Ordered Stacking Fault Arrays in Silicon Nanowires

Abstract

Correlated Raman microscopy and transmission electron microscopy were used to study the ordering of {111} planar defects in individual silicon nanowires. Detailed electron diffraction and polarization-dependent Raman analysis of individual nanowires enabled assessments of the stacking fault distribution, which varied from random to periodic, with the latter giving rise to local domains of 2H and 9R polytypes rather than the 3C diamond cubic structure. Some controversies and inconsistencies concerning earlier reports of polytypes in Si nanowires were resolved.

Asymmetric Split-Vacancy Defects in SiC Polytypes: A Combined Theoretical and Electron Spin Resonance Study

“…Polytypism has attracted growing interest in materials science among group IV [1][2][3] and group III-V [4][5][6][7][8] semiconductors. Recent efforts have been made to explore the electrical and optical properties of different polytypes of pristine crystals [9][10][11][12].…”

Raman Spectroscopy on Semiconductor Nanowires

“…The hexagonal or lonsdaleite structure is a metastable phase of silicon under normal conditions, also denominated as Si-IV. It has been reported by several authors in the form of nanowires Lopez et al, 2009;. Being Si-IV a metastable phase, it is expected that it may transform into diamond structure (Si-I) upon heating.…”

“…Additionally, the intersection of transversal and lateral twins (twins respectively along or with an angle with the growth axis) can lead to the formation of nanoscale domains with diamond hexagonal phase in the typical silicon cubic structure . As already mentioned above, one should keep in mind that even their polytypisms can have very different physical properties from the pure crystalline phases (Lopez et al, 2009). As it will be shown in the following, Raman spectroscopy is a versatile technique that helps identify materials and areas in the materials with different crystal structures and/or polytypisms.…”

“…www.intechopen.com In this context, even the incidence of stacking faults and twins in nanowires gains attention and it is currently under deep investigation (Bandet et al, 2002;Lopez et al, 2009;Algra et al, 2008;Caroff et a., 2009;Zardo et al, 2009a;Conesa-Boj et al, 2009;Arbiol et al, 2009;Spirkoska et al, 2009). Indeed, the atomic stacking can be altered locally from a rotationally twin plane, so that when it occurs in a cubic nanowire gives rise to the occurrence of a monolayer of the hexagonal phase .…”

“…Indeed, Raman spectroscopy is extremely sensitive even to structural defects such as the presence of dense stacking faults or twins (Lopez, 2009). Fig.…”