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We provide the first systematic characterization of the structural and photoluminescence properties of optically active defect centers fabricated upon implantation of 30-100 keV Mg+ ions in artificial diamond. The structural configurations of Mg-related defects were studied by the emission channeling technique for 27Mg implantations performed both at room-temperature and 800 {\deg}C, which allowed the identification of a major fraction of Mg atoms (~30-42%) in sites which are compatible with the split-vacancy structure of the MgV complex. A smaller fraction of Mg atoms (~13-17%) was found on substitutional sites. The photoluminescence emission was investigated both at the ensemble and individual defect level in a temperature range comprised between 5 K and 300 K, offering a detailed picture of the MgV-related emission properties and revealing the occurrence of previously unreported spectral features. The optical excitability of the MgV center was also studied as a function of the optical excitation wavelength enabling to identify the optimal conditions for photostable and intense emission. The results are discussed in the context of the preliminary experimental data and the theoretical models available in the literature, with appealing perspectives for the utilization of the tunable properties of the MgV center for quantum information processing applications., Comment: 7 figures

Despite the renewed interest in ion implantation doping of GaN, efficient electrical activation remains a challenge. The lattice location of $^{27}$Mg is investigated in GaN of different doping types as a function of implantation temperature and fluence at CERN's ISOLDE facility. The amphoteric nature of Mg is elucidated, i.e., the concurrent occupation of substitutional Ga and interstitial sites: following room temperature ultra-low fluence $(≈2 × 10^{10} \textrm{cm}^{-2})$ implantation, the interstitial fraction of Mg is highest (20–24%) in GaN pre-doped with stable Mg during growth, and lowest (2–6%) in n-GaN:Si, while undoped GaN shows an intermediate interstitial fraction of 10–12%. Both for p- and n-GaN prolonged implantations cause interstitial $^{27}$Mg to approach the levels found for undoped GaN. Implanting above 400 °C progressively converts interstitial Mg to substitutional Ga sites due to the onset of Mg interstitial migration (estimated activation energy 1.5–2.3 eV) and combination with Ga vacancies. In all sample types, implantations above a fluence of 10$^{14}$ cm$^{-2}$ result in >95% substitutional Mg. Ion implantation is hence a very efficient method to introduce Mg into substitutional Ga sites, i.e., challenges toward high electrical activation of implanted Mg are not related to lack of substitutional incorporation.

We report on the growth of thin NiSi films via the thermal reaction of Ni layers (13–35 nm) with Si(100) substrates modified by ion implantation. By introducing substrate damage or nitrogen impurities prior to the solid-phase reaction, several properties of the NiSi films can be modified: the formation temperature, texture, diffusion-limited growth rate and morphological stability. As some of the modifications to the NiSi films are rooted in the early silicide phases preceding the NiSi phase, particularly its formation temperature, special attention is devoted to the growth of the amorphous Ni-Si alloy and the crystalline δ-Ni2Si and θ-Ni2Si phases. We employed a number of experimental techniques, including in situ synchrotron x-ray diffraction (XRD), in situ Rutherford backscattering spectrometry (RBS), in situ sheet resistance measurements, ex situ ion beam channelling and ex situ pole figure measurements. We show that both the formation temperature of the NiSi films and the intensity of epitaxial and axiotaxial components of the NiSi texture can be either lowered or raised by selecting appropriate implantation conditions. Agglomeration of the NiSi films at high temperature (> 700 °C) can be slowed down, either by slowing down the mobility of the Ni and Si atoms, or by removing the morphologically destabilizing axiotaxial texture. Our results emphasize the strong interwoven nature of phase formation, texture and morphological degradation. We illustrate that the kinetics of the early stages of thin film reactions consist of more than just diffusion, i.e. nucleation can also play a crucial role.

© 2019 IOP Publishing Ltd. Solid-state amorphization, the growth of an amorphous phase during annealing, has been studied in a wide variety of thin film structures. Whereas research on the remarkable growth of such a metastable phase has mostly focused on strictly binary systems, far less is known about the influence of impurities on such reactions. In this paper, the influence of nitrogen, introduced via ion implantation, is studied on the solid-state amorphization reaction of thin (35 nm) Ni films with Si, using in situ x-ray diffraction (XRD), ex situ Rutherford backscattering spectrometry, XTEM, and synchrotron XRD. It is shown that due to small amounts of nitrogen (

