RBS-channeling Technique Research Articles

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.

Damage accumulation in gallium nitride irradiated with various energetic heavy ions

In this work a study of damage production in gallium nitride via elastic collision process (nuclear energy deposition) and inelastic collision process (electronic energy deposition) using various heavy ions is presented. Ordinary low-energy heavy ions (Fe+ and Mo+ ions of 110keV), swift heavy ions (208Pb27+ ions of 1.1MeV/u) and slow highly-charged heavy ions (Xen+ ions of 180keV) were employed in the irradiation. Damage accumulation in the GaN crystal films as a function of ion fluence and temperature was studied with RBS-channeling technique, Raman scattering technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).For ordinary low-energy heavy ion irradiation, the temperature dependence of damage production is moderate up to about 413K resulting in amorphization of the damaged layer. Enhanced dynamic annealing of defects dominates at higher temperatures. Correlation of amorphization with material decomposition and nitrogen bubble formation was found. In the irradiation of swift heavy ions, rapid damage accumulation and efficient erosion of the irradiated layer occur at a rather low value of electronic energy deposition (about 1.3keV/nm3), which also varies with irradiation temperature. In the irradiation of slow highly-charged heavy ions (SHCI), enhanced amorphization and surface erosion due to potential energy deposition of SHCI was found. It is indicated that damage production in GaN is remarkably more sensitive to electronic energy loss via excitation and ionization than to nuclear energy loss via elastic collisions.

Damage effects produced in the near-surface region of x-cut LiNbO3 by low dose, high energy implantation of nitrogen, oxygen, and fluorine ions

The damage effects produced in the near-surface region of x-cut LiNbO3 by low dose, high energy implantation of carbon, nitrogen, oxygen, and fluorine ions are investigated as a function of the dose and substrate temperature during the implant process. The damage profiles were obtained by the Rutherford backscattering RBS-channeling technique, whereas the compositional profiles were performed by secondary ion mass spectrometry. The experimental results showed that the mechanisms governing the damage formation at the surface are strongly connected to the interaction of defects produced when the electronic energy loss exceeds a given threshold close to 220 eV/Å. In particular, we observed a damage pileup compatible with a growth of three-dimensional defect clusters.

Damage accumulation in Si during N+ and [formula omitted] bombardment along random and channeling directions

Implantation conditions required for the correct study of the molecular effect in damage accumulation during light atomic and molecular ion irradiation of semiconductors are considered in detail. Disorder production in Si crystals implanted with 30 keV/atom N+ and N2+ ions at room temperature is examined by low angle RBS channeling technique. It is found that during irradiation along a random direction the near-surface damage produced by molecular ions (N2+) is about twice as much as one produced by atomic ion (N+) bombardment. On the other hand, no molecular effect in the near-surface damage accumulation during irradiation along 〈111〉 channeling direction is observed. These results are qualitatively explained by subcascade overlap during molecular ion implantation.

Growth and Characterization of Epitaxial Insulating CaF2 Layers on Silicon by MBE

In the course of the present work CaF2 epitaxialfilms were grown on Si(111) substrates by means ofMBE. The Si substrates were chemically cleaned priorto insertion into the system. The final volatile oxidewas desorbed in situ by heating to 850Ĉ. CaF2 was evaporated from aKnudsen-type cell by use of a graphite crucible, whilethe growth temperature was held at 650 Ĉ.RHEED (Reflection High Energy Electron Diffraction)has been used to monitor the film growth in situand to study the epitaxial quality. Also we have usedthe MeV He+ RBS channeling technique to look atdefects and to measure strain in the CaF2 layer.Usually good crystallographic properties are achievedunder optimum growth conditions, with values ofχmin < 5%. Electrical properties aremeasured by use of a special MIS structure.

Structural modifications in uranium dioxide irradiated with swift heavy ions

An extensive knowledge of radiation damage in nuclear fuel elements is of considerable importance for technological applications. Ion bombardment and ion-beam analysis techniques provide efficient tools in order to simulate and characterize the structural modifications induced by irradiation. This paper deals with the study of radiation effects induced in UO 2 single crystals irradiated with 340-MeV Xe ions which simulate high electronic excitations sensed by the nuclear fuel during the slowing-down of fission fragments. Radiation damage was characterized by the RBS-channeling techniques. Resonant scattering 16O( 4He, 4He) 16O occurring at 3.045 MeV was applied to the study of oxygen sublattice modifications. A strong disordering of both U and O sublattices was observed, even at very low ion irradiation fluence (∼ 10 13 cm −2).

