SiO2/Si衬底上石墨烯的制备与结构表征

在分子束外延(MBE)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.

Growth and characterization of graphene on SiO2/Si substrate

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-sp².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.