Different Electrode Configurations for NH3 Gas Sensing Based on Macro Porous Silicon Layer

In this work, macro porous silicon layers were fabricated by Laser Assisted Etching. The morphology, structure and luminescence characteristics of the porous Si were examined as functions of the etching time using Field Emission-Scanning Electron Microscopy (FE-SEM), Atomic Force Microscopy (AFM) and Photoluminescence (PL). FE-SEM pictures revealed that the macro porous silicon surface layer has macro pores with a similar structure, also the thickness of this layer and the average pore diameter have increased with the increase of etching time. The specific surface area was measured by BET method and it was found in range of 152–213 m2/g. The AFM images manifested the high roughness and root mean square at low current density which can affect the porous silicon for the gas sensing applications. The PL spectra gave the luminescence energy in the orange–red region of the visible spectrum with the energy band gap of around (2.01 eV) for n-Si etched for 16 min. Two electrode configurations have been investigated for the sensing performance toward the NH3 gas; planar and sandwich, the former depicted a gas response of 1.85, while the latter revealed an efficient and ultra-gas response of 3.5 with the fast response and recovery times.