Jonker Dirk, Berenschot Erwin J W, Tas Niels R, Tiggelaar Roald M, van Houselt Arie, Gardeniers Han J G E
Mesoscale Chemical Systems, University of Twente, MESA+ Institute, P.O. Box 217, 7500 AE, Enschede, The Netherlands.
Physics of Interfaces and Nanomaterials, University of Twente, MESA+ Institute, P.O. Box 217, 7500 AE, Enschede, The Netherlands.
Nanoscale Res Lett. 2022 Oct 16;17(1):100. doi: 10.1186/s11671-022-03735-y.
Convex cylindrical silicon nanostructures, also referred to as silicon nanocones, find their value in many applications ranging from photovoltaics to nanofluidics, nanophotonics, and nanoelectronic applications. To fabricate silicon nanocones, both bottom-up and top-down methods can be used. The top-down method presented in this work relies on pre-shaping of silicon nanowires by ion beam etching followed by self-limited thermal oxidation. The combination of pre-shaping and oxidation obtains high-density, high aspect ratio, periodic, and vertically aligned sharp single-crystalline silicon nanocones at the wafer-scale. The homogeneity of the presented nanocones is unprecedented and may give rise to applications where numerical modeling and experiments are combined without assumptions about morphology of the nanocone. The silicon nanocones are organized in a square periodic lattice, with 250 nm pitch giving arrays containing 1.6 billion structures per square centimeter. The nanocone arrays were several mm in size and located centimeters apart across a 100-mm-diameter single-crystalline silicon (100) substrate. For single nanocones, tip radii of curvature < 3 nm were measured. The silicon nanocones were vertically aligned, baring a height variation of < 5 nm (< 1%) for seven adjacent nanocones, whereas the height inhomogeneity is < 80 nm (< 16%) across the full wafer scale. The height inhomogeneity can be explained by inhomogeneity present in the radii of the initial columnar polymer mask. The presented method might also be applicable to silicon micro- and nanowires derived through other top-down or bottom-up methods because of the combination of ion beam etching pre-shaping and thermal oxidation sharpening. A novel method is presented where argon ion beam etching and thermal oxidation sharpening are combined to tailor a high-density single-crystalline silicon nanowire array into a vertically aligned single-crystalline silicon nanocones array with < 3 nm apex radius of curvature tips, at the wafer scale.
凸面圆柱形硅纳米结构，也被称为硅纳米锥，在从光伏到纳米流体、纳米光子学和纳米电子学等众多应用领域中都有其价值。为了制造硅纳米锥，可以采用自下而上和自上而下两种方法。本文介绍的自上而下方法依赖于通过离子束蚀刻对硅纳米线进行预成型，然后进行自限性热氧化。预成型和氧化相结合，在晶圆尺度上获得了高密度、高纵横比、周期性且垂直排列的尖锐单晶硅纳米锥。所呈现的纳米锥的均匀性是前所未有的，这可能会催生一些应用，在这些应用中，数值建模和实验可以结合起来，而无需对纳米锥的形态做出假设。硅纳米锥以方形周期晶格排列，间距为250纳米，每平方厘米的阵列包含16亿个结构。纳米锥阵列尺寸为几毫米，在直径100毫米的单晶硅（100）衬底上相隔几厘米。对于单个纳米锥，测量到的曲率半径尖端小于3纳米。硅纳米锥垂直排列，七个相邻纳米锥的高度变化小于5纳米（<1%），而在整个晶圆尺度上高度不均匀性小于80纳米（<16%）。高度不均匀性可以用初始柱状聚合物掩膜半径中存在的不均匀性来解释。由于离子束蚀刻预成型和热氧化锐化的结合，本文介绍的方法也可能适用于通过其他自上而下或自下而上方法得到的硅微线和纳米线。本文提出了一种新颖的方法，将氩离子束蚀刻和热氧化锐化相结合，在晶圆尺度上把高密度单晶硅纳米线阵列加工成曲率半径尖端小于3纳米的垂直排列的单晶硅纳米锥阵列。