Sequential multiple Eu ion implantations at low fluence (1×1013 cm-2 at 300 keV) and subsequent rapid thermal annealing (RTA) steps (30 s at 1000 °C or 1100 °C) were performed on high quality nominally undoped GaN films grown by metal organic chemical vapour deposition (MOCVD) and medium quality GaN:Mg grown by hydride vapour phase epitaxy (HVPE). Compared to samples implanted in a single step, multiple implantation/annealing shows only marginal structural improvement for the MOCVD samples, but a significant improvement of crystal quality and optical activation of Eu was achieved in the HVPE films. This improvement is attributed to the lower crystalline quality of the starting material, which probably enhances the diffusion of defects and acts to facilitate the annealing of implantation damage and the effective incorporation of the Eu ions in the crystal structure. Optical activation of Eu3+ ions in the HVPE samples was further improved by high temperature and high pressure annealing (HTHP) up to 1400 °C. After HTHP annealing the main room temperature cathodo- and photoluminescence line in Mg-doped samples lies at ∼ 619 nm, characteristic of a known Mg-related Eu3+ centre, while after RTA treatment the dominant line lies at ∼ 622 nm, typical for undoped GaN:Eu. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. ispartof: pages:253-257 ispartof: Physica Status Solidi C vol:11 issue:2 pages:253-257 ispartof: E-MRS Spring Meeting / Symposium J - Semicond Nanostructures towards Elect and Optoelectron Device Applicat - IV / Symposium L - Grp III Nitrides / Symposium P - Funct Nanowires - Synth, Characterizat and Applicat location:Strasbourg: FRANCE date:27 May - 31 May 2013 status: published

et al., The combination of lithography and ion implantation is demonstrated to be a suitable method to prepare lateral multilayers. A laterally, compositionally, and magnetically modulated microscale pattern consisting of alternating Co (1.6 µm wide) and Co-CoO (2.4 µm wide) lines has been obtained by oxygen ion implantation into a lithographically masked Au-sandwiched Co thin film. Magnetoresistance along the lines (i.e., current and applied magnetic field are parallel to the lines) reveals an effective positive giant magnetoresistance (GMR) behavior at room temperature. Conversely, anisotropic magnetoresistance and GMR contributions are distinguished at low temperature (i.e., 10 K) since the O-implanted areas become exchange coupled. This planar GMR is principally ascribed to the spatial modulation of coercivity in a spring-magnet-type configuration, which results in 180° Néel extrinsic domain walls at the Co/Co-CoO interfaces. The versatility, in terms of pattern size, morphology, and composition adjustment, of this method offers a unique route to fabricate planar systems for, among others, spintronic research and applications., This work was financed by the Research Foundation-Flanders (FWO), the Concerted Research ActionGOA/14/007, the 2014-SGR-1015 project of the Generalitat de Catalunya, and the European Commission under the 7th Framework Programme through the “Research Infrastructure” action of the “Capacities” Programme, NMI3-II Grant No. 283883. This work is based upon experiments (Proposal Nos. 5928 and 9384) performed at the MARIA instrument operated by JCNS at Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany. The authors would like to thank IMEC for access to its lithography facilities as well as J. Moonens and J. Loo for technical support. ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295).

Gallium nitride (GaN), grown by HVPE, was implanted with 300 keV Eu ions and then annealed at 1000 oC . Deep level transient spectroscopy (DLTS) and Laplace DLTS (L-DLTS) were used to characterise the ion implantation induced defects in GaN. Two of the implantation induced defects, E1 and E2, with DLTS peaks in the 100 – 200 K temperature range, had DLTS signals that could be studied with L-DLTS. We show that these two defects, with energy levels of 0.18 eV and 0.27 eV below the conduction band, respectively, are two configurations of a metastable defect. These two defect states can be reproducibly removed and re-introduced by changing the pulse, bias and temperature conditions, and the transformation processes follow first order kinetics.

Deep-level transient spectroscopy (DLTS) measurements were used to characterize the electrical properties of MOCVD grown, europium- (Eu) and xenon- (Xe) implanted GaN films on sapphire substrates. Implantation energy was 80 keV with a fluence of 110 14 cm 2 along a channeled crystallographic direction. Defect levels were observed at EC 0.19 eV for both Eu- and Xe-implantation which were predicted to be a rare-earth related donor level by theoretical calculations. Other defect levels are observed with energy levels located at 0.22, 0.68, 0.49, 0.60, 0.77 eV and 0.48, 0.64, 0.45, 0.72 eV below the conduction band for Eu and Xe implantation, respectively. Some of these levels have similar defect signatures and can be related to other implantation related defects introduced in erbium, praseodymium and helium implantations.

