电子束泵浦氧化锌基量子阱的斯塔克效应

在不同功率密度的电子束泵浦条件下,对ZnO/Zn0.85Mg0.15O非对称双量子阱的荧光光谱进行了研究,并采用蒙特卡罗仿真模拟对测试结果进行了分析。模拟的结果和实验结果高度吻合。观测到了不随穿透深度变化的阱区发光峰红移,证明表面电荷积累引起了量子限域斯塔克效应。     

Annealing effect in glass woven fabric composites,Part II. Bending properties

Effects of annealing on bending properties of composites reinforced with plain glass woven fabrics that were treated with different concentrations of silane coupling agent were investigated in this paper. Bending strength increased by annealing in the specimen treated with lower silane concentration. Higher annealing temperature in a range from 80°C to 150°C led to higher bending strength. Then, the fracture mode changed from a micro-crack type (low strength type) to a branched matrix crack type (high strength type) by annealing.     

Modified null field method for P- and SV-wave scattering from a partially debonded fiber

The modified null field approach to elastic P- and SV-wave scattering (in plane strain) from a partially debonded fiber has been developed. The debonded region on the fiber surface is subjected to traction free boundary conditions, whereas the fiber is assumed to be in welded contact with the host medium elsewhere. Additional null field equations for an elliptical extension of the actual surface of the scatterer are introduced which require additional expansions for the field in the region between the extended mathematical boundary and the actual boundary of the scatterer. The numerical accuracy of the modified null field method has been tested for the case of a perfectly bonded fiber for P- and SV-wave incidence. Scattering cross-section plots are presented for different degrees of debonding.     

Indications of bulk property changes from surface ion implantation

In the majority of cases, the effects of ion implantation are confined close to the implant zone but, potentially, the resultant distortions and chemical modifications could catalyse relaxations extending into the bulk substrate. Such possibilities are rarely considered but the present data suggest that high dose ion implantation of ZnO has induced bulk changes. Surface implants with Cu and Tb strongly modified the low temperature bulk thermoluminescence properties generated by X-ray irradiation. Suggestions are proposed for the possible mechanisms for bulk relaxations and structural characteristics, which may indicate where such instability may occur in other lattice structures.     

Vibrational spectroscopic study of poly(dimethylsiloxane)-ZnO nanocomposites

A series of poly(dimethylsiloxane)-zinc oxide (PDMS-ZnO) nanocomposites having different concentrations of ZnO nanoparticles (0, 1, 5, 10 and 20 wt%) have been prepared. Raman and FTIR-ATR spectroscopic analysis was performed in order to determine the interaction between the ZnO nanoparticles and PDMS polymer matrix. Density functional theory (DFT) using the (B3-LYP)/6-311++G(2df,2p) method was used to investigate the vibrational spectra of PDMS. A complete vibrational assignment is supported by the normal coordinate analysis, calculated Raman activities as well as IR intensities.The presence of ZnO nanoparticles in PDMS gives rise to significant differences in relative intensities of the characteristic vibrational bands with respect to the cross-linked polymer. The changes in relative intensities of Raman bands, as well as swelling measurements, were used to explain the effect of ZnO nanoparticles on the cross-linked structure of PDMS nanocomposites. It is established that ZnO nanoparticles influence the cross-linking density of the polymer matrix.     

Nanoscratch-induced deformation behaviour in B4C particle reinforced ultrafine grained Al alloy composites: a novel diagnostic approach

We report on the novel application of nanoscratch characterization to provide insight into the plasticity mechanisms responsible for the behaviour of composites. Accordingly, we conduct deformation characterization with nanoscratch testing (DCNT) to study the deformation behaviour of two B₄C reinforced ultrafine grained Al alloy tri-modal composites with average B₄C particle sizes of ~1–6?μm and ~500?nm, respectively. To highlight the type of mechanistic information revealed in a DCNT study of composites, we concentrate on the influence of B₄C particle size on deformation mechanisms.     

