Mechanical strain in the structure of array of silicon nanowires grown on a silicon substrate

We present experimental research on mechanical strains in the structure consisting of an array of silicon nanowires grown using the metal-enhanced CVD technique on boron-doped Si(111) and Si(100) substrates. Using the electron beam induced current on a cleaved substrate, electron spin resonance, and confocal micro-Raman spectroscopy, we found that growth of silicon nanowires on a native (silicon) substrate gives rise to a strain both of the substrate and grown nanowires, too. An occurrence of the strain in the substrate was revealed by an initiation of the electron spin resonance signal from boron atoms, which is not resolved usually in unstressed silicon due to a complex energy structure of a top of the valence band. Furthermore, the strain of the substrate was proved additionally by observation of spatial dependence of the current induced by electron beam on a cleaved substrate, and by the spectral shift of Raman peak related to 3С-Si near the interface “substrate – array of nanowires”. Mechanical strain in the nanowires was more pronounced in the Raman spectra, which also revealed their complex crystal structure consisting of cubic and hexagonal phases of silicon. Model of the strain rise is discussed.