Thermal stability of Al-1%Si-0.5%Cu/TiSi2 contact structure

Stable TiSi₂ was formed by rapid thermal annealing (RTA) on single-crystal Si. Subsequently a 600 nm-thick Al-1%Si-0.5%Cu layer was deposited on the top of the formed TiSi₂ followed by furnace annealing for 30 min at 400–600 C in N₂ ambient atmosphere. The thermal stability of Al-1%Si-0.5%Cu/TiSi₂ bilayer and interfacial reaction were investigated by employing four-point probe, scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The composition and the phase of precipitates formed by the reaction of Al-1%Si-0.5%Cu with TiSi₂ were studied by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). It was found that the TiSi₂ layer was consumed by the reaction between TiSi₂ and Al-1%Si-0.5%Cu layer, resulting in precipitates at 550 C. The results from EDS revealed that the precipitates were composed of Ti, Al and Si. The precipitates were identified as Ti₇Al₅Si₁₂ ternary compound from XRD analysis.     

玻璃陶瓷Ba_2TiSi_2O_8的制备研究

Ba2TiSi2O8(BTS)玻璃陶瓷具有压电性、热释电性和非线性光学性能。采用溶胶凝胶法制备了BTS玻璃陶瓷,利用差热分析仪(DTA)分析了BTS干凝胶在煅烧过程中的化学反应及能量变化;X射线衍射仪(XRD)研究了BTS粉体的物相组成;激光粒度仪分析了BTS粉体的颗粒度;扫描电子显微镜(SEM)表征了BTS玻璃陶瓷样品断面的微观结构。研究结果表明:合成BTS粉体的最佳温度为850℃,所得颗粒的平均粒径为1.73μm。1250℃烧结制得的BTS玻璃陶瓷表现出致密、孔少、均匀的外观性质。     

High-Frequency Point-Contact Spectroscopy of TiSi2, TaSi2, and VSi2

High-frequency point-contact spectroscopy as well as conventional low-frequency PC spectroscopy has been used for determining the spectral functions of the electron-phonon interaction (EPI) for three disilicides TiSi₂, TaSi₂, and VSi₂. The temperature dependences of resistivity have been calculated from obtained EPI functions. Comparison of calculated dependences with known experimental data allowed correction of the electron-phonon interaction constants for the studied disilicides.     

Cu2+对掺Pb2+的β-BaB2O4纳米材料发光特性的影响

采用共沉淀法合成了掺杂Cu2 ,Pb2 的β-BaB2O4纳米材料,通过激发光谱和发射光谱研究了其发光性质,并探讨了Cu2 对Pb2 发光性能的影响.在β-BaB2O4:Pb2 的发射光谱中观察到位于630nm的强而稳定的发射峰.由于Cu2 和Pb2 在β-BaB2O4中形成复合发光中心,Cu2 和Pb2 共掺样品的发射光谱与Pb2 单独样品的发射光谱有很大的不同,Pb2 在β-BaB2O4:Cu2 ,Pb2 中的发光强度显著增强.     

Comparison of TiSi2 films prepared by diffusion and by co-evaporation

The effect of the preparation technique of TiSi₂ films on their properties is discussed. Films formed by the diffusion of silicon into a titanium layer evaporated on top of an Si/SiO₂/n⁺-poly-Si structure (where poly-Si is poltcrystalline silicon) have some unfavorable properties for metal/oxide/semiconductor technology. A significant improvement can be achieved using the co-evaporation technique to form the silicide layer. Superior silicides are obtained by sintering the co-evaporated TiSi₂ using short-time annealing.     

常压化学气相沉积法在玻璃上制备TiSi2薄膜的研究

高导电性TiSi2薄膜对低频电磁波有高反射率.在玻璃基片上成功制备TiSi2薄膜有望开发形成一种新型低辐射镀膜玻璃.本文结合工业在线和大面积生产的特点,以常压化学气相沉积法研究了TiSi2在玻璃基板上生长、制备及其与性能间的关系.研究发现:反应在温度低于680℃时,为反应控制;在高于680℃时,为传质控制.在700℃,Si/Ti摩尔比为3时,生成的TiSi2为低电阻的正交面心晶型(C54)TiSi2.Ti5Si3相和Si相的存在,对薄膜电阻的降低不利.TiSi2晶相含量越多,结晶越好,则电阻越小.     

