Thermal stability of α-Ga2O3 films grown on c-plane sapphire substrates via mist-CVD

The thermal stability of α-Ga2O3 films grown on c-plane sapphire substrates was investigated. A strong correlation was found between thermal stability and film thickness: the more the α-Ga2O3 films maintained the α-phase upon heating at higher annealing temperature, the thinner they were. Transmission electron microscopy observations revealed that the phase transition of the α-Ga2O3 film to the thermodynamically most stable β-phase had the orientation relationship of β-Ga2O3 [2̄ 01] || sapphire [0001]. High-temperature x-ray diffraction measurement for the α-Ga2O3 film showed the relationship of β-Ga2O3 [4̄ 01]/[301] || sapphire [0001] as well. The dependence of the stability boundary on the film thickness originates from a thermal stress caused by a larger thermal expansion coefficient of α-Ga2O3 than that of sapphire. Relaxation of residual stress by introducing a selective area growth technique enhanced the thermal stability of α-Ga2O3 so that α-Ga2O3 maintained the corundum structure upon heating at 800 °C, although a small diffraction peak from β-Ga2O3 was detected by x-ray diffraction measurement. The enhanced thermal stability of α-Ga2O3 widens device process windows as well as growth windows

Natural band alignment of MgO1−xSx\rm MgO_{1-x}S_{x} alloys

We have calculated formation enthalpies, band gaps, and natural band alignment for $\rm MgO_{1-x}S_{x}$ alloys by first principles calculation based on density functional theory. The calculated formation enthalpies show that the $\rm MgO_{1-x}S_{x}$ alloys exhibit a large miscibilitygap, and a metastable region was found to occur when the S content was below 18% or over 87%. Effect of S incorporation for band gaps of $\rm MgO_{1-x}S_{x}$ alloys shows large bowing parameter (b $\simeq$ 13 eV) induced. The dependence of the band lineup of $\rm MgO_{1-x}S_{x}$ alloys on the S content by using two different methods, and the change in the energy position of valence band maximum (VBM) was larger than that of conduction band minimum. Based on the calculated VBM positions, we predicted that $\rm MgO_{1-x}S_{x}$ with S content 10 to 18% can be surface charge transfer doping by high electron affinity materials. The present work provides an example to design for p-type oxysulfide materials.Comment: 22 pages, 6 figure

Localized excitons in cubic Zn1-xCdxS lattice matched to GaAs

Excitonic properties have been studied in cubic Zn0.42Cd0.58S lattice matched to GaAs. At 2 K, the time-integrated photoluminescence spectrum was composed of single emission peaking at 2.863 eV and its LO-phonon replica. The linewidth of the main peak was 18.5 meV, which fairly well agreed with the theoretical value based on the disorder-induced broadening of exciton luminescence in alloys. In order to assess the emission mechanism, the transient luminescence decay was measured at various emission energies. At the high energy tail (2.883 eV), the luminescence showed exponential decay with a time constant of about 72 ps. On the other hand, the decay time increased with decreasing the detected emission energy. It was about 660 ps at the emission peak (2.863 eV). We interpret these features by means of the model of exciton localization

Time-resolved spectroscopy of biexciton luminescence in ZnxCd1-xSe-ZnSySe1-y multiple quantum wells

The radiative lifetime of biexcitons in ZnxCd1-xSe-ZnSySe1-y multiple quantum wells has been studied by means of time-resolved luminescence spectroscopy under high-density excitation. It is shown that the rise of the biexciton luminescence becomes more rapid with increasing excitation energy density and that the biexciton luminescence decays with a double exponential form. It is found that the decay-time constant of the faster-decay component in the double-exponential decay corresponds to the radiative lifetime of the biexciton. Its value is about 6 ps at 2 K and is about one-seventh of that in bulk ZnSe (∼40 ps)

Length-dependent recognition of double-stranded ribonucleic acids by retinoic acid–inducible gene-I and melanoma differentiation–associated gene 5

The ribonucleic acid (RNA) helicases retinoic acid-inducible gene-I (RIG-I) and melanoma differentiation–associated gene 5 (MDA5) recognize distinct viral and synthetic RNAs, leading to the production of interferons. Although 5′-triphosphate single-stranded RNA is a RIG-I ligand, the role of RIG-I and MDA5 in double-stranded (ds) RNA recognition remains to be characterized. In this study, we show that the length of dsRNA is important for differential recognition by RIG-I and MDA5. The MDA5 ligand, polyinosinic-polycytidylic acid, was converted to a RIG-I ligand after shortening of the dsRNA length. In addition, viral dsRNAs differentially activated RIG-I and MDA5, depending on their length. Vesicular stomatitis virus infection generated dsRNA, which is responsible for RIG-I–mediated recognition. Collectively, RIG-I detects dsRNAs without a 5′-triphosphate end, and RIG-I and MDA5 selectively recognize short and long dsRNAs, respectively

Autophagy requires endoplasmic reticulum targeting of the PI3-kinase complex via Atg14L

Generation of PI3P in the normally PI3P-deficient ER membrane makes the organelle a platform for autophagosome formation

シリコン窒化膜の化学構造と電子物性に関する研究

本文データは国立国会図書館の学位論文(博士)のデジタル化事業により作成された画像ファイルを基にpdf変換したものである京都大学新制・論文博士工学博士乙第7243号論工博第2369号新制||工||811(附属図書館)UT51-90-L45(主査)教授 佐々木 昭夫, 教授 松波 弘之, 教授 藤田 茂夫学位規則第5条第2項該当Kyoto UniversityDFA