μ相的平移畴与旋转畴

用JEM200CX电镜研究了GH128合金的析出物—μ相的畴结构,提出了畴界的原子结构模型。图1是沿[110]方向观察的μ相晶体的结构象及计算模拟象。在适当的成象条件下结构象的白点分布构成3~3 4~2网格,与μ相的五角反棱锥体有一一对应关系。图2是在μ相晶体里视察到的平移畴及旋转畴。图中箭头及字母P表示平移畴界,R表示旋转畴。有些平移畴内还出现MgCu_2畴(U处)及孪晶。(1)平移畴:平移畴界有(111)和(221)两种图3a是畴界为(111)的μ相平移畴的结构象。具有相同取向的μ相畴并列连接在一起构成(111)畴界两个平移畴之间的匹配是完整的,无畸变,在畴界形成两侧μ相畴之间的过渡结构。(111)畴界可以看成为与两侧μ相畴连接的4片(Co,Si)_(?) V_2类结构片(图3b)。(221)平移畴界有两种。第一种(221)畴界可以看成为旋转     

一维长周期反铁电畴界的电镜研究(Ⅱ——晶格象)

在Sn置换Zr的锆钛酸铅中(Pb_(0.99){([Zr_((?)-y)Sny]_((?)-y)、Tix)_(0.98)Nb_(0.02)}O_3,x=0.03,0.04;y=0.20)可以观察到铁电反铁电畴共存(图1),这是由于上述成份正处于相图中的准同型相界上,两相的自由能十分接近。在具有条纹状组织的A畴内,SAD具有卫星衍射。但是由电子衍射谱不能确定长周期反铁电畴是一维或二维有序,为此需用晶格象观察。在110—000—110对称衍射条件下成象。晶格象(图2)及其测微光度计描迹表明(图3),M多为8(间距为8,d 1/2 1/2 0),但也有M=7,8,9的情况,但无二维长周期现象。对应二维卫星衍射谱的晶格象如图4,证明存在的长周期是一维的。周期畴界沿(110)及(110)晶面发生,有相同的(100)晶面贯穿期间,但除以上的两相共存形式外,还观察到在反铁电区内以微畴形态存在的铁电畴叠栅图形。也有无长周期反相畴界的A畴与F畴相接。但是比祇有第三种形式的两相共存F—AF陶瓷,有长周期反畴结构的陶瓷需要更高的诱导电场才能诱发AF—F相变。     

用分子束外延在Si(100)衬底上生长CdTe和HgCdTe

用分子束外延在Si(100)衬底上生长出CdTc。可以得到两种取向:当CdTe直接沉积在Si(100)衬底上时,所得到的取向为(100)B CdTe;当首先生长ZnTe中间层时,所得到的取向为(100)CdTe。(111)B取向层由旋转90°的两个畴组成,仅具有一个畴的取向层能够在取向偏差8°的Si(100)上生长。为达此目地,还需要发现其最佳取向偏差。用反射高能电子衍射,光致发光光谱,扫描电子显微镜和x射线研究了这些取向层的特性。利用分子束外延技术,在(111)B CdTe层上还生长出Hg_(1-x)Cd_xTe;而前者被沉积在Si(100)衬底上。     

PbTiO_3/SrTiO_3(001)复杂畴组态和缺陷的研究北大核心CSCD

用透射电子显微镜对PbTiO_3/SrTiO_3(001)薄膜内部所形成的复杂畴组态以及畴壁处的位错进行了系统的研究。透射电镜结果和几何相位分析(GPA)表明,薄膜内部两个交叉的a畴内部出现了180°畴壁,导致在局部区域形成了全闭合畴结构,在铁电畴壁处观察到高密度位错。高分辨HAADF-STEM像分析显示,在90°畴壁处容易形成a<011>型位错,在180°畴壁处容易形成a<100>型位错,表明位错的形成与铁电畴壁类型存在强耦合关系。     

STM研究Si(111)7×7表面畴界结构

根据对Ｓｉ（１１１）表面各种不同畴界的研究，我们发现并提出了在畴界形成过程中决定这些畴界结构的三个重要因素：二聚体（ｄｉｍｅｒ）和顶戴原子（ａｄａｔｏｍ，亦称吸附原子）之间的相互作用；７×７单胞中层错半单元（ｆａｕｌｔｅｄｈａｌｆ）和非层错半单元（ｕｎｆａｕｌｔｅｄｈａｌｆ）的差异；亚稳态的（２ｎ＋１）×（２ｎ＋１）结构的影响。     

