氮气氛中高温退火对ZnO薄膜发光性质的影响

以二乙基锌和水汽分别作为锌源和氧源,用LP-MOCVD方法在p型Si(100)衬底上生长了单一取向的ZnO薄膜。对得到的样品在氮气气氛中进行高温热处理,退火温度分别为900,1000,1100℃。利用室温PL谱、XRD、AFM、XPS等方法对样品的性质进行了研究。研究表明:(1)随着退火温度的升高,样品的结晶性质也逐渐提高,从表面形貌观察到晶粒尺寸逐渐增大;(2)当退火温度从900℃升高至1000℃时,样品的光致发光谱中可见光波段的发光强度有所减弱,而紫外波段的发光强度明显增强;当退火温度升高至1100℃时,可见光波段的发光几乎完全被抑制,而紫外波段的发光强度急剧增强。分析认为,高温退火改善晶体结晶质量的同时调制了样品的Zn/O比,氮气气氛下的热处理使得样品内的氧原子逸出,来自受主缺陷OZn的可见发射随温度升高逐渐减弱,而当退火温度达到1000℃以上时样品成为富锌状态,此时与施主缺陷Zni有关的紫外发射急剧增强。     

Effect of Zn Interstitials on Enhancing Ultraviolet Emission of ZnO Films Deposited by MOCVD

ZnO films are grown on Si （111） substrates by a metal organic chemical vapor deposition method. Samples with different stoichiometric composition of Zn and 0 are obtained by varying Ⅱ/Ⅵ molar ratio between 3 and 1/3 in precursors. The x-ray photoelectron spectroscopy and photoluminescenee results show that the ultraviolet emission enhances with the increasing Zn/O composition ratio of the samples. It is suggested that the supertfluous Zn atoms pile up at interstitial positions to form Zn interstitial defects. The radiated recombination of the coupling of free exeitons with donor Zn interstitial enhances the ultraviolet emission of the samples.     

射频辅助N掺杂ZnO薄膜的生长及其光电特性

在MOCVD设备中采用改进的射频辅助生长装置,通过裂解N2及N-Al共掺杂的方法进行ZnO的p型掺杂研究。通过二次离子质谱(SIMS)、X射线衍射(XRD)、原子力显微镜(AFM)、光致发光(PL)谱等方法分析了薄膜中N杂质的浓度,以及射频功率与晶体质量、表面形貌以及光学特性之间的关系,并与Al掺杂和N掺杂的ZnO薄膜进行对比。实验结果表明,N掺杂的浓度高达1020cm-3;N-Al共掺杂极大地增加了ZnO的成核速率,其主要原因是N离化所起的作用;N-Al共掺的ZnO薄膜显示出p型性质,而N掺杂的ZnO薄膜由于N原子处于非激活状态而呈现高阻,这说明N-Al共掺杂对ZnO中N原子的活化起到一定作用。     

血清反应因子在心血管疾病中的作用

血清反应因子（serum response factor,SRF）属于MADS转录因子家族的成员之一,是高度保守且广泛表达的转录因子。SRF在成年或发育期的心肌组织中均有表达,主要与下游靶基因启动子上特定DNA序列CArG盒[血清反应元件（SRE）的组成部分,CC（A/T）6GG box]结合,调控抗凋亡或促细胞增殖等基因（如IEGs：c-fos、mcl-1、Egr-1）的表达,对外界因素（如：缺血、缺氧等）刺激表现出快速的基因响应,影响心肌细胞的发育、分化、增殖及凋亡[1-2]。许多辅助转录调节因子蛋白（co-activator/co-repressor,如TCF家族成员Elk-1和MRTFs家族等）与SRF/SRE发生相互作用,激活与心肌分化、增殖及凋亡相关基因的转录。因此,对SRF-CArG box依赖基因转录的调控,是影响心肌凋亡/生存的关键因素之一[3]。另外,研究表明skeletal a-actin、b-MHC、car原diac a-actin、MLC-2v、dystrophin等收缩类蛋白[4-6]及非收缩类蛋白,诸如参与心脏功能的ANF、肌质网Ca-ATPase（SERCA2）、Na+/Ca2+交换离子通道 NCX1[7-8]均为SRF依赖的基因。由此可见,SRF在调控收缩蛋白基因和收缩功能器官的重要作用充分说明SRF在心脏功能中发挥着重要的调控作用。     

Effect of High Temperature Annealing on Conduction-Type ZnO Films Prepared by Direct-Current Magnetron Sputtering

We experimentally find that the ZnO thin films deposited by dc-magnetron sputtering have different conduction types after annealing at high temperature in different ambient. Hall measurements show that ZnO films annealed at 1100℃ in N2 and in 02 ambient become n-type and p-type, respectiveIy. This is due to the generation of different intrinsic defects by annealing in different ambient. X-ray photoelectron spectroscopy and photolumineseence measurements indicate that zinc interstitial becomes a main defects after annealing at 1100℃ in N2 ambient, and these defects play an important role for n-type conductivity of ZnO. While the ZnO films annealed at 1100℃ in O2 ambient, the oxygen antisite contributes ZnO films to p-type.     

物理教学与高素质科技人才

本文总结物理教学实践，提出在物理教学中如何站在培养高素质人才的高度，用辩证唯物的观点组织物理学的设想。     

Effect of Al Doping on Properties of SiC Films

Undoped and Al-doped 3C-SiC films are deposited on Si（100） substrates by low-pressure chemical vapour deposition. Effects of aluminium incorporation on crystallinity, strain stress, surface morphology and growth rate of SiC films have been investigated. The x-ray diffraction patterns and rocking curves indicate that the crystallinity is improved with aluminium doping. Raman scatting patterns also demonstrate that the strain stress in SiC films is released due to the incorporation of Al ions and the increase of film thickness. Furthermore, due to the catalysis of surface reaction which is induced by trimethylaluminium, the growth rate is increased greatly and the growth process varies from three-dimensional island-growth mode to step-flow growth mode.