Rutherford Backscattering Channeling Research Articles

Lattice location and annealing studies of Hf implanted CaF2

Hafnium ions were implanted into calcium fluoride single crystals. The lattice damage introduced by the implantation was investigated with the Rutherford backscattering (RBS) channelling technique. The lattice location of the implanted ions was determined by performing channelling measurements for the 〈110〉 crystal direction. A comparison of the angular scan with Monte Carlo simulations leads to the conclusion that >90% of the Hf ions are on Ca sites directly after implantation. Subsequent annealing of the samples was performed in a rapid thermal annealing apparatus. Perturbed angular correlation (PAC) measurements with 181Hf(181Ta) show quadrupole interactions with νQ1=300(3) MHz (η=0.00), νQ2=1285(13) MHz (η=0.43) and νQ3=1035(10) MHz (η=0.00) after annealing up to 1200K.

Thermal and irradiation induced interdiffusion in Fe3O4/MgO(0 0 1) thin film

The interface reactions in an epitaxial 10nm-thick Fe3O4/MgO(001) film were investigated by using Rutherford Backscattering spectrometry (RBS), channeling (RBS-C) and X-ray reflectometry (XRR). The as-grown film had a good crystallinity indicated by the minimum yield and the half-angle value for Fe, respectively, χmin(Fe)=22% and ψ1/2(Fe)=0.62°. Annealing the films under partial argon pressure up to 600°C led to a large enhancement of Mg out-diffusion into the film forming a wustite-type phase, but the total layer thickness did not change much. Ion irradiation of the film by 1MeV Ar ion beam caused a strong Fe ion mixing resulting in a large interfacial zone with a thickness of 23nm.

Temperature behavior of damage in sapphire implanted with light ions

In this study, we compare and discuss the defect behavior of sapphire single crystals implanted with different fluences (1×1016–1×1017cm−2) of carbon and nitrogen with 150keV. The implantation temperatures were RT, 500°C and 1000°C to study the influence of temperature on the defect structures. For all the ions the Rutherford backscattering-channeling (RBS-C) results indicate a surface region with low residual disorder in the Al-sublattice. Near the end of range the channeled spectrum almost reaches the random indicating a high damage level for fluences of 1×1017cm−2. The transmission electron microscopy (TEM) photographs show a layered contrast feature for the C implanted sample where a buried amorphous region is present. For the N implanted sample the Electron Energy Loss Spectroscopy (EELS) elemental mapping give evidence for the presence of a buried damage layer decorated with bubbles. Samples implanted at high temperatures (500°C and 1000°C) show a strong contrast fluctuation indicating a defective crystalline structure of sapphire.

Analysis of Si crystal irradiated by highly-charged Ar ions using RBS-channeling technique

An ion-beam is one of the powerful tools applied in nanotechnology and nanoscience. It is expected that the application of highly-charged ion (HCI) beams, which have a higher reactivity in materials, would yield further developments in these fields. For effective applications of HCI beams, it is important to investigate any modifications of irradiated materials from a microscopic point of view. For this purpose, an irradiation-induced defect in a single crystal was analyzed by means of Rutherford backscattering-channeling (RBS) technique. In order to induce defects, Ar6+ and Ar9+ beams with an energy of 100keV were irradiated onto a single crystal of Si. By means of a simple analysis, the depth distribution of disordered Si atoms induced by the irradiation was extracted from the observed RBS-C spectra. The present result implies that the productivity of defects in a Si crystal is enhanced for Ar9+ ions compared with Ar6+ ions in a limited region of the surface.

Compositional analysis and evolution of defects formed on GaInP epilayers grown on Germanium

In this work, a compositional and morphological study of GaInP layers grown on Ge substrates is presented. The samples have been evaluated by means of high resolution X-ray diffraction, Rutherford backscattering channeling, atomic force microscopy and scanning electron microscopy. Compositional results from HRXRD and RBS show that the quality of samples close to the lattice match are independent on the composition (Ga or In-rich), although for Ga-rich samples, the spectra from RBS channeling measurements is not equal for one 〈 110 〉 direction and its perpendicular, an effect that does not appear in In-rich samples. Concerning, the morphological results, two typical defects appear on GaInP nucleation layer on Ge substrate–the so called arrowhead defects and asymmetric truncated pyramids–both orientated along 〈 110 〉 directions. Experiments reveal that the formation of pyramids is independent on the layer composition, while the density of arrowheads increases as the layer gets more Ga-rich.

