Synthesis of silicon dioxide layers by high dose ion implantation

Single crystal <100> silicon was implanted with molecular oxygen with energies ranging from 80 to 240 keV in a non-channeling direction. Rutherford backscattering (RBS) analysis was used to obtain the oxygen/silicon atomic ratio depth profiles and the thickness of the buried oxide layer, for doses ranging from 10¹⁶ to 1. 5 × 10¹⁸ O₂+/cm². This work links the early low energy work and the more recent higher energy work, and generally excellent agreement has been obtained. The minimum energy for formation of buried silicon dioxide has been identified as 160 keV per oxygen molecule and corresponding oxygen dose of 6 × 10¹⁷ O₂+/cm₂.     

High dose iron implantation into silicon and metals

High dose implantations of Fe into metals and semiconductors have been performed with beam energies up to 1 MeV at the UNILAC-injector at GSI. Unusual high concentrations of 70 atomic % for Si and 20 atomic % for Cu have been obtained, with doses of 10¹⁸ Fe/cm² in the case of Si and several 10¹⁷ Fe/cm² in the case of Cu. For Si the thickness of the layers were determined by Rutherford backscattering to be 4500 Å. These results are consistent with calculations, which show that these high concentrations are due to the reduction of the sputter yield at the relative high particle energies. Samples have been characterized using several complementary methods (Mössbauer Spectroscopy (MS), Rutherford Backscattering Spectroscopy (RBS), Auger electron Spectroscopy (AES). Scanning Electron Microscopy (SEM), X-ray diffraction (XRD)).     

Formation of copper silicides by high dose metal vapor vacuum arc ion implantation

Si(1 1 1) was implanted by copper ions with different doses and copper distribution in silicon matrix was obtained. The as-implanted samples were annealed at 300 and 540 °C, respectively. Formation of copper silicides in as-implanted and annealed samples were studied. Thermodynamics and kinetics of the reaction were found to be different from reaction at copper–silicon interface that was applied in conventional studies of copper–silicon interaction. The defects in silicon induced by implantation and formation of copper silicides were recognized by Si(2 2 2) X-ray diffraction (XRD).     

Laser-induced implantation and diffusion of magnesium into silicon

Laser-induced diffusion (“implantation”) of magnesium atoms into silicon was studied experimentally. Neodymium-glass laser irradiation (λ=1.06 μm, τ ∼ 0.4 ms) was found to increase the diffusion coefficient and solubility of magnesium in silicon. Current-voltage and capacity-voltage characteristics, as well as thermostimulated current spectra of 〈Si + Mg〉 crystals, were obtained.     

Hyperfine interactions of iron implanted into aluminium

Stable⁵⁷Fe implanted into Al at energies of 20 to 70 keV and doses of 10¹⁴ to 2·10¹⁷ ions/cm² was studied with conversion electron Mössbauer spectroscopy at room and liquid nitrogen temperatures. Spectra composed of a single line and a doublet were observed. Similarly as in the splat-quenched FeAl alloys iron monomers and iron associations, mostly dimers, are observed. The isomer shifts of both components differ considerably and do not change with iron concentration. The splitting of the doublet increases with iron concentration, the increase being reproduced by computer simulations of electric field gradients in lattices with a random distribution of charge defects. The observed probability of formation of iron associates is higher than in random systems, especially at high iron doses.     

Yttrium ion implantation on the surface properties of magnesium

Owing to their excellent physical and mechanical properties, magnesium and its alloys are receiving more attention. However, their application has been limited to the high reactivity and the poor corrosion resistance. The aim of the study was to investigate the beneficial effects of ion-implanted yttrium using a MEVVA ion implanter on the surface properties of pure magnesium. Isothermal oxidation tests in pure O₂ at 673 and 773 K up to 90 min indicated that the oxidation resistance of magnesium had been significantly improved. Surface morphology of the oxide scale was analyzed using scanning electron microscope (SEM). Auger electron spectroscopy (AES) and X-ray diffraction (XRD) analyses indicated that the implanted layer was mainly composed of MgO and Y₂O₃, and the implanted layer with a duplex structure could decrease the inward diffusion of oxygen and reduce the outward diffusion of Mg²⁺, which led to improving the oxidation resistance of magnesium. Potentiodynamic polarization curves were used to evaluate the corrosion resistance of the implanted magnesium. The results show yttrium implantation could enhance the corrosion resistance of implanted magnesium compared with that of pure magnesium.     

