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A yellow-orange nitrogen-doped zinc oxide (ZnO:N) film was deposited on a quartz glass substrate at 510 K by reactive radio-frequency magnetron sputtering of a ZnO target with sputtering gas of nitrogen. The lattice constants of the as-grown ZnO:N are much larger than those of undoped ZnO, and decrease with increasing annealing temperature due to escape of the nitrogen from the ZnO:N and decrease of tensile stress, accompanied with color change from yellow-orange to pale yellow. The nitrogen occupies two chemical environments in the ZnO:N based on x-ray photoelectron spectroscopy measurement. One is NO acceptor formed by substitution of N atom for O sublattice, and another is (N2)O double donors produced by substitution of N molecular for O site, which make the lattice constants expanded. The as-grown ZnO:N film shows insulating, but behaves p-type conduction in the dark after annealed at 863 K for 1 h under 10-3 Pa. Unfortunately, the p-type conduction is not stable and reverts to n type soon. However, after illuminated by sunlight for several minutes, the n-type ZnO:N transforms into p type again. The mechanism of the transformation of the conductivity behavior is discussed in the present work. [ABSTRACT FROM AUTHOR]

Vitrification from physical vapor deposition is known to be an efficient way for tuning the kinetic and thermodynamic stability of glasses and significantly improve their properties. There is a general consensus that preparing stable glasses requires the use of high substrate temperatures close to the glass transition one, Tg. Here, we challenge this empirical rule by showing the formation of Zr-based ultrastable metallic glasses (MGs) at room temperature, i.e., with a substrate temperature of only 0.43Tg. By carefully controlling the deposition rate, we can improve the stability of the obtained glasses to higher values. In contrast to conventional quenched glasses, the ultrastable MGs exhibit a large increase of Tg of ∼60 K, stronger resistance against crystallization, and more homogeneous structure with less order at longer distances. Our study circumvents the limitation of substrate temperature for developing ultrastable glasses, and provides deeper insight into glasses stability and their surface dynamics. [ABSTRACT FROM AUTHOR]

Zn1-xMgxO films were grown by radio-frequency reactive magnetron sputtering using mixture of nitrogen and argon as sputtering gases. It was found that Mg concentration, structures, electrical properties, and band gaps of the films can be tuned by changing nitrogen partial pressure ratio of the sputtering gases. The Zn1-xMgxO film consists of wurtzite phase at the ratios from 0% to 50%, mixture of wurtzite and cubic phases at the ratios of 78% to 83%, and cubic phase at 100%. The Mg concentration increased linearly with increasing the ratio. The band gap increases from 3.64 eV at x=0.172 to 4.02 eV at x=0.44 for the wurtzite Zn1-xMgxO and reaches 6.30 eV for cubic Zn1-xMgxO with x=0.84. All the as-grown Zn1-xMgxO films show high resistivity at room temperature, but transform into p-type conduction after annealing at 600 °C for 30 min under 10-4 Pa, except for the film grown at the ratio of zero. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The purpose of this study is to determine whether trichostatin A (TSA), a HDAC specific inhibitor, inhibited the induction and functional activity of hypoxia-inducible factor-1 a(HIF-1a) and hypoxia-induced angiogenesis in vitro in human osteosarcoma. The relationship between expression of HIF-1a proteion and angiogenesis in tumor specimens was also studied. Hypoxic regulation of VEGF was studied by RT-PCR, western blotting analysis and enzyme linked immunosorbent assay. The expression of HIF-la and VEGF in human osteosarcoma specimens was studied by immunohistochemical analysis. Under hypoxia, no regulation of HIF-1a mRNA expression was found. However, HIF-1a protein levels increased dramatically in response to hypoxia. Hypoxia increased VEGF mRNA level, but it was significantly inhibited by trichostatin A in a time- and dose-dependent manner (p < 0.05). Strongly positive immunostaining for HIF-1a and VEGF were detectable in the nuclear and cytoplasm of osteosarcoma cells. HIF-1a expressing cells were prominent in areas with high MVD. Significant correlation were found between HIF-1a expression and MVD (p = 0.005, r = 0.767), as well as between VEGF and MVD (p < 0.002, r = 0.701) by Spearman's rank coefficient analysis. These results indicated that HIF-1a is a key factor responsible for angiogenesis by the induction of VEGF. TSA downregulates hypoxia-response genes and hypoxia-induced angiogenesis by the suppression of HIF-1a activity.