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Research describing the porous structure of silica based intermetal dielectric materials is presented. In particular the size and depth distributions of pores for different curing conditions and film thicknesses is investigated.

Vacancy-type defects due to carburization of Si by monoenergetic positrons are studied.

A new study investigates the annealing properties of defects in separation-by-implanted-oxygen wafers.

Monoenergetic positron beams were used to probe defects in p+ -gate metal-oxide-semiconductor structures.

Dielectric multilayer mirrors, degraded through irradiation by high-energy undulator radiation, were successfully restored by surface treatment with RF-induced [O.sub.2] plasma. The mirror loss, which had been increased up to [approximately] 1000 parts in [10.sup.6] (ppm) through the mirror degradation, was drastically reduced to [approximately] 100 ppm during the treatment. Such a mirror-restoration technique has been desired especially in short-wavelength free-electron lasers (FEL's), because the laser gain is so small that even a mirror loss as small as [approximately] 1000 ppm interferes with the FEL oscillation. The mirror degradation is most likely caused by the deposition and doping of carbon atoms onto the dielectric surface. The surface analysis by the x-ray photoelectron spectroscopy revealed that the plasma treatment effectively removed the carbon contamination covering the mirror surfaces without serious surface damage by high-energy particles from the plasma. Key words: Free-electron lasers, plasma treatment, mirror restoration.

Hydrogen-terminated vacancies in Si[sup +]-implanted Si were studied by means of positron annihilation. After the Si[sup +]-ion implantation, hydrogen atoms were introduced into the damaged region using a hydrogen plasma [hydrogen-atom treatment (HAT)]. Monoenergetic positron beams were used to measure Doppler broadening spectra of the annihilation radiation and the lifetime spectra of positrons. It was found that the line shape parameter, S, corresponding to the annihilation of positrons trapped by vacancy-type defects, decreased after HAT. This was attributed to the trapping of positrons by H-decorated vacancy-type defects. Isochronal annealing experiments revealed a strong correlation between positron annihilation parameters and Raman intensities of Si-H, suggesting that hydrogen atoms are released from vacancy-type defects after annealing at 600 °C. [ABSTRACT FROM AUTHOR]

Vacancy-type defects in separation-by-implanted oxygen wafers were probed using monoenergetic positron beams. We measured the Doppler broadening spectra of annihilation radiation and the lifetime spectra of positrons. The species of the defects in Si-on-insulator (SAT) layers were identified as oxygen clusters or small oxygen precipitates, and the positrons are considered to be trapped by open spaces adjacent to such defects. The mean size of the open spaces was estimated to be larger than that of a hexavacancy. After annealing in a hydrogen atmosphere at 600 °C, both the lifetime of positrons trapped by the defects and the annihilation probability of positrons with high-momentum electrons decreased. These facts were attributed to the trapping of hydrogen atoms by the open spaces. The defects in bond-and-etchback SaT wafers and their interaction with hydrogen were also studied. [ABSTRACT FROM AUTHOR]

Thin BaTiO[sub 3] films grown on SrTiO[sub 3] substrates were characterized by means of positron annihilation. The films were deposited by molecular-beam epitaxy without using oxygen source. We measured the Doppler broadening spectra of annihilation radiation and x-ray diffraction of the films and found that vacancy-type defects such as oxygen vacancies and other related defects caused lattice relaxation in the films. These defects disappeared after the films were annealed at 600 °C in an O[sub 2] atmosphere. Lattice relaxation in the films was also observed when the films were annealed at 1050 °C, but there was no direct relationship between the lattice relaxation that occurred at this temperature and vacancy-type defects. Vacancy-type defects were introduced into the SrTiO[sub 3] substrates by the growth of the BaTiO[sub 3] films. The species of these defects were identified as oxygen vacancies or defects related to oxygen vacancies, and they appeared as a result of diffusion of oxygen toward the BaTiO[sub 3] films. Almost all oxygen vacancies in the SrTiO[sub 3] substrates were annealed out at 500 °C. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The depth distributions of oxygen-related defects in separation-by-implanted oxygen wafers were determined from measurements of Doppler broadening spectra of the annihilation radiation. Vacany-oxygen complexes were introduced by implanting 180-keV oxygen at (2–6) × 10[sup 17] cm[sup -2] into Si substrates. Their sizes decreased below the subsurface region (<100 nm) because an agglomeration of vacancy-type defects was suppressed by the interaction between vacancies and oxygen atoms. As the dosage was increased, in the region near the projected range of oxygen, atomic rearrangement of vacancy-type defects occurred, and this rearrangement is considered to introduce SiO[sub x] (x<2) that is stable at high annealing temperatures. Oxygen-related defects were presented in the superficial Si layer even after annealing at 1350 °C. The concentration of such defects was low when the substrate was implanted with a dose of 4 × 10[sup 17] cm[sup -2]. [ABSTRACT FROM AUTHOR]

Depth distributions and species of defects were determined from measurements of Doppler broadening spectra of annihilation radiation and lifetime spectra of positrons for 6H-SiC implanted with 200 keV P[sup +] at a dose of 1×10[sup 15] cm[sup -2]. The annealing behavior of an amorphous layer was divided into four stages. Stages I (100–500 °C) and II (500–1100 °C) were identified as the relaxation of amorphous networks and the agglomeration of open spaces owing to rearrangements of atoms, respectively. In states III (1100–1500 °C) and IV (1500–1700 °C), corresponding to the recrystallization of the amorphous layer, the mean size of the open volume of defects decreased with increasing annealing temperature; these defects were identified as open spaces adjacent to extended defects. Vacancy-type defects were found in the subsurface region (<100 nm) at high concentration even subsequent to an annealing at 1700 °C. The annealing behavior of defects in the specimens irradiated at elevated temperatures is also discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The defects in BaTiO3/SrTiO3 structures fabricated are studied using MBE. The introduction of vacancy-type defects is found near the interface between the films and the substrate causing lattice relaxation in the BaTiO3 films.