Arias Pedro, Ebnonnasir Abbas, Ciobanu Cristian V, Kodambaka Suneel
Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, California 90095 United States.
Department of Mechanical Engineering and Materials Science Program, Colorado School of Mines, Golden, Colorado 80401 United States.
Nano Lett. 2020 Apr 8;20(4):2886-2891. doi: 10.1021/acs.nanolett.0c00704. Epub 2020 Mar 6.
Using variable-temperature scanning tunneling microscopy (300-673 K) during chemical vapor deposition of two-dimensional hexagonal boron nitride (hBN) on Pd(111) from borazine precursor at pressures up to 10 mbar, we identify the mechanisms leading to carpetlike uphill or downhill growth across the Pd steps. Deposition at a higher rate and lower temperature promotes uphill growth via preferential attachment at the ascending and descending step-edges, whereas a lower deposition rate and higher temperature lead to downhill growth via nucleation and growth of islands on Pd terraces. We attribute this unusual growth behavior to differences in temperature-dependent rates of hBN deposition at the steps versus on the Pd terraces. Our results illustrate how growth mechanisms can be activated by a pair of parameters (substrate temperature and partial pressure of borazine) and provide new insights into the mechanisms underlying carpetlike growth of hBN and other layered materials.
在高达10毫巴的压力下，使用可变温度扫描隧道显微镜（300 - 673K），在二维六方氮化硼（hBN）从硼嗪前驱体在Pd(111)上进行化学气相沉积的过程中，我们确定了导致hBN在Pd台阶上呈地毯状向上或向下生长的机制。在较高速率和较低温度下沉积，通过在上升和下降台阶边缘的优先附着促进向上生长，而较低的沉积速率和较高的温度则通过在Pd台面上的岛状物的成核和生长导致向下生长。我们将这种不寻常的生长行为归因于台阶处与Pd台面上hBN沉积的温度依赖性速率差异。我们的结果说明了生长机制如何能由一对参数（衬底温度和硼嗪分压）激活，并为hBN和其他层状材料的地毯状生长背后的机制提供了新的见解。
