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Position-sensitive detector systems, initially developed for the detection of X-rays, have been adapted for their use in electron emission channeling experiments. Each detection system consists of a 30.8x30.8 mm$^{2}$ 22x22 -pad Si detector, either of 0.3 mm, 0.5 mm or 1 mm thickness, four 128$-$channel preamplifier chips, a backplane trigger circuit, a sampling analog to digital converter, a digital signal processor, and a personal computer for data display and storage. The operational principle of these detection systems is described, and characteristic features such as energy and position resolution and maximum count rate, which have been determined from tests with conversion electrons and $\beta^-\!$ -particles in the energy range 40--600 keV, are presented.

Trioma cells are lymphoma cells that have been fused to a hybridoma and have thereby been modified to express an immunoglobulin directed against surface receptors of antigen-presenting cells. Trioma cells that potentially include all lymphoma-derived antigens will be targeted to professional antigen-presenting cells in vivo. This allows uptake, processing, and presentation of tumor-derived antigens to T lymphocytes. In a mouse model, vaccination with trioma cells conferred long-lasting, T cell-dependent tumor immunity and was even able to eradicate established lymphomas. Here, we investigated whether this potent approach is effective in the human system.Malignant cells from 11 patients with B cell chronic-lymphocytic leukemia (B-CLL) were fused to an anti-Fc receptor hybridoma. The resulting trioma cells were extensively characterized with respect to their clonal origin. The induction of autologous tumor-specific T lymphocytes in the presence of trioma and antigen-presenting cells was examined in vitro by determining cytokine secretion in coculture assays.In seven cases, trioma cells could successfully be generated from B-CLL cells. Stimulation of autologous lymphocytes with trioma cells induced a leukemia-specific T-cell response. Immunostimulatory trioma cells were also obtained from two patients with solid B-cell lymphoma.Trioma-mediated immunization may be a promising adjuvant treatment of human malignancies of the B-cell lineage, particularly of B-CLL, which has still a very poor prognosis. Our in vitro results pave the way for clinical application.

Radioactive 67 Cu atoms were accelerated to 60 keV at the online isotope separator ISOLDE at CERN, and implanted into a type IIa natural diamond sample to a dose of 2×10 12 cm −2 . The channeling of β−-particles and conversion electrons emitted in the decay of 67 Cu and 67 Zn ∗ , respectively, were monitored about the three major axial directions with a two-dimensional position-sensitive detector. The electron emission channeling data were collected from the room-temperature-implanted sample and after annealing at 1200 K . The observed channeling patterns were fitted with simulations based on the many beam formalism of electron motion through a crystal lattice. In the as-implanted sample, 25% of the Cu atoms were located a mean, isotropic displacement of 0.25(5) A from substitutional sites, and the remainder, fR=75%, at sites that gave an isotropic emission yield. Annealing at 1200 K results in enhanced axial and planar channeling effects. The fits to the data yield either a fraction f1=45(5)% of Cu atoms located 0.24(4) A from substitutional sites and fR=57%, or a fraction f1=10(2)% at substitutional sites, a fraction f2=50(5)% at mean isotropic displacement of 0.5 A from substitutional sites, and a ‘random’ fraction fR=40%.

We report on emission channeling experiments using the radioactive isotope $^{67}$Cu implanted into single crystalline i-Ge at a dose of 2.4 $\times 10^{12}$ cm$^{-2}$. The lattice location of $^{67}$Cu was determined from the angular-dependent $\beta^{-}$ emission yield, which was measured by means of a position-sensitive detector around the , and directions. We find that already in the as-implanted state a considerable fraction of Cu (20-25%) occupies ideal substitutional lattice positions, a similar fraction is located on positions that are displaced around 0.5-0.6 from substitutional sites. Following annealing at 300°C for 10 min, the substitutional fraction of implanted Cu increased to 45% while the fraction of displaced Cu decreased to 23%. Upon further annealing at 400°C, channeling effects disappeared completely and around 10% of $^{67}$Cu diffused out of the Ge sample. From this we can estimate the activation energy for dissociation of substitutional Cu to be around 1.6-1.9 eV.