Investigation of Er-implanted KTiOPO 4 crystals

KTiOPO 4 crystals were implanted with 300 keV Er + ions at ion fluences between 1 × 10 13 cm −2 and 2 × 10 15 cm −2 and temperatures ranging from 23°C to 750°C. Some of the samples were co-implanted with oxygen at room temperature. The radiation damage as well as the Er distribution after implantation and furnace annealing were analyzed by means of the RBS-channeling technique. Additionally, photoluminescence measurements were carried out on some annealed samples. Up to an implantation temperature T 1 = 200°C amorphous layers are produced already at Er + ion fluences between N 1 = 1 × 10 13 cm −2 and 3 × 10 13 cm −2. For a dose N 1 = 2 × 10 15 cm −2 amorphization is prevented for T 1 ≥ 650°C. The remarkable redistribution of Er towards the surface observed after annealing at temperatures ≥ 750°C is reduced by oxygen co-implantation. Complete annealing of amorphous layers in a K 2O atmosphere without any surface decomposition, which normally occurs at implantation and annealing temperatures in excess of 650°C, is found for an annealing temperature of 850°C. After annealing photoluminescence at the wavelength λ = 1.53 μm was demonstrated in KTiOPO 4 for the first time.

RBS-channeling determination of damage profiles in fully relaxed Si 0.76Ge 0.24 implanted with 2 MeV Si ions

The RBS-channeling technique has been used to measure damage concentration profiles in fully relaxed Si 0.76Ge 0.24 layers implanted with 2 MeV Si ions. The method of elaboration based on the two-beam model and linear calculation of dechanneling has been compared with the more exact trial-and-error determination of defect profiles through a Monte Carlo simulation of spectra, which describes the details of each ion path in the damaged crystal. The comparison shows that a correct description of the energy loss process of channeled He particles is very important to obtain reliable results, especially in the case of deep damage profiles. When an approximate description of this effect is introduced in the two-beam model, its results show a much better agreement with those of Monte Carlo elaboration. The large discrepancies observed at low damage concentration are related to the intrinsic approximations of the two-beam model: in this range accurate results can be obtained only by a detailed description of the ion paths in the damaged crystal.

Damage production and annealing of ion implanted silicon carbide

Samples of 6HSiC were implanted with Ga + and Sb + ions in a wide dose range (10 13 to 10 16 cm −2) at various target temperatures (− 190°C to 1200°C). Short-time annealing was performed at temperatures from 600°C to 1750°C. The as-implanted and annealed samples were analyzed by means of the RBS-channeling technique, XTEM and optical measurements. The results show that amorphization can be prevented for implantation temperatures ≥ 300°C; from 500°C to 800°C minimum damage concentrations are obtained. Annealing of amorphous layers is quite difficult and non-perfect, no monocrystalline state was found up to temperatures of 1720°C. Weakly damaged layers produced by a low dose (< 1 × 10 14 cm −2) at room temperature regrow perfectly at 1200°C. Residual damage after high-dose implantation (≥ 1 × 10 15 cm −2) at elevated temperatures cannot be removed completely by annealing.

Characterization of thin Ag films deposited onto InP(001)-p(2 × 4) surface at room temperature by means of LEED, RHEED, AES and RBS-channeling techniques

Ag films of different thickness deposited onto an InP(001)-p(2 × 4) surface at room temperature have been characterized in-situ by means of LEED, RHEED, AES and RBS-channeling techniques. It is found that the LEED patterns for the Ag surfaces show faint p(1 × 1) spots at an areal density of 4.8 × 10 15/cm 2 (average thickness of 5.1 Å) and no spots at larger thickness. It is also found that the RHEED patterns show a superposition of transmission diffraction spots for the (110) and (100) faces of the Ag crystal and the transposition between the brightness of the (1, 0) and (−1, 0) spots for both faces takes place when the incidence direction of the electron beam along the direction of the 4-times superlattice is switched to that of the 2-times superlattice of the InP(001)-p(2 × 4) surface. These observations indicate that the Ag film grows in the Stranski-Krastanov mode along the 〈110〉 direction and the islands of Ag(110) crystallites prefer to orient their (100) side surface along the direction of the 4-times superlattice. From the analysis of the channeling minimum yield for the Ag films of 1.5 MeV He + ions incident along the 〈100〉 direction of the InP(001) substrate, it is shown that the crystalline quality of an epitaxially grown Ag film of 14.0 × 10 15/cm 2 in areal density is excellent.

