi2S3 films. Increased solution temperature resulted in a higher growth rate and a shorter induction time due to a higher supersaturation degree. In the solution of pH 1.12, homogeneous nucleation and the attachment process dominated the formation of Bi2S3 films. In contrast, at pH 0.47 Bi2S3 thin films were formed via heterogeneous nucleation and growth. The c-axial orientation of bismuthinite films was enhanced with the increase of reaction time. By controlling the solution supersaturation and reaction duration, highly crystalline Bi2S3 films composed of closely packed and coalescent crystallites could be realized, whose dark electrical resistivity could reach as low as 0.014 Omega cm without any post-treatment.     

Scrutinizing the facile growth of β-Ag2Se fine films

Silver selenide thin film is one of the best candidates for thermoelectric devices. In the previous report, we demonstrated that high-performanced [201] oriented β-Ag₂Se thin films can be prepared by direct metal surface element reaction (DMSER) solution selenization in a really short time at room temperature. However, the underlying mechanism of the fast reaction process were not discussed in depth. Herein, based on hard soft acid base (HASB) theory and strong oxidation, we further explored the possible reaction mechanism of the in-situ growth of β-Ag₂Se thin films as the function of the reaction time. The time-dependent experimental results showed that the formation of the β-Ag₂Se on elemental Ag precursor (∼690 nm thick) in Se/Na₂S precursor solution is in a growth driven mode with no obvious orientation or growth rate selections to the elemental Ag precursors. Our investigations provide a prerequisite for the further preparation of thermoelectric materials with excellent properties.     

一步法电化学沉积Cu(In1-x,Gax)Se2薄膜的特性

在CuCl2、InCl3、GaCl3及H2SeO3组成的酸性水溶液电沉积体系中, 对Mo/玻璃衬底上一步法电沉积Cu(In1-x, Gax)Se2(简写为CIGS)薄膜进行了研究. 为了稳定溶液的化学性质, 在溶液中加入邻苯二甲酸氢钾和氨基磺酸作为pH缓冲剂, 将溶液的pH值控制在约2.5, 并提高薄膜中Ga的含量. 通过大量实验优化了溶液组成及电沉积条件, 得到接近化学计量比贫Cu 的CIGS薄膜(当Cu与In+Ga的摩尔比为1时, 称为符合化学计量比的CIGS薄膜; 当其比值为0.8-1时, 称为贫Cu或富In的CIGS 薄膜)预置层, 薄膜表面光亮、致密、无裂纹. 利用循环伏安法初步研究了一步法电沉积CIGS薄膜的反应机理, 在沉积过程中, Se4+离子先还原生成单质Se, 再诱导Cu2+、Ga3+和In3+发生共沉积. 电沉积CIGS薄膜预置层在固态硒源280 ℃蒸发的硒气氛中进行硒化再结晶, 有效改善了薄膜的结晶结构, 且成份基本不发生变化,但是表面会产生大量的裂纹.     

Synthesis and characterization of self-assembled c-axis oriented Bi2Sr3Co2O(y) thin films by the sol-gel method

Bi(2)Sr(3)Co(2)O(y) thin films are prepared on SrTiO(3) (100), (110) and (111) single crystal substrates using the sol-gel method. All the thin films are c-axis oriented regardless of the orientation of the substrate suggesting self-assembled c-axis orientation, and X-ray photoelectron spectroscopy results give evidence of coexistence of Co(3+) and Co(2+) ions in the derived films. Transmission electronic microscopy observations reveal that all samples are c-axis oriented with no obvious differences for different samples, and the c-axis lattice constant is determined as ~15 ? suggesting the misfit structure. A phenomenological thermodynamic phase diagram for self-assembled c-axis orientation is established for misfit cobaltate-based films using chemical solution deposition. All samples behave like semiconductors due to the coexistence of Co(3+)/Co(2+) ions, and the resistivity at 350 K is ~47, 39 and 17 mΩ cm for the thin films on SrTiO(3) (100), (110) and (111), respectively, whereas the Seebeck coefficient at 300 K is 97, 89 and 77 μV K(-1). The successful attainment of Bi(2)Sr(3)Co(2)O(y) thin films with self-assembled c-axis orientation will provide an effective prototype for investigation of growth mechanisms in complex oxide thin films with a misfit structure.     