A GaN thin film was implanted with 5 × 1014 cm−2 of 60 keV stable 166Er, followed by the implantation of 2 × 1013 cm−2 radioactive 167Tm (t1/2 = 9.3 d) and an annealing sequence up to 900 °C. The emission channeling (EC) technique was applied to assess the lattice location of Er following the Tm decay from the conversion electrons emitted by 167mEr, which showed that more than 50% of 167mEr occupies substitutional Ga sites. The results are briefly compared to a 167mEr lattice location experiment in a GaN sample not pre-implanted with 166Er. In addition, high-resolution X-ray diffraction (HRXRD) was used to characterize the perpendicular strain in the high-fluence implanted film. The HRXRD experiments showed that the Er implantation resulted in an increase of the c-axis lattice constant of the GaN film around 0.5–0.7%. The presence of significant disorder within the implanted region was corroborated by the fact that the EC patterns for off-normal directions exhibit a pronounced angular broadening of the order of magnitude of 0.5°.

This paper reviews the current knowledge on rare earths (REs) implanted into GaN with a special focus on their lattice location and on the optical activation by means of thermal annealing. While emission channeling experiments have given information on the lattice location of rare earths following low-dose (≈10 13 cm −2 ) implantation, both in the as-implanted state and after annealing up to 900 °C, the lattice location of higher-dose implants (10 14 –10 15 cm −2 ) and their defect annealing behaviour were studied using the Rutherford backscattering/channeling (RBS/C) method. The available channeling and luminescence results suggest that the optical activation of implanted REs in GaN is related to their incorporation in substitutional Ga sites combined with the effective removal of the implantation damage.

We have used electrical measurements Deep level transient spectroscopy (DLTS) complemented by high-resolution X-ray diffraction (HRXRD) and Rutherford backscattering spectroscopy (RBS) measurements for assessment of the defects introduced in p-Si1-xGex during 160keV erbium ion implantation. From deep-level transient spectroscopy, it was observed that two prominent defects with discrete energy levels above the valence band, were introduced during Er ion implantation. The observed defects have similar signatures as those introduced during alpha-particle irradiation and electron beam metal deposition, indicating that these defects are more likely not related to Er but only to implantation induced damage such as primary defects. The generated defects expand the Si1-xGex lattice in the implanted region, which results in the presence of the tail in the high-resolution X-ray diffraction spectra. After rapid thermal annealing (RTA) at 850degreesC for 30 s in nitrogen ambient, a reduction in defect density as well as a relaxation of the Si1-xGex lattice is observed for all x values. A dominant Er-related sharp emission in the 1.541 mum region was observed at room temperature and neither the intensity of the Er emission nor the emission peak position were influenced by the Ge content or the strain relaxation in the epilayers.

Transmission electron microscopy and deep levels transient spectroscopy (DLTS) are used to investigate Er/Eu implanted GaN layers. We used random and channeled implantation. Microstructural analysis shows that both ion implantation geometries exhibit similar defects. For the Er doped samples, the investigated annealing conditions leave a highly disordered surface layer and the fabricated diodes exhibit high leakage currents. The Eu doped samples have reasonably good electrical characteristics and an additional deep level which might be associated with the presence of the implantation damage. We also point out two levels which have already been observed in undoped GaN, but whose energy position is displaced probably due to the strain or defects after ion implantation.

The lattice site location of excited states of 149 Eu was studied by means of the emission channeling technique. The 60 keV implantation of 149 Tb into a GaN thin film was performed at room temperature up to a dose of 2.0×1013 cm−2. This radioactive isotope eventually decays into short-lived excited states of 149 Eu . The conversion electrons emitted in the subsequent decay to the 149 Eu ground state were detected with a position sensitive detector. We measured their angular distributions around the [0 0 0 1], [ 1 1 0 2 ], [ 1 1 0 1 ] and [ 2 1 1 3 ] axes in the as-implanted state and after 600 and 900 °C vacuum annealing. Already in the as-implanted state around 65% of 149∗ Eu atoms were found on substitutional Ga sites. The root mean square (rms) displacements from the substitutional sites in the as-implanted state were found to be around 0.13–0.16 A. Annealing up to 600 °C increased the substitutional fraction by a few percent and slightly reduced the rms displacements, most likely due to the removal of crystal defects in the vicinity of the Eu atoms, resulting in a better incorporation into substitutional sites.

