退火对高压烧结Gd掺杂Bi_2Te_(2.7)Se_(0.3)纳米晶热电性能的影响

以Bi粉、Te粉、Se粉、Sb I3粉、Gd粉为原料,用高压烧结法制备了Gd掺杂的n型Bi2Te2.7Se0.3热电材料,对制备的样品分别在573、603、633 K真空退火36 h。用粉末XRD和FE-SEM研究了样品的物相及显微形貌;在298~473K范围内测定了样品的热电性能。建立了Bi2Te3基材料的禁带宽度与压力和体积的近似关系式,利用此关系式较好解释了高压烧结样品在退火前后热电性能的变化特性。研究结果表明制备的样品在退火前后均为纳米结构。高压烧结和Gd掺杂使样品晶胞尺寸变大,禁带宽度减小。退火使高压烧结样品的电导率提高,塞贝克系数增大,热导率降低。样品于633 K退火36 h后具有较好的热电性能,在423 K时其ZT达到最大值为0.74。     

Bi2-xSbxTe3热电薄膜的电化学沉积及表征

采用电化学沉积法,在ITO导电玻璃及钛片上沉积Bi2-xSbxTe3热电薄膜。采用循环伏安、SEM、XRD、EDX等技术分别对电化学沉积过程和薄膜的形貌、相结构、组成进行研究,并对其室温时的热电性能进行测试。结果表明,在含有Bi3＋、HTeO2+和SbO+的硝酸溶液中,采用控电位沉积模式,可以实现铋、锑、碲三元共沉积,得到Bi2-xSbxTe3薄膜。薄膜热处理前用冷等静压处理可以提高薄膜的密实度和平整度,并有利于热电性能的提高。     

FERROELECTRIC CHARACTERISTICS OF SrBi2Ta2O9 THIN FILMS ANNEALED IN FORMING GAS

1. IlltroductionRecently, SrBi2Ta2O9 (SBT) thin films had been attracting considerable attention forapplication to nonvolatile ferroelectric random access memory (FeRAM). It had been re-ported that SBT thin films had superior properties of free--fatigue and Iow leakage currentllJ.However, it was a serious problem that fOrming gas (5%H2+95%N2) annealing could causethe severe degradation of SBT thin films in ferroelectric polarization. It had been suggestedthat the origin of H2 damage …     

Effect of sputtering pressure and rapid thermal annealing on optical properties of Ta2O5 thin films

Ta2O5 thin films were deposited by DC reactive magnetron sputtering followed by rapid thermal annealing(RTA). Influence of sputtering pressure and annealing temperature on surface characteristics, microstructure and optical property of Ta2O5 thin films were investigated. As-deposited Ta2O5 thin films are amorphous. It takes hexagonal structure (δ-Ta2O5) after being annealed at 800 ℃. A transition from δ-Ta2O5 to orthorhombic structure (L-Ta2O5) occurs at 900-1 000 ℃. Surface roughness is decreased after annealing at low temperature. Refractive index and extinction coefficient are decreased when annealing temperature is increased.     

铁酸铋薄膜退火工艺研究进展

铁酸铋(BFO)多铁性材料因具有丰富的物理性能,以及其在存储器、传感器、电容器、光伏器件等方面的广阔应用前景,在过去几十年一直受到广泛的关注。然而,由于Bi元素在高温下容易挥发,所以很难合成纯相的BFO薄膜。此外,因存在氧空位或由于Fe离子变价导致的非化学计量比等缺陷,使其漏电流密度较大,严重影响BFO薄膜的铁电性能及实际应用。退火工艺是影响材料微结构及宏观性能的重要因素,因此通过退火工艺来调控BFO薄膜的结构及性能是一种十分有效的手段。然而,退火工艺包括退火时间、退火气氛、退火温度以及退火方式等多种形式,究竟每一种退火形式如何影响BFO薄膜的结构及性能是值得探讨的问题。为此,综述了退火工艺(括退火时间、退火气氛、退火温度以及退火方式)对BFO薄膜的结构(晶粒尺寸、形状,电畴尺寸、类型,表面形貌)和性能(磁性、铁电性、介电性、漏电性、导电机制)的影响的研究进展,并提出了一些亟待解决的问题。     

Ga、K双掺杂对N型Bi_2Te_(2.7)Se_(0.3)材料热电性能的影响

采用真空熔炼及热压方法制备了Ga和K双掺杂N型Bi2Te2.7Se0.3热电材料。XRD分析结果表明,Ga和K已经完全固溶到Bi2Te2.7Se0.3晶体结构中,形成了单相固溶体合金。SEM分析表明,材料组织致密且有层状结构特征。通过Ga和K部分替代Bi,在300~500 K的大部分温度范围内,Ga和K双掺杂对提高Bi2Te2.7Se0.3的Seebeck系数产生了积极的作用,同时双掺杂样品的电导率也得到明显的提高。Ga和K双掺杂样品的热导率都大于未掺杂的Bi2Te2.7Se0.3,Ga0.02Bi1.94K0.04Te2.7Se0.3合金在500 K获得ZT最大值为1.05。     

