We report a detailed study of the structural, chemical, electrical, and magnetic properties of undoped ZnO thin films grown under different conditions and the films that were annealed in various environments and irradiated with an ultraviolet laser. Samples prepared in low oxygen pressure or subsequently annealed in vacuum have always been strongly magnetic. Oxygen-annealed films displayed a sequential transition from the ferromagnetic to the diamagnetic state as a function of the annealing temperature. Reversible switching of room temperature ferromagnetism and n-type conductivity have been demonstrated either by annealing in different environments or by a novel laser irradiation treatment. Enhancements in both the electrical conductivity and magnetic moment have been controlled precisely with laser pulses, without altering the crystal structure. Electron paramagnetic resonance data were found to be in good agreement with the magnetization and conductivity measurements. Our secondary ion mass spectrometer and electron energy loss spectrometer studies conclusively rule out the presence of any external ferromagnetic impurities.

Systematic studies on the epitaxial growth and the effect of n-type (Al,Ga) doping on the magnetic and electrical properties of 2.0 % Cu doped ZnO dilute magnetic semiconducting thin films deposited on c-plane sapphire single crystals by pulsed laser deposition are reported here. An decrease in more than 3 orders of magnitude in resistivity from 2×101 Ohm cm for the 2.0 % Cu doped ZnO to ~5×10-3 Ohm cm for Al and Ga codoped films is observed. This increase in conductivity does not show any effect on ferromagnetic ordering thus contradicting the claim of free carrier mediated exchange as being responsible for ferromagnetic ordering in these DMS systems. A bound magnetic polaron or F-center mediated exchange is a possible explanation for the origin of ferromagnetism in these ZnO based DMS thin films.

Polycrystalline diamond films previously grown on silicon were polished to an RMS roughness of 15 nm and bonded to the silicon in a dedicated ultrahigh vacuum bonding chamber. Successful bonding under a uniaxial mechanical stress of 32 MPa was observed at temperatures as low as 950°C. Scanning acoustic microscopy indicated complete bonding at fusion temperatures above 1150°C. Cross-sectional transmission electron microscopy later revealed a 30 nm thick intermediate amorphous layer consisting of silicon, carbon and oxygen.

The early stages of a gas phase pretreatment for diamond nucleation in an oxy-acetylene flame were investigated. The pretreatment involved a low oxygen-to-acetylene ratio (Rf = 0.93) performed at 15 mm from the torch on a scratched Si substrate. The nature of the carbon species deposited was analyzed using X-ray photoelectron spectroscopy, Auger electron spectroscopy, and scanning electron microscopy. The pretreatment process produced diamond crystals after 30 seconds and a complete film in the center of the deposition area after 180 seconds. Furthermore, the pretreatment process kept the initial Siob2 layer less than the thickness generated by the control conditions, (Rf = 0.97, d = 10mm). The success of the pretreatment was attributed to changes in the flame structure and chemistry from the control conditions.