Low temperature self-ion implantation into granular aluminium films

Radiation induced effects in glass-rods and fiberoptics have been studied to determine parameters affecting the application of these materials in nuclear technology, i.e. as fiberscopes for visual inspection in severe radiation environments. Different glass and fibertypes have been exposed to fission product gamma radiation. The radiation induced transmission loss was measured with a spectrophotometer and then different annealing methods were examined to improve the transmission properties again. Especially the changes in glass and fiber recovery vs. time as a function of radiation dose and annealing temperature were investigated. Annealing experiments were performed exposing the samples either to temperature treatment or to various light sources such as quartz lamp, arc lamp or UV-laser for optical annealing. The transmission recovery was then investigated either as a function of annealing temperature or of exposure time to the light sources. The results allow conclusions on the design and composition of optical fiber endoscopes to be used in severe radiation environment where image transmission is required in the presence of high level nuclear radiation.     

Structure and phase transformations caused by oxygen ion implantation into titanium

Secondary-ion mass spectrometry and transmission electron microscopy are used to investigate structural changes and phase transformations during ¹⁶O and ¹⁸O ion implantation into titanium at 100 and 300 K. For all implanted ion energies, there are the doses (saturation doses) after which the interstitial oxygen profile takes a final steady-state shape. The steady-state profile corresponds to a definite stable set of oxide phases, including TiO, rutile TiO₂, and TiO_1.5 layers. Under steady-state conditions, the film is composed of several oxide phases, whose structures depend on the target temperatures used in the irradiation process. At 100 K, the steady-state oxide system contains an amorphous phase layer with gas-filled bubbles instead of crystalline rutile.     

Effects of high-energy ion implantation into metals

The laws and features of the formation of phase-structural states and defect formation during high-energy (E 100 MeV) ion implantation are reviewed. We consider the salient feature of such action in solids, namely, strong electron excitations in the solids and, therefore, the dominant value of electron stopping of ions; formation of buried tracks; and abrupt increase in the role of electron excitations in the generation of structural defects. High-energy and multiple-energy implantation is shown to be effective in modifying the physicomechanical properties of solids because of the formation of deep-lying doped layers and the considerable thickness of the ion-modified surface layer of the target.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 23–40, May, 1994.     

Focused ion beam gallium implantation into silicon

Samples formed of a thin metal film deposited on silicon single crystal were annealed with electron and laser (ruby and excimer) pulses over a wide range of fluences. From a comparison of the experimental results with the temperature profiles of the irradiated samples, it turns out that suicide formation starts when the metal/silicon interface reaches the lowest eutectic temperature of the binary metal/silicon system. The growth rate of reacted layers is of the order of 1 m/s.     

High dose implantation of Eu into α-Fe

Abstract

At the UNILAC injector at GSI ¹⁵¹Eu was implanted into an α-Fe foil [8]. According to our simulation code of the energy loss of the implanted ions an energy of 1.5 MeV was chosen to minimize the sputter yield during implantation and to produce the highest possible Eu concentration near the surface of the sample. After the irradiation with a dose of 3.6 · 10¹⁷ Eu/cm² the implantation profile should reach its maximum of 8 at. % Eu at the surface of the sample and its width should be 1700 Å.     

Sputtering during ion implantation into gallium arsenide

The surface erosion caused by ion bombardment of solids and its effect on the number of ions retained in the solid was studied experimentally for a variety of ions implanted into GaAs with various fluences and energies. Experimental methods were interferometry and semi quantitative X-ray analysis by means of an electron microprobe. By an easy-to-use computer calculation the change in the implantation profiles was determined and the number of retained ions were related to the surface shift caused by sputtering. Comparison of this shift with the real erosion found before and after annealing was made. From the results, we conclude that the collapse of the crystal lattice contributes to the sinking of the bombarded surface. Sputtering data necessary to estimate the technical consequences of sputtering, range data of 100 keV Fe ions, and data indicating the sensitivity of X-ray analysis are presented.     

