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Variable energy positron beam with Doppler broadening spectroscopy (DBS) was used to investigate the depth-resolved defects formed by two fluencies of 130 keV N+ implanted in Semi Insulating (SI) 6H-SiC. The implanted ions induced damages near the surface and to a depth of 300 nm as simulated by SRIM analysis. Defects recovery, accumulation, and its behavior with two annealing temperatures were also considered. Defect types and its effect on annealing were analyzed from the changes in electron momentum and modeled as layers using variable energy positron fitting (VEPFIT) methods. Inclusion of electric field strength in the fitting procedure supported layer characteristics and the state of charge carriers. Di-vacancies, vacancy complexes observed in the damaged layers were agglomerated at the surface and tend to cure on annealing.

The study is intended to investigate the low energy nitrogen ion implantation induced behavior and re-crystallization in semi-insulating 6H-SiC from surface to 5 µm, by Raman spectroscopy. The nature of defects accumulation related to the SiC bond breakages and re-crystallization on vacuum annealing were analyzed from the A1(LO) phonon mode and probed at successive depth from the surface. Variations on the asymmetrical A1(LO) peaks of as-implanted samples were made to order upon annealing, and the mode regained. The peak intensity variation of A1(LO) mode indicated the disorder accumulation. The identified damage depth was in good agreement with Stopping and Ranges of Ions in Matter (SRIM). The changes in Si-Si, deformed-Si-C, C-C vibrations and crystalline-SiC were used to explain the defect role in the implanted and annealed samples.

There are contradictory theoretical predictions of lattice location of oxygen interstitial atom at tetrahedral and octahedral interstices in bcc Fe. For validating these predictions, 300 keV O18 ions with fluence of 5 × 1015 ions/cm2 are implanted into bcc Fe single crystals at room temperature and annealed at 400 °C. The Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA)/channeling measurements are carried out with 850 keV protons. The lattice location of implanted O18 is analysed using the α-particles yield from O18(p,α)N15 nuclear reaction. The tilt angular scans of α-particle yield along 〈110〉 and 〈100〉 axial directions are performed at room temperature. Lattice location of O18 is found to be at tetrahedral interstitial site by comparing the experimental scan with simulated scans using FLUX7 software.

Germanium atomic (Ge1) and molecular ions (Ge2) of equivalent energy are implanted in silicon at an elevated temperature. The ion induced damage has been characterized by RBS channeling (RBS/C) and positron annihilation spectroscopy. The RBS/C studies indicate that the molecular ion implantation has produced more defects in the near surface regions compared to the atomic ion implantation. This paper reports a first time observation of an enhanced production of vacancy related defects in silicon implanted with molecular ions.

Metal nanocluster composite glasses (MNCGs) have been the subject of both experimental and theoretical investigation because of their peculiar optical properties. In particular, the enhanced third order optical nonlinearity could be exploited in the all-optical switching device technology. In the present work, we present some results on MNCG films prepared by ion implantation. Fused silica were implanted with Au + of fluences 3 � 10 16 and 1 � 10 17 ions/cm 2 using an energy of 1.5 MeV. Optical absorption spectra of these samples have revealed prominent linear absorption bands at characteristic surface plasmon resonance (SPR) wavelength at and around 490 nm. Rutherford backscattering spectrometry (RBS) measurements reveal a Gaussian spatial distribution of Au ions. Third order optical nonlinear properties were studied by the Z-scan technique using a nanosecond laser. Z-scan measurements on the metal nanoclusters glass composites have revealed saturable absorption signifying the nonlinear responses. � 2007 Elsevier B.V. All rights reserved.

The structural and compositional analysis of strain relaxed InGaAs/InP multi quantum wells (MQWs) have been carried out using high resolution X-ray diffraction (HRXRD), Raman spectroscopy (RS) and Rutherford backscattering spectrometry (RBS). The surface morphology has been investigated by atomic force microscopy (AFM). No satellite peaks have been observed in the symmetrical X-ray scans indicating strong strain relaxation, highly mixed InGaAs/InP interfaces and no multilayer characteristics. This limits the structural as well as compositional analysis. Dynamical scattering theory based simulation package has been used to simulate the respective spectra and compared. The RS study shows huge Raleigh scattering induced background resulting low intense phonon modes. In spite of the background we could observe the GaAs and InAs type phonon modes which have been used for the analysis. The RBS studies also indicate the mixed InGaAs/InP interfaces with preferential GaAs and InP precipitation/segregation and the results are discussed in detail comparing with other complementary techniques. Also, AFM analysis has been utilized to obtain the composition in comparison with related literature.

