Continuous phase transformation in monocrystalline silicon during indentation

Silicon undergoes complex pressure-induced phase transformations critical for semiconductor device reliability. Conventional indentation methods only infer these transitions indirectly through load–displacement curves and ex-situ residual analysis. Here, we report a novel testing method that can directly obtain Raman response in indentation contact region. Si-II phase is confirmed to generate for the first time and results in low value distribution of wave number. Si-III/XII phase amounts only ∼12.5 % of the contact area just after pop-out and constantly generates until the end of indentation, rather than to commonly considered instant transition. Meanwhile, non-uniform local deformation in silicon is synchronously observed beneath Vickers indenter. We elucidate evolution process of phase and stress state in silicon indentation, and the adopted method may help deeply understand deformation mechanisms of additional materials under local loads.