Low Resistivity C54 Phase TiSi2 Films Synthesized by a Novel Two—Step Method

Synthesis and growth properties of the TiSi2 film on a Si (001) substrate are investigated. A novel two-step method is used for deposition of the C54 phase TiSi2 film with low resistivity. The first step is the formation ofthe C49 phase TiSi2 at a relative low substrate temperature of 400℃, followed by rapid thermal annealing processat 850℃ in N2 for the formation of the C54 phase TiSi2 as the second step. Finally, selective wet, etching isemployed to remove the un-reaction Ti on the surface and the low resistivity C54 TiSi2 film can be obtained. Thefilms deposited under various parameters are evaluated by scanning electron microscopy, x-ray diffraction and the resistivity measurement. Compared with other sputtering technologies used commonly for TiSi2 synthesis,this two-step method has apparent advantages such as the mild synthesis temperature and the high purity of the final product with low resistivity, uniform large area and improving surface roughness. In addition, the film also shows that the low coefficient of resistivity-temperature appears in the temperature range from 20℃to 800℃.     

仲钨酸盐A柱撑化合物Mg12Al6(OH)36(W7O24)·4H2O的合成及其光催化性能研究

光催化降解水中有机污染物并使之矿化为无机物的技术正在引起众多学者的关注[1～3]. 目前, 两类主要的光催化剂为半导体金属氧簇和多金属氧酸盐簇(POM). 然而, 这两类催化剂在使用过程中都存在着催化剂难以回收的缺点. 将POM嵌入层柱双氢氧化物(LDH)中制备POM柱撑化合物是固载POM的有效途径之一[4]. 均相体系中仲钨酸盐A(W7O6-24)的光化学活性已有研究, 它可使22种卤代烃完全降解和矿化[5]. 本文通过阴离子交换反应制备了水不溶性的仲钨酸盐A柱撑化合物Mg12Al6(OH)36(W7O24)*4H2O(缩为Mg2Al-W7), 所用前躯体为Mg4Al2(OH)12TA*xH2O (简写为Mg2Al-TA, TA2-= 对苯二甲酸根离子). Mg2Al-W7在非均相体系中的光化学行为通过水溶液中有机氯杀虫剂六六六(C6H6Cl6, 用HCH表示)的降解与矿化进行了研究. 据报道, 由于六六六非常稳定和难于降解, 目前农田中仍存在数以千吨计的残留的六六六, 国外文献近期仍在报道TiO2光催化降解六六六的方法[6,7]. 我们的研究表明, Mg2Al-W7对降解及矿化六六六有活性, 且催化剂易于分离回收, 并可用于再循环. 这些特点为Mg2Al-W7光催化降解水中其它有机污染物的研究与应用奠定了基础.