Zn1-xFexO精细结构的第一性原理研究

计算了Fe掺杂ZnO体系几何结构和电子结构,分析了掺杂对ZnO晶体的电子结构、磁矩、电子态密度、磁学性质的影响.所有计算都是基于密度泛函理论(DFT)框架下的第一原理平面波赝势方法.计算结果表明:Fe3 并不能占据准确的Zn2 位置,而是沿c轴方向位移了一段距离Δz,这是引起Zn1-xFexO铁磁性的主要原因,理论计算结果与试验结果吻合.     

高压对Gd掺杂ZnO的电子结构和磁性影响研究

压力可以作用于物质的晶体结构内部,影响并改变物质整体性质.为进一步探究高压对Gd掺杂ZnO试样的电子结构及磁性影响,运用金刚石对顶砧压机和Materials Studio4.4软件包中的CASTEP运算程序,完成高压实验制备工作;利用基于密度泛函理论的第一性原理计算高压作用下Gd掺杂ZnO试样内部分子的变化情况,并对G...     

Fe0．875Mn0．125Si2的几何结构与电子结构的第一性原理研究

采用基于密度泛函理论的赝势平面波方法，对掺Mn的β-Fesi2的几何结构和电子结构进行了计算。计算表明：（1）杂质的掺入改变了晶胞体积及原子位置，掺杂是调制材料电子结构的有效方式；（2）在β-FeSi2中掺入杂质时掺杂原子的置换位置具有择位性，Mn掺杂时倾向于置换FeI位的Fe原子；（3）能带结构计算表明：掺Mn使得β-FeSi2的费米面向价带移动，形成了P型半导体。     

Al掺杂CeO2体系结构和电子性质的第一性原理研究

CeO2因具有较高的储氧/释氧能力、较强的氧化-还原性能,受到人们极大关注,并在工业催化领域其有重要应用.杂质对CeO2性能具有重要影响,用基于密度泛函理论的第一性原理方法和具有三维周期性边界条件的超晶胞模型,计算并分析了金属Al掺杂对CeO2原子结构、电子结构和化学特性的影响.在计算中,用DFT+U方法描述Ce 4f电子的强关联效应,用基于GGA的PAW势描述芯电子与价电子的相互作用.计算结果表明,Al掺杂降低还原能,使形成氧空位更容易,并从原子结构和电子结构等方面对掺杂降低还原能的机理进行了分析.     

玻璃衬底和Si衬底制备的Zn0.96Nd0.04O薄膜的结构研究

通过射频磁控溅射技术在玻璃衬底和Si（111）村底上制备了Zn0.96Nd0.04O薄膜。XRD分析表明,Zn0.96Nd0.04O薄膜是具有C轴择优生长的纳米多晶薄膜,Nd以替位原子的形式存在于ZnO晶格,Nd掺杂没有改变ZnO晶格结构。从AFM图中看出,薄膜表面形貌较为粗糙,Si衬底薄膜的晶粒具有规律且晶粒尺寸大于玻璃衬底。     

Mn掺杂锶铁氧体SrFe12O19电子结构及磁性的第一性原理研究

为了揭示掺杂离子对具有磁铅石构型的锶铁氧体材料磁性能的影响, 本研究探讨了锶铁氧体及其锰掺杂体系的稳定构型及其磁结构。研究结果表明, 锶铁氧体为亚铁磁性, 与前期的研究结果相吻合。通过比较GGA和GGA+U计算方法, 发现U值的选取对体系的电子结构和原子磁矩有显著影响。当U值为3.7 eV时, 体系由金属性转变为自旋向上带隙为1.71 eV的半导体。原胞总磁矩为40 μ_B。对于Mn替换掺杂的SrFe_12-xMn_xO₁₉体系, 通过不同占据位能量比较, 当单个Mn原子替换(x=0.5)时, Mn离子优先占据Fe (12k)位置; 而当两个Mn原子替换Fe原子(x=1.0)时, 两个Mn分别占据Fe (12k)和Fe (2a)位置。Mn掺杂对锶铁氧体的结构影响较小, 但对于体系的总磁矩和电子结构有较明显的影响。在Mn含量x=0.5和x=1.0时, 自旋向上带隙值分别降低到0.85和0.59 eV, 原胞的总磁矩为39和38 μ_B。本研究可为实验研究提供理论指导。     

