Relationships between strain and band structure in Si(001) and Si(110) nanomembranes

Abstract

The flexibility of single-crystal Si nanomembranes allows strain to be applied elastically without introducing dislocations in the fabrication process, resulting in uniform strain. It is also relatively easier to apply different types and orientations of strain to Si using elastic-strain sharing than by the traditional graded-strained-layer approach. We use X-ray absorption spectroscopy to measure the effect of uniform biaxial strain on several features of the conduction band structure of Si with ͑001͒ and ͑110͒ orientations. By also measuring the Si 2p photoelectric threshold, we are able to determine the absolute positions of features of the Si conduction band and their change with strain.

Silicon nanomembranes as a means to evaluate stress evolution in deposited thin films

“…In the pursuit of new physical properties, Group IV NMs have been strained in a controlled manner, among others, to modify the band structure or band offsets [11,12], to change the strain symmetry [13], or to create improved two-dimensional electron gases [14,15]. In the pursuit of nanoarchitectures or new devices, Group IV NMs have been rolled into tubes [10,[16][17][18] or supported channels [19]; or bonded to flexible supports [7,[20][21][22][23][24] or curved surfaces [25] for electronic-and optoelectronic-device applications.…”

Electronic Phase Diagram of Single-Element Silicon “Strain” Superlattices

“…A number of efforts to predict the relationship between strain and the band structure of Si have been made [4]. An amount of strain that is readily achievable in Si, of the order of 1%, leads to reduction in the band gap of approximately 20% [5]. The recognition that the band gap changes with strain suggests that if one could put strained Si next to unstrained Si, one would in essence create an electronic junction, and if one could put alternate strained and unstrained Si layers in sequence, one would produce a ''single-element strain SL,'' with the band offsets defined by strain rather than by composition difference as in the case of conventional SLs.…”

“…As shown by Van de Walle and Martin [13], the band offsets at the nonpolar A=B interface can be fully determined by the bulk bands of materials A and B, i.e., lining up the two sets of bands relative to a common reference level. So, the band offsets in the strain SL are fully determined by the strain-induced band shifting, i.e., the deformation potential, which has been widely studied for Si [5,[14][15][16]. In general, the uniaxial strain, tensile or compressive, reduces the band gap of Si and leads to a type I alignment at the interface of Si and the strained Si.…”

Valley degeneracy in biaxially strained aluminum arsenide quantum wells

“…Theoretically, Rasolt proposed an understanding of the various continuous symmetries and symmetry-breaking in a multi-valley system in terms of an SU(N ) symmetry where N is the valley degeneracy number 20 , but did not explicitly derive the vanishing intervalley exchange integral which underlies this theory. Material specific calculations of quantum confinement and strain in highmobility Si and Ge structures are well studied for highsymmetry facets [29][30][31][32][33][34][35][36][37][38][39][40] and recently, such calculations have been been made in other quantum confined systems as well 41,42 . However, a combined treatment of quantum confinement, strain, and piezoelectric fields to determine valley degeneracy in QWs is lacking, especially for low symmetry facets.…”