A new chalcogenide homologous series A2[M(5+n)Se(9+n)] (A = Rb, Cs; M = Bi, Ag, Cd)

The ternary and quaternary selenides, beta-CsBi3Se5, Rb2CdBi6Se11, CsAg(0.5)Bi(3.5)Se6, CsCdBi3Se6, Rb2Ag(1.5)Bi(7.5)Se13, and Cs2Ag(1.5)Bi(7.5)Se13, are all members of the new homologous series A2[M(5+n)Se(9+n)] and crystallize in structures related to each other in a systematic way; these compounds are mid gap semiconductors and are of interest as thermoelectric materials.     

Tropochemical cell-twinning in the new quaternary bismuth selenides KxSn(6-2x)Bi(2+x)Se9 and KSn5Bi5Se13

The quaternary K(x)Sn(6-2x)Bi(2+x)Se(9) and KSn(5)Bi(5)Se(13) were discovered from reactions involving K(2)Se, Bi(2)Se(3), Sn, and Se. The single crystal structures reveal that K(x)Sn(6-2x)Bi(2+x)Se(9) is isostructural to the mineral heyrovskyite, Pb(6)Bi(2)S(9), crystallizing in the space group Cmcm with a = 4.2096(4) A, b = 14.006(1) A, and c = 32.451(3) A while KSn(5)Bi(5)Se(13) adopts a novel monoclinic structure type (C2/m, a = 13.879(4) A, b = 4.205(1) A, c = 23.363(6) A, beta = 99.012(4) degrees ). These compounds formally belong to the lillianite homologous series xPbS.Bi(2)S(3), whose characteristic is derivation of the structure by tropochemical cell-twinning on the (311) plane of the NaCl-type lattice with a mirror as twin operation. The structures of K(x)Sn(6-2x)Bi(2+x)Se(9) and KSn(5)Bi(5)Se(13) differ in the width of the NaCl-type slabs that form the three-dimensional arrangement. While cell-twinning of 7 octahedra wide slabs results in the heyrovskyite structure, 4 and 5 octahedra wide slabs alternate in the structure of KSn(5)Bi(5)Se(13). In both structures, the Bi and Sn atoms are extensively disordered over the metal sites. Some physicochemical properties of K(x)Sn(6-2x)Bi(2+x)Se(9) and KSn(5)Bi(5)Se(13) are reported.     

溶胶-凝胶法制备高取向Bi4Ti3O12/SrTiO3(100)薄膜

Bi4Ti3O12具有良好的铁电、电光等性能山、特别是Bi4Ti3O12薄膜很适合作永久性存储材料，也可用于电光器件问．在微电子学、光电子学、集成光学、集成铁电学等领域均有广泛开发和应用前景，国外已用溅射法、激光沉积法制备出c轴取向Bi。Ti3Ol。薄膜【’，＼山东大学用MOCVD法制     

Optimization of the electrodeposition process of high-performance bismuth antimony telluride compounds for thermoelectric applications

High-quality films of bismuth antimony telluride were synthesized by electrodeposition from nitric acid electroplating baths. The influence of a surfactant, sodium ligninsulfonate, on the structure, morphology, stoichiometry, and homogeneity of the deposited films has been investigated. It was found that addition of this particular surfactant significantly improved the microstructural properties as well as homogeneity of the films with a significant improvement in the thermoelectric properties over those deposited in the absence of surfactant. A detailed microprobe analysis of the deposited films yielded a stoichiometric composition of Bi(0.35)Sb(1.33)Te(3) for the films electrodeposited in the absence of surfactant and a stoichiometry of Bi(0.32)Sb(1.33)Te(3) for films deposited in the presence of surfactant.     

