Simultaneous flattening of Si(110), (111), and (001) surfaces for three-dimensional Si nanowires

We prepared atomically flat Si(110), (111), and (001) surfaces using identical preparation conditions for a low-pH (pH < 1) HF treatment and a subsequent low-temperature (∼800 °C) anneal in H2. Atomic-resolution scanning tunneling microscopy (STM) revealed that the treated Si(110) surfaces were atomically flat with a hydrogen-terminated 1 × 1 atomic arrangement. Similar features were also confirmed by STM analysis of 1 × 1:H on Si(111) and 2 × 1:H on Si(001) surfaces. Using this technique, well-ordered cross sections of three-dimensional Si nanowires surrounded by simultaneously flattened (110), (111), (001) facets were realized for nanowires with 〈100〉, 〈110〉, 〈111〉, and 〈112〉 long-axis orientations.