Ashvani Kumar

Substrate effect on electrical transport properties of RNiO3 thin films prepared by pulsed laser deposition

We report the structural and transport properties of RNiO3 (R: Nd, Pr) thin films prepared by pulsed laser deposition over various substrates without high pressure annealing. An excimer laser KrF with wavelength of 248 nm was used for deposition. Various substrates such as single-crystal SrTiO3 (100), LaAlO3 (100) and Si (100) wafer are used for deposition of films to understand the effect of lattice mismatch on transport properties. Various parameters such as substrate temperature, O2 pressure, laser fluence and deposition time are optimized to get good quality RNiO3 films. The best quality films are found to be well textured with good crystalline properties. Well-defined first order metal–insulator phase transition (TMI) was observed in the best quality NdNiO3 films deposited on LaAlO3. However, the PrNiO3 films deposited on LaAlO3 show completely metallic behaviour throughout the temperature range with no TMI (transition temperature). Metal–semiconductor transition has been observed in the PrNiO3 films deposited on SrTiO3. We try to explain this behaviour due to strain-induced growth of the films.

Fabrication and nanoindentation properties of TiN/NiTi thin films and their applications in electrochemical sensing

Nanocrystalline TiN/NiTi thin films have been grown on silicon substrate by dc magnetron sputtering to improve the corrosion and mechanical properties of NiTi based shape memory alloys without sacrificing the phase transformation effect. Interestingly, the preferential orientation of the TiN films was observed to change from (1 1 1) to (2 0 0) with change in nature of sputtering gas from 70% Ar+30% N(2) to 100% N(2). In present study the influence of crystallographic orientation of TiN on mechanical and corrosion properties of TiN/NiTi thin films was investigated. TiN (2 0 0)/NiTi films were found to exhibit high hardness, high elastic modulus, and thereby better wear resistance as compared to pure NiTi and TiN (1 1 1)/NiTi films. Electrochemical test revealed that TiN coated NiTi film exhibits better corrosion resistance in 1M NaCl solution as compared to uncoated NiTi film. The application of TiN/NiTi films in the electrochemical sensing of dopamine, which has a critical physiological importance in Parkinsons disease, has been demonstrated. A comparison of voltammetric response of dopamine at silicon based electrodes modified with different nanocrystalline coatings indicated that these films catalyze the oxidation of dopamine.

Structural And Electrical Analysis Of Lead Free BZT-xBCT Ceramics

A comparative study of structural and electric properties of a recently discovered lead free electroceramic, Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}-x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} or BZT-xBCT, was conducted in the entire range from x = 0 to x = 1. This novel ceramic composite is being seen as a genuine understudy for commercially one of the most widely used piezoelectric ceramic, PZT, which is facing worldwide criticism due to its lead toxicity. The new system can be very extensively used like PZT in transduction applications as sensor, actuator and ultrasonic devices apart from numerous other utilities. The XRD, SEM and Ferroelectric studies establish the structural transition and different phases as function of Zr /Ti and Ba /Ca ratios.