Thermoelectric properties of nanocomposite thin films prepared with poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) and graphene

Carbon nanotubes (CNTs), either single wall carbon nanotubes (SWNTs) or multiwall carbon nanotubes (MWNTs), can improve the thermoelectric properties of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT?:?PSS), but it requires addition of 30-40 wt% CNTs. We report that the figure of merit (ZT) value of PEDOT?:?PSS thin film for thermoelectric property is increased about 10 times by incorporating 2 wt% of graphene. PEDOT?:?PSS thin films containing 1, 2, 3 wt% graphene are prepared by solution spin coating method. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses identified the strong π-π interactions which facilitated the dispersion between graphene and PEDOT?:?PSS. The uniformly distributed graphene increased the interfacial area by 2-10 times as compared with CNT based on the same weight. The power factor and ZT value of PEDOT?:?PSS thin film containing 2 wt% graphene was 11.09 μW mK(-2) and 2.1 × 10(-2), respectively. This enhancement arises from the facilitated carrier transfer between PEDOT?:?PSS and graphene as well as the high electron mobility of graphene (200,000 cm(2) V(-1) s(-1)). Furthermore the porous structure of the thin film decreases the thermal conductivity resulting in a high ZT value, which is higher by 20% than that for a PEDOT?:?PSS thin film containing 35 wt% SWNTs.     

Structure and thermoelectric properties of the new quaternary bismuth selenides A(1-x)M(4-x)Bi(11+x)Se21 (A = K and Rb and Cs; M = Sn and Pb)--members of the grand homologous series Km(M6Se8)m(M(5+n)Se(9+n))

Several members of the new family A(1-x)M(4-x)Bi(11+x)Se21 (A = K, Rb, Cs; M = Sn, Pb) were prepared by direct combination of A2Se, Bi2Se3, Sn (or Pb), and Se at 800 degrees C. The single-crystal structures of K(0.54)Sn(3.54)Bi(11.46)Se21, K(1.46)Pb(3.08)Bi(11.46)Se21, Rb(0.69)Pb(3.69)Bi(11.31)Se21, and Cs(0.65)Pb(3.65)Bi(11.35)Se21 were determined. The compounds A(1-x)M(4-x)Bi(11+x) Se21 crystallize in a new structure type with the monoclinic space group C2/m, in which building units of the Bi2Te3 and NaCl structure type join to give rise to a novel kind of three-dimensional anionic framework with alkali-ion-filled tunnels. The building units are assembled from distorted, edge-sharing (Bi,Sn)Se6 octahedra. Bi and Sn/Pb atoms are disordered over the metal sites of the chalcogenide network, while the alkali site is not fully occupied. A grand homologous series Km(M6Se8)m(M(5+n)Se(9+n)) has been identified of which the compounds A(1-x)M(4-x)Bi(11+x)Se21 are members. We discuss here the crystal structure, charge-transport properties, and very low thermal conductivity of A(1-x)M(4-x)Bi(11+x)Se21.     

Bismuth telluride (Bi2Te3) nanowires: synthesis by cyclic electrodeposition/stripping, thinning by electrooxidation, and electrical power generation

