Creation and Evaluation of Atomically Ordered Side- and Facet-Surface Structures of Three-Dimensional Silicon Nano-Architectures

Abstract

The realization of three-dimensional (3D)-architected nanostructures, that is, the transformation from novel two-dimensional (2D) film-based devices to 3D complex nanodevices, is of crucial importance with the progress of scaling down devices to nanometer order. However, little attention has been devoted to controlling the atomic ordering and structures of side-surfaces on 3D structures, while techniques for controlling and investigating 2D surfaces, namely, surface science, have been established only for planar 2D surfaces. We have established an original methodology that enables atomic orderings and arrangements of surfaces with arbitrary directions to be observed on 3D figured structures by developing diffraction and microscopy techniques. An original technique, namely, directly and quantitatively viewing the side- and facet-surfaces at the atomic scale by reflection high-energy electron diffraction (RHEED) and low-energy electron diffraction (LEED), can be used to determine process parameters in etching. This chapter introduces methods of evaluation by RHEED and LEED based on a reciprocal space map and methods of creating various atomically flat 111 and {100} side-surfaces of 3D Si nano-architectures and tilted 111 facet-surfaces fabricated by lithography dry and wet etching processes, followed by annealing treatment in vacuum.

Atomically Architected Silicon Pyramid Single-Crystalline Structure Supporting Epitaxial Material Growth and Characteristic Magnetism

“…Regarding the controllability of the magnetic states in the 3D architected structure, the scalability and tunability of the 3D structure are essential. Notably, it is possible to control the geometrical parameters of the 3D architected structures . This is due to the effect of the shape anisotropy, which determines the creation and annihilation of vortex.…”

“…The samples cut in size of 3 × 25 mm 2 were introduced into an ultrahigh vacuum (UHV) chambers with a base pressure of less than 1 × 10 –8 Pa. ,− To obtain clean sample surfaces, the samples were degassed and flashed by direct-current heating at 1250 °C below 2 × 10 –8 Pa. The surface structures were confirmed by LEED (BDL600IR, OCI) with primary electron energies ( E p ) of 40–140 eV and a beam size of ≤1 mm.…”

“…Notably, it is possible to control the geometrical parameters of the 3D architected structures. 26 This is due to the effect of the shape anisotropy, which determines the creation and annihilation of vortex. The demonstration of the magnetism in the pyramid films via the creation of the atomically flat facet surfaces of the pyramids is expected to enable to realization of 3D integrated magneto electronic devices such as spin-controlled field-effect transistors.…”

“…To overcome the remaining difficulties, we have proposed and demonstrated the creation of well-defined 3D structures by the combination of dry and wet etching processes, and the growth of epitaxial films on the side and facet surfaces of atomically constructed 3D Si templates. ,− The key advantage is a complete shift of the material growth direction from the normal c -axis on a 2D planar substrate toward flexible omnidirectional axes on a 3D patterned substrate with arbitrarily oriented planes. Reconstructed 3D Si surfaces support the epitaxial growth of target materials without misalignment or deformation, similar to the growth of thin films on 2D planar surfaces. ,,, …”

“…Reconstructed 3D Si surfaces support the epitaxial growth of target materials without misalignment or deformation, similar to the growth of thin films on 2D planar surfaces. 4,23,25,26 In this study, we created atomically ordered Si{111} pyramid structures with reconstructed surfaces for the first time. The atomically ordered surfaces in 3D space are indispensable factors for applying a Si{111} pyramid to omnidirectional planes.…”