Incorporation of radioactive $^{59}$Fe atoms in diamond was achieved by implanting precursor $^{59}$Mn isotopes, with an energy of 60 keV and to a dose of 8 $\times 10^{12}$ cm$^{-2}$, into a natural type IIa diamond sample at the online isotope separator ISOLDE at CERN. The lattice sites taken up by the Fe atoms, following $^{59}$Mn $\beta^{-}$-decays, have been investigated using the emission channeling (EC) technique. Channeling measurements were made on the electrons emitted in the $^{59}$Fe $\beta^{-}$-decay. Data were collected with a two-dimensional Si pad detector, along , and axial directions from the as-implanted sample and after annealing in vacuum at 600$^\circ$K, 900$^\circ$K and 1250$^\circ$K. The channeling effects showed considerable enhancement with annealing. Fits to the observed patterns with simulations based on the many beam formalism of electron motion through a crystal lattice, show that, after annealing at 1250$^\circ$K, 65(5)% of the Fe atoms are located at sites with a projected mean displacement $\leq$ 0.2 Å from substitutional sites.

Single crystalline InGaN epilayers with different In content were implanted with Er$^{+}$ fluences in the range of 1 $\times 10^{13}$ to 5 $\times 10^{15}$ cm$^{-2}$ at room temperature. The structural changes and lattice site location were studied with emission channeling and RBS/channeling. Photoluminescence measurements were also performed to study the optical properties of the implanted samples. After implantation of 1 $\times 10^{13}$ Er$^{+}$ cm$^{-2}$, the emission channeling results show the incorporation of a significant fraction of Er in substitutional Ga/In sites. For fluences of 1 $\times 10^{15}$ Er$^{+}$ cm$^{-2}$ the aligned RBS spectrum along the [0001] direction reveals the displacement of the Er ions into random sites in the entire implanted region. Proximity cap annealing at 400°C and 500°C leads to some damage recovery on the samples implanted with lowest fluence accompanied by an increase of the substitutional fraction of Er. Despite the lattice disorder, a fraction of the Er ions are incorporated into optically active sites and luminescence emission was observed at 1.54 micrometer after annealing at 400°C.

We report on the lattice location of Er in Si using the emission channeling technique. The angular distribution of conversion electrons emitted by the decay chain ${}^{167}\mathrm{Tm}$ $({t}_{1/2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}9.25\phantom{\rule{0ex}{0ex}}\mathrm{d}){\ensuremath{\rightarrow}}^{167m}\mathrm{Er}\phantom{\rule{0ex}{0ex}}(2.27\mathrm{s})$ was monitored with a position-sensitive detector following room temperature implantation and annealing up to 950 \ifmmode^\circ\else\textdegree\fi{}C. Our experiments give direct evidence that Er is stable on tetrahedral interstitial sites in float-zone Si. We also confirm that rare earth atoms strongly interact with oxygen, which finally leads to their incorporation on low-symmetry lattice sites in Czochralski Si.

ZnO (O face) single crystals were implanted with 150 keV Er + ions to fluences of 5 × 10 14 and 5 × 10 15 Er + /cm 2 at room temperature. For fluences of 5 × 10 15 Er + /cm 2 the implantation damage raises the minimum yield from 2% to 22%. Despite the large amount of damage a fraction of 90% of the implanted Er ions are incorporated in substitutional sites along the [0 0 0 1] axis. Photoluminescence (PL) studies reveal the presence of a weak emission near 1.54 μm at 77 K due to the 4 I 13/2 → 4 I 15/2 transition of the Er 3+ ions. Annealing in oxidizing atmosphere at 800 °C leads to a reduction of the implantation damage, which is fully recovered after annealing at 1050 °C for 30 min. The annealing at 1050 °C leads to the outdiffusion of Er, with a 50% loss from the implanted region after the annealing. Only a fraction of 25% of the remaining Er is still in regular sites after the annealing and the Er 3+ PL vanishes.

Many elements are rapidly released from oxide matrices. Some oxide powder targets show a fast sintering, thus losing their favorable release characteristics. Loosely packed oxide fiber targets are less critical since they may maintain their open structure even when starting to fuse together at some contact points. The experience with various oxide fiber targets (titania, zirconia, ceria and thoria) used in the last years at ISOLDE is reviewed. For short-lived isotopes of Cu, Ga and Xe the zirconia and ceria targets respectively provided significantly higher yields than any other target (metal foils, oxide powders, etc.) tested before. Titania fibers, which were not commercially available, were produced in a relic process by impregnation of a rayon felt in a titanium chloride solution and subsequent calcination by heating the dried felt in air. Thoria fibers were obtained either by the same process or by burning commercial gas lantern mantle cloth. In the future a beryllia fiber target could be used to produce very intense 6He beams (order of 1013 ions per second) via the 9Be(n,α) reaction using spallation neutrons.