Enhanced formation of low-resistivity TiSi2 contacts for deep submicron devices

Low resistivity C54-TiSi₂ is currently the most commonly used silicide for metal contacts in ultralarge scale integrated circuits devices. In the present paper, we review recent results of investigations on the effects of stress and high temperature sputtering on the formation of C54-TiSi₂. Enhanced formation of C54-TiSi₂ on (001)Si by tensile stress and high temperature sputtering is correlated to the growth of thicker amorphous interlayer at the Ti/(001)Si interface. The enhanced transformation is attributed to the presence of higher density of silicide crystallites, which serve as the nucleation sites for the C49-TiSi₂, in the amorphous layer. As a result, the average grain size of C49-TiSi₂ is smaller which leads to lower C49- to C54-TiSi₂ transformation temperature.     

飞秒激光诱导玻璃内Ba2TiSi2O8晶体的析出

使用聚焦后的800nm,150fs,250kHz的高重复频率飞秒脉冲激光器能够在BaO-TiO₂-SiO₂组分的玻璃内部三维选择性地诱导Ba₂TiSi₂O₈晶体的析出. 发光光谱显示这种晶体把入射的800nm光转化成了400nm的蓝光,因此这种析出的晶体具有非线性倍频特性. 通过拉曼光谱测定,在当前的玻璃组分中析出的晶体是Ba₂TiSi₂O₈. 研究表明,经250kHz的飞秒激光辐照一段时间后,在玻璃内部由于脉冲能量的连续沉积会使得激光辐照区域出现热积累效应,因此,该辐照区域的温度会不断升高以致超过玻璃析晶温度,最终诱导玻璃熔融析晶. 此外,对飞秒激光辐照区域不同部位进行拉曼光谱检测,结果表明：在整个区域Ba₂TiSi₂O₈晶体的析出呈现中间比外围明显的分布特点,因此晶体析出与辐照形成的温度梯度场有密切关系.     

Ba2TiGe2O8 and Ba2TiSi2O8 pyroelectric glass-ceramics

Pyroelectric glass-ceramics of composition Ba₂TiGe₂O₈ and Ba₂TiSi₂O₈ were prepred by crystallizing the glasses in a temperature gradient. High pyroelectric responses up to 50% of the single-crystal values were observed because of the high degree of orientation of the crystallites in the glass-ceramic samples. The piezoelectric and dielectric properties of the glasses and the glass-ceramics are also consistent with the properties of the single crystals.     

Investigation of vacancy in C54 TiSi2 using ab initio method

Investigated by ab initio plane-wave ultrasoft pseudopotential method based on generalized gradient approximation (GGA), it has been found that the formation energies of the vacancies in C54 TiSi₂ largely depend on the atomic chemical potentials of Ti and Si. In Si-rich limit, the formation energies of the Si and Ti vacancy are 2.39 eV and 2.40 eV while they are 1.53 eV and 4.07 eV in Ti-rich limit, respectively. The introduction of Si or Ti vacancy only slightly changes total density of states (DOS) and it also causes no considerable charge transfer.     

Microstructural characterization of grain-oriented glass-ceramics in the system Ba2 TiSi2O8-SiO2

In polycrystalline fresnoite, advantage of the piezo- and pyroelectric properties can be taken only if texturing along its polar [0 0 1]-axis can be achieved. We report on a novel technique to prepare grain-oriented glass-ceramics in the system fresnoite-SiO2 by electrochemically induced nucleation. Optimum conditions for grain orientation were determined by characterizing the microstructure of glass-ceramics prepared at 1150, 1200 and 1350 °C using electron microscopy and X-ray texture goniometry. At 1150 °C—due to the smallest crystal growth rate and highest nucleation rate—the most distinct orientation is obtained. The solidification of the glass-ceramic consist of three subsequent steps. First, dendritic fresnoite crystallizes most rapidly along its [0 0 1]-axis with [1 1 0] facet planes. Due to growth selection, the polar {c}-axes become oriented. Secondly, within the interdendritic areas, the pseudo-binary eutectic fresnoite-silica solidifies lamellarly. Finally, in the middle of the interspaces, a crystalline barium silicate coexisting with glassy silica is formed at 1200 °C and 1350 °C. At 1150 °C, however, a glass with the composition of the melt solidifies.     

