多层复合Bi/Sb纳米薄膜的制备及热电性能研究

选取单晶硅作为隔热衬底,Bi和Sb材料作为靶材,采用磁控溅射技术溅射制备多层复合纳米薄膜。研究了当固定调制周期为40nm,Bi和Sb的调制比分别为1∶1、3∶2、4∶1和1∶4时,Bi/Sb超晶格复合薄膜的See-beck系数、电导率和功率因子在160～250K温度范围内随温度的变化。发现当调制比为1∶4时,Bi/Sb薄膜的功率因子明显高于其它3种情况。     

气压对射频磁控溅射Bi4Ti3O12薄膜的影响

在不同溅射气压下,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）薄膜。在较低的气压（0.45-0.8Pa）下,得到了单相的Bi4Ti3O12薄膜;在较高气压（1.0-1.8Pa）下,薄膜中出现Bi2Ti2O7焦绿石相;随着气压的增加,薄膜的沉积速率和晶粒尺寸先增大后减小,表面粗糙度也逐渐增加;在适宜的气压（0.6Pa）下,得到的Bi4Ti3O12薄膜物相单一、表面平整致密、结晶良好。     

TiO2 /BiFeO3薄膜中增强的磁性和铁电性能

为改善铁酸铋(Bi Fe O3)薄膜的铁电性能,通过溶胶-凝胶和磁控溅射的方法在Au/Pt/Cr/Si基底上制备了Ti O2/Bi Fe O3(Ti O2/BFO)和Bi Fe O3薄膜.采用扫描探针显微镜、扫描电子显微镜、X射线衍射仪、铁电测试仪和物理性能测量仪对薄膜进行了物性表征.实验结果表明:Ti O2阻挡层抑制了BFO薄膜表面缺陷的形成,提高了复合薄膜的绝缘性能,使Ti O2/BFO薄膜中泄漏电流明显降低,且导电机制由欧姆型向空间电荷限制传导型转变.此外,溅射Ti O2阻挡层破坏了BFO表面的螺旋结构,使Ti O2和BFO之间晶格失配而产生界面应力,提高了薄膜的磁电性能.在顶电极和铁电层之间引入阻挡层是提高BFO薄膜磁电性能的一种有效方法.     

溅射功率对AZO／Cu／AZO多层薄膜结构与光电性能的影响

在玻璃衬底上利用磁控溅射法制备AZO／Cu／AZO多层薄膜,研究了溅射功率对AZO薄膜的微观结构和光电性能的影响。采用X射线衍射（XRD）仪、扫描电子显微镜（SEM）、紫外可见光谱仪（UVVis）等方法,对AZO薄膜的形貌结构、光电学性能进行了测试。结果表明：不同溅射功率下沉积的AZO薄膜均呈C轴择优取向,溅射功率对AZO／cu／AZO多层薄膜结构与光电性能有一定的影响。在溅射功率为120W、衬底温度为2500C、溅射气压为0．5Pa时薄膜的光透过率为75％,最低电阻率为2．2×10-4Ω·cm、结晶质量、表面形貌等得到明显改善。     

射频磁控溅射制备p-Bi2Te3热电薄膜的电学性能研究

通过射频磁控溅射并控制溅射时间在玻璃基底上沉积了不同厚度和成分的p型Bi2Te3薄膜.Bi2Te3薄膜主要以(221)晶面平行于基底进行生长,先在基底形成大量微小晶粒,合并长大成典型的纤维状组织结构;退火后薄膜沿平面方向形成片状结构.薄膜的电导率和Seebeck系数受薄膜厚度和成分的影响,退火前受薄膜厚度的影响较大,退火后受薄膜成分和均匀性的影响较大,自掺杂Bi质量分数在5%左右时,薄膜功率因子约为760μW/(K2·m).     

