Effect of gold electrode annealing on gas sensing properties of nano-and microstructures of macroporous silicon

This paper presents porous silicon (PS) with nano-and microstructures as carbon dioxide sensing layers. The p-type Si substrate is subjected to PS etching. The PS morphology has been characterized by scanning electron microscope. According to the parameters of electrochemical process, PS layers were found to have a different structure. By using dimethylformamide (DMF) in electrolyte, regular, honeycomb-like and macroporous structures were formed. PS side of the substrate is then coated with a thin layer of gold and annealed at 500°C. These devices, which operate at room temperature, are more sensitive to the applied voltages in CO2 gas. The effect of annealing of gold electrode on current-voltage and response-voltage characteristics of PS has been studied. Our results show that the conductivity and response of PS sensors improve much more when its surface is modified with annealing of gold electrode and also nanostructured PS has greater response than the others