钛酸铋薄膜的磁控溅射及其退火处理

采用射频磁控溅射技术,在Pt/Ti/SiO2/Si衬底上制备了钛酸铋(Bi4Ti3O12,简称BIT)薄膜。研究了衬底温度及后续退火处理对薄膜结构和表面形貌的影响。结果表明:适宜的衬底温度为200℃。随着退火温度(650~800℃)的升高,BIT薄膜的结晶性变好,晶粒尺寸增大,c轴取向增强。当退火温度达到850℃时,开始出现焦绿石相;700~800℃为适宜的退火温度,在此条件下得到的BIT薄膜结晶良好,尺寸均匀,表面平整致密。     

机械合金化法制备的Mn15Bi34Te51和La15Bi34Te51热电材料

用机械合金化法制备了Mn15Bi34Te51和La15Bi34Te51合金，XRD分析表明Mn15Bi34Te51和La15Bi34Te51分别在真空球磨150h和100h后实现合金化，La15Bi34Te51在真空球磨150h后形成了纳米结构的合金，镧原子的加入有助于Bi2Te3基合金的晶粒细化及非晶化。对La15Bi34Te51合金的XRD结构分析表明镧原子有可能进入了Bi2Te3层状结构的Te-Te原子层间。La15Bi34Te51合金Seebeck系数的测量表明当晶粒尺寸减小到纳米尺寸时，载流子散射机制有可能发生改变，导致了Seebeck系数的大幅上升。     

Ga、K双掺杂P型Bi_(0.5)Sb_(1.5)Te_3材料的制备及热电性能

采用真空熔炼和热压方法制备了Ga和K双掺杂Bi0.5Sb1.5Te3热电材料。XRD结果表明,Ga0.02Bi0.5Sb1.48-x Kx Te3块体材料的XRD图谱与Bi0.5Sb1.5Te3的XRD图谱对应一致,但双掺杂样品的衍射峰略微向左偏移。热压块体材料中存在明显的(00l)晶面择优取向。SEM形貌表明材料组织致密且有层状结构特征。Ga和K双掺杂可使Bi0.5Sb1.5Te3在室温附近的Seebeck系数有一定的提高,而双掺杂样品的电导率均得到了不同程度的提高,其中Ga0.02Bi0.5Sb1.42K0.06Te3样品的电导率得到较明显的改善。在300~500 K测量温度范围内,所有双掺杂样品的热导率高于Bi0.5Sb1.5Te3的热导率,在300 K附近双掺杂样品的ZT值得到提高,其中Ga0.02Bi0.5Sb1.42K0.06Te3样品在300 K时ZT值达到1.5。     

EFFECT OF ANNEALING TREATMENT ON THE STRUCTURE OF CdS FILMS

The effect of annealing treatment on the structure of CdS films was investigated. The cadmium sulfide thin films were prepared by chemical bath deposition, and were annealed at nitrogen atmosphere at different temperatures. The films were characterized by SEM and XPS (X-ray photoelectron spectroscopy). X-ray photoelectron spectroscopy was used to examine the chemical states on the CdS films surface. It was found that thermal annealing could produce large grains of CdS thin films, remove the air contamination and reduce the oxygen content on the CdS films surface. Therefore, the CdS films changed more uniform and smoother surface after thermal annealing.     

Synthesis,Fabrication and Characterization of ZnO-Based Thin Films Prepared by Sol–Gel Process and H<Subscript>2</Subscript> Gas Sensing Performance

In this paper, an attempt is made to deposit ZnO thin films using sol–gel process followed by dip-coating method on p-silicon (100) substrates for intended application as a hydrogen gas sensor owing to the low toxic nature and thermal stability of ZnO. The thin films are annealed under annealing temperatures of 350, 450 and 550 °C for 25 min. The crystalline quality of the fabricated thin films is then analyzed by field-emission scanning electron microscopy and transmission electron microscope. The gas sensing performance analysis of ZnO thin films is demonstrated at different annealing temperatures and hydrogen gas concentrations ranging from 100 to 3000 ppm. Results obtained show that the sensitivity is significantly improved as annealing temperature increases with maximum sensitivity being achieved at 550 °C annealing temperature and operating temperature of 150 °C. Hence, the modified ZnO thin films can be applicable as H₂ gas sensing device showing to the improved performance in comparison with unmodified thin-film sensor.     

