N. Fukata

Interstitial oxygen in GeSi alloys

Interstitially dissolved oxygen atoms in the Czochralski-grown Ge 1-x Si x were investigated by the infrared spectroscopy together with the analysis by the secondary ion mass spectroscopy and the X-ray fine structure. In GeSi alloys in the whole composition range 0<x< 1, oxygen atoms occupy preferentially a bond-center site between Si atoms to make a Si-O-Si quasi-molecule leading to a typical 1106cm -1 peak. The 1106 cm -1 peak shifts to low frequency side with an increase in Ge, possibly due to the expansion of Si-Si bonds.

Annealing behavior of hydrogen-defect complexes in carbon-doped Si quenched in hydrogen atmosphere

Optical absorption spectra and the annealing behavior of hydrogen (H)-point defect complexes in carbon (C)-doped Si after hydrogenation were investigated. Specimens of C-doped Si (C concentration: 1.7×1017u200acm−3) were sealed in quartz capsules together with H2 gas and were annealed at a high temperature for 1 h followed by quenching in water. We measured the optical absorption spectra at about 7 K with a Fourier-transform infrared spectrometer. The VH4 (V: monovacancy) defect was almost annealed out at 600u200a°C. The formation energy of the VH4 defect in C-doped Si was estimated to be about 3.2 eV from the quenching temperature dependence of the 2223 cm−1 peak. The observed 2192 and 2203 cm−1 peaks are probably due to the VH3 defect, which captures one H atom during annealing and become the VH4 defect. After annealing at 700u200a°C, we observed two absorption peaks at 2093 and 2086 cm−1, which are probably due to Si–H stretching vibration of H on internal surfaces of voids. From these assignments, it was found that V is introduced into C-doped Si at high temperatures, although it is known that C introduces I into Si at high temperatures.Optical absorption spectra and the annealing behavior of hydrogen (H)-point defect complexes in carbon (C)-doped Si after hydrogenation were investigated. Specimens of C-doped Si (C concentration: 1.7×1017u200acm−3) were sealed in quartz capsules together with H2 gas and were annealed at a high temperature for 1 h followed by quenching in water. We measured the optical absorption spectra at about 7 K with a Fourier-transform infrared spectrometer. The VH4 (V: monovacancy) defect was almost annealed out at 600u200a°C. The formation energy of the VH4 defect in C-doped Si was estimated to be about 3.2 eV from the quenching temperature dependence of the 2223 cm−1 peak. The observed 2192 and 2203 cm−1 peaks are probably due to the VH3 defect, which captures one H atom during annealing and become the VH4 defect. After annealing at 700u200a°C, we observed two absorption peaks at 2093 and 2086 cm−1, which are probably due to Si–H stretching vibration of H on internal surfaces of voids. From these assignments, it was found th...

Hydrogen-defect complexes formed by neutron irradiation of hydrogenated silicon observed by optical absorption measurement

Neutron-irradiation-induced defects in hydrogenated Si were investigated by detecting optical absorption due to their complexes with hydrogen. Specimens were doped with hydrogen by heating in H2 gas at 1300u200a°C followed by quenching in water. They were then irradiated with neutrons. The optical absorption spectra were measured at about 5 K with a Fourier transform infrared spectrometer. We investigated the dopant dependence and the annealing behaviors of H–interstitial (I) and H–vacancy (V) complexes. From the dopant dependence, we classified the peaks observed as I-related complexes or V-related complexes. In the annealing experiment, we observed numerous peaks after annealing above 300u200a°C in the region from 1940 to 2040 cm−1, whereas no such peaks were observed in the case of electron irradiation. This result shows that agglomerations of I and of V form more easily in neutron-irradiated Si than in electron-irradiated Si because of higher local concentrations of V and I in neutron-irradiated specimens.

Formation energy of vacancy in silicon determined by a new quenching method

Abstract By applying a new quenching method, we determined the formation energy of vacancies (V) in high-purity silicon. Specimens were sealed in quartz capsules together with H2 gas and heated at high temperatures for 1xa0h followed by quenching in water. By this method, V are quenched in the form of complexes with hydrogen and the formation energy of V can be determined from the quenching temperature dependence of the intensity of the optical absorption peak due to the complexes. The formation energy of V in high-purity silicon was determined to be about 4.0xa0eV. This value is in good agreement with results of recent theoretical calculations.

Formation energy of self-interstitials in carbon-doped Si determined by optical absorption due to hydrogen bound to self-interstitials

We determined the formation energy of self-interstitials in carbon (C)-doped Si from measurements of optical absorption due to hydrogen (H) bound to isolated self-interstitials. Specimens of C-doped Si were sealed in quartz capsules together with hydrogen (H) gas, with pressure being 1 atm at high temperature, and were annealed at high temperature for 1 h followed by quenching in water. We measured their optical absorption spectra at about 7 K with an FT-IR spectrometer. Several peaks coincided with those observed in proton-implanted Si. Hence, we conclude that complexes of simple point defects such as vacancies and self-interstitials with hydrogen atoms existed in those specimens. From the quenching temperature dependence of the peaks identified to be H bound to self-interstitials, the formation energy of self-interstitials in C-doped Si was estimated to be about 3 eV.