高压合成纳米晶Bi0.85Sb0.15的低温热电性

通过机械合金化法获得Bi0.85Sb0.15纳米晶粉末材料,在常温下冷压成型并分别在不同温度下进行高压处理,制备出块状样品.X-ray衍射实验证实已形成了Bi0.85Sb0.15单相合金.测量了样品在80～300 K温区的Seebeck系数和电导率,计算出材料的功率因子与温度的关系.在523 K 6 GPa下压制30 min的样品,其Seebeck系数在150 K达到-173μV/K,比同温度下单晶材料样品的Seebeck高大约60%,功率因子在200 K达到3.27×10-3 W/m·K2,表明高压处理可以有效改善材料热电性能.高分辨电镜分析发现材料中存在均匀分布的小于5 nm的"纳米点","纳米点"的存在导致材料Seebeck系数在低温显著提高.     

高压合成纳米晶Bi0．85Sb0．15的低温热电性能

通过机械合金化法获得Bi0．85Sb0．15纳米晶粉末材料,在常温下冷压成型并分别在不同温度下进行高压处理,制备出块状样品．X-ray衍射实验证实已形成了Bi0.85Sb0．15单相合金．测量了样品在80～300 K温区的Seebeck系数和电导率,计算出材料的功率因子与温度的关系．在523 K 6 GPa下压制30 min的样品,其Seebeck系数在150 K达到-173μV／K,比同温度下单晶材料样品的Seebeck高大约60％,功率因子在200 K达到3．27×10^-3W／m·K2,表明高压处理可以有效改善材料热电性能．高分辨电镜分析发现材料中存在均匀分布的小于5 nm的“纳米点”,“纳米点”的存在导致材料Seebeck系数在低温显著提高．     

溅射功率对InZnO薄膜晶体管电学性能的影响研究北大核心CSCD

采用射频磁控溅射法,在室温下Si/SiO_(2)衬底上制备InZnO薄膜晶体管,并研究不同溅射功率(25,50,75和100 W)对InZnO薄膜晶体管电学性能的影响。XRD表征结果表明,不同溅射功率制备的InZnO薄膜均出现晶面为(002)面的多晶态结构。通过电学特性研究发现,当溅射功率为50 W时,电流的开关比为3×10^(7),场效应迁移率为14.8 cm^(2)V^(-1)s^(-1),阈值电压为0.82 V,亚阈值摆幅为0.38 V decade^(-1),界面缺陷态密度为1.1×10^(12)cm^(-2)eV^(-1)等获得最佳器件参数。这是因为功率50 W时用原子力显微镜测得InZnO薄膜表面粗糙度为0.86 nm,说明薄膜的表面比较平滑,表面缺陷密度较少,使InZnO薄膜沟道层和源漏电极形成了良好的接触。此外,XPS结果表明,当溅射功率为50 W时,能够有效控制氧空位缺陷,最终有效改善和提高InZnO薄膜晶体管的电学性能。     

射频磁控溅射制备Bi2Te3热电薄膜

通过射频磁控溅射，在溅射气体为Ar，气压为1Pa，溅射功率为120W时分别在聚氨酯和玻璃基底上沉积了不同厚度的Bi2Te3薄膜。Bi2Te3薄膜主要是以（221）晶面平行于基底进行外延生长，先在基底形成大量微小晶粒，合并长大成典型的纤维状组织结构。在此条件下薄膜生长速率为26nm/min，通过控制溅射时间可沉积几纳米到几微米不同厚度的薄膜。得到的p-型半导体Bi2Te3薄膜，其电阻率随薄膜厚度的增大而减小。     

自燃法制备N型Bi掺杂LaNiO_3氧化物及其热电性能研究

以柠檬酸为螯合剂,各种硝酸盐为原料,采用简单的自燃法制备了金属Bi掺杂的N型钙钛矿结构的La1-xBixNiO3(x=0、0.025、0.05、0.075、0.1、0.15)热电材料前驱粉。前驱粉经煅烧、球磨、冷压、烧结等工艺获得块体材料。通过X射线衍射和扫描电镜观察等方法对样品的结构与形貌进行了分析表征。在573～1073K内测试了材料的电阻率和Seebeck系数,结果表明,该材料显示了较好的热电性能,掺杂Bi有助于显著降低材料的电阻率,优化材料的热电性能,其中试样La0.9Bi0.1NiO3组分材料在973K时的电阻率ρ=3.9606mΩ.cm,Seebeck系数S=-29.253μV/K,热电转换功率因子值p=2.16×10-5W/(m.K2)。     