Recently, interesting differences for ion – uniform film and ion – nanostructure interaction phenomena, particularly relating to ion beam mixing effects have been reported. Upon irradiation with 1.5 MeV Au 2+ ions on isolated Au nanostructures on silicon substrate, a higher probability of crater formation, larger sputtered particle size and its coverage and enhanced sputtering yield compared to the continuous films of Au on Si substrate were observed. Ion bombardment at high flux (≈6.3 × 10 12 ions cm −2 s −1 ) showed a dramatic mass transport from nanostructures extending up to a distance of about 60 nm into the substrate, much beyond their size. In this paper, RBS/Channeling results would be presented to elucidate on the arrangement of re-distributed gold atoms location in silicon and silicide matrix. Scanning transmission electron microscopy (STEM, with high angle annular dark field imaging) was used to complement the RBS results in determining the unusual mass transport and under ion–nanostructure interaction. The amorphous nature of the silicon matrix, that is deduced from both the RBS/Channeling and from TEM measurements, is an important factor in enhanced diffusion process resulting in dramatic mass flow.

Nanoscale cobalt clusters have been synthesized in an amorphous silica matrix by implanting high energy cobalt ions (2 MeV, Co 2+ ) with various doses. Surface acoustic radial vibration (phonons) modes confined to these cobalt nanoclusters have been detected using the low-frequency Raman scattering spectroscopy. Postannealing the ion implanted silica samples in a high vacuum atmosphere has led to significant growth of the cobalt nanoclusters in the silica glass matrix. Using suitable mechanism for the growth of the nanoclusters, activation energy for the diffusion of cobalt atoms in the silica matrix is calculated to be about 0.20 eV. Diffusion of the implanted cobalt atoms in the silica matrix during postannealing is further examined from the Rutherford backscattering measurements.

Thin films of Ag (1.5 nm thick) are grown on Si (1 1 1) substrates using evaporation method in high vacuum condition and due to non-wetting nature of silver, isolated islands of mean size ≈12.0 nm have been formed on the surface. Au 2+ (1.5 MeV) ions have been used to irradiate the above systems at various fluences (5 × 10 13 –1 × 10 15 cm −2 ) at an impact angle of 5° and at a flux of 6.3 × 10 12 cm −2 s −1 (corresponding to a beam current density of 2.0 μA cm −2 for Au 2+ ions). Ion beam induced embedding is observed to begin at a fluence of 1 × 10 14 cm −2 for this high flux whereas low flux irradiations (current density ≈ 0.02 μA cm −2 ) of Au 2+ ions under similar irradiation conditions did not yield embedding (impact angle 5°). High resolution transmission electron microscopy measurement showed no mixing in the form of silicide formation. These results are compared with high flux modifications in Au/Si system.

Analysis of defects by Channeling in strain relaxed In 0.18 Ga 0.82 As/GaAs heterostructures before and after swift heavy ion irradiation has been reported. Energy dependence of dechanneling parameter has been analyzed which indicates a thickness dependence of defects, involving dislocations (for 36 and 96 nm) and stacking faults (for 60 nm). The dislocation density reduces upon irradiation and the possibilities for the same have been discussed in detail. The cross-sectional transmission electron microscopy (TEM) analysis indicates the presence of stacking faults in 60 nm and dislocations in 96 nm irradiated samples complementing the dechanneling studies. Angular scans along off-normal axis have been carried out for strain analysis. A strong strain relaxation as a function of thickness is observed from the strain measurements. The strain values are almost same after irradiation compared with unirradiated ones. The flux distribution of channeled ions at smaller thicknesses is discussed in detail.

The 60 keV Fe+ ion-implantation in Ge〈1 1 1〉 at room temperature produced Fe nanoparticles embedded in a-Ge matrix and the a-Ge is recrystallised by beam annealing of the sample at 250 °C with 1 MeV Ge+ ions. The study of the irradiation-induced amorphization and subsequent recrystallisation by ion beam annealing in Ge was carried out using Raman scattering and grazing incidence X-ray diffraction (GIXRD) techniques. Raman scattering reveals the amorphization of Ge at a fluence of 5 × 1015 ions/cm2. With further irradiation, TO-like phonon mode evolves and the full-width at half-maximum (FWHM) of this mode increases with fluence. We have estimated the amount of bond disorder from the FWHM of TO-like mode. Upon self-ion irradiation of the Fe+ ion-implanted Ge at 250 °C, a partial crystallization of amorphous Ge is observed as evident from the reappearance of optical phonon mode. The GIXRD measurements also support the amorphization and crystallization of Ge. The presence of Fe nanoclusters was observed by using low-frequency Raman scattering (LFRS). The Fe-nanoclusters are expected to form directly in the collision cascade.

