Correlation between dielectric properties and strain in Pb0.5 Sr0.5TiO3 thin films prepared by using the sol–gel method

Pb_0.5Sr_0.5TiO₃ (PST) thin films were fabricated by the alkoxide-based sol–gel process using spin-coating method on Pt/Ti/SiO₂/Si substrate. The PST films annealed from 500 °C to 650 °C for 1 h show a perovskite phase and dense microstructure with a smooth surface. The grain size and dielectric constant of PST films increase with the increase in annealing temperature, which reduces the SiO₂ equivalent thickness of the PST film. The crystallinity or internal strain in the PST thin films analyzed from the diffraction-peak widths correlates well with the decrease in the dielectric losses. The dielectric constants and dielectric loss (%) of the PST films annealed at 650 °C (t_eq=0.89 nm) were 549 and 0.21%, respectively.     

Growth and applications of HVPE-GaN nanorods

We demonstrate the properties of gallium nitride nanorods by hydride vapor phase epitaxy (HVPE). Single crystalline gallium nitride nanorods are formed on a sapphire substrate by HVPE. Single crystalline p-type and n-type gallium nitride nanorods have been grown and characterized by electrical transport measurements. HVPE was used to controllably introduce either magnesium or silicon dopants during the growth of the gallium nitride nanorods. The electron emission properties of gallium nitride nanorod array electron emitters were comparable with (or displayed even lower turn-on voltage than) those of carbon nanotubes. Wide-bandgap current rectifiers with high breakdown voltage (over −10 V) and near-ultraviolet p-n junction LEDs with emission wavelength of 390 nm, based on the single-rod gallium nitride p-n junction array, were obtained.