Optical absorption study of electron-irradiated Czochralski-grown silicon doped with hydrogen

From the measurements of optical absorption spectra, we studied complexes generated by electron-irradiation of Czochralski-grown silicon (CZ.Si) pre-doped with hydrogen (H). Specimens were non-doped CZ.Si crystals with various concentrations of oxygen (O). They were doped with H by heating at 1300°C in H2 gas followed by quenching. They were then irradiated with 3-MeV electrons at room temperature. We measured their optical absorption spectra by a Fourier transform infrared spectrometer at about 7 K. In contrast to electron-irradiated floating-zone grown Si (FZ.Si) pre-doped with H, there was little optical absorption due to complexes of vacancies (V) and H. Instead, a 836 cm-1 peak due to a V–O pair was very strong. Its intensity was proportional to about 3/4 power of the electron dose. Optical absorption peaks due to complexes of H and I (self-interstitial) were stronger than those of FZ.Si. We propose that the observed 1959 cm-1 peak was due to I3H2. Due to annealing at around 100°C, VOH2 complexes were formed by reactions between V–O pairs and diffusing H2 molecules. Due to annealing at around 200°C, (VOH)2 complexes were formed probably by reactions between VOH2 complexes and diffusing V–O pairs.

Platinum–hydrogen complexes in silicon observed by measurements of optical absorption and electron spin resonance

Platinum–hydrogen (Pt–H) complexes in Si doped with Pt and H by heating at 1000–1300u200a°C followed by quenching in water were investigated from the measurements of optical absorption at 5 K and electron spin resonance (ESR) at 8 K. Optical absorption peaks at 1909.1 and 1910.3u2009cm−1 were observed in addition to the peaks due to the PtH and PtH2 complexes. The H doping temperature dependence of these peaks showed that the number of H atoms in the complex responsible for the 1909.1u2009cm−1 peak is larger than that for the 1910.3u2009cm−1 peak. We also observed ESR signals due to the PtH3 complex. The annealing behaviors of the 1910.3u2009cm−1 peak and the ESR signals were almost the same. Based on these results, the 1909.1 and 1910.3u2009cm−1 peaks are, respectively, assigned to the PtH4 complex and the PtH3 complex.

Evidence for H2∗ trapped by carbon impurities in silicon

Abstract Local mode spectroscopy and ab initio modelling are used to investigate two trigonal defects found in carbon-rich Si into which H had been in-diffused. Isotopic shifts with D and 13C are reported along with the effect of uniaxial stress. Ab initio modelling studies suggest that the two defects are two forms of the CH 2 ∗ complex where one of the two hydrogen atoms lies at an anti-bonding site attached to C or Si, respectively. The two structures are nearly degenerate and possess vibrational modes in good agreement with those observed.

Formation and annihilation of H-point defect complexes in quenched Si doped with C

We investigated the formation and annihilation of H-point defect complexes formed in C-doped Si by heating at high temperatures followed by quenching in hydrogen gas. Specimens of C-doped Si were sealed in quartz capsules together with hydrogen (H) gas, at pressure 0.8–1.5 atm at high temperature, and were heated at high temperature for 1 h followed by quenching in water. We measured their optical absorption spectra at about 7 K with an Fourier transform infrared spectrometer. We observed several optical absorption peaks due to H-point defect complexes. The optical absorption peaks observed at 2192 and 2203 cm−1 were assigned to the Si–H stretching mode of three hydrogen atoms bound to a vacancy (VH3 defect). The formation of the VH4 defect is due to the reaction between H and the VH3 defect. From isothermal annealing experiments, the activation energy for the dissociation of the VH4 defect was determined to be about 2.5 eV.

Impurity Dependence of Vacancy Formation Energy in Silicon Determined by a New Quenching Method

Impurity dependence of the formation energy of vacancies (V) in Si was investigated. Doped impurities were carbon (C), nitrogen (N) and platinum (Pt). Specimens were heated in H2 gas at high temperatures for 1 h followed by quenching in water. The optical absorption spectra were measured at about 5 K. The formation energies of V in Si were found to depend on doped impurities and those in C-, N- and Pt-doped Si were determined to be about 3.2, 3.2 and 2.7 eV, respectively. The result for magnetic field-applied Czochralski (MCZ)-Si showed that the formation energy of V is not significantly different between floating zone (FZ)-Si and CZ-Si.