Modeling of ion beam induced damage in Si during channeling Rutherford backscattering spectrometry analysis

We have modeled damage creation by an analyzing beam during channeling Rutherford backscattering spectrometry (RBS) analysis. Based on classic scattering theory and the assumption that only a dechanneled ion beam can cause displacements, a chi-square approach is used to fit the modeled spectra with experimental profiles, to extract the dechanneling cross section and the displacement creation efficiency. The study has shown that, for a 2.0 MeV He beam channeled along a Si(1 0 0) axis, the efficiency of defect creation by dechanneled beams is about 8% of the value predicted from the Kichin–Pease model. This suggests a significant dynamic annealing of point defects. The modeling procedure in this work can be used to predict the displacement creation during channeling RBS analysis.

Raman and Rutherford Backscattering Characterization of Ti-implanted Si above the Mott Limit

AbstractWe have analyzed the degree of crystalline lattice recovery in samples implanted with Ti concentrations well above the Mott limit and subsequently Pulsed-Laser Melting (PLM) annealed by means of Raman spectroscopy and Rutherford Backscattering Spectroscopy (RBS). Since very recently, theoretical studies predicted Ti interstitial sites for the Intermediate Band (IB) formation, the knowledge of the Ti impurity lattice location after PLM annealing is an essential point that can be elucidated by means of RBS measurements. After PLM annealings, Raman and RBS measurements have shown a decrease in the lattice crystalline quality as implanted dose is increased, yielding a significantly improvement of the lattice quality at the highest energy density studied. The RBS channeling spectra show that after PLM annealings Ti impurities are mostly occupying interstitial lattice sites.

Defects and magnetic properties in Mn-implanted3C-SiC epilayer on Si(100): Experiments and first-principles calculations

The effect of structural and chemical disorder on magnetism of Mn-implanted 3C-SiC epilayer on Si(100) is investigated experimentally using Rutherford backscattering channeling spectroscopy (RBS/C), x-ray diffraction (XRD), micro-Raman spectroscopy $(\ensuremath{\mu}\text{RS})$, and magnetometry, and theoretically using ab initio calculations. A single 3C-SiC epilayer on Si(001) was implanted at room temperature (RT) with Mn ions at 80 keV and at a dose of $5\ifmmode\times\else\texttimes\fi{}{10}^{15}\text{ }{\text{cm}}^{\ensuremath{-}2}$. RBS data show the formation of a highly disordered implanted layer of $\ensuremath{\sim}45\text{ }\text{nm}$ with a peak Mn atomic concentration of $\ensuremath{\sim}1.8%$ randomly distributed, in agreement with the stopping and range of ions in matter (SRIM) simulation. The experimental results of magnetic moment per Mn are interpreted by assuming that the implanted layer consists of two respective main regions, C--rich and Si--rich regions, as reflected by the presence of a graphitic phase, in which the local atomic environment of Mn is essentially C. Annealing seems to favor Mn substitution into Si sites, indicated by the substantial expansion of the lattice constant due to larger covalent Mn radius as observed by XRD and due to a high local tensile strain determined from $\ensuremath{\mu}\text{RS}$. This interpretation is also supported by recent calculations, showing that it is energetically favorable for Mn to substitute Si sites. The temperature dependence of magnetization shows an insulatinglike character for the as-implanted film and metalliclike for the annealed-implanted film with Curie temperature above RT. In addition, the magnetic moment per Mn increases strongly with annealing from 0.23 to $0.65{\ensuremath{\mu}}_{\text{B}}$. The experimental behavior is supported by our ab initio calculations, showing that magnetism in Mn-doped 3C-SiC can be enhanced by carefully growing a structure with Mn in Si sites using a C-deficient SiC host, possibly resulting in localized magnetic interactions.

Study of low energy and Cs− implantation induced amorphization effects in Si(1 0 0)

The damage growth and surface modifications in Si(1 0 0), induced by 25 keV cluster ions, as a function of fluence, ϕ, has been studied using atomic force microscopy (AFM) and channelling Rutherford backscattering spectrometry (RBS/C). RBS/C results indicate a nonlinear growth in damage from which it has been possible to get a threshold fluence, ϕ0, for amorphization as 2.5 × 1013 ions cm−2. For ϕ below ϕ0, a growth in damage as well as surface roughness has been observed. At a ϕ of 1 × 1014 ions cm−2, damage saturation coupled with a much reduced surface roughness has been found. In this case a power spectrum analysis of AFM data showed a significant drop in spectral density, as compared with the same obtained for a fluence, ϕ < ϕ0. This drop, together with damage saturation, can be correlated with a transition to a stress relaxed amorphous phase. Irradiation with similar mass Cs− ions, at the same energy and fluence, has been found to result in a reduced accumulation of defects in the near surface region leading to reduced surface features.

Defect Analysis of Silicon-Silicide-on-Insulator Substrates

The electrical reliability of silicon-silicide-on-insulator (SSOI) substrates is studied by diode analysis method. Diodes are fabricated in epitaxial silicon on silicon-on-insulator (SOI) and SSOI substrates. At low reverse bias the diodes on SSOI substrates show a general increase in leakage current. However, as the reverse bias increases to , the leakage current for diodes on SOI substrates surpasses that on SSOI substrates. The correlation between the electrical behavior of the diodes and the threading dislocations in the epitaxial layer is explored by applying a controllable preferential etching process based on an electrochemical capacitance–voltage system. The crystal quality of the SSOI substrates is also studied by Rutherford backscattering spectrometry and channeling.

