掺杂与应力对ZrO2薄膜电子结构和光学性质的影响

利用基于密度泛函理论的第一性原理平面波超软赝势方法系统地研究了掺杂和应力对ZrO_2薄膜的电子结构与光学性质的影响.本文首先研究了Hf原子替代掺杂对ZrO_2薄膜物性的影响,研究结果表明,Hf原子掺杂减小了ZrO_2薄膜的带隙和态密度大小,可在一定程度上降低其表面缺陷电荷和漏电流.掺杂Hf原子后介电峰和吸收峰的值明显下降,同时介电峰和吸收峰的波形均出现了窄化现象,半高宽显著减小.本文也着重研究了不同应力下四方晶相ZrO_2薄膜物理性质变化及规律.研究发现压应力显著调控了ZrO_2薄膜的带隙以及价带顶和导带底附近的能带结构.施加应力后吸收峰的吸收范围和强度均显著增大,峰值对应的光子能量蓝移则表明对紫外光的吸收随着应力的增加有所增强.在低能量红外和可见光区域,施加压应力后ZrO_2薄膜的折射率变大,但在紫外线区域,压应力使ZrO_2薄膜的折射率呈现出先增大后减小的波动特性.上述研究结果为ZrO_2薄膜材料的设计与应用提供了理论依据.     

Co^2＋掺杂和Co^2＋-Ni^2＋共掺杂对TiO_2光催化性能的影响

通过溶胶-凝胶法制备了掺杂钴离子和钴、镍离子共掺杂的复合纳米粒子二氧化钛光催化剂,以甲基橙的脱色降解为探针反应,评价了光催化剂的光催化活性,研究了不同掺杂量以及掺杂粒子不同时,对光催化剂催化性能的影响。结果表明：当钴的掺杂量在0.2%时,光催化剂的活性最佳,而钴镍共掺杂的掺杂量在0.4%时,光催化剂的活性最好,且钴掺杂的催化活性比钴镍掺杂的更有效。     

Heteroatom-doped graphene for electrochemical energy storage

The increasing energy consumption and envi- ronmental concerns due to burning fossil fuel are key drivers for the development of effective energy storage systems based on innovative materials. Among these materials, graphene has emerged as one of the most promising due to its chemical, electrical, and mechanical properties. Heteroatom doping has been proven as an effective way to tailor the properties of graphene and render its potential use for energy storage devices. In this view, we review the recent developments in the synthesis and applications of heteroatom-doped graphene in supercapacitors and lithium ion batteries.     

Thermoelectric properties of phase separated Ti substituted Zr_(0.75)Hf_(0.25)NiSn_(0.985)Sb_(0.015) half-Heuslers

Sb is a very effective dopant for ZrNiSn based half-Heusler alloys.The effect of Ti substitution on Zr_(0.75)Hf_(0.25)NiSn_(0.985)Sb_(0.015) half-Heusler(HH) semiconductor alloys has been investigated to explore the structural modifications and composition variation.TixHf_(0.25) Zr_(0.75-x)NiSn_(0.985)Sb_(0.015)(x=0,0.15,0.30,0.45) alloys were synthesized by induction melting.A set of samples was also annealed for comparative studies.The samples were then sintered using plasma activated sintering(PAS) technique.XRD results confirmed the existence of ZrNiSn type HH compounds.Backscattered electron(BSE) images showed phase separations in the samples.Ti substitution improved the carrier concentration and electrical conductivity of the alloys.Moreover,thermal conductivity was also significantly reduced due to the enhanced phonon scattering.Consequently,a ZT value of 1.11 at 873 K was obtained for 30% Ti substituted(annealed) sample.     

二氯二聚吡咯合铁的结构和吸附氢行为的CNDO／2研究

应用CNDO／2方法研究了二氯二聚吡咯合铁配合物（DCBPF）的结构和H2在该配合物上的吸附行为，确定了配合物的稳定结构，讨论了被吸附分子相对于配合物的不同吸附取向的影响，优化了各个体系相对于能量的分子间距，探究了吸附的微观机制，得到了一些比较有意义的结果。     

硅化物／硅欧姆接触特性研究

本文报道了利用ＸＲＤ、ＲＢＳ、ＳＰＲ、ＡＥＳ、ＳＥＭ、ＴＥＭ和Ｋｅｌｖｉｎ电阻桥法（ＣＢＫＲ）等测量技术系统地研究化钛／硅，硅化钴／硅欧姆接触特性。实验结果表明：硅化钛（硅化钴）／硅欧姆接触电阻率（Ｐｃ）不仅受表面层掺杂浓度而且也受退火温度，杂财分布及硅化物／硅介面形貌等因素影响。     

Anderson结构钼钴杂多酸盐掺杂聚苯胺的合成与表征

在盐酸介质中,以(NH4)2S2O8为氧化剂,(NH43)[CoMo6O24H6]为掺杂剂合成出了聚苯胺材料,运用UV-vis,FT-IR,TG-DTA,X-射线粉末衍射测试手段对杂多酸盐掺杂聚苯胺材料进行了表征。     

Mg掺杂GaN结构及电子结构的理论研究

采用基于密度泛函理论的赝势平面波方法研究了金属元素Mg掺杂GaN的结构及电子结构性质.计算金属Mg分别替换Ga和N原子后体系的结合能,得到Mg原子更容易替换Ga原子,与他人的结果一致.掺杂后晶格常数a和c反而略有增大,并且高压下的情况是类似的.Mg掺杂后GaN电子结构显示掺杂使得GaN带隙略有增加,压强从0增加到20GPa,掺杂前后带隙值分别增大约39.1%和38.4%.     

Tunable and enhanced luminescence of Ba2−xCaxSiO4−yN2/3y:Eu2+ phosphors for white light-emitting diodes

Color tuning and luminescence enhancement are predominant challenges for improving the performance of white light emitting diodes(LEDs) toward commercial application. In this paper, a novel promising Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y):Eu~(2+) tphosphors with tunable and enhanced luminescence for phosphors converted LEDs(pc-LEDs) have been successfully synthesized by a direct gas-reduction nitridation method. The effects of Ca and N doping on the phase purity, morphology and optical properties of Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y):Eu~(2+) tphosphors were also systematically investigated. The optical results show that Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y):Eu~(2+) tphosphors can be actively excited over a broad range from 250 to430 nm. With the adding of different concentrations of Ca~(2+) tions in phosphors, the emission color wavelength can be tailored from 501 to 441 nm by a 375 nm NUV LED excitation source. Furthermore, it has been found that the emission and absorption of Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y) tphosphor can be significantly improved when N~(3-) ions were introduced into the host lattices. The intensity of Ba_(1.5)Ca_(0.5)SiO_(4-y)N_(2/3y):Eu~(2+) tphosphor was 3.4 times higher than the phosphor without N doping. The fabrication and characterization of pc-LEDs using Ba_(2-x)Ca_xSiO_(4-y)N_(2/3y):Eu~(2+) tphosphors-silica gel as the coating layer onto 375 nm-emitting In Ga N LED caps demonstrated the superior optical and current tolerant properties,making it a promising and competitive candidate for commercial utilization in white LED applications.     

金属阳离子对〔Cdx Mg_(6-x)Al_2(OH)_(16)〕~(2+)〔S·2H_2O〕~(2-)导电性质的影响

研究了水滑石〔CdxMg6-xAl2 (OH) 16〕2 + 〔S·2H2 O〕2 -的中温水热合成 ,和掺杂Cu2 + 离子后对其导电性质的影响 ,计算得到了在一定温度下的该化合物导电活化能