(GeTe)nBi2Te3的结构与热电性能研究

在GeTe-Bi₂Te₃赝二元系统中, (GeTe)_n(Bi₂Te₃)_m化合物往往具有较低的晶格热导率, 但其中很多组分的热电性能尚未得到系统研究。本研究通过熔融、淬火、退火结合放电等离子烧结工艺制备了一系列(GeTe)_nBi₂Te₃(n=10, 11, 12, 13, 14)单相多晶样品, 并对其相组成和热电性能进行表征和研究。掺杂Bi₂Te₃可以显著增强点缺陷声子散射, 大幅度降低材料的晶格热导率, 在723 K时, (GeTe)₁₃Bi₂Te₃样品的总热导率低至1.63 W?m ^-1?K ^-1。此外, 掺杂Bi₂Te₃和调控GeTe的相对含量, 提高了材料的载流子有效质量, 即使在较高的载流子浓度下, 样品依然保持较高的塞贝克系数和功率因子, 在723 K, (GeTe)₁₃Bi₂Te₃样品获得最大的功率因子为2.88×10 ^-3 W?m ^-1?K ^-2, 最终(GeTe)₁₃Bi₂Te₃样品在723 K获得的最大ZT值达到1.27, 较未掺杂的GeTe样品提高了16%。     

退火条件对磁控溅射MgO-Ag3Sb-Sb2O4柔性薄膜热电性能的影响

MgAgSb是一种具有潜力且元素储量相对丰富的室温热电材料, 有望用于构建高性能可穿戴温差电池。本研究尝试在聚酰亚胺(PI)基底上磁控溅射制备MgAgSb薄膜, 并系统研究退火条件对其热电性能的影响。结果表明样品未形成纯相的MgAgSb柔性热电薄膜, 而是形成了由Ag₃Sb、MgO及Sb₂O₄多相组成的柔性薄膜, 其中Ag₃Sb起主要热电功能。不同气氛退火可以显著提升MgO-Ag₃Sb-Sb₂O₄ (Mg-Ag-Sb)柔性薄膜的热电性能, 其中真空处理性能最佳。在真空条件下, 随着退火温度升高, 柔性薄膜的热电性能呈现先增加后减少的趋势, 当退火温度为573 K时热电性能最佳, 室温附近功率因子达到74.16 μW∙m^-1∙K^-2。并且, 薄膜表现出较好的柔性, 弯曲900次后, 电导率仅变化了14%。本研究为MgAgSb柔性热电薄膜的制备及可穿戴应用提供了参考。     

Thermoelectric properties of Bi2Te3-In2Se3 composite thin films prepared by co-sputtering

Bi2Te3-In2Se3 films were prepared by co-sputtering followed by annealing, and their structural and thermoelectric properties were investigated. The immiscible nature of the two alloys results in precipitation of the second phase, thus leading to structures with self-assembled dots that are a few nanometers in scale. HAADF-STEM and HRTEM were used to confirm that In2Se3 nanodots that were a few nanometers in size did indeed form in the Bi2Te3 thin film. It was found that the incorporation of these nanodots can reduce the thermal conductivity of the thin film.     