一维长周期反铁电畴界的电镜研究(Ⅰ—电子衍射)

对于CuAuⅡ合金中长周期有序结构的研究表明,CuAuⅡ电子衍射谱中的卫星斑点是由于每5个有序单胞间存在反相畴界而造成的。不久后的晶格象直接观察证实了这一事实。在由Sn置换的钙钛矿结构的锆钛酸铅(PSZT)中也发现了类似的卫星衍射(图1及2)在图2b中存在的1/2 1/2 0弱衍射在图2a中即不存在。图2a的000—110衍射间有6个斑点而2b中有7个卫星点,根据有{1/2 1/2 1/2}超点阵判定其反铁电相的电偶极子具有图3所示的立方胞结构。类似CuAuⅡ的有序模型提出了图4的一维反铁电畴长周期结构。以M个反铁电胞为单元的边界上,由于是反相畴界,电偶极子作平行排列。对这种两相共存结构推导得的结构振幅表示式如(1)式:     

铁电纳米结构的浸渍涂敷法制备和微结构STEM表征(英文)

本文利用浸渍涂敷法在硅基多孔氧化铝模版介质(孔径20nm-100nm)上制备了Pb(Zr0.53Ti0.47))3(PZT)铁电纳米结构,并利用扫描透射电子显微镜(STEM)观察了其表面形貌和剖面微结构.TEM像和X-射线能谱分析结果表明在多孔氧化铝模版孔道内形成了PZT纳米结构,其横向尺寸可通过改变氧化铝模版的孔径来调节.采用浸渍涂敷法可使PZT溶液贯穿整个氧化铝纳米孔道,在其内壁形成PZT涂层,厚度为4nm-15nm.氧化铝纳米孔道内的黑色TEM衬度线证实了PZT涂层的存在,其存在方式为连续介质型或离散的晶粒形状.平面STEM像显示PZT纳米结构具有椭球状形貌,这可能是由氧化铝纳米孔道的局部扭曲或PZT溶液在退火过程中的收缩引起的.在硅基多孔氧化铝模版介质上采用浸渍涂敷法制备的PZT有序纳米结构,在将来三维结构的非挥发性铁电存储器方面具有十分诱人的应用前景.     

LSAT(111)衬底上ZnO单晶薄膜的分子束外延生长

利用射频等离子体辅助分子束外延技术,在LSAT(111)衬底上制备高质量ZnO单晶薄膜.研究了衬底表面预处理及生长温度对ZnO外延膜的生长过程、外延取向关系以及表面形貌的影响.发现在较低温度下生长ZnO时,薄膜中容易形成30°旋转畴,而在较高温度下,可完全消除薄膜中的旋转畴,得到具有单一畴的ZnO单晶薄膜,讨论了旋转畴的起源以及生长温度对于消除旋转畴的作用.锐利的3×3 RHEED图像验证了ZnO薄膜具有O极性.     

LSAT(111)衬底上ZnO单晶薄膜的分子束外延生长

利用射频等离子体辅助分子束外延技术,在LSAT(111)衬底上制备高质量ZnO单晶薄膜.研究了衬底表面预处理及生长温度对ZnO外延膜的生长过程、外延取向关系以及表面形貌的影响.发现在较低温度下生长ZnO时,薄膜中容易形成30°旋转畴,而在较高温度下,可完全消除薄膜中的旋转畴,得到具有单一畴的ZnO单晶薄膜,讨论了旋转畴的起源以及生长温度对于消除旋转畴的作用.锐利的3×3 RHEED图像验证了ZnO薄膜具有O极性.     

