三维有序大孔ZrO2的制备及其光学性质

以聚苯乙烯(PS)微球作为模板剂,采用溶胶-凝胶及煅烧处理等方法制备了三维有序大孔ZrO2材料。通过X射线衍射(XRD)以及扫描电镜(SEM)对其结构和形貌进行了表征。结果表明所制备的ZrO2材料为孔径约为180 nm的高度有序、堆叠紧密的三维有序大孔结构(3DOM)。对3DOM ZrO2的光谱分析表明:在宽禁带的ZrO2材料中存在着本征缺陷发光(氧空位缺陷)和杂质缺陷(主要杂质为TiO2)发光,掺杂浓度与基质的晶相结构对两种发光起到了至关重要的作用。对发光过程提出了简单的机理模型。     

不同氧气流量对直流磁控溅射TiO2薄膜的影响

采用直流反应磁控溅射法,以高纯Ti为靶材,高纯O2为反应气体,制备了TiO2薄膜.研究了氧气流量对薄膜结晶取向、表面形貌和光学性能的影响.研究发现,TiO2薄膜主要呈锐钛矿TiO2(101)择优取向,当氧气流量较小时,薄膜中还含有金属Ti(100),氧气流量较大时,薄膜含TiO2(101)和TiO2(004),成多晶态;薄膜的粗糙度和颗粒大小都随氧气流量的增大而增大;薄膜在400～1 100nm可见-近红外波段有较高的透射率并且其吸收峰随着氧气流量的增大而红移,当氧气流量为5sccm时,平均透射率最高.     

Surface reconstruction on stishovite SiO2,HfO2 and rutile TiO2 （001）

This paper systematically investigates the surface reconstruction processes and patterns on stishovite SiO 2,HfO 2 and rutile TiO 2 (001) by using classical molecular dynamics.It is found that these three surfaces relax instead of reconstruction at 0 K,and have little possibility to reconstruct below 40 K.Above 40 K,surface reconstructions take place as collective atomic motion which can be speeded by higher temperature or compressed strain.Several reconstruction patterns with approximate surface energies are found,and electrostatic potentials on them are also provided in comparison with possible microscopic results.     

溶胶-凝胶法制备BaTiO3/SrTiO3多层膜的介电增强效应

采用溶胶凝胶法,在PtTiSiO2Si衬底上逐层制备了BaTiO3SrTiO3多层膜.从多层膜的XRD图可看出明显的双峰,分别对应为BaTiO3和SrTiO3的特征峰,表明样品已形成了多层膜结构.与同厚度的Ba05Sr05TiO3单层膜比较,BaTiO3SrTiO3多层膜的介电系数得到了明显的增强,在频率为10kHz时,周期为66nm的BaTiO3SrTiO3多层膜相对于同厚度的Ba05Sr05TiO3薄膜的介电系数从245增强到595,而损耗依然保持较低,分别为0029和0033.研究同时表明,BaTi 关键词： 溶胶-凝胶法 多层膜 介电增强     

Ni/HfO_2/Pt阻变单元特性与机理的研究

研究了Ni/HfO2(10 nm)/Pt存储单元的阻变特性和机理.该器件具有forming-free的性质,还表现出与以往HfO2(3 nm)基器件不同的复杂的非极性阻变特性,并且具有较大的存储窗口值(105).存储单元的低阻态阻值不随单元面积改变,符合导电细丝阻变机理的特征.采用X射线光电子能谱仪分析器件处于低阻态时的阻变层HfO2薄膜的化学组分以及元素的化学态,结果表明,Ni/HfO2/Pt阻变存储器件处于低阻态时的导电细丝是由金属Ni导电细丝和氧空位导电细丝共同形成的.     

Theoretical Study on Destruction Mechanism of 2,3,7,8-TCDD by O3 and NO3

采用B3LYP/6-31G(d)方法优化获得O₃及NO₃降解2,3,7,8-TCDD反应通道上驻点的几何构型， 得到微观反应进程，并采用MP2/6-311G(d,p)//B3LYP/6-31G(d)方法计算得到相关反应的活化能. 研究表明，O₃和NO₃采用不同的方式对2,3,7,8-TCDD进行降解. O₃通过臭氧加成及碳碳双键断裂使2,3,7,8-TCDD降解，而NO₃通过氯取代反应使得2,3,7,8-TCDD上2,3,7,8取代位置上的氯原子被取代为氧原子，从而达到有效降解的目的. O₃降解2,3,7,8-TCDD的反应能垒显著小于NO₃降解2,3,7,8-TCDD的反应能垒，表明O₃降解2,3,7,8-TCDD的能力显著高于NO₃.     

