Effect of pressure on electrical and optical properties of metal doped TiO2

Abstract

A comparative study of electrical and optical properties of powder and its corresponding pellets has been done on 3d-doped TiO2. Ti1-xMxO2 (M = Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) powder and its corresponding pellet with doping concentration x = 0.05 has been prepared using solid state route. Optical and electrical measurements have been performed for all prepared samples and interestingly, it is observed that due to having external pressure (i.e. strain) both the properties change significantly. A rigorous theoretical calculation has been carried out to verify the experimental band gap obtained from optical absorption spectroscopy. In case of pellet sample band gap decreases as compared to the powder sample due to variation of pressure inside the structures. Role of doping has also been investigated both in pellet and powder forms and found that the band gap decreases as the atomic number of dopants increases. A cross-over behavior seen in pellet sample on doping with Ni, Cu and Zn (i.e. band gap increases with increase in atomic number of dopant). Electrical resistivity measurements have been carried out for both pellet and powder samples and it is found that in case of strain free samples the value of resistivity is smaller while in case of strained sample it is quite large. We believe that the present study suggests a novel approach for tuning the electrical and optical properties of semiconducting oxides either from doping or from applied pressure (or strain).