Al-Cr二元合金中的一个新正交相O-A11Cr2

通过透射电镜原位观察,发现单斜η-Al11Cr2相在800℃保温2 h后,其三个主带轴电子衍射图中的超点阵弱点逐渐减弱直至消失,且a轴和c轴所成的角度由91°变为90°.这些变化意味着单斜η-Al11Cr2相在加热后转变为一个新相.点阵参数为a≈1.2428 nm,b≈1.2658 nm,c≈3.0456 nm的体心正交相,命名为O-Al11Cr2.其[010]电子衍射图具有伪十次对称特点,因此也是一个十重对称准晶近似相.     

单斜η-Al11Cr2相的确定

本文用高温快冷的方法得到了Al-Cr二元合金系中η-Al11Cr2相的单晶,综合单晶X射线衍射、选区电子衍射以及高分辨电子显微像等研究方法确认η-Al11Cr2为单斜相,a=1.77348(10)nm,b=3.04555(17)nm,c=1.77344(10)nm,β=91.0520(12)°,空间群为C2/c.通过对名义成分为Al11Cr2的铸锭在不同温度下进行退火处理后的金相分析,首次观察到了包晶反应μ-Al4Cr L(→)η-Al11Cr2,且证实了共析反应η-Al11Cr2(→)μ-Al4Cr θ-Al7Cr的存在.     

Mg-Zn-Y合金中W′相与W相的相变研究

Mg?Zn?Y合金中面心立方结构的W′和W相均与二十面体准晶（ IQC）相有密切联系,但W′相的结构还存在争议。综合利用电子衍射分析、能谱分析和像差校正扫描透射电子显微术,确定 W′相的化学成分为Zn60?1 Mg23?9 Y16,具有Cd45 Sm11型结构,内部存在四面体对称的Friauf多面体原子团簇而非二十面体对称团簇,因此W′相不宜称为IQC相的近似相。利用原位加热透射电子显微术研究发现W′相在683 K可转变为W相。二者具有立方－立方取向关系,且W′／W界面具有良好的外延性。热激活作用下原子的扩散和平移引起W相在W′上外延形核长大。     

Cr_2O_3掺杂对钡硼硅微晶玻璃的性能影响

采用固相合成法制备了高膨胀系数钡硼硅微晶玻璃材料。通过对该微晶玻璃进行X线衍射仪(XRD)、扫描电子显微镜(SEM)测试分析研究铬掺杂对BaO-B2O3-SiO2力、热、电性能及微观机理的影响。结果显示,热膨胀系数与介电损耗随Cr2O3含量增加而增大,研究表明,加入Cr2O3会促进该体系晶粒的生长,并促使晶相由石英晶相转变为方石英晶相,方石英热膨胀系数较高,其晶相含量增多导致热膨胀系数增大。该体系Cr2O3质量分数为0.5%时,制备出具有较高热膨胀系数(18.44×10-6/℃),较高抗弯强度(187 MPa),较低相对介电常数(5.5)的封装材料。     

Mg97Zn1Y2(at.%)合金中14H型长周期相室温拉伸变形结构电子显微学表征

本文采用聚焦离子束切割技术,精确切取了固溶Mg₉₇Zn₁Y₂(at.%)合金室温拉伸样品中LPSO相及其周边镁基体的拉伸变形结构。采用高分辨透射电子显微学方法并结合HAADF-STEM技术对合金中14H型LPSO相及周边镁基体的变形结构进行了表征和分析。研究结果清楚地揭示了LPSO板条在拉伸应力下可以同时通过基面滑移和扭折两种方式协调基体变形。基面滑移优先发生在LPSO板条中与基面平行的残余纳米薄Mg层处,并沿LPSO/Mg界面开动形成明显的表面台阶。而在局域应力集中的作用下,扭折变形除了开动常见的基面位错外还证实有非常见的柱面位错的参与。     

CuO掺杂对BaZn_2Ti_4O_(11)陶瓷微波介电性能的影响

采用固相反应法制备了CuO掺杂的BaZn2Ti4O11陶瓷,研究了所制陶瓷的物相、微观结构和微波介电性能。结果表明,CuO既可以在晶界处形成低共熔体,导致液相烧结,降低烧结温度40℃,又可使部分Cu2+进入晶格取代了部分Zn2+,增加Q.f值。掺杂质量分数0.5%的CuO在1 160℃烧结2 h所制得BaZn2Ti4O11陶瓷的微波介电性能较佳:相对介电常数εr=29.4,Q.f=50 500 GHz,频率温度系数τf=–35.6×10–6/℃。     

退火温度对Fe_(40)Co_(40)Zr_7Nb_2AlB_9Cu合金的结构、热行为及磁性能的影响

采用单辊快淬法制备了Fe40Co40Zr7Nb2AlB9Cu非晶合金薄带,在不同温度下对其进行等温退火处理。研究了退火温度对合金的结构、热行为和磁性能的影响。结果表明:Fe40Co40Zr7Nb2AlB9Cu非晶合金的DTA曲线存在2个晶化放热峰,晶化激活能分别为267.3 kJ/mol和188.3 kJ/mol。其晶化过程为:非晶→非晶+α-FeCo→α-FeCo+Co2Zr+ZrCo3B2+Fe(Co)3Zr。α-FeCo相的晶化体积分数和晶粒尺寸随退火温度的升高而逐渐增大。低于873 K退火时,矫顽力变化不明显;873 K退火时,矫顽力达到最小值0.27 kA/m;高于873 K退火时,矫顽力逐渐增大。     

Yb:(Y1-xLax)2O3透明陶瓷实现激光输出

掺Yb3 的晶体是用激光二极管(LD)抽运的一种极有前景的固体激光材料.Yb3 为最简单的激光活性离子,电子构型为[Xe]4f13,仅有一个基态2F7/2和一个激发态2F5/2,两者的能量间隔为10000 cm-1,在晶场作用下,能级产生斯塔克分裂,形成准三能级的激光运行机制.     

