Two site occupation by 12B implanted in copper above T=300 K

Polarized ¹²B is produced in the reaction ¹¹B (d,p) ¹²B and recoil implanted in single crystal copper. Above room temperature two depolarization peaks are observed. They are identified as arising from ¹²B occupying the octahedral interstitial site and also the substitutional site.     

Implantation site of boron in heavily doped silicon: A β-NMR study

Using β-NMR with¹²B as nuclear probes the temperature dependence of the lattice-site occupation of boron implanted into heavily doped silicon is studied. In p-type material the unperturbed substitutional fraction of¹²B increases from 10% at 300 K to ≃40 % at 950 K. In n-type material this fraction starting from 20% at 300 K approaches the saturation value of ≃80 % at 600 K already. This behaviour suggests that the site of implanted boron in silicon is controlled by the Fermi level.     

Anomalous Temperature Dependence of the EFG in AlN Measured with the PAC-Probes 181Hf and 111In

¹⁸¹Hf and ¹¹¹In ions were implanted into AlN-layers in order to investigate their immediate lattice site environment and its temperature dependence by means of the Perturbed Angular Correlation (PAC) technique. After rapid thermal annealing at 1273 K up to 50% of the probe atoms were incorporated on undisturbed lattice sites defined by an electric field gradient (EFG) of 33 MHz for In and 572 MHz for Hf for measurement at room temperature. PAC-spectra taken at temperatures between 25 and 1200 K show that the EFG measured at the site of the undisturbed probes changes with temperature. While for Hf it decreases by 3%, for In it increases by 25% within the measured temperature range. Thus, the change cannot be due only to the thermal lattice expansion. In the case of In the fraction of probe atoms on substitutional sites increases with temperature until it reaches nearly 100% at 973 K. These effects are fully reversible. For the Hf probe, an additional EFG was detected at temperatures above 300 K.     

Magnetic hyperfine interaction after77Br implantation into iron

Radioactive⁷⁷Br ions were implanted at 60 keV and 270 keV into polycrystalline iron foils. The magnetic hyperfine interaction of the daughter nucleus⁷⁷Se in the 250 keV isomeric level was investigated using the perturbed angular correlation technique and fast BaF₂ detectors. The Larmor frequency at room temperature was determined as ω_L=1272(2) MHz, leading to a substitutional hyperfine field ofB _hf(SeFe)=62(6) T. The substitutional fraction rises from 21% at room temperature to about 100% at 790 K annealing temperature. No other well-defined magnetic or electric hyperfine component attributable to impurity-defect complexes was identified. The diffusion of Br atoms in the surface region during the annealing process was studied via Rutherford backscattering with 1.0 MeV α-particles.     

Impurity-defect complexes in non-implanted aluminum

The formation of impurity-defect complexes in ion-implanted aluminum has been studied in the temperature interval 100–400K. Radioactive¹¹⁹In isotopes have been implanted. Mössbauer spectra have been measured for the 24 keV γ-radiation emitted after the decay to¹¹⁹Sn. The spectra could be analysed satisfactorily with two lines, one of which is known to be due to substitutional Sn. A second line, which has a higher isomer shift and lower Debye temperature, is tentatively assigned to vacancy-associated Sn, formed by trapping of thermally mobile (multi-)vacancies. Comparison to similar DPAC experiments suggests that cubic Sn?V₄ complexes are formed. Some indication (～15%) for an athermal formation of impurity defects below 175K is obtained.     

Identification of substitutional and interstitial Fe in 6H-SiC

Iron impurities on interstitial (Fe_i) and substitutional sites (Fe_S) in SiC have been detected by ⁵⁷Fe emission Mössbauer spectroscopy following implantation of radioactive ⁵⁷Mn⁺ parent ions. At temperatures <900 K two Fe_i species are found, assigned to quasi-tetrahedral interstitial sites surrounded by, respectively, four C (Fe_i,C) or Si atoms (Fe_i,Si). Above 900 K, the Fe_i,Si site is proposed to “transform” into the Fe_i,C site by a single Fe_i jump during the lifetime of the Mössbauer state (T _1/2?=?100 ns). Fe_i,C and substitutional Fe_S sites are stable up to >1,070 K.     

Hyperfine Interactions of 12B in CaB6

The hyperfine interactions of short-lived β-emitter ¹²B implanted into a CaB₆ crystal have been studied by means of the β-NMR technique. An electric quadrupole splitting has been observed at room temperature from which an electric field gradient of q=−(1.34±0.05)×10²¹ V/m² was determined. From the present result, it was found that the ¹²B nuclei are mainly implanted in the substitutional boron site. This revised version was published online in September 2006 with corrections to the Cover Date.     

