An ultra low-temperature (< 300°C) silicon oxidation process in which KrF excimer laser light (λ=248 nm) is irradiated in highly concentrated ozone has been developed. The growth rate of SiO2 film was 5.2 nm/10 min at 300°C and 3.6 nm/10 min at 70°C. The leakage current densities of grown at 70°C SiO2 in an electric field of over 8 MV/cm match well the calculated curve based on the Fowler–Nordheim tunneling. The oxidation mechanisms for two growth modes are discussed.
We found a leucine aminopeptidase (LAP; EC 3.4.11.1) to be abundant in meiotic prophase tissue of a basidiomycete, Coprinus cinereus. After direct purification of the aminopeptidase component from meiocytes, we cloned the gene by degenerate PCR using partial amino‐acid sequences of the purified enzyme and 5′ and 3′ RACE. It was homologous to the eukaryotic leucine aminopeptidase gene. The recombinant protein possesses the characteristic activities of a Coprinus leucine aminopeptidase (CoLAP) with a molecular mass of 52.4 kDa, and forms a homohexamer. Northern blot and spatial distribution analysis by immunohistochemical staining indicated CoLAP to be abundant in meiotic prophase cells and the supporting cells around meiocytes, but scarce in mycelium cells. Interestingly, from zygotene to pachytene, CoLAP was mostly present in supporting cells around meiocytes, but from diplotene onwards, it was plentiful in meiocytes themselves, suggesting that its expression is required to control some of the biochemical events at meiotic prophase. Moreover, the strong expression of CoLAP mRNA immediately after treatment with methyl methanesulfonate in mycelium implies that CoLAP has a role in somatic DNA repair.
UV-light-excited O 3 prepared by irradiation of nearly 100% pure O 3 with a KrF excimer laser ͑ = 248 nm, irradiated area= 30ϫ 10 mm 2 ͒ was utilized for low-temperature Si oxidation. The initial oxidation rate was determined, and the activation energy was shown to be almost zero ͑0.049 eV͒. To clarify the optimum oxidation conditions, the dependence of the SiO 2 film growth rate on the total photon number and the photon density was investigated. The evolution of O 3 density after UV-light irradiation was experimentally measured, and the O͑ 1 D͒ density change is discussed. O͑ 1 D͒ density changes are successfully explained by using a second-order reaction model, indicating that a pulse supply of oxygen atoms is essential in the initial oxidation process. The uniform oxidation of 8 in. Si wafer has been carried out using a wafer-transfer type chamber by irradiating the wafer with KrF excimer laser light expanded linearly to the wafer width by a concave lens.
The structure of Si(111) √7×√7 R19.1°-Co reconstructed surface have been investigated by scanning tunneling microscopy (STM). Three proposed sites on the reconstructed surface, the Co atom site, the cap-adatom site and the bridge-adatom site have been all visualized by STM. The electric structure at each adatom site was measured by scanning tunneling spectroscopy, exactly. The reason why the bridge site can be visualized under the restricted condition is also explained by the local electric state above the Fermi level.
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