The effects of electric field and gate bias pulse on the migration and stability of ionized oxygen vacancies in amorphous In–Ga–Zn–O thin film transistors

Abstract

Oxygen vacancies have been considered as the origin of threshold voltage instability under negative bias illumination stress in amorphous oxide thin film transistors. Here we report the results of first-principles molecular dynamics simulations for the drift motion of oxygen vacancies. We show that oxygen vacancies, which are initially ionized by trapping photoexcited hole carriers, can easily migrate under an external electric field. Thus, accumulated hole traps near the channel/dielectric interface cause negative shift of the threshold voltage, supporting the oxygen vacancy model. In addition, we find that ionized oxygen vacancies easily recover their neutral defect configurations by capturing electrons when the Fermi level increases. Our results are in good agreement with the experimental observation that applying a positive gate bias pulse of short duration eliminates hole traps and thus leads to the recovery of device stability from persistent photoconductivity.     

金红石型TiO2(110)表面吸附TiCl4的微观机理

采用密度泛函理论平面波赝势方法研究了TiCl₄分子在TiO₂(110)表面桥位氧上的吸附,对稳定吸附构型的吸附能、电荷密度、差分电荷密度、电子态密度、Mulliken电荷布居等进行计算和分析。研究结果表明,TiCl₄在完整晶胞表面不能吸附;在有氧空位的晶胞表面,TiCl₄以面心向下吸附最稳定,吸附过程为放热。当表面氧空位密度为12.5%、25%时,面心向下吸附方式的吸附能分别为-29.780 9 kJ·mol-1和-48.641 9 kJ·mol-1,表明氧空位密度越高,吸附强度越强;带隙从1.304 eV分别减小到0. 074 eV、0.015 eV,能带结构的带隙宽度变窄,表明氧空位密度越高,带隙宽度越窄;TiCl₄分子向晶胞表面转移的电荷分别为0.2 eV、0.26 eV,说明随着表面氧空位密度增加,TiCl₄分子向晶胞表面转移的电荷量增加,表面对分子的氧化作用越强。     

聚二氧戊环聚氨酯/高氯酸锂复合体系的离子导电性能研究

合成了以聚二氧戊环（PDXL）为软段的聚氨酯（PDXL－PU）以及聚乙二醇（PEG）,聚二氧戊环混合软段的聚氨酯,并进一步制备了聚氨酯／高氯酸锂型聚合物固体电解质,通过红外光谱分析,DSC分析以及复阻抗谱分析等方法对体系的结构及离子导电性能进行了研究,结果发现,PDXL－PU具有很低的软段微区玻璃化转变温度,PDXL软段对高氯酸锂有较强的溶剂化能力,体系的室温电导率可以达到10^-1S／cm以上,而PEG软段的引入则提供了样品软段微区的Tg,无助于提高掺杂样品的电导率。     

聚邻甲氧基苯胺薄膜对pH的光学响应

在盐酸介质中,应用循环伏安法通过电聚合在氧化铟锡(ITO)透明导电玻璃上形成聚邻甲氧基苯胺薄膜.用紫外可见光谱方法测定了聚合物薄膜在不同pH下的特征吸收光谱,聚邻甲氧基苯胺薄膜的λmax在557～746nm之间,作出了相应的滴定曲线.结果表明,在pH为1～12范围内聚合物薄膜对pH的变化表现了极高的光学敏感性,其表观pKa约为6.4.应用聚邻甲氧基苯胺薄膜测定了不同pH的溶液,其测定结果与精密酸度计相比误差＜±4%.     

准单分散SnO2微球的微波溶剂热合成

以聚乙二醇(PEG, Mn=6000)为模板剂, 结晶四氯化锡(SnCl₄·5H₂O)和尿素为原料, 采用微波溶剂热法在180℃、添加0.12 mmol PEG的条件下制备出了单分散性良好的SnO₂微球. 通过XRD、SEM、TEM和FT-IR等分析手段对产物进行表征, 并结合光致发光(PL)谱研究了产物的发光性能. 结果表明: SnO₂微球是由大量细小晶粒堆积而成的, 微球直径约1.3 um. 经400℃煅烧2 h后, 微球表面致密光滑且直径未发生明显变化. FT-IR谱图中550 cm^-1处吸收峰应为表面结构改变引起的表面振动模式. PL谱表明煅烧前SnO₂微球在320~450 nm处具有宽而强的发射带, 煅烧后发射带强度大幅下降, 说明产物的晶格缺陷对近带边发射有重要影响.     

以PAMAM为模板ZnO-SnO2纳米复合氧化物的制备及其光催化性能

以PAMAM树枝状大分子为模板,制备了ZnO-SnO2纳米复合氧化物。利用XRD、EDS、DRS、UV-Vis等表征手段对纳米复合氧化物进行表征,并初步探讨了ZnO-SnO2纳米复合氧化物在可见光激发下降解罗丹明B的光催化性能及影响光催化剂活性的因素。结果表明所制备的ZnO-SnO2纳米复合氧化物对罗丹明B具有良好的可见光光催化降解活性。     

Preparation of budesonide-poly (ethylene oxide) solid dispersions using supercritical fluid technology

The purpose of this study was to investigate the possibility of preparing solid dispersions of the poorly soluble budesonide by supercritical fluid (SCF) technique, using poly (ethylene oxide) (PEO) as a hydrophilic carrier. The budesonide-PEO solid dispersions were prepared, using supercritical carbon dioxide (SC CO₂) as the processing medium, and characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), solubility test and dissolution test in order to understand the influence of the SCF process on the physical status of the drug. The endothermic peak of budesonide in the SCF-treated mixtures was significantly reduced, indicating that budesonide was in amorphous form inside the carrier system. This was further confirmed by SEM and PXRD studies. The enhanced dissolution rates of budesonide were observed from SCF-treated budesonide-PEO mixtures. The amorphous characteristic of the budesonide, the better mixing of drug and PEO powders in the presence of SC CO₂, together with the improved wettability of the drug in PEO, produced a remarkable enhancement of the in vitro drug dissolution rate. Thus, budesonide-PEO solid dispersions with enhanced dissolution rate can be prepared using organic solvent-free SCF process.     

