摘要
利用同步辐射广延X射线吸收精细结构(EXAFS),研究在不同条件下分子束外延制备的ZnO薄膜,如分别在蓝宝石(0001)、Si(100)衬底上,生长温度为200℃或300℃下得到样品的局域结构。发现这些ZnO薄膜的EXAFS函数(k2x(k))谱形状相似,说明各个样品都具有较为相近的基本局域结构。对生长温度为200℃的ZnO/Al2O3(0001)和ZnO/Si(100)样品,其Zn-O第一配位峰的无序度σ2分别为0.0054A2和0.0080 A2,当生长温度从200℃提高到300℃时,ZnO/Al203(0001)样品的Zn-O第一配位峰的无序度σ2降为0.0039 A2。结果表明衬底与ZnO的晶格失配度和生长温度对ZnO薄膜的配位数、Zn-O键长影响不大,但较小的晶格失配度和较高的生长温度下得到的ZnO薄膜局域有序性较高;且样品的局域结构越有序,相应的配位峰幅度也越高。
Effects of growth conditions including lattice mismatch and growth temperature on the local structures of ZnO films prepared by MBE have been investigated using fluorescence EXAFS at Zn K edge. The ZnO films were deposited on the Si substrate at 200℃ and on sapphire substrate at 200℃ or 300℃ respectively. The coordination number N in the first shell (number of O atoms immediately surrounding a central Zn atom) remains constant 4 or so for all samples. However, the degree of disorder σ2 (mean squared displacement) of the local structure is varied with the growth conditions. At the same growth temperature 200℃, the degree of disorder is reduced from 0.0080 A2 to 0.0054 A2 as the substrate is changed from Si to sapphire; on the same sapphire substrate, the degree of disorder decreases from 0.0054 A2 to 0.0039 A2 when the growth temperature is increased from 200℃ to 300℃. Therefore, the higher growth temperature and smaller lattice mismatch can improve the disorder of local structures; the crystal quality of ZnO film will be improved as well.
出处
《核技术》
CAS
CSCD
北大核心
2004年第7期494-496,共3页
Nuclear Techniques
基金
国家重点基础研究专项973项目(2001-cb309505)资助