LSAT(111)衬底上ZnO单晶薄膜的分子束外延生长

利用射频等离子体辅助分子束外延技术,在LSAT(111)衬底上制备高质量ZnO单晶薄膜.研究了衬底表面预处理及生长温度对ZnO外延膜的生长过程、外延取向关系以及表面形貌的影响.发现在较低温度下生长ZnO时,薄膜中容易形成30. 旋转畴,而在较高温度下,可完全消除薄膜中的旋转畴,得到具有单一畴的ZnO单晶薄膜，讨论了旋转畴的起源以及生长温度对于消除旋转畴的作用.锐利的3×3 RHEED图像验证了ZnO薄膜具有O极性     

Structure of [110] tilt grain boundaries in zirconia bicrystals

Cubic stabilized zirconia bicrystals with [110] symmetric tilt grain boundaries were fabricated by diffusion bonding of two single crystals with the composition of ZrO2-9.6mol%Y2O3. The structures of symmetric tilt small angle grain boundary and two types of symmetric tilt sigma3 grain boundaries with different grain boundary planes were observed by transmission electron microscopy (TEM). High-resolution transmission electron microscopy (HREM) observations clarified that the [110] small angle tilt grain boundary consists of periodic array of b = a/2[110] type edge dislocations. This result is consistent with Frank's dislocation model for small angle grain boundary. HREM observation also revealed that the 70.5 degrees sigma3 grain boundary shows atomically coherent grain boundary structure with the boundary plane of [111], while the 109.5 degrees sigma3 grain boundary accompanies grain boundary facets taking [111]/[115] asymmetric grain boundary plane. Because of the very low surface energy of [111] plane and/or high lattice matching of [111] and [115] type planes, the grain boundary faceting may be preferred in spite of increasing grain boundary area to about 6%. TEM-energy-dispersive X-ray spectroscopy (EDS) analyses were performed on both sigma3 grain boundaries, and the segregation of yttrium ions to the boundaries was detected in both cases. The amount of segregation is about the same in both sigma3 boundaries. It can be concluded that the segregation of yttrium ions to sigma3 grain boundary exists in cubic zirconia.     

Interactions of dislocations and antiphase (inversion) domain boundaries in III–V/IV heteroepitaxy

The potential for interactions of misfit strain relieving dislocations with inversion-type antiphase domain boundaries is considered for III–V on group IV growth. The specific cases of GaAs grown on Si (001) and vicinal (001) substrates are examined. It is shown that threading dislocation densities for these growths should be unacceptably high due to obstruction of threading dislocation motion by the antiphase domain boundaries, even when the boundaries are eliminated shortly after the inception of GaAs layer growth. Cutting of the antiphase domain boundaries by mobile dislocations would require creation of new highenergy surface area. It is suggested that more successful routes would be growth of a strain-relieving buffer or growth on a {hhk} surface.     

弛豫铁电陶瓷PST中反相畴结构的HREM研究

本工作用高分辨电子显微学方法研究了弛豫铁电陶瓷Ｐｂ（Ｓｃ０．５Ｔａ０．５）Ｏ３（ＰＳＴ）中的有序－无序结构，直接观察到有序－无序结构畴界及反相畴界（ＡＰＢｓ），对反相畴界的结构进行了分析，指出在ＰＳＴ中的反相畴往往是（１１１）面的层错，晶格位移在（１１１）方向上，位移量是１／２（１１１）。提出了在ＰＳＴ中ＡＰＢｓ形成的机制。     

A study of the evolution process of antiphase boundaries in GaAs on Si

A study by high resolution electron microscopy and conventional transmission electron microscopy of the process of closure of antiphase boundaries (APB) in atomic layer molecular beam epitaxy (ALMBE) grown GaAs on silicon is reported. A parallelepipedical shape, closed at the top by another boundary with a semispheric shape, is proposed for the during growth suppressed APBs in GaAs epilayers. Antiphase boundaries are mostly located in {100} plans. Sixty degree dislocations are involved in the process of bending of APBs from {110} to {11n} planes; this bending is the initial step which must take place to get a single domain by interaction of two APBs. The proposed shape for closed APBs is in good agreement with the quasi two-dimensional growth observed for GaAs grown on silicon by ALMBE.     

Metalorganic Chemical Vapor Deposition of CdTe(133) Epilayers on Si(211) Substrates

Single-crystalline CdTe(133) films have been grown by metalorganic chemical vapor deposition on Si(211) substrates. We studied the effect of various growth parameters on the surface morphology and structural quality of CdTe films. Proper oxide removal from the Si substrate is considered to be the principal factor that influences both the morphology and epitaxial quality of the CdTe films. In order to obtain single-crystalline CdTe(133) films, a two-stage growth method was used, i.e., a low-temperature buffer layer step and a high- temperature growth step. Even when the low-temperature buffer layer shows polycrystalline structure, the overgrown layer shows single-crystalline structure. During the subsequent high-temperature growth, two-dimensional crystallites grow faster than other, randomly distributed crystallites in the buffer layer. This is because the capturing of adatoms by steps occurs more easily due to increased adatom mobility. From the viewpoint of crystallographic orientation, it is assumed that the surface structure of Si(211) consists of (111) terrace and (100) step planes with an interplanar angle of 54.8°. This surface structure may provide many preferable nucleation sites for adatoms compared with nominally flat Si(100) or (111) surfaces. The surface morphology of the resulting films shows macroscopic rectangular-shaped terrace—step structures that are considered to be a (111) terrace with two {112} step planes directed toward 〈110〉.     

