Photoluminescence of porous silicon and zinc oxide with potential applications in chemical sensing

Porous silicon samples have been prepared from p-type single-crystal silicon {dollar}<{dollar}100{dollar}>{dollar} wafers by a galvanostatic and open circuit etch in 50% HF. The materials display bright red-orange room temperature photoluminescence in air and toluene solutions. Infrared measurements show that the porous silicon surface is partially oxidized. Exposure to anthracene or 10-methylphenothiazine results in dynamic quenching of the materials excited state(s). Nanosecond time resolved photoluminescence decays are complex and wavelength dependent, with average lifetimes in neat toluene of 0.3-16 {dollar}mu{dollar}S. Quenching by anthracene and 10-methylphenothiazine is more efficient and rapid at short observation wavelengths. The steady state and time resolved quenching data are well fit to the Stern-Volmer model. The PL decays are well described by a distribution of recombination rates.; Zinc Oxide, ZnO, has two emission bands with one band that shall be denoted band-edge emission that's sharp and narrow, in the ultraviolet region and the second band that shall be denoted deep emission, that's very broad, in the visible region. Oxygen quenches the band-edge emission while it enhances the deep emission. The reverse process occurs for an argon or nitrogen ambient. There's a reversible blue-shift in the ground state absorption spectrum of ZnO only in the presence of either argon or nitrogen with continous ultraviolet irradiation. Nanosecond time resolved photoluminescence shows that the decay process for the deep emission is bimodal in nature and could be fit to a bi-exponential function. The excited state lifetime could only be decreased if the sample was exposed to continous ultraviolet irradiation.