Bi2O3薄膜的制备及其电阻开关特性的研究

电阻式存储器由于具有众多的优点有望成为最有前景的下一代高速非挥发性存储器的选择之一.实验利用射频磁控溅射法在重掺硅上沉积了Bi2O3薄膜,并对该薄膜的结晶状态和Au/Bi2O3/n+Si/Al结构的电阻开关特性进行了研究.XRD分析结果表明,射频磁控溅射法沉积所得的Bi2O3薄膜结晶性能好,(201)取向明显.I-V曲线测试结果表明,Au/Bi2O3/n+Si/Al结构具有单极性电阻开关特性.通过对不同厚度Bi2O3薄膜的Au/Bi2O3/n+Si/Al结构I-V特性比较发现,随着薄膜厚度的增加,电阻开关的Forming、Set和Reset阈值电压均随之增加.对于Bi2O3薄膜厚度为31.2 nm的Au/Bi2O3/n+Si/Al结构,其Forming、Set和Reset阈值电压均低于4 V,符合存储器低电压工作的要求.     

Enhanced thermoelectric properties of solution grown Bi2Te(3-x)Se(x) nanoplatelet composites

We report on the enhanced thermoelectric properties of selenium (Se) doped bismuth telluride (Bi(2)Te(3-x)Se(x)) nanoplatelet (NP) composites synthesized by the polyol method. Variation of the Se composition within NPs is demonstrated by X-ray diffraction and Raman spectroscopy. While the calculated lattice parameters closely follow the Vegard's law, a discontinuity in the shifting of the high frequency (E(g)(2) and A(1g)(2)) phonon modes illustrates a two mode behavior for Bi(2)Te(3-x)Se(x) NPs. The electrical resistivity (ρ) of spark plasma sintered pellet composites shows metallic conduction for pure Bi(2)Te(3) NP composites and semiconducting behavior for intermediate Se compositions. The thermal conductivity (κ) for all NP composites is much smaller than the bulk values and is dominated by microstructural grain boundary scattering. With temperature dependent electrical and thermal transport measurements, we show that both the thermoelectric power S (-259 μV/K) and the figure of merit ZT (0.54) are enhanced by nearly a factor of 4 for SPS pellets of Bi(2)Te(2.7)Se(0.3) in comparison to Bi(2)Te(3) NP composites. Tentatively, such an enhancement of the thermoelectric performance in nanoplatelet composites is attributed to the energy filtering of low energy electrons by abundant grain boundaries in aligned nanocomposites.     

Effect of oxygen on the dielectric and energy storage performances of lead-free Bi2Mg2/3Nb4/3O7 thin films prepared by magnetron sputtering

Journal of Materials Science: Materials in Electronics - Bi2Mg2/3Nb4/3O7 (BMN) thin films are prepared on Pt–Si substrates by magnetron sputtering, the influence of oxygen on dielectric and...     

Electrical properties of Bi2S3 thin films prepared by the dip-dry method

Bi₂S₃ thin films have been prepared by the dip-dry method and their electrical properties such as conductivity, thermoelectric power and spectral response of photoconductivity were investigated. Some uncommon findings, such as a simultaneous increase in conductivity and thermoelectric power with thickness of film, are explained by Seto's model for polycrystalline silicon film duly modified for in homogeneities.     

Microstructure and Thermoelectric Properties of Bi- and Cu-Substituted Ca3Co4O9 Oxides

Bi- and Cu-substituted Ca3Co4O9 samples were prepared by conventional solid-state reaction method and the effect of element substitution on the microstructures and thermoelectric properties was investigated. Partial substitution of Cu for Co leads to an increase in electrical conductivity and a decrease in Seebeck coefficient due to the rise of hole concentration. The microstructure of Cu-substituted sample is almost unchanged compared with undoped Ca3Co4O9. On the other hand, partial substitution of Bi for Ca gives rise to a significant increase in the grain size, and c-axis-oriented structure can be formed in Ca2.7Bi0.3Co4O9, resulting in an obvious increase in electrical conductivity. Cu and Bi co-substitution further increases the grain growth and the electrical conductivity of Ca2.7Bi0.3Co3.7Cu0.3O9. Thus, Cu and Bi co-substitution samples possess the optimal thermoelectric performance at high temperature and the highest value of power factor can reach 3.1×10-4 Wm-1·K-2 at 1000 K.