Lattice locations of 8Li in Cu

The dipolar broadening of the NMR on short-lived β-emitter ⁸Li implanted in single crystal Cu has been observed as a function of crystal orientation at several temperatures. From the orientation angle dependence of the line width, it was found that the main component of the ⁸Li occupies substitutional site, while about 30% of ⁸Li occupies octahedral interstitial site at temperatures below 300 K. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pulsed electron-beam annealing of high-dose arsenic implanted silicon

The effects of pulsed electron-beam annealing of high-dose As implanted {111} Si single crystals has been studied. The depth distributions and lattice location of the As atoms were obtained using MeV⁴He⁺ backscattering and channeling technique. The implantation energy was 100 keV with a total dose of 3.5·10¹⁶/cm². Above the threshold energy of 0.9 J/cm² the single-crystal transition was observed with about 95% of the As atoms on substitutional lattice sites. This leads to an As concentration of 2·10²¹/cm³ which was demonstrated to be a metastable one.     

Sites and diffusion for muons and hydrogen in titanium hydrides

Low temperature sites for muons implanted in TiHx have been found to be a mixture of interstitial and substitutional sites, with substitutional occupancy determined by the probability that a muon in an interstitial site will have a vacant nearest neighbor substitutional site. As with ZrHx, activation from the interstitial site is observed below 300 K. From the depolarization rate in the substitutional site, the muon likely displaces the neighboring H atoms by about 0.1 A. Diffusion for the substitutional muons occurs above room temperature with an activation of about 0.38 eV, which is less than the 0.505 eV for hydrogen vacancy motion observed by NMR. To explain this the muon transition rate to a vacancy must be less than that of hydrogen.     

Vacancy trapping and helium decoration in Sb ion-implanted tungsten studied by Mössbauer spectroscopy

Mössbauer effect measurements have been performed using sources of¹¹⁹Sb implanted in W without and with post-implanted helium. Each of the sources was subjected to an isochronal annealing sequence in order to study vacancy trapping, helium decoration and recovery of damage. Four sites have been identified for Sb implanted in tungsten; one of these corresponds with substitutional Sb atoms, two others are assigned to Sb atoms associated with vacancies, while the last one can be either vacancy or impurity associated. The development of site occupation as a function of annealing temperature is in accordance with the one-interstitial model. Injection of 2·10¹⁶ He/cm² leads to nucleation of helium bubbles. Helium atoms that are released from these bubbles at about 1300 K are retrapped by Sb atoms to form new bubbles.     

Lattice locations and electric field gradients of boron implanted into vanadium

Polarised emitting¹²B nuclei were recoil implanted into single crystalline vanadium atT=305 K. radiation detected nuclear magnetic resonance measurements showed that two implanation sites occur simultaneously which were identified as the substitutional site and an interstitial site with axial symmetry. Extensive cross-relaxation measurements were performed on¹²B in both lattice positions. By this means the interstitial site could be identified as the octahedral one. The impurity induced electric field gradients at nearest and at next nearest⁵¹V neighbours about¹²B could be determined for both implantation sites.     

Dopant activation in Sb-implanted relaxed Si1−xGex alloy layers grown on compositionally graded buffers

Supersaturated solid solutions of substitutional, electrically active Sb have been obtained by ion implantation of relaxed epitaxial Si_1?xGe_x alloy layers grown on compositionally graded buffers. Substitutional and nonsubstitutional Sb fractions in relaxed Si_0.85Ge_0.15, Si_0.65Ge_0.35 and Si_0.50Ge_0.50 alloy layers implanted to a dose of 5×10¹⁵ Sb cm^?2 and annealed isothermally at temperatures ranging from 400 to 850°C have been studied by Rutherford backscattering/channeling, transmission electron microscopy and Hall-effect and sheet resistivity measurements. A supersaturated solution of Sb corresponding to a peak carrier concentration of 4×10²⁰ cm^?3 and an electrically active fraction of 40% of the implanted dose is observed by Hall measurements for the case of Si_0.85Ge_0.15 and Si_0.65Ge_0.35 alloys annealed at 550°C.     

Electronic structure of substitutional nitrogen impurity in TiO 2 studied by the β-NMR method

In order to study the local electronic structure of nitrogen impurity in rutile TiO₂, we have measured double-quantum NMR spectra of short lived β-emitter ¹²N(I = 1, T _1/2 = 11 ms) implanted into a rutile single crystal by means of the β-NMR technique. The resonance line obtained at room temperature is well accounted for by the second order shift due to the quadrupole interaction at the oxygen substitutional site. The spectrum at 25 K has shown the other lines than the central diamagnetic line shifted by 10?15 kHz to both sides, which has been already shown in the previous data obtained with a different crystal orientation and an external field. The present results supports the existence of a paramagnetic state formed by the substitutional nitrogen impurities.     

