Preparation of AlN film grown on sputter-deposited and annealed AlN buffer layer via HVPE

AlN films grown on sputter-deposited and annealed AlN buffer layer by high temperature hydride vapor phase epitaxy(HVPE)have been fabricated and structurally characterized.The crystalline quality and surface morphology of as-grown AlN films with various V/III ratios were studied and compared.The XRD results showed that the crystalline quality of the AlN film could be optimized when the growth V/III ratio was 150.At the same time,the full width at half-maximum(FWHM)values of(0002)-and(10¯12)-plane were 64 arcsec and 648 arcsec,respectively.As revealed by AFM,the AlN films grown with higher V/III ratios of 150 and 300 exhibited apparent hillock-like surface structure due to the low density of screw threading dislocation(TD).The defects microstructure and strain field around the HVPE-AlN/sputtered-AlN/sapphire interfaces have been investigated by transmission electron microscopy(TEM)technique combined with geometric phase analysis(GPA).It was found that the screw TDs within AlN films intend to turn into loops or half-loops after originating from the AlN/sapphire interface,while the edge ones would bend first and then reacted with others within a region of 400 nm above the interface.Consequently,part of the edge TDs propagated to the surface vertically.The GPA analysis indicated that the voids extending from sapphire to HVPE-AlN layer were beneficial to relax the interfacial strain of the best quality AlN film grown with a V/III ratio of 150.

Growth and crystallization behaviors of anodic oxide films on sputter-deposited titanium at very low potentials

Growth and crystallization of titanium anodized films were studied by performing the anodization of the sputter-deposited titanium samples under cyclic voltammetry （CV） mode at very low potentials. The surface features, crystalline behaviors and chemical compositions of the formed anodic oxide layers were detected by AFM, SE and XPS. It was found that the structure of the titanium anodized films is crystalline, even though the maximum oxidation potential （（Pmax） is very low （as low as 1000 mY）. Both enlarging the applied voltage and reducing the potential scanning rate are beneficial for the growth and crystallization of titanium oxide films. It was thought that the internal compressive stress, other than the local joule heating accepted for many researchers, is the main force of stimulating the crystallization of anodic titanium oxide films at very low potentials.

PREPARATION OF AMORPHOUS Ti-Pd ALLOYS AND THEIR PHYSICAL PROPERTIES

The amorphous Ti_(l_x)Pd_x alloys within a wider composition range of 0.25<x<0.6 have been prepared using sputter-deposition method on the liquid-nitrogen-cooled substrates.The for- mation of amorphous Ti-Pd alloys relates to the topologically close-packed intermetallic compounds existing in the equilibrium phase diagram.These amorphous Ti-Pd alloys are identified by differential scanning calorimetry that the crystallization begins at about 700 K. The insensitive dependence of the crystallization temperature on composition of the alloys is explained with a model proposed by Miedema and Buschow.The electric resistivity of the amorphous Ti-Pd alloys in the range of 4.2 to 270 K decreases monotonously with in- creasing temperature.

Surface configurations during annealing of sputter-deposited NiTi thin films

SPUTTER-DEPOSITED NiTi thin films are becoming more and more important because of their po-tential applications to the intelligent thin-film systems. The as-deposited NiTi thin films pre-pared by magnetron sputtering are generally amorphous. Because the amorphous NiTi thinfilms cannot show shape memory effect, they should be crystallized under appropriate anneal-