Trioma cell vaccination is a potent new immunologic approach for the therapy of malignant B-cell lymphoma. It is based on targeting tumor antigens to internalizing receptors on antigen-presenting cells (APCs). Tumor cells are fused to an APC-specific hybridoma, where they are converted to trioma cells that include potentially all lymphoma-derived antigens and that express the APC-binding arm. In this study, the mechanisms of trioma-mediated tumor immunity in immunocompetent mice were dissected, and it was shown in this model system that humoral anti-idiotypic immunity is indeed detectable after idiotype-specific immunization but that it does not reflect the degree of tumor protection obtained in vivo. Immunization against the idiotype alone was not sufficient for efficient tumor rejection in vivo. Targeting tumor antigens to APCs is only successful in terms of inducing tumor protection when designed as a polyvalent vaccination protocol.

In this work we report on the lattice site location of rare earths in single-crystalline ZnO by means of the emission channeling (EC) technique. Following low dose (3×1013at/cm2) 60 keV ion implantation of the precursor isotope 169Yb, a position-sensitive electron detector was used to monitor the angular distribution of the conversion electrons emitted from 169Tm* as a function of the annealing temperature up to 600°C in vacuum. An additional annealing at 800°C in flowing O2 was performed. The EC measurements revealed that around 95–100% of the rare earth atoms occupy substitutional Zn sites up to an annealing temperature of 600°C/vacuum. After the 800°C/O2 annealing, the emission channeling effects decreased considerably.

Radioactive 8Li (t1/2=0.8 s) was ion implanted into single‐crystalline n‐Si of low resistivity (9×1019 P cm−3) at temperatures between 50 and 670 K. Channeling measurements of the alpha‐particles emitted during the decay of 8Li gave direct evidence that 35% of the implanted Li occupied substitutional sites between 350 and 670 K. Below room temperature the major fraction of Li was found to be on tetrahedral sites. The increase in the substitutional fraction around room temperature is attributed to diffusion of Li and capture by vacancy‐related defects.

We have investigated the lattice location of implanted in silicon. By means of emission channeling, three different lattice sites have been identified: ideal substitutional sites, displaced bond-centered sites and displaced tetrahedral interstitial sites. To assess the origin of the observed lattice sites we have compared our results to emission channeling studies on and and to Mossbauer spectroscopy experiments on , present in literature. The possible interpretation of several Mossbauer lines is discussed in the light of our new results on the lattice location. The conclusions are relevant for the microscopic understanding of some gettering techniques.

We present lattice site location and diffusion studies of ion implanted 8Li in ZnSe single crystals at sample temperatures between 180 K and 550 K using the emission channeling technique. Below 200 K, Li is immobile in ZnSe and occupies tetrahedral interstitial sites. Above 250 K, interstitial Li becomes mobile and for an accumulated dose above 1×1012 cm-2 the majority of the implanted Li atoms occupy substitutional sites, presumably Zn sites. However, for room temperature implantation at doses below 1×1012 cm-2, the majority of implanted Li still occupies interstitial sites. This behavior is explained by recombination processes between Zn interstitials and vacancies, thus reducing the vacancy concentration and maintaining a high fraction of interstitial Li. Substitutional Li is stable up to about 500 K and diffuses out for temperatures above. We calculate 0.5 eV for the migration energy of interstitial Li and 1.38 eV for the binding energy of substitutional Li.

The lattice site location of radioactive 27 Mg implanted in AlN was determined by means of emission channeling. The majority of the 27 Mg was found to substitute for Al, yet significant fractions (up to 33%) were also identified close to the octahedral interstitial site. The activation energy for interstitial Mg diffusion is estimated to be between 1.1 eV and 1.7 eV. Substitutional Mg is shown to occupy ideal Al sites within a 0.1 Å experimental uncertainty. We discuss the absence of significant displacements from ideal Al sites, in the context of the current debate, on Mg doped nitride semiconductors. © 2013 AIP Publishing LLC. ispartof: Applied Physics Letters vol:103 issue:26 status: published

