Resumen de Understanding the Origin of Luminescence in Porous Silicon:: An Undergraduate Solid-State Chemistry Experiment
D. P. Lasher, B. A. DeGraff, Brian H. Augustine
We report a modular solid-state chemistry experiment based on the chemical and electrochemical etching of crystalline silicon wafers to produce porous silicon (PSi) layers. Under relatively simple etching conditions, porous silicon exhibits efficient room-temperature photoluminescence (PL) at approximately 680 nm. While the luminescence mechanism is still a source of debate, it is generally agreed that the light emission is due to the spatial confinement of electron-hole pairs in nanometer-scale silicon particles that remain after etching. Using this explanation, students are able to apply a three-dimensional particle-in-a-box solution to Schrödinger's equation to explain the energy of the PL as a function of nanoparticle size. We have also compared PSi surfaces with unetched silicon wafers using atomic force microscopy to demonstrate how surface morphology can influence a material's optical properties. This experiment is a tool for introducing chemistry majors to the fabrication and characterization techniques used to study microelectronic materials and provides a solid-state counterpart to molecular absorption measurements typically used to demonstrate the particle-in-a-box principle