Monocrystalline Si(1 1 1) targets are implanted (at room temperature) with antimony ions at 120 keV energy to 5 � /10 14 or 5 � / 10 15 Sbcm � 2 dose. The samples are heat treated by means of rapid thermal processing (RTP) at 1000 8C during 60 s, under nitrogen atmosphere. In this work, we report the measured evolution of the silicon surface damage and the radiation damage recovery in relation to antimony dose and RTP processing. We also study the behavior of antimony dopant into Si(1 1 1) specimens. The investigation is carried out by HeRutherford backscattering spectrometry (RBS; operating at 1.57 MeV energy in both random and channeling modes), X-ray diffraction (XRD) and atomic force microscopy (AFM) techniques. It is shown that a good surface damage recovery is obtained for all the annealed samples. However, after RTP, a significant loss of antimony has occurred for the specimens which are implanted with 5 � /10 15 Sbcm � 2 dose. This suggests an antimony out-diffusion. Finally, a good morphological characterization of the specimens is provided by AFM. # 2003 Elsevier B.V. All rights reserved.

Erbium has been implanted into (0 0 0 1) epitaxial GaN grown on sapphire with an energy of 80 keV and a dose of 2.5 × 1014 Er/cm2. Rutherford backscattering and channelling spectrometry were used to investigate the effect of the implantation geometry on the defect generation. The defect density is significantly reduced when implanting along the GaN c-axis and gradually increases when changing the implantation angle towards random implantation (i.e. 10° off the c-axis). A rather large critical angle of ∼6.5° is found, indicating that channelling of the Er ions occurs easily. The generated defects expand the GaN lattice in the implanted region, which results in a satellite peak in the high-resolution X-ray diffraction spectra. After annealing the samples at 950 °C for 30 min in nitrogen ambient, a reduction in defect density as well as a relaxation of the GaN lattice towards the bulk value is observed for all implantation angles.

Zn (140 keV) channeled (along 〈0001〉) implantations in GaN are performed at room temperature and in a dose range from 1×1013 to 4×1016 cm−2, respectively. Channeling RBS measurements and the high-resolution XTEM investigations show the two damage regimes after implantation: one at the surface and another in the projected range. The damage level is very small at low doses and then gradually rises with increasing dose. The backscattering yield from the near surface region reaches the random level at doses higher than 2×1016 cm−2 and the broken crystals and the amorphous in nanometer size are formed in the top thin surface layer after implantation at a dose of 3×1016 cm−2. In the followed defective crystalline layer, the density of defects decreases with increasing the depth. The thread defects and loops are dominant in the region close to the surface at high dose and the clustered point defects are dominant in the deeper layer.

Strained Si/Si0.8Ge0.2/Si heterostructures are implanted at room temperature with 7.5 keV B+ and 33 keV BF2+ ions to a high dose of 2×1015 ions/cm2, respectively. The samples are subsequently subjected to three-step anneals (spacer anneal, oxidation anneal and rapid thermal anneal), which are used to simulate a real fabrication process of SiGe-based MOSFET devices. The damage induced by implantation and its recovery are characterized by 2 MeV 4He+ RBS/channeling spectrometry. A damage layer on the surface is induced by B+ implantation, but BF+2 ion implantation amorphizes the surface of Si/Si0.8Ge0.2/Si heterostructure. Channeling angular scans along the 〈110〉 axial direction demonstrate that the strain stored in the SiGe layer could be nearly completely retained for the B+ implantated and subsequently annealed sample. However, the strain in the BF2+ implanted/annealed SiGe layer has decreased drastically.

140 keV Zn channeled implantations in GaN are performed at room temperature and in a dose range from 1×1013 to 4×1016/cm2, respectively. The lattice expansion is calculated from (0 0 0 2) and (0 0 0 4) X-ray diffractions of GaN after channeled implantation. Three dose dependence regimes are observed: the perpendicular lattice parameter initially increases with dose, subsequently varies slowly in an intermediate dose range, and finally diminishes at very high dose. The high-resolution XTEM observations show the different defects, such as the clustered point defect, the thread defects and loops, the broken crystals and the amorphous in nanometer sizes. The variation of lattice expansion is attributed to the changes of density and types of defects.