Al掺杂纤锌矿ZnO的电子结构研究

采用基于密度泛函理论(DFT)的总体能量平面波超软赝势法,电子交换关联能结合广义梯度近似(GGA)PW91形式,对Al原子不同掺杂位置的ZnO超原胞进行了几何优化,计算分析了晶体结构参数及掺杂模型的电子结构.结果表明,几何优化后掺杂晶胞z轴方向出现收缩现象,两种模型在杂质掺入后半导体ZnO导电能力提高,形成置换杂质模型的可能性要大于间隙杂质模型,掺杂Al和基体ZnO的原子数配比直接影响导电性能,最后给出了电子轨道跃迁规律.     

镍间隙掺杂硅纳米线电子结构的研究

采用基于密度泛函理论的第一性原理的方法,对[100]方向镍间隙掺杂硅纳米线结构的稳定性和电子性质进行了计算。计算结果表明Ni原子更喜欢占据硅纳米线内部六角形间隙位置;掺杂体系费米能级附近的电子态密度来源于Ni3d态电子的贡献;同时发现不同构型的Ni掺杂硅纳米线,其带隙不同,且与未掺杂硅纳米线相比,带隙普遍减小。     

p型ZnO掺杂及其发光器件研究进展与展望

ZnO是一种新型的Ⅱ-Ⅵ族宽带隙半导体,具有很多优异的的光电性能.但一般制备出的ZnO薄膜材料均是n型,很难实现p型的掺杂.ZnO的p型掺杂是实现其光电器件应用的关键技术,也是目前ZnO研究的关键课题.目前在p型ZnO的掺杂理论和实验方面都有很大的进展,对此进行了详细的分析与论述,并且展望了p型ZnO薄膜制备的前景.     

Effect of annealing on the structure and magnetic property of Zn0.9Fe0.1S nanoparticles

Zn_0.9Fe_0.1S nanoparticles were synthesized in microemulsion and then annealed in nitrogen atmosphere at different temperatures. The XRD results show that the samples annealed below 300 °C are pure cubic ZnS. Higher annealing temperature introduces the Fe₃O₄ phase. The X-ray absorbing fine structure (XAFS) results indicate that annealing induces the Fe ions to change from divalence to trivalence and crystalline quality gradually improves with the increase of annealing temperature. In view of the structural characteristics indicated by XRD and XAFS, the origin of ferromagnetism at low annealing temperature may be attributed to trivalent Fe ions.     

Effects of Cu-doping on the magnetic state of Zn(0.9-x)Fe0.1Cu(x)O

Magnetization measurements were performed on a series of Zn(0.9-x)Fe0.1Cu(x)O samples (0 < x approximately 0.1) prepared using solid state reaction and sol-gel methods. Although Cu is nonmagnetic, we found that increasing Cu content increases the saturation magnetization and enhances the hysteresis losses. Curie behavior of the susceptibility at high temperature indicates the presence of ferromagnetic exchange interaction. Moreover, we found that the exchange interaction and the molecular field coefficient are both ferromagnetic and greatly enhanced with Cu-doping; however, the Arrott-Belov-Kouvel plot did not reveal the presence of spontaneous magnetization down to 4.2 K.     