Na-irradiated alpha-quartz: chemical epitaxy and luminescence

Doping of α-quartz by ion implantation leads to amorphization even at low fluences, but subsequent annealing in air or oxygen can restore the crystalline order (chemical epitaxy). Here we report on measurements of RBS channeling and cathodoluminescence (CL) spectra during chemical epitaxy of α-quartz irradiated with 50-keV Na-ions and annealed in 18O2-gas. In particular, the variation of the damage profile and CL spectra (the latter taken at 10 K and 300 K) as functions of the ion fluence will be discussed. The CL spectra at 10 K are dominated by a 2.90-eV band and differ greatly from the ones taken at 300 K; the intensity of this band increases strongly with the Na ion fluence. Some conclusions concerning the underlying photoactive defect structures will be drawn.

High electron mobility of phosphorous-doped homoepitaxial ZnO thin films grown by pulsed-laser deposition

The transport properties of phosphorous-doped ZnO thin films, grown by pulsed-laser deposition on thermally pretreated hydrothermally grown ZnO single-crystal substrates, are reported. The ZnO:P thin films show very good morphological and structural properties as confirmed by atomic force microscopy (AFM), high resolution x-ray diffraction, and Rutherford backscattering (RBS) channeling. Steps of height c/2 are visible in AFM investigations for all samples. For an oxygen partial pressure of 0.1 mbar, two-dimensional growth was found. RBS channeling of a ZnO:P film shows a minimum yield of 0.034 which is comparable to that of an annealed substrate (0.033). Hall effect measurements revealed that all films are n-type for the present growth conditions. Peak mobilities of 800 cm2/Vs have been observed around 70 K, in line with the high structural quality of the samples. Room-temperature mobility in ZnO:P is up to 170 cm2/Vs.

Coulomb heating of channeledC+andC2+molecules in Si

is shown that this effect results from the Coulomb explosion of the molecule during the channeling motion. By combining the Rutherford backscattering channeling RBS-C and the x-ray results we were able to determine the value of the transverse energy transfer as a function of the beam energy due to the break up process Coulomb heating. This energy increases monotonically from 14 eV for 900 keV/atom up to 30 eV for 2200 keV/atom. In addition, we were able to predict the theoretical Coulomb heating values by combining calculations and simulations, the theoretical-experimental agreement, within the experimental errors, being quite reasonable.

Structure, composition and crystallinity of epitaxial magnetite thin films

Epitaxially-grown Fe 3O 4(0 0 1) thin films by reactive deposition on MgO(1 0 0) substrates were studied using low-energy electron diffraction (LEED), conversion electron Mössbauer spectroscopy (CEMS), Rutherford backscattering spectrometry (RBS), channeling (RBS-C) experiments and X-ray reflectometry (XRR). No visible influence from the ion irradiation of the samples on the CEMS spectra was found, while surface oxidation of the samples was observed after exposure to the atmospheric pressure. RBS analysis indicated the presence of magnesium with an average amount of 3% in the films. RBS-C experiments yielded a value of 22% for the minimum yield of Fe and a value of 0.62° for the half-angle for Fe in the film indicating a good crystal quality of the films. The value for film-thickness obtained from XRR is in a good agreement with that from RBS and the nominal value.

Influence of strain on the magnetic properties of thin Cr(001) films

We report on the influence of strain on the magnetic properties of thin Cr(001) layers in the Fe/Cr/Fe(001) trilayers. The epitaxial strain in the Cr layer is measured via channeling Rutherford backscattering spectroscopy and x-ray diffraction spectroscopy. The magnetic properties of the Cr spacer layer are probed via perturbed angular correlation spectroscopy on the $^{111}\text{I}\text{n}(^{111}\text{C}\text{d})$ radioactive probe. The results indicate that the strain in the Cr spacer layer influences its N\'eel temperature, the orientation of the magnetic moments, and the strength of the magnetic hyperfine field on the diamagnetic $^{111}\text{C}\text{d}$ probe.

