SIMOX薄膜材料的电学性能

本文主要研究高剂量氧离子 (1 4～ 2 5× 10 1 8/cm2 )注入Si (10 0 )中 ,形成SOI SIMOX材料的表面Si单晶薄层的电学性能。用扩展电阻和霍耳测量 ,研究了不同的注入条件和退火条件对表面Si单晶层的载流子度和迁移率的影响。     

薄膜SOI结构中反型层厚度与薄膜厚度的关系

本文从理论上分析了薄膜SOI结构中反型层厚度与薄膜厚度的关系。为设计薄膜MOS/SOI器件引进了一个新的参数──薄膜整体反型临界厚度。分析认为,为使超薄膜MOS/SOI器件高速和高功率工作,有必要使薄膜厚度接近整体强反型临界厚度。     

厚度对a-Si∶H薄膜性能的影响

用等离子体增强化学气相沉积法在最佳工艺参数下在硼玻璃基片上沉积了厚度为1 μm以下的不同厚度的a-Si∶H薄膜.测量了薄膜厚度对它的光电性质的影响.结果表明,当膜厚增加时,a-Si∶H薄膜暗电导、光电导和阈值电压增大,光学带隙和Raman谱的TA模与TO模峰值比减小,折射率几乎不变,光吸收系数和通断电流比先增大,达到最大值后又减小.     

厚度对a—Si：H薄膜性能的影响

用等离子体增强化学气相沉积法在最佳工艺参数下在硼玻璃基片上沉积了厚度为1μm以下的不同厚度的a-Si:H薄膜。测量了薄膜厚度对它的光电性质的影响。结果表明，当膜厚增加时，a-Si:H薄膜暗电导、光电导和阈值电压增大，光学带隙和Raman谱的TA模与TO模峰值比减小，折射率几乎不变，光吸收系数和通断电流比先增大，达到最大值后又减小。     

射频磁控溅射参数对 Ba0.7Sr0.3TiO3薄膜结构和性能的影响

采用射频磁控溅射法在 Pt/TiO2/SiO2/Si(100) 衬底上制备了Ba0.7Sr0.3TiO3薄膜,研究了工作气压、衬底温度等溅射参数对Ba0.7Sr0.3TiO3薄膜结构和电学性质的影响.使用 XRD 分析了工作气压为 2Pa、衬底温度分别为 200 ℃、400 ℃、600℃(组a),以及衬底温度为600℃、工作气压分别为 1.5Pa、2.0Pa、2.5Pa、3.0Pa 和 5.0Pa (组b)两组薄膜的微结构,结果表明工作气压在 2.5Pa 以下、衬底温度为 600℃时沉积的薄膜具有较好的钙钛矿结构.在 1.5Pa 条件下溅射的薄膜具有明显的(111)择优取向.在2.5Pa时,Pt/Ba0.7Sr0.3TiO3/Pt电容有最优铁电性能,在外加4 V电压(电场为 80 kV/cm)下,剩余极化 (Pr) 和矫顽场(Ec)分别为 2.32 μC/cm2、21.1 kV/cm.     

BST薄膜的Sol-Gel法制备及其电学性能的研究

应用溶胶-凝胶（Sol-Gel)工艺制备了组分为r（Ba:Sr)=0.65:0.35的BST薄膜，研究了BST薄膜的显微结构、介电特性和漏电流特性，实验结果表明：BST薄膜经650℃热处理后，巳形成完整的立方钙钛矿结构，薄膜经900℃热处理后，其表面光滑、致密、无裂纹、无针孔，圆球形的小颗粒均匀分布。当偏置电压为0时，BST薄膜的介电常数和损耗因子分别为542和0.035。漏电流特性分析结果表明：采用RuO2作为底电极，在1.5V的偏压下BST薄膜的漏电流密度为0.52μA/Cm^2，该值比Pt/RuO2混合底电极上制备的BST薄膜的漏电流密度（72nA/cm^2)大1个数量级，因此，Pt/RuO2混合底电极既克服了RuO2底电极漏电流大的缺点，又解决了Pt底电极难以刻蚀的困难，是制备大规模动态随机存取存储器的电容器列阵的最低底电极材料。     

中频磁控溅射AlN薄膜的电学性能研究

利用中频反应磁控溅射在玻璃衬底上沉积了不同溅射功率的AlN薄膜.采用X射线衍射仪、原子力显微镜和电击穿场强测试系统研究了薄膜的结构和电学性能,并对该介质薄膜的导通机制进行了分析.结果表明,所制备的薄膜呈非晶态,5 kw溅射功率下制备的薄膜具有较好的表面结构,并具有较高的耐击穿场强,约为2.1 MV/cm;结合理论分析发现,AlN在不同的场强条件下以某一种导通作为主要的导通机制:低场强区服从欧姆定律,随着场强升高,在不同的阶段分别以肖特基效应,普尔-弗兰凯尔效应和F-N效应为主.     

