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

Abstract

Thin-film deposition on ultra-thin substrates poses unique challenges because of the potential for a dynamic response to the film stress during deposition. While theoretical studies have investigated film stress related changes in the substrate, little has been done to learn how stress might evolve in a film growing on a compliant substrate. We use silicon nanomembranes (SiNMs), extremely thin sheets of single-crystalline Si, as a substrate for the growth of amorphous SiN x to begin to address this question. Nanomembranes are released from a silicon-oninsulator wafer with selective etching, transferred over a hole etched into a Si wafer, and bonded to the edges of the hole. The nanomembrane window provides the substrate for SiN x deposition and a platform, using Raman spectroscopy, for measurements of the evolving strain in the nanomembrane. From the strain in the nanomembrane, the film stress can be inferred from the required balance of forces in the film/substrate system. We observe that the strain in the tethered 2 NM increases as the NM is made thinner while the intrinsic steady-state stress in the deposited film is reduced.

Dy uniform film morphologies on graphene studied with SPA-LEED and STM

“…2D growth on graphene was shown in Co films on graphene on Ir(111) [17] with Laser Pulse Deposition (LPD) with effective flux rates~10 6 times higher than rates in typical epitaxial experiments. Introducing stress in thin films in controlled ways as a function of thickness can also result in modifying nucleation, it can increase island density and promote layer-by-layer growth [18].…”

Quality Improvement of GaN Epi-layers Grown with a Strain-Releasing Scheme on Suspended Ultrathin Si Nanofilm Substrate

“…Besides, the transfer process tends to introduce contaminations that can significantly degrade the growth quality. As a result, the method for fabricating a suspended silicon substrate from SOI with the thickness under 20 nm is still missing in the literature [30][31][32][33][34][35].…”

Modelling wrinkling interactions produced by patterned defects in metal thin films

“…These wrinkling patterns manifest in structural [14,21], biological [6,22], electronic (e.g., 2D materials) [23], and metrology applications [3,9], but most modelling efforts treat materials as defect-free. Defects in such 2D and layered materials are common and may control the nucleation and propagation of wrinkling patterns [24][25][26][27][28]. However, despite intense research efforts on the mechanical response of thin films ranging from necking instabilities to wrinkling mechanisms [29][30][31][32][33], all of which are crucial for thin film heterostructures and flexible electronics applications, the influence of defects within thin membranes in controlling the wrinkling patterns has not received much attention, particularly in metallic thin films.…”