In0.18Ga0.82As/GaAs heterostructures of various layer thicknesses grown by molecular beam epitaxy (MBE) were irradiated by silver ions with a fixed energy and fluence. The thicknesses of the layers were beyond critical thickness and expected to be partially strain relaxed. The defects generated by partial strain relaxation and the effects of irradiation on these defects have been characterized by RBS/channeling. The dechanneling parameter and its dependence on incident ion energy has been determined. The resulting E0.5 dependence of the dechanneling parameter has been attributed to the presence of misfit dislocations at the interface. The effect of swift heavy ion (SHI) irradiation on partial relaxations is discussed in detail.

La0.67Ca0.33MnO3 films are known to release oxygen upon vacuum annealing due to lattice expansion caused by change of valence state of Mn from Mn4+ to Mn3+. RBS measurements using O(α,α) resonance reaction at 3.043 MeV show that oxygen concentration decreases from 60% to 57% in 450 °C-vacuum annealed samples. There is also oxygen loss from the SrTiO3 substrate upto a certain depth. The measure of crystalline quality χmin degrades from 5.9% to 10%. A 45° in-plane orientation is observed which is due to the dominant presence of [1 1 0]0 texture in the epilayer. The measured channeling half width ψ1/2 decreases upon vacuum annealing. In the samples annealed in oxygen at high pressure at 700 °C, there is no measurable change in oxygen concentration and χmin improved to 4.4%. ψ1/2 increases upon high pressure oxygen annealing. Our measurements directly show that there is lattice disorder upon vacuum annealing and ordering upon high pressure oxygen annealing and it is the largest for the oxygen lattice sites.

AlN thin films were prepared on Si(1 0 0) substrates by reactive ion beam coating (RIBC). The composition and morphology of these films have been analyzed through non-Rutherford backscattering (NBS), Auger electron spectroscopy (AES) and atomic force microscopy (AFM). It was found that the A1/N ratio and the surface morphology depend on the deposition conditions. We also concluded that those films which are nearly stoichiometric all have smooth surfaces. When beyond stoichiometry, the surplus A1 atoms will condense to form protruding tips.

Epitaxial Ag(1 1 1) thin films (∼125 nm) have been grown on Br-passivated Si(1 1 1) surfaces under high vacuum. Growth features observed from XRD, RBS/channeling and TEM/TED experiments are comparable to those grown under UHV conditions. RBS/channeling measurements on the Ag layer showed a minimum yield (χmin) of 62% indicating a poor crystalline quality. We irradiated the Ag(1 1 1) layer with 1 MeV Si+ at fluences of 5×1015 and 1×10 16 ions / cm 2 with the substrate at room temperature and an ion current density of 50 nA/cm2. Following irradiation, the measured χmin values are 40% and 38%, respectively, indicating an improvement in crystalline quality of the Ag layer. This behaviour is also seen in thermal annealing upto 500∘C due to some grain boundary melting. In thermal annealing at ⩾600∘C desorption of Ag occurs leaving holes in the Ag layer. Morphology of the annealed layer has been analyzed with RBS/PIXE studies with an ion microbeam of He+ ions.

100 keV hydrogen ion implantation has been carried out on undoped semi-insulating 〈1 0 0〉 gallium arsenide single crystals for various ion doses at room temperature. The structural properties due to high dose, low energy hydrogen ion implantation has been investigated using X-ray double crystal diffractometry (DCD) analysis, Rutherford backscattering spectrometry and channeling (RBS/C) experiments and transmission electron microscopy (TEM) analysis. By using DCD analysis, the value of elastic lattice strain for the ion doses of 1 × 10 16 , 1 × 10 18 ions/cm 2 has been estimated to be 2.1 × 10 −3 and 3.2 × 10 -3 , respectively. The RBS spectra in the channeling mode for the high dose implantations (10 17 and 10 18 ions/cm 2 ) show a high yield indicating a highly damaged region near the range of the implanted hydrogen ions. Particularly, for the dose 10 18 ions/cm 2 , a heavily damaged region at the surface can be observed. The TEM results evidenced that no amorphisation occurred for the dose 10 18 ions/cm 2 . From TEM characterisation, it is also observed that there are no hydrogen bubbles present in the implanted region. But small dislocation loops have been identified. The projected range of implanted hydrogen ions and the thickness of the implanted layer obtained by RBS and TEM analysis are compared with the TRIM calculations.