Co1−xFexSi2 and Ni1−xFexSi2 metastable ternary phases were formed by sequentially implanting Co, Ni, and Fe into Si (111) at 623 K. In order to compare the phases formed by ion implantation, the Ni1−xFexSi2 stable bulk ternary phase with a wide variety of x values was synthesized. The samples were studied by Mossbauer effect, transmission electron microscopy (TEM), x-ray diffraction, and Rutherford backscattering and channeling. X-ray diffraction and TEM results on the as-implanted samples with x=0.5 indicate a cubic (fluorite) structure. 57Fe Mossbauer spectra show three resonanceline components. Comparison of the isomer shift values of the components with those measured in the stable and metastable transition-metal silicide phases indicated three different sites for iron atoms: Fe substituting Co or Ni; Fe in the empty cubes of the fluorite-type lattices; and Fe populating sites in the CsCl-type B2 lattice. In samples of Ni1−xFexSi2 annealed at 1273 K, α-FeSi2 and a fraction of Fe dissolved in NiSi2 app...

The lattice location of implanted silver in Si was studied by means of the emission channeling technique. Following 60 keV room temperature implantation of radioactive $^{111}$Ag at a dose of 2-3 $\times 10^{12}$ cm$^{-2}$, we identify around 30% of Ag on near-substitutional sites (around 0.45 from ideal S-sites). Upon annealing at 200-300°C, the fraction on near-S sites reaches a maximum around 60-80%. For higher annealing temperatures it decreases again and at 600°C Ag starts to diffuse out of the Si samples. We estimate the activation energy for the dissociation of near-substitutional Ag to be 1.8-2.2 eV. The experimental results are compared to those of Cu in Si, and common features and characteristic differences in the behavior of the two group 1B metals are discussed.

A variety of nuclear techniques rely on the incorporation of radioactive atoms to investigate the microscopic structural, electronic and magnetic properties of a material. In the past, ion implantation has been utilized to introduce these radioactive probes, resulting in a depth distribution of typically several hundreds of A, and damaging the sample. Both implantation-related deficiencies are incompatible with the ever shrinking sizes relevant in nanostructures. This problem can be circumvented by using ultra-low energy ion beams – of the order of 5 eV, i.e. below the displacement energy of the substrate atoms. Consequently, the radioactive probes are “deposited” on top of the sample, without generating damage to the substrate. Since the implantation chamber is in vacuo connected with the molecular beam epitaxy deposition chamber, the probe layer can be introduced at any stage during the sample growth (from surface to interface) – with monolayer depth resolution. As an example, we discuss the ultra-low energy ion deposition of 111 In in Cr, followed by analysis with perturbed angular correlation spectroscopy. The aim of the study is to explore the magnetic ordering of Cr thin films.

Epitaxial GdSi1.7 layers have been produced by channeled ion beam synthesis. The crystalline quality improves with implant dose and substrate temperature. The latter determines the extent of dynamic annealing whereas both factors are instrumental in driving precipitate growth. This, in turn, promotes the formation of a continuous silicide layer following annealing. The information obtained in this study allows the production of high quality layers with a room temperature resistivity of 86 μΩ cm. Evidence of magnetic ordering is apparent below 44 K.

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).-- et al., The interdependence between training and magnetization reversal in granular Co-CoO exchange bias (EB) systems prepared by O ion implantation in Co thin films is demonstrated by polarized neutron reflectometry. While high-fluence O-implanted thin films show reduced relative training values and no asymmetry in magnetization reversal (all reversals take place by domain wall nucleation and motion), low-fluence O ion implantation results in an increased relative training and a magnetization reversal asymmetry between the first descending and the first ascending branches. Whereas the untrained decreasing field reversal occurs mainly by domain wall nucleation and motion, traces of a domain rotation contribution are evidenced in the increasing field reversal. This is explained by the evolution of the CoO structure and the contribution of the out-of-plane magnetization with ion implantation. The amount of incorporated O, which determines the threshold between both behaviors, is around 20 at.%. This reveals that the interdependence between training and magnetization reversal is insensitive to the morphology of the constituents (i.e., granular or layered), indicating that this is an intrinsic EB effect, which can be conveniently tailored by the interplay between the intrinsic properties of the investigated materials and ion implantation., This work was financed by the Research Foundation - Flanders (FWO), the KU Leuven Concerted Action (GOA/09/006 and GOA/14/007) programs, the 2009-SGR-1292 project of the Generalitat de Catalunya, the MAT2010-20616-C02 project of the Spanish Ministerio de Economía y Competitividad, and the European Commission under the 7th Framework Programme through the “Research Infrastructure” action of the “Capacities” Programme, NMI3-II Grant No. 283883. We thank HZB (Proposal No. PHY-04-2130) and ESRF (Proposal No. HC-1012, BM20 beamline) for the allocation of neutron and synchrotron radiation beamtime, respectively, and C. Bähtz for the assistance during the synchrotron measurements. E.M. and L.M.C.P. also thank the FWO for financial support. T.D. thanks the CNPq agency (Project No. 245897/2012-7) for financial support.

