Department of Electrical Engineering, Stanford University, Stanford, CA 94305, United States of America.
Nanotechnology. 2017 Mar 17;28(11):115301. doi: 10.1088/1361-6528/aa5aec. Epub 2017 Jan 20.
One-dimensional (1D) nanowires (NWs) and two-dimensional (2D) thin films of Ni were deposited on highly ordered pyrolytic graphite (HOPG) by atomic layer deposition (ALD), using NH as a counter reactant. Thermal ALD using NH gas forms 1D NWs along step edges, while NH plasma enables the deposition of a continuous 2D film over the whole surface. The lateral and vertical growth rates of the Ni NWs are numerically modeled as a function of the number of ALD cycles. Pretreatment with NH gas promotes selectivity in deposition by the reduction of oxygenated functionalities on the HOPG surface. On the other hand, NH plasma pretreatment generates surface nitrogen species, and results in a morphological change in the basal plane of graphite, leading to active nucleation across the surface during ALD. The effects of surface nitrogen species on the nucleation of ALD Ni were theoretically studied by density functional theory calculations. Our results suggest that the properties of Ni NWs, such as their density and width, and the formation of Ni thin films on carbon surfaces can be controlled by appropriate use of NH.
通过原子层沉积（ALD），使用 NH3 作为反应用于在高度有序的热解石墨（HOPG）上沉积一维（1D）纳米线（NWs）和二维（2D）的 Ni 薄膜。NH3 热 ALD 沿台阶边缘形成 1D NWs，而 NH3 等离子体则可以在整个表面上沉积连续的 2D 薄膜。Ni NWs 的横向和纵向生长速率被数值建模为 ALD 循环数的函数。NH3 气体预处理通过还原 HOPG 表面的含氧官能团来促进沉积的选择性。另一方面，NH3 等离子体预处理会产生表面氮物种，并导致石墨基面的形态发生变化，从而在 ALD 过程中在整个表面上进行活性成核。通过密度泛函理论计算对表面氮物种对 ALD Ni 成核的影响进行了理论研究。我们的结果表明，通过适当使用 NH3，可以控制 Ni NWs 的性质，例如密度和宽度，以及 Ni 薄膜在碳表面上的形成。
