A new approach of pH-IEGFET sensor based on the surface modification of macro porous silicon with palladium nanoparticles

Abstract

This work investigates the effect of the Palladium nanoparticles (PdNPs) on the characteristics and pH sensitivity of an interdigitated electrode extended-gate field-effect transistor (pH-IEGFET) sensors based on the bare n-type macro porous Si (n-macro PSi) layer. The synthesized bare porous layer was fabricated by photo electrochemical etching process of n-type (100) using short-wavelength 410 nm and intensive laser power density 80 mW/cm2. The surface morphology of n-macro PSi was modified by inserting PdNPs to form PdNPs/n-macro PSi hetero structure layers via simple and fast immersing process in PdCl2 solution for about 14 min and 20 min by the ion reduction process. The fabricated sensors have been verified in the range of pH from 3 to 11 at the ambient temperature. Specific features of n-macro PSi and hybrid structure were investigated using a scanning electron microscope, energy dispersive x-ray spectroscopy (EDX) analysis and x-ray diffraction. It was found that the morphology and the size of the deposited PdNPs intensely influence on the PdNPs/ n-macro PSi hetero structure pH-IEGFET sensor. The efficient pH sensing process was obtained for n-macro PSi pH sensor with the lowest size of PdNPs deposited on the external walls of the n-macro PSi pores. Significant enhancement of sensitivity of about 42.89 mV/pH and linearity of 0.9948 was achieved, compared with the bare n-macro PSi pH sensor having a sensitivity of 25.12 mV/pH and linearity of 0.9392. This sensitivity enhancement is due to the additional specific surface area of PdNPs which causes improved it.