Localized exfoliation versus delamination in H and He coimplanted (001) Si

Abstract

X-ray diffraction measurements as well as electron (scanning and transmission), optical, and atomic force microscopies are used to study the thermally induced stress relief mechanisms in coimplanted H+ and He+ ions into (001) Si substrates at moderate energies, resulting in damage layers located at ≈1.5 μm underneath the surface. By changing the implantation fluence rate from 0.25 to 1.5 μA cm−2, two distinct phenomena take place: localized blistering/exfoliations or complete surface delamination, resulting into freestanding 1.5 μm thick single crystalline Si films. The results are discussed on the basis of linear fracture mechanics arguments. Localized exfoliation is explained by means of distinct coarsening processes linking the initially formed gas filled nanosized platelets to crack structures of several micrometers in diameter. The delamination behavior is explained in terms of unstable crack propagation process triggered at a single nucleation site.