I. Hashimoto

Annealing behavior of krypton-implanted aluminum: I. Diffraction effects from krypton bubbles

Abstract Thin aluminum foils, implanted with krypton ions at an energy of 50 keV with a dose of 10 16 ions/cm 2 , have been investigated by the analysis of electron diffraction patterns. The spots due to double diffraction are observed at room temperature and are interpreted to originate from the well isolated solid krypton bubbles. During annealing, these spots remain up to around 483 K, while the diffraction from solid krypton disappears just above 618 K, indicating the melting of solid bubbles. Streaks in the diffraction patterns are also observed above 618 K. It is demonstrated that the streaks are caused by the growth of microcracks in the specimen.

Behaviour of krypton atoms in aluminium

Abstract The behaviour of Kr atoms in Al has been investigated by ion channelling and electron microscopy of Al specimens implanted at room temperature with a dose of 1 × 10 15 Kr/cm 2 or 1 × 10 16 Kr/cm 2 . At the high dose most of Kr atoms are in the form of precipitates of solid phase. At the low dose about 55–57% of Kr atoms are in the precipitates, 23–25% are at substitutional sites, and the remaining atoms (~ 20%) are at tetrahedral (T) and octahedral (O) sites. The T- and O-site occupancies are interpreted as being a result of the strong interaction of Kr atoms with vacancies to form Kr-vacancy complexes having configurations similar to a trivacancy and a pentavacancy. The T- and O-site occupancies disappeared after annealing at 593 K for 30 min.

Evolution of krypton precipitates in kr-implanted aluminium

Abstract The behaviour of Kr atoms in Al has been investigated by an ion channelling method and transmission electron microscopy (TEM) on Al specimens implanted at room temperature with 50 keV Kr+ to various doses from 1 × 1014 to 1 × 1016 Kr/cm2. The Kr atoms are distributed over random (R) sites (in the form of precipitates), substitutional (S), tetrahedral (T) and octahedral (O) sites. The T- and O-site occupancies are interpreted as resulting from the formation of Kr-vacancy complexes. It is proposed that in the early stage of implantation such Kr-vacancy complexes are formed and act as nucleation centres for Kr precipitation. As to the room temperature implantation, for a dose of 1 × 1016 Kr/cm2 Kr precipitates of a solid phase (solid Kr bubbles) are formed, but at least up to a dose of 1 × 1015 Kr/cm2 they are not formed. On the 1 × 1015 Kr/cm2 implanted specimen, solid Kr is observed after annealing at 683 K for 30 min by the channelling method, although the electron diffraction pattern exhibits no extra reflection spots for the solid Kr.

The random motion of bubbles in krypton-implanted aluminum

Abstract Thin foil specimens of A1 single crystals are implanted with 50 keV Kr ions to a fluence of 10 16 Kr/cm 2 . The motion of Kr bubbles formed by the Kr implantation has been examined with a transmission electron microscope after isothermal annealing treatments and is analyzed by an image scanner attached to a personal computer. It is revealed that the bubbles can move at random at a given temperature for a given annealing time. The diffusion coefficients of the bubbles are calculated from the moving distances and are estimated to be D B = 7.5 × 10 −18 , 1.8 × 10 −17 , and 6.2 × 10 −17 cm 2 / s at 573, 603, and 633 K, respectively. The activation energy for the motion of bubbles is estimated to be 1.50 eV, suggesting volume diffusion of A1 atoms.

Measurement of local lattice parameter in ion-implanted silicon using HOLZ lines

A simple algorithm based on a dynamical fitting simulation of higher-order Laue zone (HOLZ) lines is demonstrated, which presents a profile of lattice parameter with a spatial resolution of several nanometers. The proposed procedure is tested on arsenic ion-implanted silicon, being shown to be appreciable to accurate determination of lattice parameter by selecting a weak zone axis with any restriction. By comparing with the arsenic distribution, the small lattice elongation observed beneath the ion-implanted surface is due to As m V n complexes and the small increase beneath the amorphous-crystalline interface due to self-interstitials or their complexes.

