Glucose sensing characteristics of Pd-doped tin oxide thin films deposited by plasma enhanced CVD

This work presents glucose sensing characteristics of palladium doped tin oxide (SnO ₂) thin films deposited by modified plasma enhanced chemical vapor deposition (CVD) technique as a function of deposition temperature (400-600°C) and at fixed radio frequency (RF) plasma power of 150 W. Stannic chloride (SnCl ₄) and palladium hexafluroacetyleacetonate (Pd(C ₅HF ₆O ₂) ₂) were used as precursors for tin and palladium respectively whereas oxygen (O ₂, 100 sccm) was used as reactant gas. Granular morphology is observed with tetragonal rutile structure. Diffraction peaks related to SnO ₂ and Pd ₂Sn are observed at all the deposition temperatures. Photoelectron peaks related to Sn (3d, 3p, 4d), Pd 3d, O 1s, C 1s and N 1s were detected with varying intensities as a function of deposition temperature. Glucose oxidase (GOx) was immobilized by physical adsorption (by soaking films in 1000 units of GOx solution for three hours). The sensitivity to glucose increases with slight non-linearity from 5 mg/dl to 360 mg/dl and found decreasing with increasing deposition temperature. Electrochemical studies indicated rapid electron transfer kinetics and hence reversible electron transfer reactions.