An optical study of the D-D neutron irradiation-induced defects in Co-and Cu-doped ZnO wafers

Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped(1×1014,5×1016,and 1×1017cm-2) and Cu-doped(5×1016cm-2) ZnO wafers irradiated by D-D neutrons(fluence of 2.9×1010 cm-2) have been investigated.After irradiation,the Co or Cu metal and oxide clusters in doped ZnO wafers are dissolved,and the wu¨rtzite structure of ZnO substrate for each sample remains unchanged and keeps in high c-axis preferential orientation.The degree of irradiation-induced crystal disorder reflected from the absorption band tail parameter(E0) is far greater for doped ZnO than the undoped one.Under the same doping concentration,the Cu-doped ZnO wafer has much higher irradiation-induced disorder than the Co-doped one.Photoluminescence measurements indicate that the introduction rate of both the zinc vacancy and the zinc interstitial is much higher for the doped ZnO wafer with a high doping level than the undoped one.In addition,both crystal lattice distortion and defect complexes are suggested to be formed in doped ZnO wafers.Consequently,the Co-or Cu-doped ZnO wafer(especially with a high doping level) exhibits very low radiation hardness compared with the undoped one,and the Cu-doped ZnO wafer is much less radiation-hard than the Co-doped one.     

The effects of Zn vacancies on ferromagnetism in Cu-doped ZnO films controlled by oxygen pressure and Li doping

Zn0.99Cu0.01O films were studied experimentally and theoretically.The films were prepared by pulsed-laser deposi tion on Pt(111)/Ti/SiO2/Si substrates under various oxygen pressures to investigate the growth-dependence of the ferromag netic properties.The structural,magnetic,and optical properties were studied,and it was found that all the samples possess a typical wurtzite structure,and that the films exhibit room-temperature ferromagnetism.The sample deposited at 600℃and an oxygen pressure of 10 Pa showed a large saturation magnetization of 0.83μB/Cu.The enhanced ferromagnetism in the(Cu,Li)-codoped ZnO is attributable to the existence of Zn vacancies(VZn),as shown by first-principles calcu lations.The photoluminescence analysis demonstrated the existence of V Zn in both Zn0.99Cu0.01O and(Cu,Li)-codoped ZnO thin films,and this plays an important role in the increase of ferromagnetism,according to the results of first-principles calculations.     

控制纳米结构以调控氧化锌的发光、磁性和细胞毒性

氧化锌(ZnO) 纳米材料因其在UV 激光器、发光二极管、太阳能电池、稀磁半导体、生物荧光标示、靶向药物等领域中的广泛应用而成为最热门的研究课题之一. 调节和优化ZnO 纳米结构的性质是ZnO 的实际应用迫切所需. 在此, 通过发展聚乙烯吡咯烷酮导向结晶法、微波加热强制水解法、表面活性剂后处理法, 成功地制备出了尺寸、表面电荷或成分可调的球、半球、棒、管、T 型管、三脚架、片、齿轮、两层、多层、带盖罐子、碗等一系列ZnO 纳米结构. 通过简单地改变ZnO 纳米粒子的尺寸、形貌和表面电荷或成分, 有效地调控ZnO 本身的发光强度和位置, 并近90 倍地增强了荧光素染料的荧光强度; 诱使了强度可调的室温铁磁性; 实现了对ZnO纳米颗粒的细胞毒性的系统性调控.     

纤锌矿结构Zn1-xMgxO电子结构及吸收光谱的第一性原理研究

采用第一性原理计算方法,计算了纤锌矿结构Zn_1-xMg_xO(x=0,00625,0125,025)的电子结构及吸收光谱. 计算结果表明,Mg的掺入使ZnO的电子结构发生了较大的改变,与Mg邻近的O原子得到电子的数目明显增大,进而O原子返回部分电子给邻近Zn原子. Zn-O间相互作用减弱,禁带宽度变大,这也从同一合金中Zn4s上移的程度得到证实. 其吸收光谱也随着Mg的掺入出现蓝移现象,其吸收边对应波长分别为379, 关键词： 第一性原理计算 电子结构 吸收光谱 纤锌矿结构ZnO