Depth Distribution of Boron and Radiation Defects in Silicon Dual Implanted with B+ and N+ Ions

Silicon wafers (〈100〉, n-type) are implanted by 40 keV B+ ions to the doses of 1.2 × 1014 or 1.2 × 1015 cm−2 and then by 50 or 100 keV N+ ions to the doses in the range of 1.2 × 1014 to 1.2 × 1015 cm−2. The depth profiles of the implanted boron atoms are obtained using the 10B(n, α)7 Li nuclear reaction. The distributions of radiation defects are studied by the RBS-channeling technique. The boron depth profiles show strong inward asymmetry which may be due to resisdual channeling. Additional nitrogen implantation almost does not affect the distribution of implanted boron ions. The effects of the implantation dose and energy of both B+ and N+ ions on the resulting damage formation in the dual implanted silicon are studied. Radiation (self) annealing is observed in the case of high dose dual implantation with boron and nitrogen ions.

Ion Damage Production in GaAs/Al0.6Ga0.4As Heterostructures

AbstractThe non-uniform distribution of damage with depth and the onset of amorphization produced in Al0.6Ga0.4As/GaAs heterostructures by 1.5 MeV Kr+ ion implantation at 77K have been investigated by using a combination of RBS channeling and cross-sectional high-resolution TEM techniques. The extent of damage increases with increasing depth in the Al0.6Ga0.4As layer. This depth dependence of the damage can be correlated with an increase in the number of recoil events with an energy between 30 and 50 keV. We propose that the amorphization of Al0.6Ga0.4As requires the superposition of cascade-type damage on a background population of point defects which is created by implantation with high energy ions.

Characterization of an InP(001)−p(2 × 4) surface exposed to atomic deuterium at room temperature by means of LEED, AES, NRA and RBS-channeling techniques

The exposure of the cleaned InP(001)-p(2 × 4) surface to atomic deuterium at room temperature has been studied by means of LEED, AES, NRA and RBS-channeling techniques. It is found that the LEED pattern for the InP(001) surface changed from p(2 × 4), through p(1 × 4), to p(1 × 1) with increasing the coverage of adsorbed deuterium up to 2 ML, which is the saturation coverage, and that the p(1 × 1) pattern also completely returned to p(2 × 4) by isochronal annealing up to 320°C for 15 min. The intensity of In MNN Auger electrons increases slightly, while the intensity of P LMM Auger electrons decreases with increasing the deuterium coverage. The In surface peak by RBS-channeling also decreases slightly. Based on these data, the change of the atomic structure of InP(001) surface due to deuterium adsorption is discussed.

Characterization of an InP(001)-p(2×4) surface exposed to atomic deuterium at room temperature by means of LEED, AES, NRA and RBS-channeling techniques

Characterization of an InP(001)-p(2×4) surface exposed to atomic deuterium at room temperature by means of LEED, AES, NRA and RBS-channeling techniques

Study of martensitic transformation in stainless steel by CEMS and RBS channeling

The effect of Xe ion irradiation in a single crystal of 17/13 stainless steel has been studied, using RBS channeling techniques and conversion electron Mössbauer spectroscopy (CEMS). 300 keV Xe ions were used to induce martensitic transformation in the austenitic steel. A dynamic behavior of the transformation was observed as functions of the fluence and depth dependence. The martensite appears abruptly at a critical fluence, in contrast with polycrystalline 17/7 stainless steel.

Formation of SiGe and SiGeC Layers on Si by Ge and C Ion Implantation and Subsequent Ion-Beam-Induced Epitaxial Crystallization

ABSTRACTFabrication of Si1-xGex and Si-1-x-yGexCy layers on Si(100) by high-dose ion implantation of 72Ge ions without and with 12C ions and subsequent high-energy and low-energy ion-beam-induced epitaxial crystallization (IBIEC) has been investigated. Structural properties of the surface layers were observed by RBS-channeling technique. Si(100) wafers were implanted with 150keV and 80keV Ge ions at room temperature so as to produce a peak concentration of Ge amounting to approximately 2 and 14 at.%, respectively. C ions were additionally implanted to a fluence of 10% of Ge concentration for the SiGeC samples. IBΓEC experiments performed with 400keV 18Ar ion bombardments have induced crystallization of the amorphous layers of SiGe and SiGeC on Si up to the surface at 400°C for both samples with low Ge concentration (2%) and high Ge concentration (14%). IBIEC using 72Ge ions with energies whose projected ranges are within the amorphous layer was alternatively performed for SiGe layer on Si. Bombardments of 140keV and 40keV Ge ions at 400°C have induced crystallization up to the surface with a slight disorder in the grown layer. Present experimental results suggest a novel ion beam synthesis method of fabrication of SiGe (SiGeC) on Si at low temperatures.

