A general expression of the steady state composition for multicomponent system during ion sputtering

A general expression of the steady state composition during sputtering has been derived based on the preferential sputtering model. The resulting formula has been applied to calculate the steady state concentration in a AgAuPd ternary system and the calculated values are in agreement, at least qualitatively, with the experimental data.     

Instrument for analyzing the composition of multicomponent ion beams

A compact multichannel mass analyzer is described, which enables one to analyze the composition of multicomponent ion beams.     

Composition separation in the surface layers of a Ni-Cu foil during ion implantation

The effect of ion implantation on the composition and mechanical properties of rolled Ni-Cu foils is studied. The formation of a non-monotonic oscillating dependence of the chemical composition on depth associated with a presumable change in the defect structure of the material has been observed. Possible mechanisms of the observed phenomena are proposed.     

Surface composition and surface energy of Teflon treated by metal plasma immersion ion implantation

Plasma immersion ion implantation using a metal vacuum vapor arc (MEVVA) or cathodic arc source was used to modify the fluorine-based polymer, Teflon. Several transition metal ions such as Co, Ni, Cu were introduced into plasma and implanted into the Teflon surface. The chemical composition of the modified surface was determined by Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). The metals were found to be distributed several nanometers from the surface and XPS results showed the formation of metallic carbides and fluorides on the surface. Contact angle measurement results demonstrate the favorable change in the wettability from being hydrophobic to hydrophilic. Our study shows that the increase of the surface energy is due to the change of the surface interaction properties after metal plasma implantation.     

Effect of ion implantation on the chemical composition and structure of surface layers of heat-resistant alloys

We present a critical analysis of literature data devoted to the effect of ion implantation on the physicochemical state of surface layers of heat-resistant materials. We pay special attention to the problem of choosing the type of ions to be implanted, the bombardment conditions, and the finishing heat treatment with the goal of achieving the optimal level of operating properties. We show that for complex heterogeneous systems, the optimal treatment conditions can be estimated by methods of local equilibrium thermodynamics, chemical kinetics, and the theory of interaction of fast ions with solids using the basic principles of bulk alloying of heat-resistant alloys. We consider the characteristics features of continuous and pulsed implantation in heat-resistant materials. We formulate the requirements for techniques for investigating the chemical composition and the structural phase state of the near-surface regions of the bombarded targets. Analysis of the literature data on the effect of the bombardment conditions on the structure of the metals has shown that the data are ambiguous, that different authors use different terminology, and that the question of the phenomenology of the long-range effect is under dispute.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 72–91, May, 1994.     

Concerning bounds on the transport and mechanical properties of multicomponent composite materials

The Hashin-Shtrikman and Walpole bounds for the transport properties and bulk modulus of multicomponent composite materials are shown to be attained in a wide range of cases. Thus in these cases the bounds are the best possible bounds that can be given in terms of the properties of the components and the volume fractions. For three-component materials new bounds are conjectured. The conjectured bounds are presumed to apply in the cases where the Hashin-Shtrikman and Walpole bounds are not attained.     

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.     

Radiation enhanced outdiffusion during ion implantation

For a systematic prediction of the radiation-enhanced outdiffusion occurring during implantation, the use of a model based on the effect of vacancy flow on diffusion is described. The model agrees reasonably well with experiments in all twentysix measured cases. For the systematic understanding of the radiation enhanced outdiffusion, an approximative diagram based on the activation energy of self-diffusion is constructed for all pure elements and its application possibilities are discussed.     

Negative-ion emission during laser ablation of multicomponent materials

The time of flight technique coupled with an electrostatic energy filter has been used for composition and energy-distribution analysis of the ion species emitted during laser ablation of multicomponent materials Y-Ba-Cu-O, Pb-Sn-Te. The negative-ion output and kinetic-energy distribution as a function of the laser wavelength and the laser fluence on the target were measured. A high output of the negative ions of matrix elements comparable with the positive-ion emission was detected. The barium negative-ion formation was observed in spite of the negative electron affinity of alkaline earth elements in the ground electronic state. The mechanism of negative-ion formation based on the ternary collisional recombination in the laser plasma is analyzed.     

Atom and ion recombination in spurs

The proportion of singlets generated during a recombination of atoms or ions in a radiolytic spur reaction is examined from the viewpoint of a combinatorial analysis. The results obtained differ from other, already conflicting, published work. The problem is formulated in a way that enables spin relaxation effects to be incorporated.     

Target heating during ion implantation and related problems

We have undertaken a general analysis of wafer heating during implantation and first, we present general considerations of this problem with respect to amorphization doses extracted from Morehead and Crowder theory. Then, radiative properties of silicon wafers are measured: a law of variation of the emissivity with temperature is given; a comparison is made with values found in the literature. Dependence with experimental conditions (heat reflector, conductive losses) is also studied. Three methods for temperature measurement are used: temperature coefficient of a small resistor vacuum deposited on a face, thermocouple measurement and infrared detection. We compare the three kinds of results which are in good agreement and we make some comments about the temperature measurements using infrared detection.     

