J. W. Petersen

Identification of band‐gap states by deep level transient spectroscopy on radioactive probes: The case of Au and Pt in silicon

The deep level transient spectroscopy technique has been applied to silicon doped with radioactive impurities. The disappearance or appearance of features in the spectra following the transmutation of the incorporated radioactive atoms identifies an impurity involved in the centers observed. Results for Au and Pt diffused in Si are presented showing that Au occupies the same lattice position as Pt, which is known from electron paramagnetic resonance measurements to be substitutional.

Point defect injection into silicon due to low‐temperature surface modifications

Deep level transient spectroscopy has been applied to study the appearance of phosphorus‐vacancy pairs in n‐type silicon following different low‐temperature surface modifications. It is established that at most 107 cm−2 vacancy is injected into the bulk of the silicon substrate during Pd2Si silicide formation. On the other hand, phosphorus‐vacancies pairs are observed after electron irradiation, low energy ion bombardment, and electron gun evaporation of metal films.

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.

Room-temperature vacancy migration in crystalline Si from an ion-implanted surface layer

Migration of vacancies in crystalline, n-type silicon at room temperature from Ge+-implanted (150 keV, 5×109–1×1011 cm−2) surface layers was studied by tracing the presence of P–V pairs (E centers) in the underlying layer using deep level transient spectroscopy (DLTS). Under the conditions we have examined, the vacancies migrate to a maximum depth of about 1 μm and at least one vacancy per implanted Ge ion migrates into the silicon crystal. The annealing of the E centers is accompanied, in an almost one-to-one fashion, by the appearance of a new DLTS line corresponding to a level at EC−Et≈0.15 eV that has donor character. It is argued that the center associated with this line is most probably the P2–V complex; it anneals at about 550 K. A lower limit of the RT-diffusion coefficient of the doubly charged, negative vacancy is estimated to be 4×10−11 cm2/s.

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.

Magnetic hyperfine fields of119Sn in vacancy-associated defect structures in 3d ferromagnets

Defect structures associated with Sb or In impurity atoms in iron, cobalt, and nickel hosts have been detected by Sn-119 Mössbauer spectroscopy. With substitutional values as reference, the structures found are uniquely characterized by large, positive shifts in the Sn-119 magnetic hyperfine field and correlated increases in isomer shift. Further characterization are lower effective Debye temperatures. Preferably, the defects form and anneal in the resistivity stage III; the specific behaviou depending on whether Sb or In make up their kernel. They are interpreted as unique vacancy-type, relaxed structures SbVn or InVn. The vacancy trapping leads to order-of-magnitude field enhancements in fcc Co and Ni hosts, uniquely reflecting that here the substitutinal Sn fields happen to be small due to almost cancellation of large positive and negative contributions.

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.