Ion implantation induced disorder in single‐crystal and sputter‐deposited polycrystalline CdTe characterized by ellipsometry and backscattering spectrometry

AbstractBulk single‐crystal CdTe, sputter‐deposited polycrystalline CdTe films of about 2.5 micron thickness, and single‐crystal Si (c‐Si) have been ion implanted using 350 keV Xe at fluences ranging from 1×1013 to 16×1013 cm–2 so as to create disorder in a controlled way from fully single‐crystalline to fully amorphous material. The general purpose of the investigations is to seek a parameterization of the critical point structures and establish a database for fitting the optical properties of CdTe films having different unknown grain sizes whereby the grain size will be described in terms of an effective defect density. The polycrystalline CdTe samples were magnetron sputtered onto c‐Si followed by CdCl2 and Br2‐methanol treatment to improve properties in terms of grain size and surface smoothness, respectively. The fluences for use in the ion implantation of CdTe were estimated using the SRIM (Stopping and Range of Ions in Matter) software, and cross‐checked by simultaneous implantation of bulk c‐Si samples. The optical properties were characterized by second derivative analysis and by a generalized critical point model. Although the damage created by 350 keV Xe in the simultaneously implanted c‐Si samples, as measured by both spectroscopic ellipsometry and Rutherford backscattering/ channeling spectrometry (RBS/C), agrees well with the expectations based on the SRIM simulation, the damage created in CdTe remains at a very low level even for doses several times higher than the amorphization level estimated by simulation. The character of the dechanneling of the RBS/C spectra indicates extended defects (presumably dislocation loops). This effect was similar in both single‐crystal and thin film polycrystalline CdTe, although less pronounced in thin film samples. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Defect profiling by ellipsometry using ion implantation through wedge masks

AbstractWe measured 3.5 MeV energy He‐ and N‐implanted Si by spectroscopic ellipsometry (SE) and Rutherford backscattering/channeling spectrometry (RBS/C). The He and N ions were implanted in the range of 1–5x1016/cm2 and 0.2–1.2x1016/cm2, respectively through a wedge‐shape silicon membrane (∼4.5 micron/mm slope) which was fixed to the target wafer and was moved laterally to the ion beam spot causing the disorder (mainly point defects) profile “moving” in depth. The doses and energies were in both cases set to have all the positions of the Gaussian damage at the surface, and to cover the damage range from slightly damaged to the maximum. We used ∼0.1 mm wide measuring spots for both SE and RBS/C making possible to “scan” the disorder profiles with ∼0.5 micron depth resolution. Several nm thick, surface amorphous damage peak was observed with low level (far below the modified Kinchin‐Pease model predictions) point defect region beneath the surface, possibly due to dynamic annealing processes. Using critical point analysis we make an attempt to determine the optical response (dielectric function) of the point defects or defect complexes. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Determination of ion track and shapes with damage simulations on the base of ellipsometric and backscattering spectrometric measurements

AbstractOn the base of geometrical and statistical considerations a damage simulator was created in order to determine the ion track‐radius and ‐shape of ion‐implantation caused damage in single‐crystalline Si. Damage vs. dose curves calculated by spectroscopic ellipsometry (SE) and Rutherford backscattering/channeling spectrometry (RBS/C) measurements, using different doses of 100 keV Xe implantation, gave information about the damage profile in depth. Both methods are required, because of dose‐dependent discrepancies of SE compared with RBS/C [Fried et al., Thin Solid Films 455/456, 404 (2004)]. Different kinds of damage models were investigated to calculate the ion track‐radius and to describe the damages in depth and the shape of ion track. Comparing directly the simulated and the measured damage vs. dose curves, the damage function and the other simulation parameters were optimized and hence the ion track size and even the shape can be determined. The dose dependent mean size of the unchanged crystalline regions, obtained from the simulation was correlated with the complex dielectric functions, obtained from the SE analysis. The results clearly show the effect of decreasing size of the unchanged crystalline regions. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Anisotropy effects on the formation of new phases in α-Al2O3 by high fluence Zn implantation

The synthesis of embedded nanoparticles in sapphire was achieved through high fluence Zn ion implantation at room temperature, followed by furnace annealing in vacuum. Sapphire single crystals with different orientations (c- and m-cut samples), were implanted and subsequently subjected to post-implantation thermal treatments to grow the nanoparticles. The anisotropy of α-Al2O3 influences the amount of defects produced through implantation and allows fast diffusion along c-planes which determines the nature and morphology of the systems formed. The structural characterization of the new structures was performed with Rutherford backscattering/channelling (RBS-C) and X-ray diffraction (XRD). The optical properties were studied with optical absorption (OA) in the zinc surface plasmon resonance (SPR) region.

A systematic study on analysis-induced radiation damage in silicon during channeling Rutherford backscattering spectrometry analysis

Channeling Rutherford backscattering spectrometry (RBS) is an essential analysis technique in materials science. However, the accuracy of RBS can be significantly affected by disorders in materials induced by the analyzing ion beam even under channeling mode. We have studied RBS analysis-induced radiation damage in silicon. A 140-keV H+ ion beam was incident along 〈100〉 Si axis at room temperature to a fluence ranging from 1.6×1016cm−2 to 7.0×1016cm−2. The evolution of the aligned yields versus fluences has been examined and found to agree well with a model proposed by us.