Preparation of Budesonide-Poly (Ethylene Oxide) Solid Dispersions Using Supercritical Fluid Technology

The purpose of this study was to investigate the possibility of preparing solid dispersions of the poorly soluble budesonide by supercritical fluid (SCF) technique, using poly (ethylene oxide) (PEO) as a hydrophilic carrier. The budesonide-PEO solid dispersions were prepared, using supercritical carbon dioxide (SC CO₂) as the processing medium, and characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), solubility test and dissolution test in order to understand the influence of the SCF process on the physical status of the drug. The endothermic peak of budesonide in the SCF-treated mixtures was significantly reduced, indicating that budesonide was in amorphous form inside the carrier system. This was further confirmed by SEM and PXRD studies. The enhanced dissolution rates of budesonide were observed from SCF-treated budesonide-PEO mixtures. The amorphous characteristic of the budesonide, the better mixing of drug and PEO powders in the presence of SC CO₂, together with the improved wettability of the drug in PEO, produced a remarkable enhancement of the in vitro drug dissolution rate. Thus, budesonide-PEO solid dispersions with enhanced dissolution rate can be prepared using organic solvent-free SCF process.     

聚氨酯型固体电解质的体系组成与形态研究

制备了一种聚氧化乙烯聚氨酯,并制备了一种结构与该聚氨酯硬段一致的模型化合物,通过与聚氧化乙烯、高氯酸钠盐的共混,制备了一系列聚氨酯型聚合物固体电解质,通过红外光谱分析以及AFM分析的方法对该体系的聚集形态,离子-聚合物相互作用进行了研究,讨论了盐浓度、模型化合物的含量以及聚氧化乙烯的加入对体系的影响。     

聚氧化乙烯(PEO)及其与高氯酸锂复合体系的等温结晶动力学研究

用示差扫描量热法研究了PEO及其与高氯酸锂复合体系的等温结晶过程。用Avrami方程分析了PEO和复合体系中PEO的等温结晶动力学,得到了PEO在不同体系中等温结晶时的动力学参数。PEO的Avrami指数n都趋近2．5,说明PEO晶体以三维方式依热成核生长。动力学参数表明,复合体系中PEO结晶时以异相成核为主。LiClO4对PEO等温结晶过程的影响如下：作为PEO结晶的成核剂而加快其结晶过程;增加了复合体系的粘度,缩短了PEO的结晶半时间,使其结晶总速率增大;降低了复合体系中PEO的绝对结晶度。     

集成电极的复合混沌混合芯片的快速制备及表征

试剂的有效混合是化学和生化反应的前提条件,因此混合成为微全分析系统的重要功能单元.本文介绍了一种通道中集成氧化铟锡(ITO)电极的聚二甲基硅氧烷(PDMS)-玻璃复合混沌混合芯片的快速制备方法,对PDMS的混合通道表面进行了硅溶胶改性.首次用集成的电极和酸碱反应过程中的电导变化对其混合效果进行了评价.利用玻璃各向同性刻蚀特点,一次曝光和一次刻蚀得到了混沌混合微通道结构的母板.利用光辅助原位聚合的方法快速制备了与母板微结构互补的聚甲基丙烯酸甲酯(PMMA)阳模,利用PI)MS原位聚合的方法复制得到了与玻璃母板结构相同的混沌混合通道结构的芯片.用电导法对芯片的混合有效性进行了表征.PDMS复制芯片与ITO玻璃永久封合即得全透明的复合混沌混合芯片.本文介绍的加工方法无需二次曝光及SU-8光刻胶,容易多次复制,在微流控分析芯片中将有广泛应用.     

硫酸钙催化环氧乙烷的聚合反应

用硫酸钙催化环氧乙烷聚合得到了一种中高分子量的聚乙二醇。用红外、核磁等仪器对产物进行了表征。通过测定反应体系压降速率定性描述了聚合速率,研究发现,聚合速率与单体浓度呈二次关系,与催化剂用量呈一次关系;该反应具有准活性聚合特点。     

聚氧化乙烯(PEO)及其与高氯酸锂复合体系的非等温结晶动力学研究

用示差扫描量热法(DSC)研究了PEO及其与高氯酸锂复合体系的非等温结晶过程.分别用Jeziorny方法、一种结合Avrami和Ozawa方程的方法对该体系的非等温结晶过程进行了研究,分别得到PEO进行非等温结晶时的动力学参数.结果表明LiClO4晶粒缩短了PEO的结晶时间,使复合体系中PEO的结晶速率要大于纯PEO;但纯PEO结晶时形成的晶体更完善.为使二者达到相同的相对结晶度,纯PEO体系需要更大的冷却速度.LiClO4微粒能有效地将PEO的结晶相转变成非晶相,也就是说LiClO4可有效地抑制PEO的结晶过程.