We report on the lattice location of implanted $^{59}$Fe in n$^{+}$ and p$^{+}$ type Si by means of emission channeling. We found clear evidence that the preferred lattice location of Fe changes with the doping of the material. While in n$^{+}$ type Si Fe prefers displaced bond-centered (BC) sites for annealing temperatures up to 600°C, changing to ideal substitutional sites above 700°C, in p$^{+}$ type Si, Fe prefers to be in displaced tetrahedral interstitial positions after all annealing steps. The dominant lattice sites of Fe in n$^{+}$ type Si therefore seem to be well characterized for all annealing temperatures by the incorporation of Fe into vacancy-related complexes, either into single vacancies which leads to Fe on ideal substitutional sites, or multiple vacancies, which leads to its incorporation near BC sites. In contrast, in p$^{+}$ type Si, the major fraction of Fe is clearly interstitial (near-T or ideal T) for all annealing temperatures. The formation and possible lattice sites of Fe in FeB pairs in p$^{+}$ Si are discussed. We also address the relevance of our findings for the understanding of the gettering effects caused by radiation damage or P-diffusion, the latter involving n$^{+}$ doped regions.

We report on the lattice location of implanted Ni in ZnO using the β - emission channeling technique. In addition to the majority substituting for the cation (Zn), a significant fraction of the Ni atoms occupy anion (O) sites. Since Ni is chemically more similar to Zn than it is to O, the observed O substitution is rather puzzling. We discuss these findings with respect to the general understanding of lattice location of dopants in compound semiconductors. In particular, we discuss potential implications on the magnetic behavior of transition metal doped dilute magnetic semiconductors. © 2013 AIP Publishing LLC. ispartof: Applied Physics Letters vol:103 issue:4 status: published

The concept and functionality of an apparatus dedicated to emission channeling experiments using short-lived isotopes on-line at ISOLDE∕CERN is described. The setup is assembled in two functional blocks - (a) base stand including beam collimation, implantation and measurement chamber, cryogenic extension, and vacuum control system and (b) Panmure goniometer extension including maneuvering cradle and sample heating furnace. This setup allows for in situ implantation and sample analysis in the as-implanted state and upon cooling down to 50 K and during annealing up to 1200 K. The functionality of the setup will be illustrated with the example of establishing the lattice location of (56)Mn probes implanted into GaAs. ispartof: Review of Scientific Instruments vol:84 issue:7 ispartof: location:United States status: published

The lattice site occupation of Li in CdTe at temperatures between 40 and 500 K was investigated with the emission channeling method. Radioactive 8Li ions were implanted at low doses into CdTe single crystals. Emission channeling patterns of α-particles emitted in the nuclear decay of 8 Li (t 1 2 = 838 ms ) were measured and compared to calculated emission channeling and blocking effects. At temperatures below 130 K the Li ions occupy mainly tetrahedral interstitial sites and about 10% substitutional sites. In the temperature range between 130 and 190 K, a site change from the tetrahedral interstitial sites to substitutional sites is observed. Between 190 and 470 K, in addition to the substitutional Li, all samples show Li at sites, which are displaced 0.7(1) A from the substitutional position, either along the 〈111〉 axis or 〈100〉 axis. Above 470 K out-diffusion of Li to the surface is observed.

We present a lattice location study of the n-type dopant arsenic after ion implantation into germanium. By means of electron emission channeling experiments, we have observed that the implanted As atoms substitute the Ge host atoms and that, in contrast to several implanted metal impurities in Ge, no significant fraction of As is found on interstitial sites. The substitutional As impurities are found to be thermally stable up to 600 °C. After 700 °C annealing a strong reduction of emission channeling effects was observed, in full accordance with the expected diffusion-induced broadening of the As profile.

The issue of lattice sites of Fr in Fe has been studied with two different techniques, integral low temperature nuclear orientation (LTNO) and emission channelling. Monte Carlo simulations of the system fitted to the channelling spectra reveal a large fraction of Fr in substitutional sites and hint at a possible complex site distribution. Using a two-site model for the LTNO data, a large fraction in high field site, in agreement with the channelling data, is deduced. © 1993 J.C. Baltzer AG, Science Publishers.