Annealing behavior of krypton-implanted aluminum: II. SEM study on surface structure during emission of krypton atoms

Thin aluminum specimens implanted with krypton ions at an energy of 50 keV with a dose of 1016 ions/cm2 are examined by means of scanning electron microscopy. Various structural changes of the surface are observed after annealing at temperatures above 623 K. It is revealed that the extraction of krypton atoms from aluminum can be divided qualitatively into four temperature regions. In the first region (< 673 K), bubble growth takes place. In the second region (673–873 K), the bombarded surface peels off and a new surface appears. In the third region (873–933 K) the surface structural changes in the above two regions are repeated in the new surface and, finally, (⪢ 933 K) almost all krypton atoms are extracted from aluminum.

The Morphology and Formation of Precipitates in Al–Ge Alloys

The morphology and orientation relationship of Ge precipitates in quenched and aged (QA) Al-0.04 to 1.20 at% Ge alloys and in the same composite alloys slowly cooled to room temperature (SC), have been investigated using transmission electron microscopy. The morphology of precipitates in the QA specimen depends on Ge concentration; octahedral shape in Al-0.04 at% Ge and plate- and rod-like ones in Al-0.4 to 1.20 at% Ge are predominant. Particularly, the observed octahedral precipitate with pure Ge phase has the anomalous orientation relationship: (001)Ge || (111)Al and [l10] Ge || [110] Al . In the SC specimen, a spherical precipitate with amorphous Ge phase has been observed. It is suggested that the nucleation of precipitates originates from vacancy aggregates in the QA specimen, and from Ge-vacancy complexes in the SC specimen, respectively.

Effects of interstitial impurities on the grain-boundary strength of molybdenum

Abstract The effects of interstitial impurities (carbon, nitrogen and oxygen) on the strength of the grain boundaries of molybdenum have been investigated from the point of view of the electronic structure using a discrete variational-Xα calculation. The grain boundary structures of molybdenum for the purpose of the calculations are constructed from tetrahedral clusters which include the impurity at the centre (Mo4X, X = C, N or O). The atomic cohesion due to covalent bonding between molybdenum and an impurity is obtained for each cluster and increases in the order Mo4O, Mo4N and Mo4C. The results are in good agreement with experimental knowledge of the effects of impurities on the strength of the grain boundaries. The interaction between impurities at the grain boundaries is also discussed.

Effect of Surface Plasmons on Energy Filtered RHEED Rocking Curves from a Si(111)-7×7 Surface

Energy filtered (EF) RHEED rocking curves of the specular beam from the Si(111)-7×7 surface in the [112-] azimuth have been measured and analyzed by means of a dynamical calculation of two-dimensional (2D) Bloch waves taking account of the surface plasmon loss. It is demonstrated that the surface plasmon loss plays an important role in the explanation of RHEED rocking curves. The effect of the surface plasmon loss does not decrease in a simple way as the glancing angle increases and is classified into two groups depending on the localization of the Bloch wave field.

ELECTRICAL RESISTIVITY OF HIGH PURITY CHROMIUM SINGLE CRYSTAL

This paper reports the results of a study of high purity chromium single crystal electric resistivity. The chromium single crystal used in this study was produced from commercially available 5N electrolytic chromium. The gaseous impurity level improved during single crystal production. The crystal structure was investigated by means of the Laue method and the sample was confirmed to be a single crystal. The single crystal was carefully cut into a rectangular bar in preparation for the resistivity measurement. The electrical resistivity was measured for the [100], [111] and [110] crystal orientations utilizing the four-probe method. One measurement indicated 1.08 × 10—7 Ωm at [100] at 20 °C; that is less than the previously reported pure chromium resistivity of 1.25 × 10—7 Ωm.