Characterization of rapid thermally processed LiMn204 thin films derived from solution deposition

Cathode material LiMn₂O₄ thin films were prepared through solution deposition followed by rapid thermal annealing. The phase identification and surface morphology were studied by X-ray diffraction and scanning electron microscopy. Electrical and electrochemical properties were examined by four-probe method, cyclic voltammetry and galvanostatic charge-discharge experiments. The results show that the film prepared by this method is homogeneous, dense and crack-free. As the annealing temperature and annealing time increase, the electronic resistivity decreases, while the capacity of the films increases generally. For the thin films annealed at different temperatures for 2 min, the thin film annealed at 800 °C has the best cycling behavior with the capacity loss of 0.021% per cycle. While for the thin films annealed at 750 °C for different times, the film annealed for 4 min possesses the best cycling performance with a capacity loss of 0.025% per cycle. For the lithium diffusion coefficient in LiMn₂O₄ thin film, its magnitude order is 10⁻¹¹ cm²·s⁻¹.     

Analysis of Temperature Dependence of Phases and Surface Morphology of Bi2Sr2Cax-1CuxOy Thin Films Using Reactive Co-Deposition Method

A reactive co-deposition processing for obtaining high-quality single-phase Bi2Sr2Cax-1CuxOy (Bi2212) thin films has been investigated using molecular beam epitaxy (MBE) with 2.7 × 10-3Pa ozone gas introduction for oxidation. The thin films with a constant composition of almost 2 : 2 : 1 : 2 were designed to be fabricated at the substrate temperature between 675 and 780℃, the substrate temperature dependence of the surface morphology and the emergence phases were investigated in detail. A noticeable result is that the distribution of Cu element in the thin films is sensitively changed with the substrate temperature. At 750℃ it is inclined to locate in the periphery of each grain through the diffusion process. At 780℃ the Cu-compositional fluctuation brought around the dendritic crystal growth in the thin films. Below 705℃, the Bi2212 single-phase cannot be achieved in the thin films.     

Growth of bismuth telluride thin film on Pt by electrochemical atomic layer epitaxy

An automated thin-layer flow cell electrodeposition system was developed for growing Bi2Te3 thin film by ECALE. The dependence of the Bi and Te deposition potentials on Pt electrode was studied. In the first attempt,this reductive Te underpotential deposition (UPD)/reductive Bi UPD cycle was performed to 100 layers. A better linearity of the stripping charge with the number of cycles has been shown and confirmed a layer-by-layer growth mode, which is consistent with an epitaxial growth. The 4 : 3 stoichiometric ratio of Bi to Te suggests that the incomplete charge transfer in HTeO reduction excludes the possibility of Bi2Te3 formation. X-ray photoelectron spectroscopy (XPS) analysis also reveals that the incomplete charge transfer in HTeO2^ occurs in Te direct deposition. The effective way of depositing Bi2Te3 on Pt consists in oxidative Te UPD and reductive Bi UPD. The thin film deposited by this procedure was characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). A polycrystalline characteristic was confirmed by XRD. The 2 : 3 stoichiometric ratio was confirmed by XPS. The SEM image indicates that the deposit looks like a series of buttons about 0.3 - 0.4/~m in diameter, which is corresponding with calculated thickness of the epitaxial film. This suggests that the particle growth appears to be linear with the number of cycles, as it is consistent with a layer by layer growth mode.     

Optical properties of Se or S-doped hydrogenated amorphous silicon thin films with annealing temperature and dopant concentration

We report the effects of the thermal annealing and dopant concentration on the optical properties of Se or S-doped hydrogenated amorphous silicon thin films. The Se and S-doped a-Si:H (a-Si,Se:H and a-Si,S:H) thin films were prepared by glow discharge plasma enhanced chemical vapor deposition (GD-PECVD) on 7059 corning glass. The films were subsequently annealed in vacuum in the temperature range from 100 to 500 °C. Influence of doping and annealing was examined by means of optical transmission spectroscopy of the films in the wavelength range of 300-1100 nm taken at room temperature. The absorption coefficients and refractive indices decreased as the annealing temperature increased from 100 to 300 °C and then increased again as the annealing temperature further increased to 500 °C, while the highest bandgap was observed at 300 °C for all of the samples. For a given dopant concentration bandgap was observed to be higher in a-Si,S:H than a-Si,Se:H thin films.     