The lattice location of ion implanted antimony in zinc oxide has been determined by means of beta(-) emission channeling from the radioactive Sb-124 isotope. Following 30 keV implantation of Sb-124 into a single-crystalline ZnO sample to a fluence of 1x10(14) cm(-2), the angular-dependent emission rate of beta(-) particles around several crystallographic directions was measured with a position-sensitive Si detector. The majority of Sb was found to occupy Zn sites, with the possible fraction on O sites being at maximum 5%-6%. ispartof: Applied Physics Letters vol:94 issue:26 status: published

We report on an emission channeling study of the lattice site location of implanted Er in Ge together with its thermal stability. We found direct experimental evidence of Er atoms located on the tetrahedral (T) interstitial site and on the bond-centered (BC) site, with a maximum total occupancy after annealing at 400 degrees C. Whereas Er is expected to occupy the T site in a diamond crystal structure, the observation of BC Er in Ge is more surprising and believed to be related to the Er-vacancy defect in the split-vacancy complex configuration. (C) 2008 American Institute of Physics. ispartof: Applied Physics Letters vol:93 issue:14 status: published

Considering the input of Chernobyl radionuclides into Lake Constance on April 30, 1986, as the starting point of an unplanned radiotracer experiment, we followed the fate of five long-lived, gamma-emitting radionuclides (137Cs, 106Ru, 125Sb, 110mAg, and 144Ce) in order to obtain information about their scavenging and sedimentation properties, and their transfer into and within the food-web. In particular, we studied the uptake and excretion by fish of 137Cs. With respect to the transfer of 137Cs into fish, we also performed comparative investigations in the Schreckensee, a small shallow lake in the vicinity of Lake Constance.

We report on the lattice location of ion-implanted Ca and Sr in thin films of single-crystalline wurtzite GaN. Using the emission channeling technique the angular distributions of β− particles emitted by the radioactive isotopes 45Ca (t1/2=163.8 d) and 89Sr (t1/2=50.53 d) were monitored with a position-sensitive detector following 60 keV room-temperature implantation. Our experiments give direct evidence that ∼90% of Ca and >60% of Sr atoms were occupying substitutional Ga sites with root mean square displacements of the order of 0.15–0.30 A, i.e., larger than the expected thermal vibration amplitude of 0.074 A. Annealing the Ca implanted samples at 1100–1350 °C in high-pressure N2 atmosphere resulted in a better incorporation into the substitutional Ga site. The Sr implanted sample showed a small decrease in rms displacements for vacuum annealing up to 900 °C, while the substitutional fraction remained nearly constant. The annealing behavior of the rms displacements can explain why annealing temperatures...

We report the observation of slow emission bands overlapped with the near-band-edge steady-state luminescence of nominally undoped ZnO crystals. At low temperatures the time-resolved spectra are dominated by the emission of several high-energy bound exciton lines and the two-electron satellite spectral region. Furthermore, two donor-acceptor pair transitions at 3.22 and 3.238 eV are clearly identified in temperature-dependent time-resolved spectroscopy. These donor-acceptor pairs involve a common shallow donor at 67 meV and deep acceptor levels at 250 and 232 meV. FCT/FEDER - POCTI/CTM/45236/02

Ein Teil des Tschernobyl-Fallouts waren mikrometergrose Staubpartikel mit hoher spezifischer Radioaktivitat, auch „heise Teilchen“ oder “hot particles” genannt. Solche Partikel wurden schon kurz nach dem Reaktorunfall in Schweden mit Aktivitaten bis zu mehreren Tausend Becquerel beobachtet [7] und von anderen Messtellen bestatigt (siehe unten). Die “hot particles” wurden daraufhin zum Objekt weiterer Untersuchungen, zum einen zur Klarung offener Fragen uber den Verlauf des Reaktorunfalles, zum anderen, da kontroverse Meinungen uber ihre strahlenbiologische Gefahrlichkeit vertreten werden.

We report on the lattice location of ion-implanted $^{67}$Cu in $p^{+}$- and $n^{+}$-Si using the emission channeling technique. Following room-temperature implantation, the majority of Cu was found on near-substitutional sites in both $p^{+}$- and $n^{+}$-Si. Annealing in the temperature range 200-600°C resulted in changes of near-substitutional Cu to random sites in $p^{+}$-Si, while in $n^{+}$-Si all of the near-substitutional Cu was converted to ideal substitutional lattice sites. The activation energy for dissociation is estimated to be 1.7-2.0 eV for near-substitutional Cu in $p^{+}$-Si and 2.9(2) eV for ideal substitutional Cu in $n^{+}$-Si.

