Search

We fabricated all-epitaxial Ba0.5Sr0.5TiO3 (BST) (111)/β-Ga2O3 (− 201) thin films on GaN (002)/Al2O3 (001) substrates by pulsed laser deposition. BST films with different textures were obtained by depositing β-Ga2O3 buffer layers on GaN substrates under varied deposition conditions. The results for dielectric constant, tunability, and dielectric loss of the BST/Ga2O3/GaN and BST/GaN layers at an applied voltage of 20 V, were 225 and 199, 20% and 14%, and 0.006 and 0.018, respectively. The epitaxial growth of the BST film and enhancement of the dielectric properties of the BST/Ga2O3/GaN heterostructure were achieved in the presence of an epitaxial Ga2O3 buffer layer.

This report discusses the structural and spectroscopic analysis of yttria-stabilized-zirconia (YSZ) thin films grown on Al 2 O 3 (0001) substrates. It is found that the changes of oxygen partial pressure during the growth are closely related to the surface chemical compositions and the surface crystal orientations of the thin films. The presence of oxygen partial pressure produces a polycrystalline structure on the thin film while a preferred orientation of crystal structures is formed under no oxygen partial pressure. Difficulty arises in identifying the structure of the thin films due to the broad characteristics of the x-ray diffraction (XRD) peaks; however, the XRD rocking scan suggests the existence of two lateral domain sizes. The chemical analysis of the thin films from x-ray photoelectron spectroscopy measurements indicates the enrichment of surface yttrium-oxide as the oxygen partial pressure increases. The detailed analysis of valence band spectra also suggests that the thin films undergo a surface structural phase transition, i.e., transforming from a single tetragonal structure to a mixed (cubic + monoclinic) structure. Furthermore, the optical data display the small increments of the band gap as the oxygen partial pressure increases, which reflects the presence of the structural phase transition of the thin films.

Electrospun polyacrylonitrile (PAN) nanofibers were subjected to surface modification by atmospheric pressure (AP) plasma treatment with reactive gases. There was no damage to the surfaces after this plasma treatment, and no significant changes were observed in the morphologies of the nanofibers. The surface energies of O2- and N2-plasma-treated PAN (abbreviated as OPP and NPP, respectively) nanofibers increased by almost 138.7% and 190.6%, respectively, in comparison with that of an untreated nanofiber (256.6 mJ/m2). The binding energies of both OPP and NPP samples increased through the formation of many hydrophilic bonds involving oxygen. The current–voltage (I–V) characteristics of the nanofibers were determined for the different reactive gases, and the plasma-treated nanofibers showed higher protein immobilization compared to the untreated ones. This result indicates that electrospun PAN nanofibers have the potential to be used in protein biosensor systems.

In this paper, we report on the high-performance photocatalysis of polymeric TiO 2 membranes modified by oxygen plasma treatment for water purification. TiO 2 -nanopowder-incorporated poly e-caprolactone (PCL/TiO 2 ; PT) nanofibers were prepared by electrospinning at various concentrations of TiO 2 (1, 3, 5, and 7 wt.%) and then treated by atmospheric plasma with oxygen gas (OAP). As the TiO 2 content increased, the surface roughness and photocatalytic efficiency of the nanofibers increased. The tensile strength of the membranes increased until the TiO 2 content reached 3 wt.% but led to a degradation of the mechanical property at higher concentrations owing to significant agglomeration of TiO 2 . The hydrophilicity of OAP membranes increased as the TiO 2 nanopowders were exposed and the production of polar species was induced at the surface of the PT nanofibers. The OAP-PT membranes were observed to enhance the degradation of harmful organics. The results indicate that OAP-PT membranes are useful photocatalysts for purifying water.