Synthesis, microstructure and visible luminescence properties of vertically aligned lightly doped porous silicon nanowalls

Abstract

Abstract Silicon nanowall templates in nonporous and porous forms have been prepared by 4.8 M HF and 0.2 M H2O2 etching of lightly boron doped silicon (100) wafers at room temperature and their morphology, microstructure and visible photoluminescence properties were studied. Metal assisted chemical and metal assisted anodic polarization etching methods were used respectively to produce these morphologically distinct silicon nanowalls. It is shown from the analysis of photoluminescence results that porous silicon nanowalls emit red and orange radiation signals. This observation is in contrast with nonporous silicon nanowalls that did not show any visible luminescence features. The microscopy results revealed that pores and inter-pore Si regions in porous silicon nanowalls are interconnected in the form of skeletal morphology with quantum dimensions. Based on the temperature dependent luminescence results and the structure dimensions evaluated from the microscopy results, it is concluded that the red and orange emission in porous silicon nanowalls originates from silicon quantum structures and Si-O-Si bonded amorphous structures respectively. The effect of Si nanostructures and its dimensional dependence on photoluminescence properties in porous silicon nanowalls are also discussed. The synthesis and photoluminescence mechanism discussed in this work is very much useful for the development of silicon based functional porous materials for nanoscale devices application.