Nanowires composed of the thermoelectric material Bi2Te3 were synthesized on highly oriented pyrolytic graphite (HOPG) electrodes using the electrochemical step edge decoration (ESED) method. Nanowire synthesis was initiated by applying a voltage pulse of -0.75 V versus SCE for 5 ms to an HOPG electrode in an aqueous solution containing both Bi3+ and TeO22-, thereby producing nuclei at the step edges. Bi2Te3 was electrodeposited onto these nuclei using a cyclic electrodeposition-stripping scheme that involved the electrodeposition of bismuth-rich Bi2Te3 on a negative-going voltammetric scan (to -0.05 V) and the subsequent anodic stripping of excess bismuth from these nanowires during a positive-going scan (to +0.35 V). When this cycle was repeated 10-50 times, Bi2Te3 nanowires in the 100-300-nm-diameter range were obtained. These nanowires were narrowly dispersed in diameter (RSDdia = 10-20%), were more than 100 microm in length, and were organized into parallel arrays containing hundreds of wires. Smaller nanowires, with diameters down to 30 nm, were obtained by electrooxidizing 150-nm-diameter Bi2Te3 nanowires at +0.37 V under conditions of kinetic control. This oxidation process unexpectedly improved the uniformity of Bi2Te3 nanowires, and X-ray photoelectron spectroscopy (XPS) shows that these nanowires retain a Bi2Te3 core but also have a thin surface layer composed of Bi and Te oxides. The ability of Bi2Te3 nanowires to generate electrical power was assessed by transferring ensembles of these nanowires onto cyanoacrylate-coated glass surfaces and evaporating 4-point nickel contacts. A dimensionless figure of merit, ZT, ranging from 0 to 0.85 was measured for fresh samples that were less than 1 day old. XPS reveals that Bi2Te3 nanowires are oxidized within a week to Bi2O3 and TeO2. These oxides may interfere with the application by evaporation of electrical contacts to these nanowires.     

Structure and Optical Properties of 0.1BiFeO3-0.9SrBi2Nb2O9 Thin Films Using a Modified Sol-Gel Technique

Fe-doped SrBi₂Nb₂O₉ precursor solution was synthesized using bismuth nitrate Bi(NO₃)₃·5H₂O, strontium nitrate Sr(NO₃)₂, iron nitrate Fe(NO₃)₃·9H₂O, and niobium ethoxide Nb(OC₂H₅)₅ as starting materials, ethylene glycol monomethyl ether (C₃H₈O₂) as the solvent. 0.1BiFeO₃-0.9SrBi₂Nb₂O₉ thin films were prepared on fused quartz substrates using sol-gel processing. The surface morphology and crystal structure and optical properties of the thin films were investigated. The thin film annealing at 400°C were found to be amorphous, and the thin films crystallize to a perovskite structure after a post-deposition annealing at 600°C for 1 h in air. The grain of thin film was evenly distributed. The thin films exhibit the designed optical transmission, while the optical transition is indirect in nature. Their optical band gap is about 2.5 eV.     

Nanostructured Bi(2-x)Cu(x)S3 bulk materials with enhanced thermoelectric performance

Nanostructured Bi(2-x)Cu(x)S(3) (x = 0, 0.002, 0.005, 0.007, 0.01, 0.03) thermoelectric polycrystals were fabricated by combining mechanical alloying (MA) and spark plasma sintering (SPS) methods. The effect of Cu content on the microstructure and thermoelectric property of Bi(2-x)Cu(x)S(3) bulk samples was investigated. It was found that the subtle tailoring of Cu content could reduce both the electrical resistivity and the thermal conductivity at the same time, and consequently enhancing the thermoelectric property. A low electrical resistivity of 1.34 × 10(-4)Ω m(-1) and a low thermal conductivity of 0.52 W m(-1) K(-1) were obtained for the Bi(1.995)Cu(0.005)S(3) sample at 573 K. The low thermal conductivity is supposed to be due to the nanoscopic Cu-rich regions embedded in the host matrix. A peak ZT value of 0.34 at 573 K was achieved for the Bi(1.995)Cu(0.005)S(3) composition, which is the highest value in the Bi(2)S(3) system reported so far.     

以乙醇作溶剂电沉积制备CIGS薄膜

利用恒电位电沉积法在以乙醇为溶剂的溶液中制备了铜铟镓硒(CIGS)薄膜.并采用扫描电子显微镜(SEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)和紫外-可见-近红外(UV-VIS-NIR)分光光度计分别对薄膜的形貌、成分、晶体结构和吸收特性进行了表征.结果表明在-1.6V(相对于饱和甘汞电极电位)工作电位下沉积的薄膜经450°C退火后能够形成形貌均匀致密、结晶性良好、带隙约为1.17eV的黄铜矿结构CuIn0.7Ga0.3Se2薄膜.实验过程中发现,以乙醇为溶剂可以有效避免在水溶液中出现的析氢现象,减小了沉积电位的限制.     