Optical Constant and Electrical Resistivity of Annealed Sn_3Sb_2S_6 Thin Films

In this study,we report the annealing effects on the physical properties of Sn_3Sb_2S_6 thin films.Sn_3Sb_2S_6 thin films were prepared onto non-heated glass substrates via thermal evaporation technique.The as-deposited films were annealed in air for 1 h in the temperature range from 100 to 300 °C.X-ray diffraction results show that the crystallinity of the thin films increased after annealing.The microstructure parameters crystallite size,dislocation density,lattice strain and stacking fault probability were calculated.The optical properties were obtained from the analysis of the experimental recorded transmittance and reflectance spectral data over the wavelength range 300–1800 nm.High absorption coefficient(10~5cm~(-1)) reached to the visible and near-IR spectral range.A decrease in optical band gap from 1.92 to 1.71 e V by increasing the air annealing temperature was observed.Oscillator energy E_o and dispersion energy E_d of the films after annealing were estimated according to the model of Wemple–Di Domenico single oscillator.Spitzer–Fan model was applied to determine the electron free carrier susceptibility and the ratio of carrier concentration to the effective mass.The layers annealed at temperatures 150 ℃ undergo abrupt changes in their electrical properties and exhibit a resistive hysteresis behavior.These properties confer to the material interest perspectives for its application in diverse advanced technologies such as photovoltaic applications and optical storage.     

Effect of annealing temperature on structure and electrochemical properties of LiCoO2 cathode thin films

LiCoO2 thin films, which can be used as a cathode material in microbatteries, were deposited using radio frequency (r.f.) magnetron sputtering system from a LiCoO2 target and in an O2+Ar atmosphere.The films were characterized by various methods such as XRD, SEM and AFM.The LiCoO2 films were annealed in air at 300, 500, 700 and 800 ℃ respectively.The effect of the annealing temperature on the structure, the surface morphology and the electrochemical properties of the films were investigated.The LiCoO2 thin film deposited at room temperature is amorphous and has smaller grain size.With increasing of annealing temperature, the crystallinity of the films is promoted.When the annealing temperature increases to 700 ℃, the films have a perfect crystalline LiCoO2 phase.The LiCoO2 thin film without annealing has no discharge plateau and small discharge capacity (about 27 μAh·cm-2μm).The discharge capacity increases with the increasing of annealing temperature and reaches 47 μAh·cm-2μm for the film annealed with 700 ℃, which also shows the typical discharge plateau of 3.9 V.The cycle performance of LiCoO2 thin films of as grown and annealed at different temperatures were studied.In the case of the film without thermal treatment, the capacity fading is much faster than that of the film annealed at different temperature, showing about 40% capacity loss only after 25 cycles.However, in the case of the film annealed at 700 ℃, the capacity reaches to steady state gradually and maintained constantly with cycling.After 25 times cycling, the discharge capacity of the film annealed at 700 ℃ decreases to about 36.9 μAh·cm-2·μm, only 0.8% capacity loss per cycle.     

钨钒共溅热致变色薄膜的制备及其红外光学性能

为解决VO2薄膜相变温度过高,热滞回线温宽过大以及掺杂后红外透过率变低等问题,开展了低成本钨钒共溅热致变色薄膜制备工艺的探索。先在室温条件下采用磁控共溅射的方法于玻璃基片上制备得到含钨量为1.4%的金属薄膜,再在空气中采用后退火工艺使金属薄膜充分氧化为热致变色薄膜。对薄膜样品的物理结构和光学性能进行了分析,发现钨钒共溅没有改变VO2薄膜在玻璃表面择优取向生长,但显著改变了VO2薄膜的表面形貌特征。观察到钨钒共溅热致变色薄膜的相变温度较普通VO2薄膜从68℃降低至40℃,热滞回线温宽由6℃缩小为3℃,低温半导体相的红外透过率分别为62%和57%。结果表明,钨钒共溅可达到相变温度降低,热滞回线温宽变窄,掺杂前后红外透过率变化不大之目的。     

Effects of la concentration on the texturing and the electrical properties of sol-gel derived PLT thin films

Lanthanum doped lead titanate (PLT) thin films consisting of different La concentrations were fabricated on Pt/Ti/SiO₂/Si using sol-gel method. The films were dried at 440°C for 5 min and fired at 600°C using rapid thermal annealing (RTA) for 1min. The preferred orientation (texturing) and the morphology of the PLT film were changed with La concentration and a possible cause of the texturing has been discussed. The effects of La doping to the Lead titanate films on the dielectric constants, P-E hysteresis loop and pyroelectric coefficient were measured and discussed.     

AgI掺杂量对n型Bi2Te2.85Se0.15材料热电性能的影响

采用机械合金化(MA)结合热压烧结(HP)技术制备了n型Bi2 Te2.85Se0.15热电材料,在常温下测量了电阻率(ρ)、塞贝克系数(α)和热导率(κ)等热电性能参数,考察了掺杂剂AgI的含量(质量百分比分别为0,0.1,0.2,0.3和0.4％)对材料热电性能的影响.结果表明:试样的电阻率和塞贝克系数的绝对值均随AgI掺杂量的提高而增大,热导率则随AgI掺杂量的提高而大幅降低,在AgI掺杂量为0.2％(质量)时有最大热电优值,为2.0×10-3/K.