The lattice sites of implanted radioactive 8Li atoms in si-InP:Fe have been investigated with the α-emission channeling method using a position-sensitive Si-detector. It is shown that after room temperature implantation the major part of the Li atoms is located on tetrahedral interstitial sites with four P atoms as nearest neighbours, whereas after implantation at a temperature of about 450 K almost only substitutional In-sites are occupied.

Emission channeling allows the determination of the lattice location of radioactive impurities in crystalline solids at very low impurity concentrations of typically 10 17 cm −3 by measuring the channeling effects of electrons, positrons or α-particles emitted in the nuclear decay. Lattice sites of ion implanted dopants in semiconductors and subsequent recovery of implantation defects can be studied after implantation without amorphizing the lattice. An introduction to the emission channeling technique and experiments for the investigation of defect recovery and impurity lattice location after implantation of In, Cd and Te into III–V semiconductors in the temperature range 50 K to 600 K are presented. The α-emitting isotope 8 Li offers a novel access to study the behavior of vacancy-like defects via lattice site changes of implanted Li probe atoms, α-emission channeling experiments in GaP and GaAs are compared to results from heavy ion implantation.

The implantation of high doses of rare-earth metals into Si single crystals results in amorphization of the implanted rigion, even when the target is held at temperatures exceeding 500°C during the implantation. The situation changes drastically when the ion implantation is performed under channeling conditions, i.e., when the ion beam is aligned with a major crystal axis during implantation. A target temperature of 450°C is sufficient for recovery of a majority of implantation-related defects, resulting in an RBS-channeling minimum yield of 13% after implantation. MARLOWE simulations have been performed to explain the difference between non-channeled and channeled implantation. High temperature annealing of such samples results in the formation of continuous rare-earth silicide layers of high structural quality. Polar axial scans around the perpendicular axis result in a minimum yield of 1.5% in the Er signal. In the Si signal, however, a value of 20% is found. This high value is shown to be related to the large difference in atomic number between the rare-earth atoms and Si, which, in the case of planar channeling, can even result in missing channeling dips. The experimental backscattering and channeling results are compared to theoretical predictions for channeling in polyatomic crystals, and to Monte Carlo simulations performed with the FLUX code.

GaN epilayers grown by MOCVD were implanted with different fluences of thulium at room temperature and at 500 °C in order to find the optimum implantation conditions. Rutherford backscattering spectrometry in the channeling mode was used to monitor the damage evolution in the Ga-sublattice and to establish the lattice site location of the thulium ions. The nature of structural defects was studied with transmission electron microscopy and the optical properties of the samples with room temperature cathodoluminescence. The introduced damage could be significantly reduced by implantation at high temperature for fluences up to 5×1015 Tm/cm2. Annealing was necessary for optical activation of the implanted samples, in all cases. After annealing, sharp rare earth related emissions were observed in the blue and in the near infra-red spectral region.

The emission channeling technique using position sensitive detection of α-particles was applied to locate the lattice sites of ion-implanted 8Li in high-resistivity p-type Si. Below room temperature mainly tetrahedral and substitutional sites are occupied by the Li atoms. Above room temperature the diffusing Li is captured by defects probably containing oxygen or implantation-induced vacancies.

Electron emission channeling allows direct lattice location studies of low doses of radioactive atoms implanted in single crystals. For that purpose the anisotropic emission yield of conversion electrons from the crystal surface is measured, most conveniently by use of position-sensitive detectors. We discuss characteristic features of this method, including quantitative data analysis procedures, which are achieved by fitting simulated two-dimensional emission distributions for different lattice sites to the experimental patterns. The capabilities of this approach are illustrated by the case of rare earth atoms (Er, Tm, Yb) in Si, where we were able to do lattice location experiments down to implanted doses which are 150 times lower compared to previous RBS studies.

