聚酰亚胺/纳米Al2O3复合薄膜的介电性能

为了提高聚酰亚胺(PI)的耐电晕性能,采用原位分散聚合法制备了聚酰亚胺/纳米Al2O3复合材料,并采用透射电子显微镜(TEM)对纳米Al2O3的分散状态进行了表征。研究了纳米Al2O3填加量对该复合材料耐电晕性能和其它介电性能的影响,结果表明,随着纳米Al2O3含量的增加,材料的耐电晕性能显著增强,在±910V(双极性)、15kHz条件下,纳米Al2O3质量分数为20%的PI薄膜的耐电晕寿命达到极大值,为纯PI薄膜寿命的25倍,聚酰亚胺/纳米Al2O3复合材料的体积电阻率和击穿场强没有明显的劣化,而相对介电常数和损耗角正切有所增加。     

耐电晕PI/无机纳米氧化物复合薄膜设计及性能

采用热液法制备了纳米无机氧化物分散液,其中水解所需的水由醇缩水成醚反应提供.所得的MTES改性的纳米氧化铝与聚酰亚胺复合制成杂化聚酰亚胺复合薄膜(PI/Al2O3 - SiO2),另外还制备了未改性的纳米氧化铝杂化聚酰亚胺复合薄膜(PI/Al2O3),在试样厚度均为25 μm的情况下,采用双极性脉冲方波电压、峰-峰值2500V、频率20 kHz、占空比50％、测试温度155℃的条件下,分别测试上述两种薄膜以及Kapton 100 CR薄膜的耐电晕时间,结果表明,PI/Al2O3 - SiO2薄膜的耐电晕寿命最长,是Kapton 100 CR薄膜的6倍以上,是PI/Al2O3薄膜的12倍以上.由SEM的测试结果分析表明,PI/Al2O3 - SiO2薄膜中的无机纳米复合结构可以更有效地保护PI基体,从而提高材料的耐电晕性.     

惰性载体Al_2O_3对Fe_2O_3及CuO氧载体煤化学链燃烧的影响

氧载体是煤化学链燃烧技术的基础,惰性载体则是其中的必要组成部分,起着重要的作用。以Al2O3作为典型惰性载体,采用热重分析仪、红外频谱仪、场发射扫描电镜和能谱分析仪以及X衍射仪,对六盘水贫煤与Fe2O3、CuO基氧载体的反应进行了详细的研究。研究发现,Al2O3的引入,使得Fe2O3、CuO基氧载体表面积增大、孔径分布更为优化,而且对氧载体与六盘水贫煤一次热解产物的反应是有利的,能够促进氧载体中更多晶格氧的传递,Fe2O3基氧载体中有更多的Fe2O3还原为低于Fe3O4价态的氧化物,而CuO基氧载体中CuO除了还原为Cu、Cu2O外,其中的CuAl2O4也有一定的反应活性,被还原为CuAlO2。与LPS煤反应时,Fe2O3深度还原产物与部分Al2O3及煤中的SiO2反应生成Fe3Al2（SiO4）3,而CuO则与Al2O3及六盘水贫煤反应生成了（Cu0.215Mg1.785）（Al4Si5O18）复合物。     

无机纳米杂化聚酰亚胺薄膜的研究进展

无机纳米杂化聚酰亚胺复合薄膜因无机填料在聚合物基体中纳米尺度的分散以及与基体间强的化学结合而具有较常规聚酰亚胺薄膜材料更优异的力学性能、热稳定性能、高绝缘性能及耐电晕性能等.依据国内外聚酰亚胺纳米杂化薄膜材料的最新研究情况,重点综述了SiO2/Al2O3、SiO2/Ti2O3、SiO2、TiO2、Al2O3、SiC、MMT等纳米杂化聚酰亚胺薄膜的研究进展,表明其是一种性能优异、具有广泛应用前途的有机一无机纳米复合材料,但尚存在许多需进一步深入研究的问题.     

