不同退火条件对纳米Ge/Al2O3相嵌薄膜中纳米Ge颗粒的氧化态影响

采用脉冲激光沉积法制备了纳米Ge/Al2O3相嵌薄膜.用X射线光电子谱(XPS)研究了薄膜的热稳定性.结果表明纳米Ge颗粒的氧化态与已经发表的结果不同,而与Si的氧化态的结果相似.用纯高斯函数拟合可以得到Ge的四种不同的氧化态,分别为:Ge 1,Ge 2,Ge 3,Ge 4.这种大的差别来自纳米Ge颗粒的不同环境的影响.在真空退火条件下,由于缺少外部氧的供给和供给速度慢,很奇妙地,在薄膜表层的Ge 2,Ge 4氧化态不如其他氧化态和未氧化态(Ge0)稳定.而在清洁的大气环境退火条件下,外部氧的供给充分和供给速度快,在薄膜表层最稳定的氧化态是Ge 4.

The effect of different annealing conditions on oxidation states of Ge nanoparticles embedded in Al2O3 matrices

Thin films of Ge/Al2O3 composite materials were prepared by using the pulsed laser deposition method.The thermal stability of the film was studied by X-ray photoelectron spectroscopy(XPS).The oxidation states of Ge were found to be much different from that of the previous work,and to be similar to those of Si,and,using a simple deconvolution technique,it was possible to separately distinguish all the four possible states,namely Ge 1,Ge 2,Ge 3,Ge 4.These large differences may cause by the different environment of the Ge nanpaprticles.Under vacuum annealing conditions where the supply of external oxygen was severely limited,the oxidation states of Ge 2,Ge 4 in the film surface layer were,paradoxically,found to be less stable than the other oxidation states,or the unoxidized state,Ge0.However,when the samples were annealed in the open but clean atmosphere with plentiful supply of external oxygen,then the most stable oxidation state of Ge in the film surface layer was Ge 4.