Study of threading dislocations in the plan-view sample of SiGe/Si(001) superlattices by transmission electron microscopy

Interfacial defects due to a mismatch of 1.378% between substrate and epilayer were examined in a Si_0.67Ge_0.33/Si(001) superlattice by transmission electron microscopy (TEM). Plan-view specimens from the superlattice were prepared to investigate the defects in the structure. It was observed that 60°C-type misfit dislocations associate with point contrast on and at their ends. This point contrast was found to represent threading dislocations by using tilt experiments in the microscope. Consequently, stereo electron microscopy was used to examine the threading dislocations. It was discovered that the threading dislocations are not on the {111} slip planes but can be almost parallel to the [001] zone axis.     

A new precipitate phase in Al-4wt. % Cu thin-film interconnects

We report here the identification of a new precipitate phase in thin-film Al-4wt.%Cu metallization used for interconnects on integrated circuits. The phase is based on a trigonal distortion of a face centered cubic lattice. Computer simulation of electron diffraction intensities suggests that the basis structure is isomorphous with Al₂Ca but with a large and ordered population of vacancies on Cu sites. The reason for the formation of the new phase and its implications for electromigration reliability are discussed.     

Study on stacking faults and microtwins in wide bandgap II-VI semiconductor heterostructures grown on GaAs

ZnMgSSe and ZnSSe layers grown on GaAs substrates with GaAs buffer layers by molecular beam epitaxy have been examined by transmission electron microscopy (TEM). The depth level at which paired triangular stacking faults are nucleated in the ZnMgSSe/GaAs heterostructure has been investigated by using the plan-view TEM technique. It has been found that in the ZnMgSSe/GaAs heterostructure the nucleation of the paired stacking faults occurs within a range of depth which starts at the II-VI/GaAs interface and ends at a level that is above the interface by about 120 nm. The dominant type of defects in ZnSSe layers, which have the single triangular shape, has been identified to be microtwins by high resolution TEM.     

Structural study of GaN grown on (001) GaAs by organometallic vapor phase epitaxy

Detailed transmission electron microscope (TEM) and transmission electron diffraction (TED) examination has been performed on organometallic vapor phase epitaxial GaN layers grown on (001) GaAs substrate to investigate microstructures and phase stability. TED and TEM results exhibit the occurrence of a mixed phase of GaN. The wurtzite (α) phase grains are embedded in the zinc-blende (β) phase matrix. It is shown that there are two types of the wurtzite GaN phase, namely, the epitaxial wurtzite and the tilted wurtzite. The tilted wurtzite grains are rotated some degrees ranging from ∼5° to ∼35° regarding the GaAs substrate. A simple model is presented to describe the occurrence of the mixed phases and the two types of the wurtzite phase.     

氨化Si基Ga2O3/Co薄膜合成GaN纳米线及其表征

采用磁控溅射技术先在Si衬底上制备Ga2O3/Co薄膜,然后在950"C下流动的氨气中进行氨化反应制备GaN纳米棒.应用X射线衍射、扫描电镜、傅里叶红外吸收光谱、选区电子衍射和高分辨透射电子显微镜对样品进行表征.结果表明,采用此方法得到了六方纤锌矿结构的GaN单晶纳米棒.观察发现纳米棒表面光滑.并讨论了GaN纳米棒的生长机制.     

氨化Si基Ga2O3/Co薄膜合成GaN纳米线及其表征

采用磁控溅射技术先在Si衬底上制备Ga2O3/Co薄膜,然后在950"C下流动的氨气中进行氨化反应制备GaN纳米棒.应用X射线衍射、扫描电镜、傅里叶红外吸收光谱、选区电子衍射和高分辨透射电子显微镜对样品进行表征.结果表明,采用此方法得到了六方纤锌矿结构的GaN单晶纳米棒.观察发现纳米棒表面光滑.并讨论了GaN纳米棒的生长机制.     

On GF（p）-linear complexities of binary sequences

also presented.     

Diffuse diffracted features and ordered domain structures in GalnP layers grown by organometallic vapor phase epitaxy

Transmission electron diffraction (TED) and transmission electron microscope (TEM) studies have been made of organometallic vapor phase epitaxial Ga_xIn_1−xP layers (x ≈ 0.5) grown at temperatures in the range 570–690°C to investigate ordering and ordered domain structures. TED and TEM examination shows that the size and morphology of ordered domains depend on the growth temperature. The ordered domains change from a fine rod-like shape to a plate-like shape as the growth temperature increases. The domains are of width 0.6∼2 nm and of length 1∼10 nm. Characteristic diffuse features observed in TED patterns are found to depend on the growth temperature. Extensive computer simulations show a direct correlation between the ordered domain structures and such diffuse features. A possible model is suggested to describe the temperature dependence of the ordered domain structure.