中文摘要：

在分子束外延设备中,利用直接沉积C原子的方法在覆盖有SiO2的Si衬底（SiO2/Si）上生长石墨烯,并通过Raman光谱和近边X射线吸收精细结构谱等实验技术对不同衬底温度（500℃,600℃,700℃,900℃,1100℃,1200℃）生长的薄膜进行结构表征.实验结果表明,在衬底温度较低时生长的薄膜是无定形碳,在衬底温度高于700℃时薄膜具有石墨烯的特征,而且石墨烯的结晶质量随着衬底温度的升高而改善,但过高的衬底温度会使石墨烯质量降低.衬底温度为1100℃时结晶质量最好.衬底温度较低时C原子活性较低,难以形成有序的C-sp2六方环.而衬底温度过高时（1200℃）,衬底表面部分SiO2分解,C原子与表面的Si原子或者O原子结合而阻止石墨烯的形成,并产生表面缺陷导致石墨烯结晶变差.

英文摘要：

Graphene thin films are grown on Si substrates covered by SiO2 layers（SiO2/Si） with the method of directly depositing carbon atoms in the molecular beam epitaxy（MBE） equipment.The structural properties of the samples produced at different substrate temperatures（500℃,600℃,900℃,1100℃,1200℃） are investigated by Raman spectroscopy and near-edge x-ray absorption fine structure.The results indicate that the thin films grown at lower temperatures are amorphous carbon thin films.While the thin films grown above 700℃exhibit the characteristics of graphene.As the substrate temperature increases,the crystalline quality of graphene is improved.However,very high temperature can reduce the quality of grapheme.The best graphene films are obtained at a substrate temperature of 1100℃.When the substrate temperature is low,the activity of the carbon atoms is not enough to form the ordered six member rings of C-sp~2.While the substrate temperature is too high,the decomposition of some SiO2 induces the deposited carbon atoms to bond with decomposed oxygen atoms or silicon atoms,resulting in the defects on the surface,which leads to the poor crystalline quality of graphene films.