Organometallic Vapor Phase Epitaxy (OMVPE) grown layered structures of In0.1Ga0.9As/GaAs have been analyzed by He++ ion backscattering and channeling. From the random spectrum, the InxGa1 − xAs layer thickness was determined to be around 300 A and the composition of In to be In0.1 within an experimental error of around 5%. The χmin obtained from the In signal is around 7% which shows that the epilayer is of good crystallinity. The normalized yield vs. the tilt angle for the epilayer and the substrate along the off-axis (along [1 1 0] direction of the substrate) shows a shift in the minimum yield χmin dip, which is a direct measure of the strain present. This shift is found to be 0.2 ± 0.05° corresponding to a tetragonal distortion of 0.7 ± 0.2%. Shifting of the minimum yield dip of the overlayer towards left side with respect to the substrate indicates that the strain is compressive which is what is expected. X-ray diffraction is also carried out on the same sample which gives us ϵ⊥=1.01% and the in-plane lattice mismatch is nearly zero.

An Al 0.2 Ga 0.8 As thick film (∼3 μm) on a GaAs (1 1 1) substrate, grown by liquid phase epitaxy (LPE), has been analyzed by Rutherford Backscattering Spectrometry (RBS) and channeling experiments with He + ions. The channeling minimum yield, χ min , value of 5% indicates a good quality of the LPE-grown film. An RBS measurement with 1.62 MeV H + ions was carried out to locate the substrate–epilayer interface and to measure the thickness of the epilayer. A comparison on the measurements with He + and H + beams for characterizing a thick epitaxial layer is presented and discussed. Since the Al signal was not directly identifiable in the RBS spectra, proton induced γ-ray emission (PIGE) measurements were also taken up as a direct method to determine the Al content in the epilayer.

Samples of GaAs(100) single crystals have been implanted with Au ++ ions of 1.43 MeV energy to a dose of ∼ 1.5 × 10 15 atoms/cm 2 at a tilted geometry. Rutherford backscattering spectrometry together with ion channeling analysis with a B ++ beam have been used to study the Au distribution and radiation damage after implantation and subsequent vacuum annealing in the temperature range of 500–850°C. The experiments reveal the existence of extensive damage (possibly an amorphous layer) in the crystal surface region and annealing up to 850°C for 30 minutes does not result in the complete recovery of the lattice order. A two component split profile of Au is observed at higher temperature annealing. Most of the Au atoms have diffused slightly towards the bulk of GaAs whereas a small fraction is diffused out towards the surface. These results suggest that the defect structure which results from ion implantation has a strong influence on the diffusion of Au. A tentative explanation for these results is presented.

1.43 MeV Au ++ ions have been implanted into semi-insulating GaAs(100) single crystal wafers to a dose of 1.5 × 10 15 atoms/cm 2 at a tilted geometry. Samples were subsequently annealed in vacuum in the temperature range of 500 to 850°C. PIXE and XRF measurements, carried out with 2.61 MeV H + and 14.8 keV X-rays respectively, indicate practically no As loss from the implanted region. A significant As loss from the unimplanted region has been measured. Optical micrographs taken on both the implanted and the unimplanted regions show the formation of Ga droplets on the unimplanted region above 600°C annealing. However, no such features were observed in the implanted region up to 850°C. This indicates that MeV Au ion implantation inhibits the As release from GaAs. For a given annealing temperature and duration the amount of As loss depends on the dose of implanted Au. A tentative explanation for these results is presented.

MeV As+ ions into Si and Au2+ ions into Si, GaP, GaAs, InSb and LiNbO3 crystal substrates have been implanted at room temperature and tilted geometry. Using Rutherford backscattering spectrometry and channeling techniques, measurements of the range profile and lattice location of As atoms (dose: 1.0×1015/cm2) were made. It appears that 95% As atoms are substitutional. For Au implantation, range parameters have been determined for ion energies 1.37-2.03 MeV for the Si substrate. Measurements were also made on other substrates implanted with 1.43 MeV Au ions. The measured range values have been compared with TRIM and the so called universal range-energy theories. Our experimental results show that the theoretically predicted values are underestimated in all the cases. We also present a new approach for the determination of the projected range and straggling—both longitudinal and transverse—from a single measurement.