Engineering of ultra-thin sintered porous silicon virtual substrates for lattice-mismatched growth compliance and epilayer detachability

Abstract

The air-sensitivity of mesoporous silicon layers etched on p-type wafers was evaluated comparing ambientoxidized to methyl-capped samples, from which the unaltered pore/interpore sizes were obtained and linked to diffraction patterns and reflectivity data. Sintering of oxide-free nano/mesoporous bilayers produced ultrathin porous epi-foils with full surface reconstruction at temperatures below 1000 ◦C. The epi-foils were inplane tensely strained and exhibited good crystallinity and polished wafer-like surface roughness (RMSmin = 0.23 nm), emerging as potential compliant substrates for crack-free epitaxy of flat heterostructures. Furthermore, they were conveniently formed over a weakly bonded macroporous mesh that provided both structural stability and ease for detachment, establishing sintering below 1000 ◦C as a promising route to avoid collapsing and premature delamination of ultra-thin films.