R. Nithya

Synthesis of nanocrystalline α-Al2O3 by ultrasonic flame pyrolysis

Nanocrystalline alpha-alumina was synthesized in an indigenously built ultrasonic flame pyrolysis (UFP) setup. This paper describes the technical aspects of the apparatus and particle formation in the flame. Ultrasonically atomized aluminium nitrate dissolved in methanol-water mixture was pyrolyzed in an oxy-propane flame for yielding nanocrystalline alpha-alumina. The formation of nanophase alumina was confirmed by powder XRD analysis. Scanning electron microscopy (SEM) analysis was carried out to study particulate morphology

Synthesis of nanostructured titanium nitride films by PLD through reactive processing

Abstract High quality TiN films were synthesised from elemental metallic target using reactive and plasma assisted pulsed laser deposition (RPLD and PAPLD) techniques. In these processes, a high pure titanium target is ablated using a nanosecond pulsed Nd:YAG laser operating at 1064 nm wavelength at different nitrogen pressures. In RPLD process, the titanium plume reacts directly with the nitrogen gas at pressures less than 0·07 mbar to yield TiN films. In PAPLD process, additional nitrogen plasma was generated and confined by a DC coil positioned between target and substrate. Resultant films were characterised for phase, composition and morphology using glancing incidence X-ray diffraction, Auger Electron Spectroscopy (AES), Rutherford back-scattering and Atomic Force Microscope (AFM). Reactive pulsed laser deposition grown TiN films were found to contain traces of unreacted titanium. The crystallite size is estimated to be 15 and 50 nm respectively by using X-ray diffraction and AFM. Rutherford backscattering investigations helped the authors in arriving at the stoichiometry and AES analysis revealed the formation of TiN with low oxygen contamination.

Reactive Pulsed Laser Deposition of Titanium Nitride Thin Films: Effect of Reactive Gas Pressure on the Structure, Composition, and Properties

Titanium nitride (TiN) thin films were deposited by reactive pulsed laser deposition (RPLD) technique. For the first time, the composition evaluated from proton elastic backscattering spectrometry, in a quantitative manner, revealed a dependence on the partial pressure of nitrogen from 1 to 10 Pa. Grazing incidence-XRD (GI-XRD) confirmed the formation of predominantly nanocrystalline TiN phase with a crystallite size of around 30 nm. The hardness showed maximum value of ~30 GPa when the composition is near stoichiometric and the friction coefficient was found to be as low as 0.3. In addition, a systematic optical response was observed as a function of deposition pressure from the surface of the TiN films using spectroscopic ellipsometry.

Evolution of temperature dependent properties of oriented YBaCo4O7 thin films

Bulk YBaCo4O7 was synthesized using a ceramic route in air. Thin films of this compound were grown on (100) oriented LaAlO3 substrate using a Pulsed Laser Deposition technique. X-ray diffraction results of thin film indicate that the film has (110) orientation. Electrical resistivity measurements, in 300K to 100K temperature range showed that the film is insulating, similar to that of the bulk. Spectroscopic ellipsometric measurements on thin films in the energy range 1.5 to 5 eV and at temperatures from 300 K to 400 K showed that the direct band gap s 2.45 eV at ambient temperature while its value increases with increase in temperature. The increase in band gap with temperature is attributed to the Moss-Burstein effect.