准分子脉冲激光沉积法制备的ZrO2薄膜结构和电学性能的研究

采用准分子脉冲激光沉积法 (PLD)分别在Pt/Ti/SiO2 /Si和SiO2 /Si衬底上制备了ZrO2 薄膜 ,采用扩展电阻法 (SRP)研究了薄膜纵向电阻分布 ;采用X射线衍射法 (XRD)研究了衬底温度对ZrO2 薄膜结晶性能的影响 ;精确测试了薄膜的表面粗糙度 ;讨论了薄膜结晶性能与其电学I V特性之间的关系。     

BiFeO3薄膜中的电学输运性质

报道了铁酸铋薄膜样品在80K~300K温度范围直流电学输运性质的研究结果.利用同一前驱体不同老化时间,用化学溶液沉积法在钛酸锶衬底上制备出两种样品.在低阻样品中,低场下电流随电压变化遵从欧姆定律,电阻不随温度变化;而在中等强度外场下显示出肖特基二极管性质.在高阻样品中,低场下电流密度沿晶界分布,输运中的势垒能级为0.57eV;高场下电流的传输则遵从Frenkel-Poole模型,相关势垒能级0.12eV.低阻和高阻两种样品在85K温度下可测最大剩余极化分别为2.6μC/cm2和28.8μC/cm2.     

薄膜厚度对ZnO：Zr透明导电薄膜光电性能的影响

利用射频磁控溅射法在室温水冷玻璃衬底上制备出了可见光透过率高、电阻率低的ZnO:Zr透明导电薄膜.讨论了厚度对ZnO:Zr透明导电薄膜光学、电学性能的影响.当薄膜厚度为213 nm时,薄膜电阻率达到最小值1.81×10-3 Ω·cm.所制备的薄膜样品都具有高透光率,其可见光区平均透过率超过了93.0%.当薄膜厚度从125 nm增加到350 nm时,薄膜的光学带隙从3.58 eV减小到3.50 eV.     

氮掺杂浓度对氮掺杂PbTiO3电子结构和光学性能的影响

用第一性原理计算研究了不同N掺杂浓度的P型N掺杂PbTiO3的电荷密度差分、能带结构、态密度和光学性质。用N原子取代PbTiO3中的O原子后,PbTiO3的价带向高能级发生移动,费米能级进入价带顶部。随着N掺杂浓度的增加,能带带隙值变窄,结构稳定性变差。掺杂浓度2.5 at%时,N掺杂PbTiO3显示最好的P型导电性和最强的可见光吸收。N掺杂PbTiO3在半导体光电器件和光催化领域具有重要的应用价值。     

ZnO过渡层对BiFeO_3薄膜铁电性能的影响

采用溶胶–凝胶法,在Pt(111)/Ti/SiO2/Si(100)衬底上采用逐层退火工艺制备了BFO(BiFeO3)、ZnO/BFO和ZAO(掺铝氧化锌)/BFO薄膜,研究了ZnO、ZAO过渡层对BFO薄膜晶相以及铁电、漏电和介电性能的影响。结果表明:与BFO薄膜相比,ZnO/BFO薄膜的表面更加致密、平整,结晶性更好,双剩余极化强度(2Pr)有非常大的提高,漏电和介电性能也均有改善。ZAO/BFO薄膜的铁电性能比ZnO/BFO薄膜的铁电性能差,这与ZAO的导电性强于ZnO有关。     

N掺杂和氧空位对PbTiO3电子结构和导电性的影响研究

用第一性原理计算了P型N掺杂PbTiO3的电子密度差分、能带结构和态密度,讨论了氧空位对N掺杂PbTiO3性能的影响。在PbTiO3中掺杂N杂质后,PbTiO3的价带向高能级发生移动,费米能级进入价带顶部,带隙变窄,N掺杂PbTiO3表现出典型的P型半导体性能。当N掺杂PbTiO3中含有氧空位时,导带发生下移,受主被完全补偿。计算结果与实验数据相吻合。     

Effect of titanium dioxide (TiO2) seed layer on the phase composition of 0.7Pb (Mg1/3Nb2/3)O3-0.3PbTiO3 film prepared by pulsed laser deposition

Lead-magnesium niobate-lead titanate (PMN-PT) thin films with and without the TiO₂ seed layer were deposited on Pt/Ti/SiO₂/Si substrates through pulsed laser deposition. The study aimed to characterize the effect of the TiO₂ seed layer on the phase composition and properties of PMN-PT film. Without the TiO₂ seed layer, the pure perovskite phase could be obtained in the thinner PMN-PT film while with the TiO₂ seed layer, the pure perovskite phase was formed in the thicker PMN-PT film. The ferroelectric properties of PMN-PT films with the TiO₂ seed layer were exhibited. As a result, the maximum amount of remnant polarization reached the amount of 32 μC/cm² for the PMN-PT thin film with the TiO₂ seed layer.     

