S. Damgaard

EFG sign for Sn in Zn, Cd, and Sb

Mössbauer spectroscopy on ion-implanted sources of119Cd in single-crystals was applied to study the electric field gradients (EFG) at119Sn in three non-cubic metals. The signs and magnitudes determined are in agreement with presently known systematics. The measured isomer shifts and the recoilless fractions are discussed.

Mössbauer study of119Sn defects in silicon from ion implantations of radioactive119In

Radioactive119In+ ions (T1/2=2.1 min) obtained from the ISOLDE facility at CERN have been implanted into silicon single crystals at room temperature. Mössbauer emission spectra from the 24 keV γ-radiation of the daughter119Sn have been measured by fast resonance-counting technique. Five independent lines, characterized by their hyperfine parameters and Debye temperatures, have been found in the spectra. From the bonding configurations, deduced for the Sn impurity atoms, these are concluded to be located in four different defects in the silicon lattice. Simple models are proposed for the defects.

Systematic experimental and theoretical studies of the lattice vibrations of host atoms and substitutional Sn impurities in III–V semiconductors

AbstractThe lattice vibrations of the two constituent atoms in the III–V semiconductors GaP, GaAs, GaSb, InP, InAs, and InSb have been studied experimentally by neutron diffraction and theoretically by calculations within the framework of various phonon models proposed in the literature for these compounds. The mean-square amplitudes (measured at 295 K) show a general increase with increasing lattice constant and seem furthermore to reflect the partial ionicity of the compounds. The different phonon models for the lattice dynamics are compared with each other and tested critically against the experimental data. Several models are found to be insufficient. The most satisfactory ones are some shell models. 119Sn Mössbauer impurity atoms have been implanted site-selectively on the two different substitutional lattice sites and their Debye temperatures have been determined. A rigorous result relating Debye temperatures of host and impurity atoms permits a simplified interpretation of the experimental results in terms of “Einstein-Debye force constants”. Both lower and higher force constants are deduced for the impurities as compared with the host atoms. Larger force constants are found on V sites than on the III sites for Sn in the Ga compounds, whereas the opposite holds in the In compounds. Further details can be obtained in an extended version of this paper available from the authors.

A Mössbauer study of impurity-vacancy defects in copper

Abstract Impurity-vacancy complexes in copper have been formed with radioactive 119 In and 119 Sb by ion implantation and trapping. The defects are studied by Mossbauer spectroscopy on the 119 Sn daughter atoms. Comparison with 111 In PAC studies reveals that various different defects are formed in stage III, some of which are “invisible” in PAC experiments.

Mossbauer study of a complex Sn impurity defect in GaAs from implantations of radioactive 119In ions

A complex Sn impurity defect created by room-temperature implantation of radioactive 119In+ ions in GaAs has been studied by Mossbauer emission spectroscopy on the 24 keV gamma transition of the daughter 119Sn. From the Mossbauer parameters for the Sn impurity atoms, the defect structure is proposed to consist of (nearly) substitutional Sn atoms on Ga sites associated with vacancies.

Sn impurity defects in germanium from ion implantations of radioactive 119In

Abstract Sn impurity defects in germanium have been produced by implantation of radioactive 119In and studied by Mossbauer emission spectroscopy on the daughter 119Sn. Four independent lines in the spectra are assigned to different Sn bonding configurations in different defects.

119Sn Mössbauer study of the implantation behaviour of119In,119Sn,119mSn,119Sb and119mTe ions in SiC

The implantation behaviour of stable119Sn+ ions and radioactive119In+,119mSn+,119Sb+ and119mTe+ ions in SiC has been investigated by, respectively, conversion-electron Mössbauer spectroscopy on the 24 keV transition of119Sn, and by Mössbauer emission spectroscopy on the 24 keVγ radiation emitted by the119Sn daughter after the decays of the radioactive isotopes. The Mössbauer spectra could be decomposed in most cases into two groups of lines, one originating from119Sn atoms on substitutional Si sites, the other from various Sn-vacancy complexes distinguished by their Mössbauer parameters. Annealing experiments reveal a strong dependence of the structure of the defects and the formation and annealing kinetics on the chemical nature of the impurities. Defects formed in 297 K implantations with119mSn and119Sb anneal above 500 ‡C, resulting in a preferential location of the impurities on substitutional Si sites, whereas119mTe atoms are efficient defect-trapping centres and no stable, substitutional fraction is observed on either lattice site. Possible structures for the Sn-vacancy complexes are discussed and comparison is made to similar defect complexes in group IV and in III–V semiconductors.

Isomer shifts and force constants of substitutional 119Sn impurity atoms in FCC metals

Isomer shifts and Debye temperatures for substitutional 119Sn impurity atoms in the FCC metals Al, Ag, Au, Cu, Pb, Pd, Pt and Rb were determined by Mossbauer emission spectroscopy on the 24 keV gamma radiation of 119Sn. The radiation sources were prepared by ion implantations of radioactive 119In and 119Sb isotopes into single crystals and high-purity foils of the respective metals. Correlations are discussed between measured isomer shifts and electronic properties of the host materials (the Fermi-level free-electron density nF1/3 and the cell-boundary electron-density parameter nWS1/3 from the Miedema theory of alloy formation). The Debye temperatures for 119Sn are interpreted in terms of the Einstein-Debye and the Mannheim models for impurity lattice vibrations.

Sn In silicon carbide: A mossbauer and channeling study

ConclusionImplantation of Sn at ∼550°C into SiC and post-annealing at 1120°C has been demonstrated to lead to a predominant population of the substitutional Si sites. The electronic structure of the Sn atoms in substitutional Si sites has been shown to be strongly influenced by the partial ionicity of the host material.

Internal oxidation of sp-Impurities in silver studied by119Sn Mössbauer spectroscopy

The internal oxidation of the ion-implanted radioactive precursors119Cd and119Sb to the Mössbauer isotope119Sn in silver has been investigated. The oxidation is monitored by the intensity of a line in the Mössbauer spectra, which is characteristic of SnO2 (δ=(0–0.23)mm/s relative to CaSnO3, ΔEQ ≈ 0.5 mm/s, ϑ ≈ 220 K). This line is attributed to an internal oxidation of the implanted impurities by interstitially diffusing oxygen pairs. The formation and annealing kinetics of the impurity-oxygen complexes are interpreted in terms of the diffusion coefficients of oxygen and the sp-impurities in silver, respectively, and the reactivity between them. Comparison is made to Mössbauer experiments on SnAg alloys and to PAC measurements on111cd in silver.