单步电沉积法制备CuInS2薄膜

采用单步电沉积法在Mo基底上制备了高质量的CuInS2薄膜. 用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了样品的结构和形貌, 研究了沉积电位、退火温度、pH值、反应物浓度等工艺条件对制备的CuInS2薄膜形貌、组分及性能的影响. 制备的CuInS2薄膜致密平整, 呈黄铜矿结构, 晶粒大小为1-2 μm. 用紫外-可见光分光光度计测试了其光学性能, 计算得到常温下禁带宽度为1.41 eV, 非常适合用作薄膜太阳电池的吸收层材料.     

Systematic study on structural phase behavior of CdSe thin films

Cadmium selenide (CdSe) thin films were chemically deposited at room temperature, from aqueous ammoniacal solution using Cd(CH(3)COO)(2) as Cd2+ and Na(2)SeSO(3) as Se2- ion sources. The as-deposited films were uniform, well adherent to the glass substrate, specularly reflective, and red-orange in color. The as-deposited CdSe layers grew with nanocrystalline sphalerite cubic structure along with the amorphous phase present in it, with optical band gap E(g) = 2.3 eV. The films were annealed in air atmosphere for 4 h at different temperatures and characterized for compositional, structural, morphological, and optical properties. XRD and SEM studies clearly revealed the systematic phase transformation of CdSe films from metastable nanocrystalline cubic (zinc blende type) to a mixture of cubic and hexagonal (wurtzite type), and finally into stable hexagonal through different intermediate phases with an improvement in the crystal quality. The films showed a red shift in their optical spectra after annealing.     

Indium selenide thin film preparation by sol–gel technique

Preparation and characterization of In–Se compound thin films prepared by sol–gel methods on glass substrate have been studied. X-ray diffraction analyses and optical transmission spectrum of In–Se compound thin film samples show that the fabricated sol–gel In–Se thin films features formed mainly as an In₂Se₃ crystal structure. From transmission spectra of In–Se thin films band gap energy were estimated approximately as ∼1.24 eV.     

Electrochemical Synthesis of In2Se3 Thin Films from Citrate Bath. Structural,Optical and Morphological Investigations

Russian Journal of Electrochemistry - In this work, indium selenide In2Se3 thin films were synthesized by electrodeposition in potentiostatic mode from aqueous solution containing InCl3 and SeO2 in...     

Film-forming microgels for pH-triggered capture and release

The pH-responsive behavior for a series of lightly cross-linked, sterically stabilized poly(tertiary amine methacrylate)-based latexes adsorbed onto mica and silica was investigated using in situ tapping mode AFM at room temperature. The adsorbed layer structure was primarily determined by the glass transition temperature, T(g), of the latex: poly[2-(diethylamino)ethyl methacrylate]-based particles coalesced to form relatively featureless uniform thin films, whereas the higher T(g) poly[2-(diisopropylamino)ethyl methacrylate] latexes retained their original particulate character. Adsorption was enhanced by using a cationic poly[2-(dimethylamino)ethyl methacrylate] steric stabilizer, rather than a nonionic poly(ethylene glycol)-based stabilizer, since the former led to stronger electrostatic binding to the oppositely charged substrate. Both types of adsorbed latexes acquired cationic microgel character and swelled appreciably at low pH, even those that had coalesced to form films. Fluorescence spectroscopy was used to study the capture of a model hydrophobic probe, pyrene, by these adsorbed latex layers followed by its subsequent release by lowering the solution pH. The repeated capture and release of pyrene through several pH cycles was also demonstrated. Since these poly(tertiary amine methacrylate) latexes are readily prepared by aqueous emulsion polymerization and adsorption occurs spontaneously from aqueous solution, this may constitute an attractive route for the surface modification of silica, mica and other oxides.