A TDPAC study of the lattice location of implanted indium in silicon

Abstract

The annealing behaviour of indium implanted silicon (doses 10¹¹?10¹³ atoms/cm²) was studied by time differential perturbed angular correlation spectroscopy. Besides the substitutional site two types of defect configurations were observed. In the as-implanted condition the substitutional In fraction remains below 20% even at the lowest dose. This result is in accordance with the prediction of the track amorphization model.     

Channeling study of boron implanted silicon: Liquid nitrogen temperature implantation

Silicon samples have been boron implanted at 150 keV at liquid nitrogen temperature to a dose of 3.6 × 10¹⁵/cm². This dose rendered the implanted layer amorphous as viewed by helium ion backscattering. Four kinds of room temperature measurements were made on the same set of samples as a function of the isochronal annealing temperature. The measurements made were the determination of the substitutional boron content by the channeling technique using the B¹¹(p, α) nuclear reaction, observation of the disorder by helium ion backscattering, determination of the carrier concentration by van der Pauw Hall measurements, and the sheet resistivity by four point probe measurements. These measurements are compared with results from samples implanted at room temperature. The carrier concentration correlates well with the substitutional boron content for both room temperature and liquid nitrogen temperature implantations. Following annealing temperatures in the 600 to 800°C range, a much larger percentage of the boron lies on substitutional lattice sites, and therefore the carrier concentration is larger, if the implantation is done at liquid nitrogen temperature rather than at room temperature. Following liquid nitrogen temperature implantation, reverse annealing is observed from 600 to 800°C in the substitutional boron content, carrier concentration and sheet resistivity. The boron is more than 90 per cent substitutional after annealing to 1100°C for both the room temperature and liquid nitrogen temperature implantations. The low temperature implantation produced a buried amorphous layer, and this layer was observed to regrow from both the surface and substrate sides at approximately equal rates.     

A CEMS investigation of57Fe implanted in Al and Cu at low temperature

A new type of CEM-spectrometer allows in situ measurements on metal foils implanted at low temperatures. It has been used to study defect association and clustering of⁵⁷Fe in Al and Cu. For⁵⁷FeAl, the substitutional fraction (f _s) in samples implanted at 120 K is somewhat smaller than expected for a random impurity distribution but much larger than after room temperature implantation. For⁵⁷FeCu,f _s for samples implanted at 120 K is less than 0.5 of the value expected for a random distribution and it falls to zero after annealing at 600 K, where more extensive Fe clustering occurs. Vacancy trapping in stage III does not contribute significantly to the observed defect sites.     

Mössbauer spectra obtained using β − γ coincidence method after 57Mn implantation into LiH and LiD

Highly energetic ⁵⁷Mn (T_1/2 = 1.45 m) was generated by nuclear projectile fragmentation in a heavy-ion accelerator, and implanted into lithium hydride (LiH) and lithium deuteride (LiD) at 578 K. Mössbauer spectroscopy with β ? γ coincidence detection was then carried out on the ⁵⁷Fe obtained from β^?decay of the ⁵⁷Mn to study the time dependence of the site distributions and coordination environments of dilute Fe atoms implanted in the LiH and LiD. The results suggest that the Fe atoms can substitute for either the Li and H or D atoms within 100 ns. Additionally, the displacement behavior of the substitutional ⁵⁷Fe atoms on the lattice sites is discussed.     

57Co impurity-interstitial configurations in NbMo alloys observed by Mössbauer spectroscopy

Lattice defects in NbMo⁵⁷Co alloys produced by neutron irradiation at 4.6 K and by cold working were investigated by Mössbauer spectroscopy. On isochronal annealing up to about 100 K, trapping of two different types of mobile interstitials at the⁵⁷Co probe atoms was observed as additional lines in the spectra. These are characterized by centre shifts of +0.44 mm/s and +0.41 mm/s relative to⁵⁷Co on substitutional lattice sites and by large quadrupole splittings of 1.50 mm/s. Above 640 K, vacancy trapping was observed. With the onset of recrystallization, dislocation pinning was found in both the neutron irradiated and the cold worked sample.     

57Fe-Mössbauer study of the high-T c system GdBa2Cu3O7−x: local binding strength and oxygen coordination of the Fe sites

The GdBa₂(Cu_1?yFe_y)₃O_7?x system with y=0.005–0.01 and various oxygen concentrations was investigated in the temperature range 20 K to 300 K. The⁵⁷Fe-Mössbauer spectra of the orthorhombic phase were analyzed with four quadrupole doublets. Three of them are attributed to substitutional Cu(1) sites and one (with the smallest quadrupole splitting) to the substitutional Cu(2) site. From an analysis of the temperature dependence of the relative site intensities, different local Debye temperatures for the Cu(1) sites were derived. Measurements of texturized absorbers at various angles give evidence for a vibrational anisotropy of the Cu(1) sites. The Cu(1) site with the largest quadrupole splitting exhibits the lowest Debye temperature and the largest vibrational anisotropy.