GaN films doped with rare earth (RE) elements have attracted considerable attention due to the unique optical luminescent properties of the RE intra 4ƒ(n)-shell electron transitions which lead to sharp blue (Tm), green (Er) and red (Eu) emissions. This paper presents an overview of investigations of GaN films implanted with each of these ions using a combination of electron-beam and optical techniques. The ion implantations were performed under a wide range of conditions, covering variations in fluences, energies and temperatures and followed by different high-temperature annealing steps. The resulting RE:GaN films were analysed using an electron probe micro-analyser modified to allow cathodoluminescence (CL) spectroscopy. Elemental microanalysis data obtained by wavelength dispersive X-ray analysis (WDX) is correlated with simultaneously collected room temperature CL spectra.WDX allows the quantification of the RE elemental concentrations in GaN down to ∼ 0.03 at. % in very thin layers (∼ 100 nm deep). Furthermore, by varying the incident electron beam energy, details concerning the depth profile of RE implants can be determined. The effects of both implantation conditions and rapid thermal annealing on the depth profile and on the luminescence properties are reported. CL measurements performed on annealed samples reveal sharp visible and near IR emission lines characteristic of the RE3+ intra-4ƒ(n) atomic shell transitions.

We have studied the lattice sites of Er in CZ Si single crystals by using conversion electron emission channeling from the isotope 167mEr (2.27 s) which is the decay product of radioactive Tm 167m(9.25 d). Following 60 keV implantation of 167Tm at a dose of 4×1013 cm−2 and annealing at 600°C, more than 90% of 167mEr is found close to tetrahedral insterstitial(T) sites. The tetra-hedral fraction of 167mEr decreases considerably after 10min annealing at 800°C and above. We attribute this to the onset of diffusion of the parent 167Tm and its trapping at other defects, presumably oxygen atoms or clusters of Tm/Er.

We report on the lattice location of Pr in thin film, single-crystalline hexagonal GaN using the emission channeling technique. The angular distribution of $\beta^{-}$-particles emitted by the radioactive isotope $^{143}$Pr was monitored by a position-sensitive electron detector following 60 keV room temperature implantation of the precursor isotope $^{143}$Cs at a dose of 1 $\times 10^{13}$ cm$^{-2}$ and annealing up to 900°C. Our experiments provide direct evidence that Pr is thermally stable at substitutional Ga sites.

In this work we present preliminary results of a low-energy ion scattering (LEIS) study of a H-induced (1 × 2) reconstruction of the Cu(1 1 0) surface. The surface was bombarded with 6 keV Ar + ions. Time-of-flight (TOF) azimuthal and polar scans of scattered Ar and recoiled Cu and H were measured at a scattering angle of 45°. To interpret the results obtained, the azimuthal scans were simulated using a new computer program “MATCH” and fitted to the experimental data. The surface was found to be of the (1 × 2) “missing row” reconstruction type. A number of positions for H atoms at the reconstructed surface mentioned were analyzed. The H atoms were observed to be situated in one of two possible trigonal hollow sites as was found before. The desorption and adsorption of H were studied. Desorption from the Cu (1 1 0)-(1 × 2) surface was observed in the temperature range 250–300 K. Above 300 K complete desorption results in de-reconstruction. In the adsorption measurements, the H-saturation took place after an exposure equivalent to 1.4 L at a sample temperature 230 K.

In this work we report on the lattice site location of rare earths in single-crystalline ZnO by means of the emission channeling (EC) technique. Following low dose (3 $\times 10^{13}$at/cm$^{2}$) 60 keV ion implantation of the precursor isotope $^{169}$Yb, a position-sensitive electron detector was used to monitor the angular distribution of the conversion electrons emitted from $^{169}$Tm$^{*}$ as a function of the annealing temperature up to 600$^\circ$C in vacuum. An additional annealing at 800$^\circ$C in flowing O$_{2}$ was performed. The EC measurements revealed that around 95-100% of the rare earth atoms occupy substitutional Zn sites up to an annealing temperature of 600$^\circ$C/vacuum. After the 800$^\circ$C/O$_{2}$ annealing, the emission channeling effects decreased considerably.

The lattice sites of ion implanted Li atoms in GaN were studied as a function of implantation temperature between room temperature and 770 K. We measured the channeling and blocking patterns of α-particles emitted in the radioactive decay of implanted 8Li ions to determine the Li lattice sites. Below 700 K Li atoms occupy mainly interstitial sites in the center of the c-axis hexagons at positions c/4 and 3c/4, where c is the lattice constant in c-axis direction. Around 700 K Li starts to diffuse and presumably interacts with vacancies created in the implantation process. This leads to the formation of substitutional Li above 700 K. An activation energy of about 1.7 eV for interstitial Li diffusion was determined.