Yoshiaki Kido

Ion scattering analysis programs for studying surface and interface structures

We have synthesized ion scattering analysis programs for studying surface and interface structures. The probing ion energies can be selected in a wide energy range from 10 keV up to several MeV. One of the present programs allows the simulation of both random and aligned spectra from perfect or partially disordered heteroepitaxial films. For defect profiling, the following types are available: (1) asymmetric Gaussian, (2) exponential reduction shape, and (3) step function. Another is used to analyze the structures of islands formed on the top surfaces of substrates. The targets have basically multielemental and multilayered structures comprising the units of amorphous/single crystal. These simulation programs are applied to disorder profiling of Ar+‐implanted LiNbO3, mechanically polished Mn‐Zn ferrite, and GaAs/Si heteroepitaxial films, and to characterizing the Cu‐Si islands on Si substrates.

Versatile computer programs for analysis of random and channeling backscattering spectra

Two types of computer programs have been developed to simulate random and channeling backscattering spectra with high speed. One is applicable to analysis of multielemental and multilayered structures. Depth profiles of interdiffusion and of impurities distributed inhomogeneously can be analyzed simultaneously with this program. Another allows the simulation of channeling spectrum from a perfect or partially damaged single crystal whose top surface consists of an amorphous layer with an arbitrary thickness. These simulation programs are applied to determine the thicknesses of the ten‐layered structure of Ag/Al/Ag/.../Al, the mixing rates for the Al/Sb system irradiated with Xe ions, and the damage profile of GaP induced by Ar+ irradiation.

Computer analysis of random and channeled backscattering spectra

Abstract Three types of computer codes are described which simulate random and channeled backscattering spectra from: (1) multielemental, multilayered structures, (2) specimens with inhomogneously distributed impurities and (3) single crystals damaged by ion implantation. Both effects of energy fluctuation and isotopic shifts from each constituent element are taken into account in the simulation. The elemental compositions and layer thicknesses of multielemental, multilayered films and the damage distributions induced by ion implantation are determined by fitting the simulated spectrum to the corresponding experimental one. The effect of surface and interface roughness on the spectrum shape is also discussed.

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.

Characterisation of aluminium nitride layers formed directly by 700-800 keV 15N2+ implantation into aluminium

Accelerated 15N2+ ions were implanted into polycrystal and single-crystal, Al sheets with fluences of 8*1016-1.2*1018 N+ cm-2. The depth profiles of the implanted 15N were measured by 15N(p, alpha gamma )12C and 15N(p, alpha 0)12C nuclear reactions. A change in the depth profile of the implanted 15N significant recovery of the damaged Al lattice were not observed even after annealing above 400 degrees C over a wide range of implantation dose. In the case of low-dose implantation, channelling analysis combined with nuclear reaction analysis showed that the implanted 15N was located near the tetrahedral interstitial site in the FCC Al lattice, while for high-dose hot implantation ordered structures were not observed. Direct evidence for AlN formation was obtained by ESCA. Measurements of electrical capacitance and DC resistance for the 15N2+-implanted Al sheets were also performed.

Analysis of ion‐implanted surface and interface structures by computer‐simulated backscattering spectra

Computer codes for synthesizing random and channeling backscattering spectra have been elaborated to characterize the surface and interface structures formed or modified by ion implantation. Both effects of isotopes and energy fluctuation are taken into account in the spectrum simulation. This backscattering measurement combined with the simulation method is applied to characterization of the N+‐implanted Al films and to quantitative analysis of chemical reaction and interdiffusion induced by ion‐beam mixing. An ion‐beam‐induced damage profile and its epitaxial recovery of crystallinity are analyzed by the simulation of channeling spectra from ion‐implanted Al2O3 substrates.

Universal expressions for average projected range and average damage depth in ion-implanted substrates

Abstract Substrates of Al, Si, LiF, Al 2 O 3 , GaP, and GaAs were implanted with 45 to 420 keV N, Al, Ar, Mn, Ni, Zn, Te, and Xe ions. The reduced energies cover the range from 0.1 to 5. Depth distributions of implanted ions and displaced host atoms were determined by means of backscattering (including channeling) and nuclear resonance reaction measurements followed by computer-simulated spectrum analyses. The results are compared with other experimental data and theoretical predictions given by Gibbons et al. (GJM) and Winterbon et al. (WSS). For the latter theory, optimum WSS parameters are determined to give a good fit to the experimental data. It is concluded that reduced projected range and reduced damage depth are proportional to reduced energy but cannot be expressed by unified relations for all ion-substrate combinations. However, systematic investigation reveals that introduction of a new scaling coefficient gives two universal expressions for modified reduced projected range and modified reduced damage depth as a function of average reduced energy.

Growth mechanism and magnetic properties of AlMn metastable phase formed by ion beam mixing

Abstract The kinetics of ion beam mixing and the growth mechanism of metastable phases have been investigated for the Al-Mn system. It is revealed that the residual diffusive motion induced by a collision cascade is the decisive factor for metastable phase formation. The residual diffusivity depends strongly on the substrate temperature during ion irradiation. Its relaxation time at temperatures of 350–550 K is estimated to be of the order of 10−7−10−6 s. More rapid quenching produces an amorphous phase, whereas slower cooling leads to thermally stable phases. The metastable τ phase with ferromagnetism is formed directly by ion beam mixing in the above temperature range. The dependences of mixing temperature and ion dose on the magnetic properties are accounted for by the kinetics of ion beam mixing and the induced internal stress. Finally, a model describing the ion beam mixing effect is proposed.

Universal relation between electron channeling line intensity and thickness of disordered layers on single crystals

Electron channeling patterns (ECP’s) were measured for Si and GaAs single crystals with thin polycrystal films or ion‐damaged layers on the top surfaces. The intensity scans along channeling lines provide quantitative information on the above disordered layer thickness. We have derived a universal relation between the channeling line intensity and disordered layer thickness. This scaling law is independent of channeling planes and species of the single crystals and disordered layers.

Study of phosphorus implantation in silicon by channeling and nuclear resonance techniques

Depth profiles of 31P implanted in Si were measured nondestructively by the 31P( p,γ)32S nuclear resonant reactions. It was observed that a large amount of the implanted 31P migrated to the front surface by annealing at 600 °C for 10 min and escaped from the surface by annealing at 800 °C for 10 min in a high vacuum. Channeling analysis revealed this phenomenon to be intimately related to thermal recovery of the damaged layer introduced by high‐dose implantation. The implantation dose and energy dependence of the distributions of lattice disorder was also measured by channeling methods.