Ion beam sputtering of multicomponent targets: Surface composition change and cluster emission

Preferential sputtering effect, which occurs during irradiation of a multicomponent target by medium energy ions, was under our investigation. A new term characterizing the preferential sputtering, called “surface sputtering yield” and defined as average number of components i sputtered from a top surface layer per one primary ion, was suggested. A direct proportionality between the dimer emission and surface concentration of the component, forming the dimer, was concluded; this let us estimate the preferential sputtering of any target from the composition of the flux of secondary particles, analyzed directly during the ion sputtering process, and define the composition of the ion sputtered surface.     

Structure and composition of silicon carbide films synthesized by ion implantation

The mathematical decomposition of the IR absorption spectrum obtained from a Si layer after the C⁺ ion implantation with an energy of 10 or 40 keV or from a homogeneous SiC_0.7 film has demonstrated that fractions of weak elongated Si-C bonds in the amorphous phase, strong shortened Si-C bonds on the surface of small nanocrystals, and tetrahedral Si-C bonds in the crystalline phase (degree of crystallinity) after high-temperature annealing (1250–1400°C) of the layers are equal to 29/29/42, 22/7/71, and 21/31/48%, respectively. A system of SiC_2.0, SiO₂, SiC_0.8, and SiC_0.6 layers in the film on the Si substrate has been identified using X-ray reflectometry and the simulation with the Release software. The reflectometry data on fluctuations of the intensity of X-ray reflections in the region of the main maximum have been interpreted in terms of variations in the density over the depth of the layer with a Gaussian distribution of carbon atoms from 2.55 and 2.90 g/cm³ for the SiC_0.25 and SiC_0.65 layers, respectively, to 3.29 g/cm³ for the SiC_1.36 layer.     

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.     

Indications of bulk property changes from surface ion implantation

In the majority of cases, the effects of ion implantation are confined close to the implant zone but, potentially, the resultant distortions and chemical modifications could catalyse relaxations extending into the bulk substrate. Such possibilities are rarely considered but the present data suggest that high dose ion implantation of ZnO has induced bulk changes. Surface implants with Cu and Tb strongly modified the low temperature bulk thermoluminescence properties generated by X-ray irradiation. Suggestions are proposed for the possible mechanisms for bulk relaxations and structural characteristics, which may indicate where such instability may occur in other lattice structures.     

XPS study of silicon surface after ultra-low-energy ion implantation

Ultra-low-energy ion implantation of silicon with a hydrogen-terminated (0 0 1) surface was carried out using a mass-separated ³¹P⁺ ion beam. The ion energy was 30 eV, the displacement energy of silicon, and the ion doses were 6 × 10¹³ ions/cm². Annealing after the implantation was not carried out. The effects of ion implantation on the surface electrical state of silicon were investigated using X-ray photoelectron spectroscopy (XPS). The Si 2p peak position using XPS depends on the doping conditions because the Fermi level of the hydrogen-terminated silicon surface is unpinned. The Si 2p peak position of the specimen after ion implantation at a vacuum pressure of 3 × 10⁻⁷ Pa was shifted to the higher energy region. It suggested the possibility of phosphorus doping in silicon without annealing. In the case of ion implantation at 5 × 10⁻⁵ Pa, the Si 2p peak position was not shifted, and the peak was broadened because of the damage by the fast neutrals. Ultra-low-energy ion doping can be achieved at ultra-high-vacuum conditions.     

Radiation-enhanced diffusion of boron in germanium during ion implantation

An effect of radiation-enhanced diffusion during boron ion implantation into 200-500°C germanium substrates has been found. The boron-enhanced diffusion coefficient is independent of the temperature over the range 200-500°C during ion implantation, depends upon the dose rate of the incident ions and its value corresponds to the thermal diffusion of boron in germanium at 800°C.     

Formation of silicon carbide and diamond nanoparticles in the surface layer of a silicon target during short-pulse carbon ion implantation

Synthesis of silicon carbide and diamond nanoparticles is studied during short-pulse implantation of carbon ions and protons into a silicon target. The experiments are carried out using a TEMP source of pulsed powerful ion beams based on a magnetically insulated diode with radial magnetic field B _r . The beam parameters are as follows: the ion energy is 300 keV, the pulse duration is 80 ns, the beam consists of carbon ions and protons, and the ion current density is 30 A/cm². Single-crystal silicon wafers serve as a target. SiC nanoparticles and nanodiamonds form in the surface layer of silicon subjected to more than 100 pulses. The average coherent domain sizes in the SiC particles and nanodiamonds are 12–16 and 8–9 nm, respectively.