The microwave properties of Li doped 0.7(Ba,Sr)TiO3-0.3MgO thick film interdigital capacitors on the alumina substrates

The crystalline and electrical properties of Li doped 0.7(Ba,Sr)TiO₃-0.3MgO thick film interdigital capacitors have been investigated. Screen printing method was employed to fabricate Li doped 0.7(Ba,Sr)TiO₃-0.3MgO thick films on the alumina substrates. (Ba,Sr)TiO₃ materials have high dielectric permittivity (>500 @ 1 MHz) and low loss tangent (0.01 @ 1 MHz) in the epitaxial thin film form. To improve dielectric properties and reduce sintering temperature, MgO and Li were added, respectively. 10 μm thick films were screen printed on the alumina substrates and then interdigital capacitors with seven fingers of 200 μm finger gap were patterned with Ag electrode. Current-voltage characteristics were analyzed with elevated temperature range. Up to 50 °C, the thick films showed positive temperature coefficient of resistivity (dρ/dT) of 6.11 × 10⁸ Ω cm/°C, then film showed negative temperature coefficient of resistivity (dρ/dT) of −1.74 × 10⁸ Ω cm/°C. From the microwave measurement, the relative dielectric permittivity of Li doped 0.7(Ba,Sr)TiO₃-0.3MgO thick films interdigital capacitors were between 313 at 1 GHz and 265 at 7 GHz.     

不同厚度PZT薄膜的制备及电性能特性研究

采用sol-gel（溶胶-凝胶）法在Pt/Ti/SiO2/Si基底上分别制备了厚度为400nm,600nm,800nm的PZT（锆钛酸铅,Zr/Ti=52/48）薄膜,研究了厚度对薄膜介电性能与铁电性能的影响。通过对薄膜的铁电性能与介电性能进行测试,分析了不同厚度薄膜的剩余极化强度、介电常数与介电损耗;通过对介电调谐率与最大正切损耗的计算,进一步分析了薄膜的介电调谐性能。实验结果表明,薄膜的介电常数与介电损耗随薄膜厚度的增大而增加;厚度为600nm的薄膜具有最好的介电调谐性能与铁电性能。     

Effects of fluorine-implanted treatment on Ba0.7Sr0.3TiO3 films

The effects of F-ion implantation on the leakage and dielectric properties of the Ba_0.7Sr_0.3TiO₃ (BST) films were investigated. The BST film implanted with 1×10¹⁵ cm^–2 shows the optimum leakage performance. The leakage current density can be decreased by one order of magnitude as compared to that of the non-implanted sample at an applied voltage of 2 V. On increasing the implanted dose from 5×10¹⁴ to 5×10¹⁵ cm^–2, the dielectric constant first increases and then decreases due to the deteriorated crystallinity. It is found that the suitable F-ion dose can reduce the –OH contaminants and improve the dielectric and leakage properties.     

Effects of O2 plasma treatment on the electric and dielectric characteristics of Ba0.7Sr0.3TiO3 thin films

The effects of the O₂ plasma treatment on the electric and dielectric characteristics of Ba_0.7Sr_0.3TiO₃ (BST) thin films were investigated. As a result of the exposure of the as-deposited or the annealed BST films to the O₂ plasma, the leakage current density of the BST films can be improved. Typically, the leakage current density can decrease by three orders of magnitude as compared that of the non-plasma treated sample at an applied voltage of 1.5 V. It is found that the plasma treatment changes the surface morphology. The capacitance of the BST films was reduced by 10%30%. The improvement of the leakage current density and the reduction of a dielectric constant for the plasma treated samples could be attributed to the reduction of carbon contaminations of BST thin films. The 10 year life time of the time-dependent dielectric breakdown (TDDB) studies indicates that all the samples have a life time of over 10 years of operation at a voltage bias of 1 V.     

Effects of vertical electric field and compressive strain on electronic properties of bilayer ZrS2

Using first-principles calculations, including Grimme D2 method for van der Waals interactions, we investigate the tuning electronic properties of bilayer zirconium disulfides (ZrS₂) subjected to vertical electric field and normal compressive strain. The band gap of ZrS₂ bilayer can be flexibly tuned by vertical external electric field. Due to the Stark effect, at critical electric fields about 1.4 V/Å, semiconducting-metallic transition presents. In addition, our results also demonstrated that the compressive strain has an important impact on the electronic properties of ZrS₂ bilayer sheet. The widely tunable band gaps confirm possibilities for its applications in electronics and optoelectronics.     

Controllable nanostructures on La0.7Sr0.3MnO3 thin film surfaces formed by scanning tunneling microscopy

Nanoscale structuring on La_0.7Sr_0.3MnO₃ (LSMO) thin film surfaces has been performed by scanning tunneling microscopy (STM) under ambient conditions. From line etching experiments we found that the line-depth increases in a stepwise fashion with increasing bias voltage. It also increases with decreasing scan speed and increasing scan repetition. We observed that the line-depth is an integral multiple of the LSMO out-of-plane lattice constant about 0.4 nm. Lateral structure with minimum feature size of 1 nm is possible to obtain. In addition, a four-level inverse-pyramid structure has been created on LSMO thin film surfaces. Our work shows the feasibility of using STM to fabricate controllable and complex nanostructures in LSMO thin film.