We have studied the damage induced by 80 keV Er implantation in epitaxial GaN/sapphire layers at room temperature and at 450°C. The dopant distribution and lattice damage were investigated using Rutherford backscattering, channeling spectrometry and X-ray diffraction, whereas photoluminescence was used to probe the optical response. Random implantation results in substantial damage accumulation, which is difficult to recover during subsequent annealing. To reduce the ion-induced damage, we applied channeled implantation, i.e. directing the Er-beam along the nitride c-axis. Using this implantation geometry, a drastic decrease in the induced damage is observed. Channeled implantation generally results in green luminescence lines at room temperature, whereas no Er-related luminescence is observed after random implantation.

High dose (∼1×1017/cm2) channelled implantation of Er into Si along the 〈111〉 direction has been investigated. These doses are suitable for channelled ion beam synthesis (CIBS) of ErSi1.7 layers. A study of the influence of the implantation temperature between 470–800°C and the effect of the angle up to ±5° from the 〈111〉 direction has been carried out. Increasing the temperature results in significant improvements in the as-implanted material. The optimal temperature range is 600–700°C. Higher temperatures result in diffusion of the implanted Er to the surface where it is sputtered away by the incoming ions. Comparison of the experimental angular dependence with simulations and theory shows good agreement. Implantations at

We have used conversion electron emission channeling to determine the lattice location of $^{167m}$Er ($t_{1/2}$=2.28 s) in InP after 60 keV room temperature implantation of $^{167}$Tm ($t_{1/2}$=9.25 d) at a dose of 6.8 $\times 10^{12}$ cm$^{-2}$. Following annealing at temperatures above the major recovery step of the implantation damage at 100-150°C, we observe around 75% of Er on substitutional In sites. A smaller fraction of Er (7%) is found on substitutional P sites, the remainder on random sites. Annealing the unprotected InP crystal at temperatures above 250°C in vacuum causes a decrease in the channeling effects.

A buried hexagonal Nd0.32Y0.68Si1.7 layer is formed by a sequential implantation of Y and Nd ions into (1 1 1)-oriented silicon wafers. The orientation relationship between the epitaxial Nd0.32Y0.68Si1.7 and the silicon is (0 0 0 1) Nd 0.32 Y 0.68 Si 1.7 //(1 1 1) Si with 〈1 1 2 0〉 Nd 0.32 Y 0.68 Si 1.7 //〈1 1 0〉 Si . High temperature annealing (1000°C) results in a gradual transition into an orthorhombic ternary (Nd,Y)-silicide. Between the orthorhombic (Nd,Y)-silicide and the Si a preferential orientation relationship exists: (1 1 0) orth //(1 1 0) Si with 〈0 0 1〉 orth //〈1 1 1〉 Si . However, as not all orthorhombic silicide grains follow this epitaxial relationship, the minimum yield in the Rutherford backscattering spectrometry (RBS) spectrum increases compared to the results after a low temperature annealing.

Electrical measurements have been performed on ErSi 1.7 , YSi 1.7 and Er 0.5 Y 0.5 Si 1.7 , produced by channeled ion beam synthesis. The results have been compared with thin films of the same rare earth silicides produced by other methods. The room temperature resistivities of the ErSi 1.7 , YSi 1.7 and Er 0.5 Y 0.5 Si 1.7 are 52, 69 and 87 μΩ cm, respectively, significantly higher than the reported values for MBE synthesised layers. The ErSi 1.7 shows evidence of magnetic ordering, but this is not observed in either the YSi 1.7 or the Er 0.5 Y 0.5 Si 1.7 down to 3 K.