单相Na0.5Bi0.5Ti1-xMnxO3陶瓷中的多铁性

溶胶凝胶法制备了Na0.5Bi0.5Ti1-xMnxO3(x=0,0.02,0.04)陶瓷样品,X射线衍射(XRD)分析表明陶瓷样品均形成了单一的钙钛矿(ABO3)型结构且没有杂质相的形成.随着Mn含量的增加,XRD峰向高角度方向移动,表明Mn离子进入Na0.5Bi0.5TiO3晶格.掺杂样品均表现出室温铁磁性和铁电性.磁测量表明样品中存在复杂的磁相互作用,包括铁磁,反铁磁和顺磁相互作用.以上结果表明,通过Mn的掺杂可以使铁电材料Na0.5Bi0.5TiO3转变为多铁材料.     

HfO2中ZrO2含量对266nm HfO2/SiO2多层膜反射率的影响

用两种不同纯度的HfO2材料与同一纯度的SiO2材料组合，沉积Λ／4规整膜系(HL)^11H形成266nm的紫外反射镜，发现反射率相差0．7％左右。用X光电子能谱法分析了高反膜中表层HfO2中的成分，发现ZrO2的含量相差一个数量级左右。为确定形成这种差别的原因，用辉光放电质谱法测定了这两种HfO2材料中锆(Zr)及其钛(Ti)、铁(Fe)的含量，发现Zr是其中的最主要的杂质，两种HfO2材料中Zr含量有一个数量级的差别。说明在266nm波段，HfO2中ZrO2的含量会对HfO2／SiO2高反膜的反射率造成影响。根据HfO2单层膜的光谱曲线，推算出了这两种材料的消光系数的差别，并用Tfcalc膜系设计软件进行理论和镀制结果的模拟，得到与实验测试一致的结果。     

溶胶-凝胶法制备Bi0.5Na0.5TiO3陶瓷及其电学特性

用溶胶-凝胶工艺成功制备出Bi05Na05TiO3纳米微粉，并利用此微粉烧结出高致密度的Bi05Na05TiO3陶瓷.这种新工艺制备的Bi05Na05TiO3陶瓷，其压电性能远远高于普通方法制备的陶瓷，其中压电常数d33和机电耦合系数kt分别高达102×10-12C/N和58%.同时发现，对于这种Bi05Na05TiO3陶瓷，室温时只需施加100kV/cm左右的交变电场，就可得到矩形度极好的饱和回线，得到的剩余极化Pr和矫顽场Ec分别为32μC/cm2和61kV/cm.而在100℃以上只需施加35kV/cm的极化电场就可使样品充分极化.     

HfO2/SiO2高反射膜的缺陷及其激光损伤

用原子力、Normaski和扫描电子显微镜等分析仪器,对高损伤阈值薄膜常采用的HfO2光损伤所形成的孔洞,与镀制过程中形成的孔洞形貌相似,激光再损伤能力也相似。低能量密度的激光把节瘤缺陷变为孔洞缺陷是激光预处理提高薄膜损伤阈值的原因之一。     

Phase Relations and EOS of ZrO 2 and HfO 2 Under High-temperature and High-pressure

