Green Nanoelectronics Center (GNC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
J Am Chem Soc. 2012 Aug 1;134(30):12492-8. doi: 10.1021/ja300811p. Epub 2012 Jul 18.
Selective graphene growth on copper twin crystals by chemical vapor deposition has been achieved. Graphene ribbons can be formed only on narrow twin crystal regions with a (001) or high-index surface sandwiched between Cu crystals having (111) surfaces by tuning the growth conditions, especially by controlling the partial pressure of CH(4) in Ar/H(2) carrier gas. At a relatively low CH(4) pressure, graphene nucleation at steps on Cu (111) surfaces is suppressed, and graphene is preferentially nucleated and formed on twin crystal regions. Graphene ribbons as narrow as ~100 nm have been obtained in experiments. The preferential graphene nucleation and formation seem to be caused primarily by a difference in surface-dependent adsorption energies of reactants, which has been estimated by first principles calculations. Concentrations of reactants on a Cu surface have also been analyzed by solving a diffusion equation that qualitatively explains our experimental observations of the preferential graphene nucleation. Our findings may lead to self-organizing formation of graphene nanoribbons without reliance on top-down approaches in the future.
通过化学气相沉积在铜孪晶上选择性地生长石墨烯已经实现。通过调整生长条件，特别是通过控制 Ar/H2 载气中的 CH4 分压，可以仅在具有（001）或高指数表面的狭窄孪晶区域上形成石墨烯带，这些区域夹在具有（111）表面的 Cu 晶体之间。在相对较低的 CH4 压力下，Cu（111）表面上的石墨烯形核被抑制，并且石墨烯优先在孪晶区域上形核和形成。在实验中已经获得了宽度窄至约 100nm 的石墨烯带。优先的石墨烯形核和形成似乎主要是由于反应物的表面依赖性吸附能的差异引起的，这已经通过第一性原理计算进行了估计。通过求解扩散方程分析了 Cu 表面上反应物的浓度，该方程定性地解释了我们对优先石墨烯形核的实验观察。我们的发现可能会导致未来无需依赖自上而下的方法就能实现石墨烯纳米带的自组织形成。