聚酰亚胺/氧化硅/氧化铝纳米杂化薄膜的制备及结构与性能研究

用溶胶-凝胶法制备了纳米氧化硅(SiO2)及纳米氧化铝(Al2O3)溶胶,并将二者掺入到聚酰胺酸基体中,亚胺化得到聚酰亚胺(PI)/SiO2/Al2O3杂化薄膜,采用红外光谱、原子力显微镜、热失重及阻抗分析仪对薄膜的结构及热性能、介电性能进行表征。结果表明,SiO2和Al2O3粒子呈纳米级均匀分散在薄膜基体中,并且与有机相存在键合;材料的热分解温度有所提高;介电常数随无机含量的增加而增加。     

LED散热用镜面铝不同表面处理的性能

为改善LED散热基板铝材的高温下反射率衰减、防硫化性、表面镀层粘接力。本文采用阳极氧化和、电镀以及溅射工艺在纯铝基材表面制备Nb2O5和Al2O3镀层作为铝材表面的防氧化层,将该镀层结构在LED灯光照射下180℃高温持续2000 h下的全反射率、450 nm、550 nm单波长的反射率和防硫化以及镀层结合力测试,并与目前常用的SiO2和TiO2,TiO2和Al2O3两种防氧化镀层进行对比研究。采用Nb2O5和Al2O3镀层处理的镜面铝在LED灯光照射下180℃高温持续2000 h全反射衰减3.6%,450 nm单波长反射率测试衰减4.38%,550 nm单波长反射率衰减3.5%,防硫化性能优异,镀层粘接力优异,3M胶带测试无镀层脱落;采用TiO2和SiO2镀层处理的镜面铝全反射衰减26.5%,450 nm单波长反射率测试衰减31%,550 nm单波长反射率衰减27%,防硫化性能差,镀层粘接力差,3M胶带测试镀层脱落;采用TiO2和Al2O3镀层处理的镜面铝全反射衰减13.9%,450 nm单波长反射率测试衰减16.2%,550 nm单波长反射率衰减13.8%,防硫化性能较差,镀层粘接力差较差,3M胶带测试镀层轻微脱落。实验结果表明,由Al2O3和Nb2O5作为防氧化层的镜面铝基板可有效改善基板在防硫化、高温反射衰减、镀层粘接力方面的性能。     

退火时间对FeGaB/Al2O3多层薄膜性能的影响

现代电子元器件的高速发展,以及磁性元器件小型化、集成化需求日益增长,推动了纳米级磁性功能薄膜材料的研究。以高饱和磁致伸缩系数、低矫顽力的FeGaB薄膜材料为研究基础,以提高薄膜软磁性能为目标,使用脉冲激光沉积系统制备了FeGaB/Al2O3复合多层薄膜,发现在350℃的生长环境下,未退火的样品成膜质量较好,但软磁性能一般。为了提高磁性能,进行一组不同退火时间下的退火实验,实验发现样品的铁磁共振线宽较大,且退火时间对吸收峰强度影响较大。     

纳米改性有机硅压敏胶的电性能研究

分别采用纳米SiO2和纳米Al2O3改性有机硅压敏胶,利用超声波和机械搅拌协同处理纳米粉体.以云母纸、聚酰亚胺薄膜,玻璃布为基材,改性有机硅压敏胶为胶粘剂,制备耐高温绝缘多层柔软复合材料,研究纳米粒子含量对复合材料电性能的影响.结果表明:有机硅压敏胶的初粘性随纳米组分的增加而降低,剥离强度随着纳米组分的增加而增大.柔软...     

方波脉冲下纳米氧化铝掺杂对聚酰亚胺介电性能的影响

为了研究方波条件下纳米Al2O3对PI膜介电性能的影响,将粒径为60 nm的Al2O3纳米粒子作为无机填料添加到PI基体中,制作了掺杂量质量分数为1%,2%,5%,7%,10%的PI薄膜。测量了PI/Al2O3薄膜耐电晕性能和介电温度谱以及介电频谱,并用SEM镜观察了放电前后PI/Al2O3薄膜微观形貌。研究结果表明:Al2O3纳米粒子的掺入提高了复合薄膜的耐电晕性能;PI/Al2O3复合薄膜的相对介电常数(εr)与介质损耗正切(tanδ)值随着Al2O3含量升高而升高,其tanδ值随着频率的增加先减小后增大,在200 Hz处有最小值。在同一频率下,PI/Al2O3薄膜εr和tanδ表现出对温度的依赖性,tanδ在70℃与170℃附近出现两个峰值;且随着Al2O3含量的增高,tanδ介电峰向高温方向移动。PI基体中高分子链缠结在纳米粒子周围,纳米粒子所引入的界面以及在聚合物中表现的"钉扎效应"是影响PI/Al2O3复合薄膜介电性能的主要原因。     