Microstructure and Orientation of TiSi2Layers on (111) Si

The microstructure and orientation of TiSi₂films produced by pulsed illumination of Ti layers on (111) Si with incoherent light and by vacuum evaporation of Ti onto heated (111) Si substrates were studied by transmission electron microscopy. Both theC49- and C54-TiSi₂grains were found to have a number of orientations satisfying the basic crystallographic rules: a high density of coinciding sites at the interface and continuity of high-density planes across the interface. The TiSi₂/Si interfaces studied were shown to be incoherent. The major structural defects in TiSi₂layers were identified.     

Addition of Ba2TiSi2O8 to manganese-doped barium titanate: effect on oxygen diffusion and grain-boundary composition

The effect of barium titanium silicate additions to pure and manganese-doped barium titanate was studied by high-temperature conductivity and analytical electron microscopy. The results show that this addition precipitates during cooling as a second crystalline phase with only a small amount of amorphous phase left in a few grain boundaries. The secondary crystalline phase incorporates excess manganese left from the heterogeneous doping of barium titanate.     

CeO2掺杂TiO2光催化剂的性能研究

采用液相合成法制备CeO2掺杂TiO2光催化粉体,利用X射线衍射仪、紫外-可见分光光度计、FT-IR傅里叶变换红外光谱仪等对粉体的晶相组成、光谱吸收性能进行了表征,结果表明,掺杂后的TiO2经800℃热处理后仍呈锐钛矿型;CeO2/TiO2吸收光谱的阈值波长发生红移,但Ce掺杂浓度的增大对粉体的可见光吸收影响不大.光催化降解甲醛的结果表明,粉体在普通日光灯下对甲醛气体的降解率明显优于P25.     

掺C60磷酸盐玻璃的显微结构特征

本文报道了掺Ｃ６０磷酸盐玻璃显微结构特征的研究结果。透射电子显微镜观察表明：在玻璃介质中，Ｃ６０分子晶体能以结晶固体的形式稳定存在。     

Devitrification of TeO2-doped Fluoroaluminate Glass

Crystallization behavior of the glass system AlF3-MgF2-CaF2-SrF2-BaF2-YFa-TeO2 （AMCSBY-TeO2） was studied by the nonisothermal method using differential thermal analysis. The activation energy E and Avrami exponent g were determined by nonisothermal method. It is found that the value of E varies with increasing TeO2 and reaches a minimum at 10 mol fraction TeO2, while g decreases from 3.65 to 1.78 with the addition of TeO2. X-ray diffraction shows that Ba2TeaOs, MgTe205, and SrTeOa phase formed when the glasses were reheated. The addition of TeO2 changes the crystallization mechanism and improves the stability of the fluoroaluminate glass.     

Tunable light emission from quantum-confined excitons in TiSi2-catalyzed silicon nanowires

Visible and near-infrared photoluminescence (PL) at room temperature is reported from Si nanowires (NWs) grown by chemical vapor deposition from TiSi2 catalyst sites. NWs grown with average diameter of 20 nm were etched and oxidized to thin and passivate the wires. The PL emission blue shifted continuously with decreasing nanowire diameter. Slowed oxidation was observed for small nanowire diameters and provides a high degree of control over the emission wavelength. Transmission electron microscopy, PL, and time-resolved PL data are fully consistent with quantum confinement of charge carriers in the Si nanowire core being the source of luminescence. These light emitting nanowires could find application in future CMOS-compatible photonic devices.