The phase relations and equations of state of ZrO 2 and HfO 2 high-pressure polymorphs have been investigated by means of in situ observation using multi-anvil type high-pressure devices and synchrotron radiation. Baddeleyite (monoclinic ZrO 2 ) transforms to two distorted fluorite (CaF 2 )-type phases at 3-4 GPa depending on temperature: an orthorhombic phase, orthoI, below 600 °C and a tetragonal phase, which is one of the high-temperature forms of ZrO 2 , above 600 °C. Both orthoI and tetragonal phases then transform into another orthorhombic phase, orthoII, with a cotunnite (PbCl 2 )-type structure above 12.5 GPa and the phase boundary is almost independent of temperature. OrthoII is stable up to 1800 °C and 24 GPa. In case of HfO 2 , orthoI is stable from 4 to 14.5 GPa below 1250-1400 °C and transforms to the tetragonal phase above these temperatures. OrthoII of HfO 2 appears above 14.5 GPa and is stable up to 1800 °C at 21 GPa. The unit cell parameters and the volumes of these high-pressure phases have been determined as functions of pressure and temperature. The orthoI/tetragonal-to-orthoII transition of both ZrO 2 and HfO 2 is accompanied by about 9% volume decrease. The bulk moduli of orthoII calculated using Birch-Murnaghan's equations of state are 296 GPa and 312 GPa for ZrO 2 and HfO 2 , respectively. Since orthoII of both ZrO 2 and HfO 2 are quenchable to ambient conditions, these are candidates for super-hard materials.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Theoretical evaluation of zirconia and hafnia as gate oxides for si microelectronics

Parameters determining the performance of the crystalline oxides zirconia (ZrO2) and hafnia (HfO2) as gate insulators in nanometric Si electronics are estimated via ab initio calculations of the energetics, dielectric properties, and band alignment of bulk and thin-film oxides on Si (001). With their large dielectric constants, stable and low-formation-energy interfaces, large valence offsets, and reasonable (though not optimal) conduction offsets (electron injection barriers), zirconia and hafnia appear to have considerable potential as gate oxides for Si electronics.     

Bonding, energies, and band offsets of Si-ZrO2 and HfO2 gate oxide interfaces

New oxides with high dielectric constant are required for gate oxides. ZrO2 is a typical example with ionic bonding. We give the rules for bonding at interfaces between Si and ionic oxides, to satisfy valence requirements and give an insulating interface. Total energies and band offsets are calculated for various (100)Si:ZrO(2) and HfO2 interface structures. The oxygen-terminated interface is found to be favored for devices, because it has no gap states and has a band offset which is rather independent of interfacial bonding.     

The isoelectronic series ScF through ThO—I notes on the band spectra of TiO,HfO and ThO

The band spectra of TiO, HfO and ThO are treated, especially for later use in connection with the isoelectronic (in valence electrons) series ScF, TiO, ZrO, HfO and ThO. Franck-Condon factors and r-centroids for 12 HfO and ThO band systems are presented. Some recommendations for future spectral studies on UO are given, based on ThO results, since ThO apparently is the only diatomic oxide of the actinides to have known electronic band spectra.     

Study on Laser Conditioning of Optical Coatings

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Two-dimensional polaronic behavior in the binary oxides m-HfO2 and m-ZrO2

We demonstrate that the three-dimensional (3D) binary monoclinic oxides HfO2 and ZrO2 exhibit quasi-2D polaron localization and conductivity, which results from a small difference in the coordination of two oxygen sublattices in these materials. The transition between a 2D large polaron into a zero-dimensional small polaron state requires overcoming a small energetic barrier. These results demonstrate how a small asymmetry in the lattice structure can determine the qualitative character of polaron localization and significantly broaden the realm of quasi-2D polaron systems.     

掺杂BaHfO3电子结构与力学性能的第一性原理研究

在广义梯度近似（GGA）下,采用基于密度泛函理论的第一性原理方法研究了掺杂对BaHfO3的电子结构与力学性能的影响．电子结构计算表明：优化的BaHfO3晶格常数与实验值吻合较好,BaHfO3为一种间接带隙的绝缘体材料．掺杂Sr和Ti后该材料仍为间接带隙材料,Ba0.5Sr0.5HfO3的带隙增大,绝缘体特征增强,而BaHf0.5Ti0.5O3的带隙显著减小,呈现出半导体材料的特征．由态密度分析可知,掺杂后带隙的变化主要是由于导带底的移动造成的．力学性能分析表明：与BaHfO3相比,Ba0.5Sr0.5HfO3的剪切模量和杨氏模量均明显减小,材料硬度减弱;BaHf0.5Ti0.5O3的剪切模量及杨氏模量均明显增大,材料硬度增强．电子密度分布分析揭示了掺杂改变体系价电子浓度的分布情况,使BaHfO3的价健特性发生了变化,这是材料硬度改变的内在原因．可见,掺杂能够有效地调控体系的硬度,该研究结果为掺杂BaHfO3力电材料的设计与应用提供了理论依据．