MgxZn1−xO films were grown on quartz substrates at 773 K by using radio frequency magnetron sputtering with a mixture of argon and nitrogen as sputtering gases. The nitrogen concentration in the mixture is characterized by the nitrogen partial pressure ratio, which is determined by the ratio of nitrogen flow rate to the flow rates of nitrogen and argon. It was found that Mg concentration, structure, and band gap of the MgxZn1−xO film could be tuned by changing the nitrogen partial pressure ratio of the sputtering gases. The Mg concentration in the MgxZn1−xO film increases with increasing nitrogen partial pressure ratio. The MgxZn1−xO film consists of wurtzite phase at the ratios from 0% to 50%, mixture of wurtzite and cubic phases at the ratios between 50% and 83%, and cubic phase at 100%. The band gap of the MgxZn1−xO film with wurtzite and cubic structure increases as the ratio rises. The variation of the structure and band gap is attributed to change of the Mg concentration, which results from loss of the O and Zn atoms during growth process, the former is induced by reaction between N and O, and the latter by re-evaporation of Zn atoms due to high substrate temperature. The mechanism of the loss of the O and Zn atoms is discussed based on thermodynamics.

A wurtzite nitrogen-doped MgZnO (MgZnO:N) film was grown by plasma-assisted molecular-beam epitaxy (PAMBE) on c-plane sapphire using radical NO as oxygen source and nitrogen dopant. The as-grown film shows n-type conduction at room temperature, but transforms into p-type conduction after annealed. Photoluminescence (PL) spectrum measured at 80 K is dominated by neutral donor-bound exciton emission (D0X) located at 3.522 eV for the n-type MgZnO:N film, but by neutral acceptor-bound exciton emission (A0X) located at 3.515 eV for the p-type MgZnO:N film. By fitting exciton emission intensity of temperature-dependent PL spectra, the binding energies of the D0X and A0X were estimated to be 32 and 43 meV, respectively. Based on the energy shift of exciton emission, the band gap of the MgZnO:N film is estimated to be 3.613 eV, which is 179 meV larger than that of ZnO. Using the Haynes rule, the acceptor energy level of the MgZnO:N film was evaluated to be about 176 meV above the valence band.

We have demonstrated a uniform, robust interface for high-k deposition with significant improvements in device electrical performance compared to conventional surface preparation techniques. The interface was a thin thermal oxide that was grown and then etched back in a controlled manner to the desired thickness. Utilizing this approach, an equivalent oxide thickness (EOT) as low as 0.87 nm has been demonstrated on high-k gate stacks having improved electrical characteristics as compared to more conventionally prepared starting surfaces.

Electron diffraction has been recently used in the pharmaceutical industry to study the polymorphism in crystalline drug substances. While conventional X-ray diffraction patterns could not be used to determine the cell parameters of two forms of the microcrystalline GP IIb/IIIa receptor antagonist roxifiban, a combination of electron single-crystal and synchrotron powder diffraction techniques were able to clearly distinguish the two polymorphs. The unit-cell parameters of the two polymorphs were ultimately determined using new software routines designed to take advantage of each technique's unique capabilities. The combined use of transmission electron microscopy (TEM) and synchrotron patterns appears to be a good general approach for characterizing complex (low-symmetry, large-unit-cell, micron-sized) polymorphic pharmaceutical compounds.

Texture, i.e. preferred orientation (PO), of crystallites can cause serious systematic errors in quantitative analysis of crystalline materials using x-ray powder diffraction (XRPD) data. The singleparameter model of March (1932), proposed by Dollase (1986) for use in powder diffractometry is a promising mathematical formalism for correcting PO in XRPD analysis of uniaxially-oriented specimens. O'Connor et al. (1991) successfully applied the March formula in applying preferred orientation corrections for gibbsites, Al(OH)3, using Rietveld pattern-fitting and a line ratio method in which corrections are determined according to the intensity ratios of selected lines. The paper gives an appraisal of the general applicability of the methods considered by Li and O'Connor with particular reference to powder diffraction data for gibbsite, molybdite (MoO3), calcite (CaCO3) and kaolinite specimens. It is shown that some caution should be exercised when using the March formula to describe PO in Rietveld analysis.

Quantitative phase analysis (QPA) methods which employ only one diffraction line for each phase arc generally unreliable due to the influence of systematic errors such as preferred orientation and extinction. Gazzara and Messier (1977) proposed a multi-line QPA method using normalised line intensities for line j of phase i,

where Iij = measured Bragg intensity, m = multiplicity, Lp = Lorentz-polarisation factor, |F| = structure amplitude and Vi = cell volume. The method proposed here is a refinement of the Gazzara-Messier procedure. Phase compositions are calculated directly from the mean normalised Intensity for resolved lines which span the 2θ range of the instrument. The method makes use of the variance in to estimate standard deviations for the phase compositions. Test results are given for binaries of corundum-quartz and corundum-ceria.

Li et al (1990) reported experiments with gibbsite powder specimens on the use of Rietveld pattern-fitting, involving the March preferred orientation model, to characterise preferred orientation according to the March r parameter. It was shown that intensity corrections may be applied with the March r parameter derived from Rietveld analysis or with the related line intensity ratio MR which is sensitive to preferred orientation. The present paper reports an analytic expression involving r and MR which has proved highly reliable for the correction of preferred orientation bias in quantitative phase analysis of gibbsite. Similar expressions may be readily derived for other materials for which the March model is appropriate. Therefore the line ratio approach has considerable potential for rapid correction of intensities for preferred orientation.

The X-ray Analytical Science Group at Curtin university of Technology has been developing and evaluating Rietveld pattern-fitting for materials analysis since 1985. The results are reviewed with particular reference to preferred orientation, crystallinity and phase abundance.