An optical bridge reflectometer for sensitive measurement of ion implantation dose

An instrument is described that can be used to monitor, with unprecedented sensitivity, changes in the optical reflectivity due to crystailine damage incurred during ion implantation. It is shown that at the shot-noise limit, changes in the optical reflectivity of silicon as small as 5·10^–7 can be measured in a 10 Hz bandwidth with a signal-to-noise ratio of 100, corresponding to an extrapolated uniform implantation dose of 5·10⁸ cm^–2 for ¹¹B⁺ at 50 keV in silicon.     

Thermal migration of iron implanted in aluminium at high doses

Abstract

This paper summarizes recent progress in the understanding of energetic displacement cascades in metals achieved with the molecular-dynamics (MD) simulation technique. Recoil events with primary-knock-on-atom (PKA) energies up to 5 keV were simulated in Cu and Ni. The initial development of displacement cascades was similar in both metals, with replacement collision sequences providing the most efficient mechanism for the separation of interstitials and vacancies. The thermal-spike behavior in these metals, however, is quite different; Cu cascades are characterized by lower defect production and greater atomic disordering than those in Ni. The thermal spike significantly influences various other properties of cascades, such as total defect production and defect clustering.     

Irradiation effect of yttria-stabilized zirconia by high dose dual ion beam irradiation

Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.     

Amorphization of metals by ion implantation and ion mixing methods

In this paper, we present a review of the experimentally determined characteristics of solid-phase amorphization of metals and alloys under ion implantation and ion mixing conditions. For the first time we systematically consider the characteristic features and the thermodynamic, structural, and kinetic criteria for amorphization in different metallic systems, and we demonstrate the expediency of the following classification of alloys undergoing amorphization: metal-metalloid systems, intermetallics, heterophase alloys, alloys with high positive heat of mixing. We compare solid-phase amorphization under conditions of bombardment by beams of charged particles, thermal mixing of the alloy components, and mechanical alloying. We consider the phase and structural states preceding amorphization and the possibilities for predicting metallic systems which can undergo amorphization.V. D. Kuznets Siberian Physicotechnical Institute, Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 3–30, August, 1994.     

Chemical effects of carbon ion implantation into alkali halides

Abstract

The implantation of 230 keV carbon ions into alkali halide single crystals AX (A=Na, K, Rb, Cs; X=F, CI, Br, I) at temperatures T ? 77 K gives rise to intensive, highly resolved, optical absorption bands in the visible region (2.3-2.8 eV, peak half width ～0.004 eV). They resemble very much the Swan band system of matrix isolated C₂. The influence of the matrix on the fine structure of the absorption bands is discussed. These carbon-centres are formed to a lesser extent or not at all when implanting at 200 K and 300 K, respectively. They bleach out at room temperature. Radiochemical experiments at room temperature with carbon atoms stemming from the ¹¹C(ρ, α) ¹¹C-nuclear reaction in BN/AX mixtures show the formation of carbon compounds such as CX₄, CX₃H, CX₂H₂, CXH₃ and CH₄. Thus, the primarily formed C₂-aggregate or C-X intermediates which are stable at T ? 77 K, at higher temperature are gradually transformed to stable carbon-halogen compounds. The reactions of matrix isolated carbon upon dissolving the ionic crystals are of interest for the labelling of organic compounds with ¹¹C     

Phosphor preparation by ion implantation

6H silicon carbide crystals have been subjected to ¹¹B⁺ ion implantation and subsequent annealing and found to show the yellow boron photoluminescence.     

Surface treatment by ion implantation

The advantages and limitations of ion implantation considered as a surface treatment process are presented. The importance of the implantation conditions (dose, temperature, vacuum quality) on the mechanical and tribological properties of steels and ceramics is pointed out. In the case of nitrogen implantation the wear rate of steels is generally decreased while boron implantation is believed to improve their friction coefficient. In fact a careful elemental analysis of the surface shows the predominant role of carbon pollution. In the case of implanted ceramics, ion implantation generally decreases the Young modulus and the hardness but under certain conditions the toughness can be greatly increased. This revised version was published online in August 2006 with corrections to the Cover Date.