To utilize the excellent properties of silica (SiO2) glass for a glass laser host, neodymium-aluminum (Nd–Al) and neodymium-phosphorous (Nd–P) co-doped SiO2 glasses were studied. They were prepared by plasma-torch chemical vapor deposition (CVD). It was found that a doping level less than ten times the number of Nd for the Al co-dopant and less than about fifteen times for the P co-dopant was enough to remove undesirable fluorescence properties of Nd-doped SiO2 glasses and make them suitable for laser application. The clustering Nd ions disperse well in a glass matrix and lasing fluorescence increases. The effects of the Al dopant on the density and Raman spectra were also studied to obtain structural information. On the basis of glass science and solution chemistry, the marked effects of both dopants were explained by the following model. Nd ions can be well incorporated into a SiO2 glass network through co-dopant oxide forming a solvation shell around the Nd ions. This model leads to an expansible method for coordination control around active ions in SiO2 glass. A preliminary experiment on laser oscillation using Nd–Al co-doped SiO2 glass was also carried out.

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Effects of intrinsic defects on defect formation by excimer-laser irradiation were examined in synthetic silica glasses prepared by different methods. In samples containing oxygen-deficient centers (ODC s), laser-induced E' centers were stable at room temperature. In contrast, in samples heat treated in H, atmosphere, in which almost all ODC's changed into Si -H bonds, the induced-E'-center concentration increased by about two orders of magnitude, and the resulting E' centers were unstable, decaying at room temperature. We thus conclude that the formation efficiency of E' centers from Si -H bonds is much higher than that of ODC's and that the induced-E' centers recombine with radiolytic molecular H~to restore Si -H bonds. It is suggested that a trace amount of Si -H bonds plays an essential role in defect creation and annihilation in OH-containing silica glasses.

The effects of hydrogen annealing on capacitance–voltage (C–V) characteristics and interface-state density (Dit) of 4H–SiC metal–oxide–semiconductor (MOS) structures have been investigated. The Dit was reduced to as low as 1×1011 eV−1 cm−2 at Ec−E=0.6 eV using hydrogen annealing above 800 °C, where Ec−E is the energy level from the conduction-band edge. Secondary ion mass spectroscopy and Dit analysis revealed that Dit decreased with the increase of hydrogen concentration accumulated at the SiO2/4H–SiC interface. The interface states at SiO2/4H–SiC are thought to be originated from the dangling bonds of C atoms as well as Si atoms, because Dit decreases as the hydrogen annealing temperature increases and saturates around 800 °C. This high-temperature hydrogen annealing is useful for accumulation-type SiC metal–oxide–semiconductor field-effect transistors, which have n-type MOS structures to reduce the Dit.