Effect of porous silicon buffer under different porosities on lateral overgrowth of TiO2 nanorods on silicon substrate

• Mesoporous silicon films with porosity ranging from 42% to 77% were fabricated.
• An out-of-plane tensile strain evolution with porosity occurs in PS layers.
• PS buffer improves density and ratio of hydrothermally grown TiO2 NRs on silicon.
• Lower porous buffer more improves crystalline quality of TiO2 NRs than higher one.

Hydrothermal growth of TiO2 nanorods (NRs) on silicon with and without porous silicon buffer was reported. Lattice parameter and elastic properties of the PS buffer layers have been studied using high resolution X-ray diffraction measurements. The present work deals with how tensile strains, arising from the SiH groups at the surface of PS, affect the growth and the lattice deformation of the TiO2 NRs, along to what makes excessive etching unsuitable for the work. Increasing the porosity of the PS buffers up to 58% leads to a more aligned and dense array of the NRs. This result can be attributed to enhanced roughness and reduced Young’s modulus of the PS buffers. But the trend is not observed for higher porosity buffers because of their higher fragility. Also, according to the XRD measurement, crystalline quality of the TiO2 NRs is affected by the buffer porosity.