The ternary silicide, Er0.5Y0.5Si1.7 has been produced by channeled ion beam synthesis (CIBS) in a Si(1 1 1) substrate. The properties of the material have been compared with those of the binary silicides (i.e. ErSi1.7 and YSi1.7) produced by the same method. Analysis was carried out using Rutherford backscattering (RBS) and X-ray diffraction (XRD). The study revealed that the layer produced is of good crystalline quality, and is indeed composed of the Er0.5Y0.5Si1.7 ternary silicide as opposed to a mixture of the two binaries. It is epitaxial with respect to the Si substrate and possesses the same hexagonal (AlB2) structure exhibited by both binary silicides. The azimuthal orientation with respect to the substrate is Er0.5Y0.5Si1.7[0 0 0 1]//Si[1 1 1] and Er0.5Y0.5Si1.7{1 1 2 0}//Si{1 1 0}. The epilayer was found to be elastically strained with the perpendicular strain=−0.67% and the parallel strain=+0.34% similar to the values found for the Er and Y silicides.

We have used conversion electron emission channeling to determine the lattice location of $^{167m}$Er ($t_{1/2}$=2.28 s) in GaAs after 60 keV room temperature implantation of $^{167}$Tm ($t_{1/2}$=9.25 d) at low doses (0.6-3 $\times 10^{13}$ cm$^{-2}$). Following a recovery step of the implantation damage at 200-300°C, we observe a large fraction of Er (45-68%) on substitutional Ga sites. A second fraction of Er is found on the T$_{As}$ sites (the tetrahedral interstitial sites with nearest As neighbours). The fraction on T$_{As}$ sites reaches a maximum of 12-23% following annealing at 500-600°C. At higher annealing temperatures the channeling effects decrease markedly, which we attribute to the well-known degradation of GaAs due to As evaporation.

We have used deep-level transient spectroscopy (DLTS) in an investigation of the electronic properties of defects introduced in n-Si0.96Ge0.04 during 180 keV erbium ion implantation (fluence= 1 × 1010 cm−2 ). Five defects with discrete energy levels, ranging from 0.17 to 0.59 eV below the conduction band, were introduced during Er ion implantation. These defects are compared to those introduced during He-ion etching and alpha particle irradiation. By comparing the DLTS spectra and DLTS signatures, it was noted that certain defects (Eer3, Eer4 and Eer5) are only observed in the Er implanted SiGe. Photoluminescence in the 1.54 μm region due to the erbium implantation in Si0.96Ge0.04 was observed after a thermal treatment at 900°C for 30 s.

A buried hexagonal YSi 1.7 layer is formed by channelled implantation of Y ions into (1 1 1) oriented silicon wafers. The orientation relationship between the epitaxial YSi 1.7 and the silicon is (0 0 0 1) YSi 1.7 ‖(1 1 1) Si with 〈1 1 2 0〉 YSi 1.7 ‖〈1 1 0〉 Si . Annealing at 600°C for 1 h and subsequently at 1000°C for 0.5 h improves the crystalline quality of the buried YSi 1.7 layer. On the other hand, Nd-disilicide cannot be grown epitaxially on a Si(1 1 1) substrate. However, by using a sequential implantation of Y and Nd ions, a buried hexagonal Nd 0.32 Y 0.68 Si 1.7 layer with good crystalline quality is formed in the Si(1 1 1) substrate.

Epitaxial ternary silicide Er0.49Gd0.51Si1.7 layers with a good crystalline quality (χmin of Er and Gd is 3.7%) have been formed by 60 keV Er and Gd ion implantation into Si(1 1 1) substrates to a total dose of 1.0 × 1017/cm2 at 450°C using channeled ion beam synthesis (CIBS). The composition, the structure, the strain and the thermal stability of these layers have been studied using energy dispersive spectroscopy (EDS), Rutherford backscattering (RBS)/channeling and X-ray diffraction (XRD). It is shown that the perpendicular and parallel elastic strains of the Er0.49Gd0.51Si1.7 epilayer are e⊥=−0.46% ± 0.02% and e‖=+0.73% ± 0.19%. The layer is stable up to 900°C. Annealing at 950°C results in a phase transformation.

A continuous buried GdSi1.7 layer is formed by channelled implantation of 90 keV Gd ions into Si(111). In the case of (001) oriented silicon substrates, the silicide film is formed on the silicon surface. Its worse crystalline quality is due to the epitaxy occurring relative to all four {111}Si planes resulting in a textured GdSi1.7 layer. Annealing at a temperature of ⩾850 °C for 30 min results in the presence of only the orthorhombic GdSi2 phase on the silicon surface for both (111) and (001) silicon substrates. However, the precipitates embedded in the silicon substrate are still hexagonal GdSi1.7. The phase transformation temperature is higher for (111) than for (001) silicon.

