Ichiro Konomi

Damage profiling of Ar+ -irradiated Si(100) and GaAs(100) by medium energy ion scattering

Damage profiles of 0.5–3 keV Ar+-irradiated Si(100) and 1–3 keV Ar+-irradiated GaAs(100) were measured by medium energy ion scattering (MEIS) with an electrostatic analyzer of the modified toroidal type. We have achieved good energy and depth resolutions of 5 × 10−3 and about 1 nm, respectively. The observed random and channeling MEIS spectra were analyzed precisely by computer-simulated spectrum fitting. The damage width (nm) determined experimentally is expressed by 5.7E23 for Ar+-Si and by 4.0E12 for Ar+-GaAs, where E is the Ar+ energy (keV). The above energy dependences are consistent with the universal relation between the projected range and ion energy proposed by Kalbitzer and Oetzmann and with the prediction of the power approximation.

Angular distribution of atoms ejected by laser ablation of different metals

Angular distributions of 13 different metals ejected by laser ablation using fourth harmonics (wavelength=266 nm) of neodymium doped yttrium aluminum garnet laser and a fluence close to near-threshold value (2.3 J/cm2) have been investigated with a high angular resolution. The angular distribution which is characterized by the exponent n of cosn θ distribution showed very broad range of values between 3 and 24 for different metals. A simple relation that the exponent n is proportional to the square root of particle atomic weight as reported previously has not been observed. Instead, a general trend has been found that the metals with higher sublimation energy such as Ta and Zr show narrower angular distribution than those with lower sublimation energy such as Sn and In. While the sublimation energy of metals has a great influence on the angular distribution of ejected atoms, a simple consideration suggests that their thermal conductivity and specific heat have little effect on it.

Influence of bismuth as a surfactant on the growth of germanium on silicon

The influence of a Bi surfactant layer on the growth of Ge on Si(100) substrates was investigated by using a medium‐energy ion‐backscattering spectrometer and a transmission electron microscope. A monolayer of Bi predeposited on the Si substrates suppressed islanding in the subsequent molecular‐beam‐epitaxial growth of Ge. The Bi atoms moved on top of the Ge film during the growth process.

GROWTH OF MICROCRYSTALLINE SILICON FILM BY ELECTRON BEAM EXCITED PLASMA CHEMICAL VAPOR DEPOSITION WITHOUT HYDROGEN DILUTION

Unique characteristics have been obtained for silicon films grown by electron beam excited plasma chemical vapor deposition (EBEP-CVD) in comparison with films grown by conventional plasma CVD. The EBEP-CVD growth of silicon films on single-crystal Si and SiO2 substrates was investigated using SiH4 without hydrogen dilution as a function of SiH4 flow rate, discharge current, chamber pressure, substrate temperature, and electron acceleration voltage. Typical growth rate was ∼0.1 nm/s. Characterization by Raman scattering spectroscopy showed that all the films were microcrystalline with a grain size of approximately 10 nm; the peak intensity ratio of the crystalline portion was greater than 0.6. The hydrogen concentration in the silicon layer under “standard” growth condition was determined by elastic recoil detection analysis to be as much as 19 at. %. This high level of hydrogen incorporation, considered to be facilitated by EBEP of SiH4 gas, seems to play a critical role in the growth process.

Wavelength-Dispersive Total Reflection X-Ray Fluorescence with High-Brilliance Undulator Radiation at SPring-8

Wavelength-dispersive total reflection X-ray fluorescence (WD-TXRF) equipment supported by an energy-dispersive (ED) solid-state detector (SSD) has been developed and installed in the BL16XU Industrial Consortium ID Beamline for Material Research at the SPring-8 synchrotron radiation research facility. Equipment specifications are given and results from our initial experiment are discussed in this paper. In the experiment on the sensitivity of detection of metallic impurities on a Si wafer, the lower limit of detection (LLD) using a Ge-SSD reached an order of 108 atoms/cm2 with a corresponding absolute weight of approximately 10 fg for ED-TXRF. In comparison, an order of 109 atoms/cm2 with a corresponding weight of around 100 fg was obtained for WD-TXRF for the first time. Although ED-TXRF still has a lower LLD, using WD-TXRF can provide good energy resolution with a high count rate, opening up a new field of X-ray fluorescence measurement.

Thermally Induced Structural Modification of Nanometer-Order Mo/Si Multilayers by the Spectral Reflectance of Laser-Plasma Soft X-Rays

Thermally induced structural modification of a nm-order multilayer of Mo/Si was investigated by spectral reflect-ance of soft X-rays from laser-produced plasma. Dependence of reflectivity of the nm-order multilayers on the incidence angle of soft X-rays indicated that some structural changes start to occur at 300°C and that the nm-order multilayer structures shrink at 500°C because of the formation of Mo-silicide. These results were found to be consistent with the cross-sectional transmission electron microscope observations. It is clearly shown that measurement of spectral reflectance of soft X-rays from laser plasma is a powerful method for analyzing nm-order structural modifications of multilayers.

Effects of hydrogen on the growth of nanocrystalline silicon films by electron-beam excited plasma chemical vapor deposition

It has been shown that nanocrystalline silicon films can be grown from silane gas without hydrogen dilution by electron-beam excited plasma chemical vapor deposition (EBEP–CVD). A high density of atomic hydrogen, which is derived from the dissociation of silane molecule, is confirmed in the plasma by optical emission spectroscopy. This fact is thought to be a reason for the growth of nanocrystalline silicon films without the introduction of hydrogen gas. Transmission electron spectroscopy reveals that crystallites are not distributed uniformly, but rather form the mosaic-like clusters in an amorphous silicon matrix in the film. Hydrogen gas is introduced into the EBEP–CVD silicon film growth so as to study the effects of the hydrogen gas. The growth rate increases proportionally to the hydrogen flow rate, and it is about 2.5 times greater than when no hydrogen gas is introduced. Also, a decrease in both the hydrogen content and the density of dangling bonds in the film is confirmed. These results imply th...

Growth Rate and Crystallinity of Nanocrystalline Silicon Film Grown by Electron Beam Excited Plasma Chemical Vapor Deposition

Using electron beam excited plasma chemical vapor deposition, nanocrystalline Si films can be grown without H2 dilution. This paper describes the effects of growth parameters on the growth rate and the crystallinity of Si films.

Lattice Location of 15N Atoms in SiC Analyzed by Nuclear Resonant Reaction

The nuclear resonant reaction 15 N(p, αγ)12 C and channeling effect of proton beams have been applied to the study of the lattice location of ion-implanted 15N atoms to a dose of 1×101615N2+/cm2 at an energy of 100 keV in 6H-SiC. The structural recovery of the damaged layer has also been studied by the conventional Rutherford backscattering technique combined with channeling effect measurements. Elevated-temperature implantation, in particular, at above 1000° C, facilitates substitution of the 15N atoms into the SiC lattice sites as well as implantation-induced-damage reduction of the SiC host crystal. Postimplantation annealing (at 1300° C) promotes the recovery of the damaged layer. However, it does not promote the substitution of 15N atoms.

Medium-Energy Ion Scattering Analysis with 50 keV He+ by the Time-of-Flight Technique

A newly developed time-of-flight spectrometer for medium-energy ion scattering is presented. The system mainly consists of a 60 kV duoplasmatron ion source, a beam chopper and an annular microchannel plate. Time and depth resolutions are found to be 7.8 ns and 2.9 nm, respectively. The probing depth is limited by the multiple scattering effect and is estimated experimentally to be up to ~20 nm for Au.