Ion Damage Studies in GaAs/Al0.6Ga0.4As/GaAs Heterostructures

ABSTRACTThe development of the damage structure produced in (100) GaAs/Al0.6Ga0.4As/GaAs by 1 MeV Kr+ ion irradiation at 77 and 293 K has been investigated by RBS channeling and cross-sectional high-resolution TEM techniques. Following an implantation to a dose of 1014 ions cm-2 at 77 K, RBS channeling spectra indicate that the Al0.6Ga0.4 layer contained a high defect density and was possibly amorphous. Warming to room temperature resulted in a change in the channeling spectrum, which indicated that the damage in the Al0.6Ga0.4As layer had partially recovered. The degree of recovery was greatest at the GaAs/ Al0.6Ga0.4As interface, and decreased with increasing depth. TEM observations show the damage in the Al0.6Ga0.4As to be comprised of planar defects, the density of which increases with depth, and an amorphous layer at the bottom interface. This difference in the damage distribution is consistent with the asymmetry in the channeling spectrum. A model based on the depth variation of cascade density is proposed to account for the observations.

Study of proton-bombardment-induced radiation damage in elemental and compound semiconductors by RBS channeling

In selected AIIIBV, AIIBVI and elemental semiconductors, which were bombarded with 0.3 MeV protons, the radiation damage is studied with the RBS channeling technique and compared to the theoretically determined primary damage profiles. It has been observed that the various material groups exhibit a different sensitivity to radiation damage. The sensitivity within each group scales approximately with the primary defect production rates resulting from TRIM calculations. The experimental damage profiles are described by the TRIM results concerning the depth and shape of the maxima. The fluence dependent saturation behaviour of point defect density indicates that defect recombination processes are important at room temperature. The higher degree of remaining defects in compounds is attributed to the formation of antisite defects.

Epitaxial growth of thin Au layers by room temperature deposition on a InP(001)-p(2 × 4) surface

Au layers with different thickness, deposited at a deposition rate of 3Å/min on the InP(001)-p(2 × 4) surface at room temperature have been studied in situ by means of LEED. AES and RBS-channeling techniques. For the Au layer of 20Åin thickness a clear LEED pattern of p(1 × 1) spots has been observed, which corresponds to a LEED pattern of c(2 × 2) spots at the (001) surface of a Au single crystal. The RBS-channeling spectrum of 1.5 MeV He + ions incident along the 〈001¯〉 direction of the InP substrate indicates that the average minimum yield for Au layer is 32.5%. The minimum yield of 32.5% for the Au layer is well explained in terms of lateral pairing-displacement by 0.18Åof Au atoms in a c(2 × 2) unit cell at the surface producing the reconstructed structure. This fact indicates that the Au layer is excellent in crystalline quality.

Transient phosphorus depletion in the InP(001) surface layers induced by room temperature deposition of a thin Au film

Au layers deposited on the InP(001)-p(2 × 4) surfaces at different deposition rates at room temperature have been studied in situ by means of LEED, AES and RBS-channeling techniques. At a deposition rate of 0.3Å/min, smaller by one order of magnitude than that for a Au layer epitaxially grown only by room-temperature deposition, it was found that the deposition of a Au film of monolayer thickness enhances the RBS intensity from In atoms within an interface region about 400Åthick by a factor of about 1.5, which represents complete depletion of P atoms over the corresponding depth. The depletion of P atoms was confirmed by direct detection by means of the QMA technique of the species with mass number 31 ejected just after Au deposition. It was also found that the anomalously enhanced RBS yield from In decays with a time constant of about 6 h and at the same time the AES yield from P increases somewhat. Furthermore, it was confirmed that no depletion of P atoms is induced by a blank test, namely only by heating at the same thermal flow as the Au layer was deposited. Such anomalous P depletion is discussed in relation to the mechanism for room-temperature epitaxial growth.