Investigation of porosity effects in the photoluminescence and terahertz emission of electrochemically synthesized silicon nanostructures
We report increased visible luminescence and terahertz (THz) emission of various silicon (Si) nanostructures, namely porous Si (PS) and Si nanowires (NW). The NW were synthesized by one- and two-step metal-assisted chemical etching.The PS were fabricated using low and high etching current, resulting to low and high-porosity PS, respectively. From photoluminescence spectroscopy, broader and more intense luminescence were observed from the more porous sample in both PS and NW sets. The inverse was observed THz emission of the samples, as probed by THz-time domain spectroscopy. These changes in the intensity of the two types of emitted radiation is attributed to increase in the surface states in the more porous samples.