We induced Co to form inclusions in Ag by ion implantation of Co into Ag and by coevaporation of both elements in a MBE system. Mossbauer spectroscopy at 4.2 K reveals the hyperfine fields present in the bulk and at the interface of the precipitates. By post-implanting the 57Co activity into the coevaporated samples, we strongly enhanced this interface population, which facilitates the determination of the associated magnetic hyperfine field. The dependence of the precipitate size on the Co concentration and annealing treatment is monitored. We propose a simple model which allows to estimate the precipitate size in the case of preferential interface population.

As the intrinsic origin of the high-temperature ferromagnetism often observed in wide-gap dilute magnetic semiconductors becomes increasingly debated, there is a growing need for comprehensive studies on the single-phase region of the phase diagram of these materials. Here we report on the magnetic and structural properties of Fe-doped ZnO prepared by ion implantation of ZnO single crystals. A detailed structural characterization shows that the Fe impurities substitute for Zn in ZnO in a wurtzite Zn(1-x)Fe(x)O phase which is coherent with the ZnO host. In addition, the density of beam-induced defects is progressively decreased by thermal annealing up to 900 ° C, from highly disordered after implantation to highly crystalline upon subsequent annealing. Based on a detailed analysis of the magnetometry data, we demonstrate that isolated Fe impurities occupying Zn-substitutional sites behave as localized paramagnetic moments down to 2 K, irrespective of the Fe concentration and the density of beam-induced defects. With increasing local concentration of Zn-substitutional Fe, strong nearest-cation-neighbor antiferromagnetic interactions favor the antiparallel alignment of the Fe moments. ispartof: Journal of Physics - Condensed Matter vol:25 issue:41 ispartof: location:England status: published

The magnetic character and the ordering process of \ensuremath{\gamma}-${\mathrm{FeSi}}_{2}$ precipitates formed by Fe implantation into Si(100) followed by ion-beam epitaxial crystallization (IBIEC) have been studied using the M\"ossbauer technique. Measurements performed at 4 K have shown no evidence of magnetic interaction indicating that the \ensuremath{\gamma}-${\mathrm{FeSi}}_{2}$ phase is not of magnetic character. Conversely, conversion-electron M\"ossbauer experiments performed after the IBIEC procedure show basically the presence of a doublet, despite the cubic structure of the \ensuremath{\gamma}-${\mathrm{FeSi}}_{2}$ precipitates. However, after 1 h of annealing at 600 \ifmmode^\circ\else\textdegree\fi{}C, a singlet, which before was barely recognizable, became more pronounced. The singlet-to-doublet proportion increases with increasing Fe concentration (2 at. %\ensuremath{\leqslant}${\mathit{C}}_{\mathit{p}}$\ensuremath{\leqslant}8.5 at. %), indicating that after annealing a better ordering in the\ensuremath{\gamma}-${\mathrm{FeSi}}_{2}$ precipitates is achieved. This ordering is obtained by an adequate combination of Fe-implanted concentration and thermal annealing. These studies have been complemented by Rutherford backscattering and/or channeling and transmission electron microscopy experiments. \textcopyright{} 1996 The American Physical Society.

Si(111) substrates were implanted with 70 or 90 keV 166 Er atoms to doses from 1.3 to 2.0×10 17 cm −2 at substrate temperatures from 450 to 530°C. During implantation, the Si substrates were tilted by 7° to minimize the channeling effect. The Er silicide layers formed under these conditions are not as good as Co silicide layers formed by Co implantation under similar conditions and the reason is discussed. One of the best results is an annealed sample containing a discontinuous epitaxial ErSi 1.7 layer with χ min of 40%. Rutherford backscattering and channeling spectrometry, X-ray diffraction and transmission electron microscopy have been used to study this heteroepitaxial ErSi 1.7 layer, showing that the epilayer is compressively strained and the azimuthal orientation of the epilayer is ErSi 1.7 [0001]∥Si[111] and ErSi 1.7 (10 1 0)∥Si( 11 2)

Results of Mossbauer measurements on -implanted are reported. It is demonstrated that Co atoms are mobile during applied annealing. Co enters into both possible sites of iron with a slight preference for one of them. Because of this weak preferential occupancy of iron sites, two models can explain the Mossbauer spectrum equally well.