Dell'Anna Rossana, Iacob Erica, Barozzi Mario, Vanzetti Lia, Hübner René, Böttger Roman, Giubertoni Damiano, Pepponi Giancarlo
Fondazione Bruno Kessler, Centre for Materials and Microsystems, Micro Nano Facility, Via Sommarive 18, 38123 Trento, Italy.
J Phys Condens Matter. 2018 Aug 15;30(32):324001. doi: 10.1088/1361-648X/aacf5f. Epub 2018 Jun 27.
Germanium (Ge) surfaces have been irradiated with 26 keV gold (Au) ions at a constant fluence and at incidence angles varying from 0° to 85°. The evolution of the emerging nanostructures is studied by atomic force microscopy (AFM), scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), and cross-sectional transmission electron microscopy. The obtained results are compared with findings reported in the literature. Periodic rippled patterns with the wave vector parallel to the projection of the ion beam direction onto the Ge surface develop between 30° and 45°. From 75° the morphology changes from parallel-mode ripples to parallel-mode terraces, and by further increasing the incidence angle the terraces coarsen and show a progressive break-up of the front facing the ion beam. No perpendicular-mode ripples or terraces have been observed. The analysis of the AFM height profiles and slope distributions shows in the 45°-85° range an angular dependence of the temporal scale for the onset of nonlinear processes. For incidence angles below 45°, the surface develops a sponge-like structure, which persists at higher incidence angles on the top and partially on the face of the facets facing the ion beam. The XPS and the energy-dispersive x-ray spectroscopy evidence the presence of Au nano-aggregates of different sizes for the different incidence angles. This study points out the peculiar behavior of Ge surfaces irradiated with medium-energy Au ions and warns about the differences to be faced when trying to build a universal framework for the description of semiconductor pattern evolution under ion-beam irradiation.
已使用能量为26 keV的金（Au）离子，以恒定的注量、0°至85°的不同入射角对锗（Ge）表面进行辐照。通过原子力显微镜（AFM）、扫描电子显微镜、X射线光电子能谱（XPS）和截面透射电子显微镜研究了所形成纳米结构的演变。将所得结果与文献报道的研究结果进行了比较。在30°至45°之间形成了波矢平行于离子束方向在Ge表面投影的周期性波纹图案。从75°起，形态从平行模式波纹变为平行模式平台，并且通过进一步增大入射角，平台变粗，且面向离子束的前沿逐渐破碎。未观察到垂直模式的波纹或平台。对AFM高度轮廓和斜率分布的分析表明，在45° - 85°范围内，非线性过程开始的时间尺度存在角度依赖性。对于入射角低于45°的情况，表面形成海绵状结构，该结构在较高入射角下在面向离子束的小面顶部和部分表面持续存在。XPS和能量色散X射线光谱证明了不同入射角下存在不同尺寸的金纳米聚集体。本研究指出了中能Au离子辐照Ge表面的特殊行为，并警示在试图构建离子束辐照下半导体图案演变描述的通用框架时所面临的差异。
