High-density ferroelectric BiFeO₃ (BFO) nanodot arrays were developed through template-assisted tailoring of epitaxial thin films. By combining piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM) imaging techniques, we found that oxygen vacancies in nanodot arrays can be transported in the presence of an electric field. Besides triple-center domains, quadruple-center domains with different vertical polarizations were also identified. This was confirmed by combining the measurements of the domain switching and polarization vector distribution. The competition between the accumulation of mobile charges, such as oxygen vacancies, on the interface and the geometric constraints of nanodots led to the formation of these topological domain states. These abnormal multi-center topological defect states pave the way for improving the storage density of ferroelectric memory devices.

Most widely used dielectrics for MLCC are based on BaTiO₃ composition which inevitably shows performance degradation during the application due to the migration of oxygen vacancies (Vo⋅⋅). Here, the BaTiO₃, (Ba0.97Ca0.03)TiO₃, Ba(Ti0.98Mg0.02)O₃, (Ba0.97Ca0.03)(Ti0.98Mg0.02)O₃, (Ba0.96Ca0.03Dy0.01)(Ti0.98Mg0.02)O₃ ceramics (denoted as BT, BCT, BTM, BCTM and BCDTM, respectively) were prepared by a solid-state reaction method. The core-shell structured grains (∼200 nm) featured with 10-20 nm wide shell were observed and contributed to the relatively flat dielectric constant-temperature spectra of BTM, BCTM and BCDTM ceramics. The TSDC study found that the single/ mix doping of Ca2+, especially the Mg2+, Mg2+/Ca2+ and Mg2+/Ca2+/Dy3+ could limit the emergence of Vo⋅⋅ during the sintering and suppress its long-range migration under the electric-field. Because of this, the highly accelerated lifetimes of the ceramics were increased and the value of BCDTM is 377 times higher than that of BT ceramics. The p−n junction model was built to explain the correlation mechanism between the long-range migration of Vo⋅⋅ and the significantly increased leakage current of BT-based dielectrics in the late stage of HALT.

The theoretical possibility of the temperature-activation process of the temperature dependence of the dielectric constant of samples of ferroelectric ceramics lead zirconate titanate (PZT) at temperatures below the Curie point is considered. The model takes into account the 180° motion of the domain wall, which is located in the potential well. The values of activation energies (∼ 0.01, 0.1, 1 eV) were obtained from the experimental dependences of the logarithm of the dielectric constant on the reciprocal temperature. This is associated with three processes: initial vibrations of domain walls; separation of domain walls (DWs) from oxygen vacancies; the motion of DWs as a result of the motion of oxygen vacancies.The theoretical possibility of the temperature-activation process of the temperature dependence of the dielectric constant of samples of ferroelectric ceramics lead zirconate titanate (PZT) at temperatures below the Curie point is considered. The model takes into account the 180° motion of the domain wall, which is located in the potential well. The values of activation energies (∼ 0.01, 0.1, 1 eV) were obtained from the experimental dependences of the logarithm of the dielectric constant on the reciprocal temperature. This is associated with three processes: initial vibrations of domain walls; separation of domain walls (DWs) from oxygen vacancies; the motion of DWs as a result of the motion of oxygen vacancies.

半导体光催化技术具有低能耗和环境友好等优点, 在众多氮氧化物去除技术中具有较大的发展潜力。本研究在室温下成功制备了碳酸氧铋(Bi₂O₂CO₃, BOC)/聚吡咯(PPy)光催化剂, 并在可见光下对一氧化氮(NO)进行光催化氧化去除。可见光催化NO氧化性能测试结果表明, BOC复合PPy之后, 其NO去除率从9.4%提高到20.4%, 毒副产物NO₂的生成率从2%降到接近零。这是因为在BOC和PPy界面氢键作用下, 在BOC和PPy界面形成了氧空位。光电流和交流阻抗测试表明氧空位的形成改善了BOC光生载流子分离和迁移过程, 从而提高其光催化活性。此外, BOC/PPy光催化氧化NO机理分析表明, 氧空位促进O₂生成更多的·O₂^-, 进而与·OH共同作用, 提高BOC的NO氧化反应活性和安全性。

利用化学气相沉积法(CVD), 在不同压强下分别得到β-Ga2O3纳米线(NWs)和纳米带(NBs)。研究结果表明, 获得的NWs与NBs均为单斜结构的β-Ga2O3, 且NWs结晶质量优于NBs。在阴极射线发光(CL)光谱中, 发现NWs与NBs在近紫外和蓝光波段有较强的发光。对比NWs与NBs的CL光谱, 推断β-Ga2O3在374 nm和459 nm的近紫外和蓝色发光峰分别来自于Ⅰ型和Ⅱ型氧空位(VO(I)和VO(Ⅱ))的缺陷复合。

采用γ射线对SrAl2O4∶Eu2+,Dy3+长余辉荧光材料进行辐照处理, 研究样品经辐照后的长余辉性能。用60Co~γ射线源照射固相合成的SrAl2O4∶Eu2+,Dy3+长余辉荧光材料样品, 累积辐照剂量为100 kGy。利用X射线衍射仪(XRD)、拉曼光谱仪、紫外可见分光光度计、荧光分光光度计及热释光(TL)光谱仪对辐照前后样品的晶体结构、光吸收特性、余辉及热释光特性进行了研究。结果表明：辐照后样品的晶胞体积减小, 氧空位的浓度增加; 由于辐照使样品中引入更多的缺陷, 其吸收光谱的强度提高。辐照后样品的余辉寿命延长, 余辉光谱强度增加; 热释光强度增加, 且光谱向高温方向偏移, 经计算得到辐照后样品中陷阱能级深度增加0.0039 eV, 表明辐照影响了样品中陷阱能级分布且增加了样品中的深能级陷阱数目。

采用高温固相法制备Ca2-xSnO4∶xEu3+(x=0, 0.001, 0.005, 0.01, 0.015, 0.02)发光材料, 分别在空气和真空氛围中进行烧结, 研究Eu3+掺杂浓度及基质中氧空位对样品发光性能的影响。随着Eu3+离子浓度的增加, 发射强度呈逐渐增大的趋势, 主发射峰由两个分别位于614 nm和618 nm的峰逐步合为一个位于616 nm的发射峰。在Ca2-xSnO4∶xEu3+样品的激发光谱中, 存在着200～295 nm的Eu3+-O2-电荷迁移带, 随着Eu3+离子浓度的增加, 电荷迁移带的峰位由271 nm红移到286 nm。此外, 在Eu3+离子掺杂浓度相同的情况下, 真空中烧结得到样品的发光强度是空气中烧结得到样品的2倍。这是由于在真空氛围中烧结产生的氧空位增加使得传导电子密度升高, 导致发光强度增加。而且, 氧空位的增加导致电子陷阱的增多, 这使得Ca2-xSnO4∶xEu3+样品的余辉性能得到了很大程度的提高。

非晶铟钨氧(a-IWO)薄膜晶体管(TFT)具有高迁移率和高稳定性的优点，但其适合于实际生产的制备工艺条件尚有待摸索。本文研究了退火温度对a-IWO TFT电学特性影响的基本规律和内部机理。实验结果表明，随着退火温度的升高，a-IWO TFT的场效应迁移率也相应增加，这是由于高温退火下a-IWO薄膜中氧空位含量增多并进而导致载流子浓度增加的缘故。此外，a-IWO TFT的亚阈值摆幅和阈值电压在200 ℃下退火达到最佳，我们认为主要原因在于此时a-IWO薄膜的表面粗糙度最小并形成了最佳的前沟道界面状态。