大马士革铜互连线织构的研究

采用EBSD研究了不同线宽和退火前后Cu互连线的织构和晶界特征分布.Cu互连线均具有多重织构,其中(111)织构强度最高.沉积态样品在室温下发生了自退火现象,并出现了一些异常长大的晶粒.随高宽比降低和退火处理,Cu互连线晶粒尺寸变大,(111)织构得到加强,而具有较低应变程度的织构与(111)织构强度的比例下降.沉积态样品出现了(111)<112>和(111)<231>织构组分.退火后,出现了(111)<110>组分,而且(111)<112>和(111)<231>组分得到增强.Cu互连线以大角度晶界为主,其中具有55°～60°错配角的晶界和∑3晶界比例最高,35°～40°的错配角和∑9晶界次之.随高宽比增加和退火处理,∑3晶界比例逐渐升高,∑9晶界比例下降.     

SBT材料微结构的TEM研究

本文利用透射电子显微术(TEM)对 SrBi2Ta2O9 (SBT) 材料(单晶、陶瓷及薄膜)的微结构进行了研究. 在(001)取向的SBT单晶材料及多晶陶瓷中观察到90°铁电畴结构.在SBT晶体中观察到大量的条带状四度反相畴界结构和少量的三度反相畴界结构,利用TaO6氧八面体的扭转和四态自旋结构模型,对反相畴界结构的实验观测结果进行了解释.在(001)取向的SBT铁电薄膜中,观察到小角晶界(倾角为8 2°)的位错分解现象,导致不全位错和层错的出现.利用平衡状态下两个不全位错之间的排斥力等于层错的吸引力,估算了小角晶界处的层错能量,大小为0 27～0 29 J/m2.小角晶界位错的分解对(001)取向的SBT铁电薄膜漏电流及耐疲劳特性具有重要的影响.     

Microstructure and domain configurations in ferroelectric PbTiO3 and Pb(Zr,Ti)O3 thin fims

Ferroelectric domain configurations in PbTiO₃ and Pb(Zr_xT_1−x)O₃ (PZT, x = 0.3 or 0.5) thin films have been studied by transmission electron microscopy. The PbTiOg and PZT thin films have been deposited by the ionized cluster beam technique and radio frequency sputtering, respectively. The grain size in these thin films is typically less than 0.5 μm. Lamellar 90°-domain features have been observed in both PbTiO₃ and PZT (30/70) samples. The domain walls correspond to the {011} twin boundaries. La-doping and Ca-modification are shown to affect the microstructure of the PZT films. No clear domain feature occurs in the PZT thin film that has composition near the morphotropic phase boundary. The effects of grain sizes are briefly discussed.     

Structure of CdTe(111)B grown by MBE on misoriented Si(001)

Single domain CdTe(111)B has been grown on Si(001) substrates tilted 1^o 2^o, and 4^o toward [110]. All the layers started with a double-domain structure, then a transition from a double- to a single-domain was observed by reflection high energy electron diffraction. A microscopic picture of this transition is presented. We also measured the tilt between CdTe(111)B and Si(001). The result does not follow the tilt predicted by the currently existing model. A new model of the microscopic mechanism of CdTe(111)B growth is presented. New evidence indicates that optimizing the tilt of the substrate surface is very crucial in improving the CdTe(111)B crystal quality.     

Raney合金中NiAl3相在脱铝过程中结构的转变

ａｎｅｙ催化剂由纳米级镍晶粒、未转变的ＮｉＡｌ３和Ｎｉ２Ａｌ３母相以及包围着它们的界面区组成。Ｘ射线衍射和高分辨电子显微镜观察发现，在脱铝过程中，ＮｉＡｌ３晶粒碎裂为纳米级尺寸，而Ｎｉ２Ａｌ３相则不出现这现象。