重掺杂Bi:YIG溅射薄膜的磁和磁光性能

用磁控溅射 快速退火晶化处理在YAG、Al2O3基片上制备了重掺杂Bi:YIG磁光薄膜,利用X射线衍射(XRD)、原子力显微镜(AFM)、磁光克尔仪/光学分度计、振动样品磁强计(VSM)分别研究了薄膜的微结构、磁光性能和磁性能.薄膜的饱和磁化强度为135～139 kA/m,不同基片上制备的薄膜的矫顽力不同,薄膜的法拉第角在450～610nm的光波段范围内约为3～5°/μm;当退火温度在600℃时,在两种基片上制备的薄膜透射率谱非常相似,当退火温度为800℃时,在Al2O3基片上的薄膜透射率谱将出现一个台阶.     

等离子体辅助原子层沉积氧化铝薄膜的研究

为在室温条件下进行氧化铝薄膜的原子层沉积,自行设计了一套微波回旋共振等离子体辅助原子层沉积装置,以三甲基铝作为铝源前躯体,氧气作为氧化剂,在室温下于氢氟酸溶液中处理过的单晶硅基片上进行了氧化铝薄膜的沉积。利用扫描电子显微镜、原子力显微镜、高分辨率透射电子显微镜、X-ray射线衍射、X-ray射线光电子能谱等分析手段测试了薄膜的表面形貌和成分,结果表明制备的氧化铝薄膜为非晶态结构,铝、氧元素含量配比接近2/3,同时薄膜表面非常光滑平整而且致密,表面粗糙度<0.4nm。通过高分辨率透射电子显微镜的截面图,可以估算出薄膜厚度约为80nm,界面非常清晰、平整,薄膜质量较高,沉积速率为0.27nm/周期,沉积速率较热沉积大大提高。     

热氧化温度对基于硅纳米线阵列太阳电池性能的影响

通过干氧热氧化方法在硅纳米线阵列表面生长一层SiO2钝化膜,研究不同热氧化温度对硅纳米线阵列的钝化效果的影响。实验结果表明,在850℃热氧化温度下得到SiO2钝化膜具有最佳的钝化效果。经过该方式钝化后的硅纳米线阵列具有最大的有效少子寿命,最好的内量子效率曲线,以及最好的太阳能转换效率。与未做热氧化钝化处理的基于硅纳米线阵列电池相比,该电池的短路电流、开路电压和转换效率分别提高了96mA、12．7mV和0．99％。     

Selective growth of InAs quantum dots by metalorganic chemical vapor deposition

We report results of both strain-driven surface segregation of indium from InGaAs thin films as well as selective area epitaxy of InAs quantum dots using these films. InAs segregation from an underlying InGaAs film allows for preferential growth of quantum dots when additional InAs is deposited. By using standard lithography techniques, a two-step selective growth process for quantum dots is achieved. Furthermore, by utilizing self-assembled nanostructures as a template, selective growth of coalesced wires and dots with 100-nm feature sizes are realized.     

Study of Hf—Al—O High-k Gate Dielectric Thin Films Grown on Si

Ultrathin amorphous films of Hf-aluminate (Hf—Al—O) have been deposited on p-type (100) Si substrates by pulsed-laser deposition. Transmission electron microscopy study revealed that for the films deposited in oxygen ambient with partial pressure of 1 × 10^?3 Pa, the amorphous structure of Hf—Al—O films is stable under rapid thermal annealing at temperatures up to at least 1000°C. Electrical properties have been characterized by means of high-frequency capacitance-voltage measurements at 1 MHz on the metal-oxide-semiconductor (MOS) capacitors using Pt dot electrode. The relative permittivity of the Hf—Al—O dielectric film is calculated approximately to be about 10 and the equivalent oxide thickness to SiO₂ is 30 Å. However, for the Hf—Al—O films deposited in a relatively higher vacuum condition (1 × 10^?4 Pa), islands of Hf silicide formed from interfacial reaction between the films and Si substrates. The formation of Hf silicide was attributed to the presence of Al oxide in the films that altered the Gibbs free energy for the reaction between the Hf atoms in the amorphous Hf—Al—O films and Si under an oxygen deficient condition. X-ray photoelectron spectroscope results suggested that there is Hf silicide formation in the interfacial region.     