Cd0.9Zn0.1Te晶体中的In掺杂研究

采用电感耦合等离子质谱仪（ICP-MS）和光致发光的手段研究了In在Cd0.9Zn0.1Te晶体中的分布及存在状态,浓度测试结果表明，In的分凝特性受生长条件影响很大，沿晶体轴向有效分凝因数在0．19到0．5之间变化。对高电阻和低电阻In掺杂Cd0.9Zn0.1Te晶体光致发光强度与温度依赖关系的研究表明，高电阻晶体D^0X峰存在两个热激活能2．8meV和21meV，低电阻晶体A^0X热激活能为3．4meV。分析认为In掺杂导致的自补偿效应是导致掺杂效率低下的原因。     

Structural,optical and magnetic properties of nanocrystalline Zn0.9Co0.1O-based diluted magnetic semiconductors

With a view to understand the influence of nano size on various properties of cobalt-doped ZnO-based diluted magnetic semiconductors, a series of materials were prepared by the citrate gel route. The phase and morphology studies have been carried out by X-ray diffraction and transmission electron microscopy, respectively. All the samples of the present investigation are found to have hexagonal wurtzite structure and crystallite sizes are found to vary from 25 nm to 65 nm. From the optical absorption measurements it has been observed that upon doping with cobalt, the energy band gap is found to shift towards lower energy side (red shift) while it shifts towards higher energy side (blue shift) when the crystallite size is increased continuously. It has been observed from the XPS results that oxidation state of Cobalt is +2 and that the difference in binding energies of Co 2p_3/2 and Co 2p_1/2 is found to increase continuously with increasing crystallite size. Finally, all the samples are found to exhibit room temperature ferromagnetism and the specific magnetization decreases with increasing crystallite size.     

Pt修饰的SrCe0.9Y0.1O3-δ膜的制备与电性能研究

为了提高质子-电子混合导电膜的电子导电性,采用浸渍法对SrCe0.9Y0.1O3-δ粉体进行Pt修饰,制备出含Pt的SrCe0.9Y0.1O3-δ质子导电膜(Pt/SCY膜),并对其致密性、物相、微结构、电子导电性进行了研究.研究结果表明,在1450℃保温3h,得到的Pt含量≤0.2%(质量分数)的Pt/SCY膜具有正交钙钛矿结构,且相对密度达98%.当保温时间延长或Pt掺入量增加时,Pt/SCY膜中出现SrY2O4和Y2O3相.Pt/SCY膜在H2还原前后具有不同的微观结构,通过对膜在空气中的交流阻抗谱测试,发现Pt修饰改变了400℃以下电子的传导机制,显著地提高了低温区电子导电率.     

衬底温度对Mg0.1Zn0.9O薄膜结构及光学性能的影响

利用射频磁控溅射技术在不同温度的(100)Si和玻璃衬底上成功地制备了c轴择优取向的Mg0.1Zn0.9O薄膜.通过X射线衍射(XRD)、场发射扫描电镜(FESEM)、紫外可见光分光光度计和光致发光谱研究了衬底温度对Mg0.1Zn0.9O薄膜结构、表面形貌和光学性能的影响,结果表明,在衬底温度为400℃时生长的Mg0.1Zn0.9O薄膜具有很好的c轴取向和较好的光学性能.用激发波长为300nm的氙灯作为激发光源得到不同衬底温度下Mg0.1Zn0.9O薄膜的室温PL谱.分析表明,紫外发光峰与薄膜的结晶质量密切相关,蓝光发射与氧空位有关.简单探讨了衬底温度影响紫外光致发光峰红移和蓝移的可能机理.     

A comparable study on temperature-dependent photo-luminescence spectra of Mg0.1Zn0.9O alloy films and ZnO nanoflakes

We make a comparison on the photoluminescence (PL) from the Mg_0.1Zn_0.9O film and ZnO nanoflakes (NFs) over the range of 10–300 K. It is clear that their PL spectra are dominated by the radiative recombination of localized or bound excitons at 10 K. As the temperature increases, these excitons are gradually converted toward free excitons (FX) or annihilate through a thermal dissociation/activation or a non-radiative recombination channel. In addition, it is found that the quenching behavior of integrated PL intensity exhibit two activation energies in the different temperature ranges for the NFs, suggesting that a re-localization of FX might occur during the range of 70–300 K.     

The point defect and electronic structure of K doped LaCo0.9Fe0.1O3 perovskite with enhanced microwave absorbing ability

ABO3 perovskites,owning unique properties,have great research prospect in electromagnetic wave absorption field.Normally,doping can significantly regulate the d...