Phase transition and thermal expansion studies of alumina thin films prepared by reactive pulsed laser deposition.

Aluminium oxide (Al2O3) thin films were deposited on Si (100) substrates at an optimized oxygen partial pressure of 3 x 10(-3) mbar at room temperature by pulsed laser deposition (PLD). The films were characterized by high temperature X-ray diffraction (HTXRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The HTXRD pattern showed the cubic y-Al2O3 phase in the temperature range 300-973 K. At temperatures ≥ 1073 K, the δ and θ-phases of Al2O3 were observed. The mean linear thermal expansion coefficient and volume thermal expansion coefficient of γ-Al2O3 was found to be 12.66 x 10(-6) K(-1) and 38.87 x 10(-6) K(-1) in the temperature range 300 K-1073 K. The field emission scanning electron microscopy revealed a smooth and structureless morphology of the films deposited on Si (100). The atomic force microscopy study indicated the increased crystallinity and surface roughness of the films after annealing at high temperature.

Synthesis and properties of ceria thin films prepared by pulsed laser deposition.

Cerium oxide (CeO2) thin films were prepared on (100) Si and glass substrates using pulsed laser ablation at different oxygen partial pressures (2.5 x 10(-5)-3.5 x 10(-1) mbar) and at a substrate temperature of 873 K. XRD studies on the films showed that the films are polycrystalline having fluorite structure. The oxygen partial pressure has a dominant effect on the thickness, crystallite size and preferred orientation of the films. At an oxygen partial pressure of 3.5 x 10(-2) mbar, the intensity of (200) reflection is maximum and film possesses the maximum crystallite size of about 50 nm. Though all the films are highly transparent in the visible region, films prepared at an oxygen partial pressure of 3.5 x 10(-1) mbar, exhibits maximum transmittance (>90% @ 632 nm). The optical band gap is found to decrease from 3.66 to 3.42 eV with the increasing oxygen partial pressure.

A study on the influence of copper content in CrN/Cu nanocomposite thin films prepared by pulsed DC magnetron sputtering.

Synthesis of nanocomposite thin films of CrN/Cu deposited on (100) Si and D-9 alloy substrates by pulsed magnetron sputtering as a function of copper content in the range 15.1-35.8 at.% is investigated. XRD analysis of the films deposited at 773 K with nitrogen flow rate of 10 sccm indicated that the films are nanorystalline and bi-phasic (fcc-CrN and fcc-Cu). Scanning electron microscopy showed a structureless morphology for CrN, while agglomerates were obtained for CrN/Cu nanocomposite thin films. Atomic force microscopy also confirmed the agglomeration of particles with increasing Cu content. The amount of copper content in the nanocomposite films had also shown a significant reduction in the crystallite size of CrN. The nano hardness measurements showed a peak hardness of 17 GPa for the films with copper content of 15.1 at.%. The hardness values were found to decrease significantly with Cu content > 31.1 at.%.

Microstructural studies of nanocomposite thin films of Ni/CrN prepared by reactive magnetron sputtering.

Synthesis and characterization of nanocomposites of Ni/CrN thin films prepared by DC magnetron sputtering from a target of 50 wt.%Ni-50 wt.%Cr is investigated. The films prepared as a function of nitrogen flow rate and substrate temperature showed that the films contained Ni and CrN phases with crystallite sizes in the nanometer range. Measurement of nanomechanical properties of the composite films exhibited a significant decrease in the values of hardness and Young's modulus than those of pure CrN films.