An Effective Interlayer Dielectric and Passivation Scheme Using Reactively Sputtered AL 2 O 3 for (Ba,Sr)TiO 3 Capacitors

Interlayer dielectric and passivation layers for BST capacitors are often very hydrogen rich as a result of the by-products generated during the fabrication process. This hydrogen is well known to significantly degrade the leakage characteristics of the underlying BST capacitors. [1] While it is possible to focus on modifying interlayer dielectric (ILD) or passivation processes to minimize hydrogen exposure, it is preferable to maintain standard process modules available in silicon fabrication lines for case of manufacturing. However, post-deposition annealing is frequently required to reduce the effects of hydrogen, which may migrate into the capacitor during these deposition processes. It is known that Al 2 O 3 films provide an effective barrier to hydrogen migration, even at high temperatures. This paper discusses the integration of a reactively sputtered Al 2 O 3 barrier layer into the interlayer dielectric and passivation process flows of BST thin film capacitors to reduce device degradation during backend processing. Reactively sputtered Al 2 O 3 films were integrated into the production ILD process flow for BST thin film capacitors. Results indicate significant reduction in the post-deposition annealing time is possible while maintaining stable I-V characteristics on the finished devices. The barrier layer can also be etched by standard RIE tools used to etch other common oxides in silicon processing. Aggressive backend passivation schemes were also evaluated to determine the process window available for robust backend integration.     

An Alternative Route for the Synthesis of Oriented LiNbO 3 Thin Films

A new 2-step growth process was developed, combining both the r.f. sputtering and the pyrosol techniques, in which nucleation and growth stages could be partially separated and controlled. Using this refined deposition method, d c -oriented LiNbO 3 thin films could be successfully grown on (111) silicon and (001) sapphire substrates. Thin film structures have been determined by X-ray diffraction and pole figure analyses. Depositions performed on Si (111) templates led to fiber textures, characteristic of oriented polycrystalline samples. Al 2 O 3 (001) substrates allowed the growth of in-plane oriented layers with two distinguishable variants in the interfacial plane, namely, an aligned variant d 110 LiNbO 3 //[110]Al 2 O 3 and a 60 -rotated one.     

GaN基多量子阱蓝色发光二极管的实验与理论分析

本研究采用量子点模型对蓝色InGaN/GaN多量子阱发光二极管电致发光光谱进行考察,并和实验测量结果进行了比对。结果发现,利用量子点模型计算出的自发辐射发光峰位与实验得出的电致发光的峰位很好地吻合,表明了在多量子阱发光二极管中由于InN和GaN相分离而形成的富In类量子点结构,主导着InGaN基发光二极管发光波长,体现了InGaN基发光二极管量子点发光的本质。同时,基于量子点模型的理论,本文讨论了以合适组分的四元A lInGaN材料取代传统的GaN材料作为量子阱垒层对发光二极管发光特性的影响。     

Lasing at 1.28 /spl mu/m of InAs-GaAs quantum dots with AlGaAs cladding layer grown by metal-organic chemical vapor deposition

We report the device characteristics of stacked InAs-GaAs quantum dot (QD) lasers cladded by an Al/sub 0.4/Ga/sub 0.6/As layer grown at low temperature by metal-organic chemical vapor deposition. In the growth of quantum dot lasers, an emission wavelength shifts toward a shorter value due to the effect of postgrowth annealing on quantum dots. This blueshift can be suppressed when the annealing temperature is below 570/spl deg/C. We achieved 1.28-/spl mu/m continuous-wave lasing at room temperature of five layers stacked InAs-GaAs quantum dots embedded in an In/sub 0.13/Ga/sub 0.87/As strain-reducing layer whose p-cladding layer was grown at 560/spl deg/C. From the experiments and calculations of the gain spectra of fabricated quantum dot lasers, the observed lasing originates from the first excited state of stacked InAs quantum dots. We also discuss the device characteristics of fabricated quantum dot lasers at various growth temperatures of the p-cladding layer.