Ion Beam Mixing Technique Research Articles

Ion beam mixing of [formula omitted] and [formula omitted] multilayers

We have submitted bilayers of La(OH) 3 Cu and multilayers of La(OH) 3 SrOCu to energetic heavy ion irradiation at 300 K and 700 K in order to investigate the possibility of preparing La 2CuO 4 and (La 1 − xSr x) 2 CuO 4 through the ion beam mixing technique. For comparison purposes, similar samples were annealed at 700 K. Results are given concerning the modification of the atomic compositions (La, Sr, Cu, O and H), the atomic depth distributions, the compound formation, induced either by irradiation or by thermal annealing. The specific role of the ion beam mixing process is emphasized.

Electrocatalytic Behavior of Ion‐Beam Mixed Ni‐Pd Surface Alloys for the Hydrogen Evolution Reaction in KOH

The hydrogen evolution reaction in aqueous 30 weight percent electrolyte at 80°C was investigated for Ni‐Pd surface alloys, produced by the ion beam mixing technique. Surface alloys, containing 55–90 atom percent (a/o) Pd, were produced by subjecting evaporated layers of Ni and Pd on Ni substrates to 120 keV Ar+ ion bombardment; the alloy composition vs. depth was monitored by Rutherford backscattering using 2 MeV 4He+ ions. Polarization of the electrodes was determined by potentiodynamic techniques at a sweep rate of 2 mV/s. Unbombarded Ni and Ni/Pd cathodes exhibited only a single Tafel region; the alloy electrodes fabricated by ion beam mixing, on the other hand, exhibited at least two Tafel‐type regions, a low slope 40–50 mV/decade region between 0 and −0.1V and an increasing slope at larger negative potentials. The superior current‐potential behavior corresponding to most effective catalytic activity of the cathodes was characterized by the existence of the low Tafel slope region on the alloys which was most prominent in the case of the Ni‐55 a/o Pd cathode.

The improvement of passivity by ion implantation

The ion implantation is an effective surface modification method to improve corrosion performance of metal materials. In this paper the effect of nitrogen ion implantation and nitrogen ion recoiling implantation on the passivation properties of metals were studied. The experimental results indicated that the stability of passive films and the pitting resistance of 18-8 austenitic stainless steel are improved by nitrogen ion implantation and the anodic dissolution process of metal is inhibited by nitrogen in implanted layer. The mechanism of the effect of alloyed nitrogen on pitting corrosion is proposed. The surface alloys of FeNi and FeCr are formed in the iron substrate using the ion beam mixing technique. The influence of the ion beam mixing on electrochemical behavior of iron in acetate buffer solution was investigated.

Ion beam mixing of Pd/V superlattices studied by X-ray diffractometry

The ion beam mixing technique was applied to the fabrication of Pd-V metallic alloys. Layered Pd(fcc)/V(bcc) thin films were produced by sequential deposition of palladium and vanadium on heated glass substrates. Measured X-ray diffraction spectra showed the peaks characteristic for superlattices. Numerically simulated X-ray diffraction spectra were compared with experimental data. The crystallographic structure of Pd/V superlattices after implantation has been studied as a function of the ion dose using the θ-2θ X-ray diffraction technique.

Modification of chemical properties by ion beam mixing techniques

Important chemical surface properties which may be modified by ion beam techniques are the resistance against oxidation and corrosion and the catalytic activity. Many studies using ion implantation showed in the past its potential for improving and understanding chemical reactions at the surface of materials. However, in most cases the surface concentration of implanted atoms was not high enough to obtain the desired effects and to maintain them for a longer period of time, respectively. Ion beam mixing and especially ion beam assisted deposition (IBAD) improve this situation greatly. With both techniques impurity concentrations up to 100 atom% can be introduced in the surface region of any material. With IBAD well adhering surface layers consisting of elements or compounds up to 10 μm thick may be produced. In this contribution ion beam mixing techniques are reviewed, and recent results of chemically oriented studies are presented. The examples will deal with heterogeneous catalysis in the liquid phase, protection against aqueous corrosion and high temperature oxidation. Metals and ceramic substrates will find consideration.

Pulsed-laser-induced and ion-beam-induced surface synthesis and modification of oxides, nitrides and carbides

New routes of pulsed-laser-induced and ion-beam-induced surface synthesis and modification of oxides, nitrides and carbides are discussed. Specifically, the processes of pulsed-laser-induced reactive quenching at liquid-solid interfaces and pulsed laser evaporation for compound film formation are discussed at length. In the context of ion beam applications, interesting examples of the use of ion implantation and ion beam mixing techniques are presented.

Effects of ion-beam mixing on the performance and reliability of devices with self-aligned silicide structure

The uniformity of Ti silicide resistance has been greatly improved by using an ion-beam mixing technique. The integrity of both MOS capacitors and p-n junction diodes has been improved. N-channel MOS field-effect transistors fabricated with this technique show better electrical characteristics, less electron trapping in the gate oxide, and better hot-carrier resistance than with devices made without the use of ion-beam mixing. >

Ion beam mixing: A new method in the study of metastable superconductors

A newly developed ion beam mixing technique was applied to the study of the superconductivity of AlSi alloys. The highest superconducting transition temperature T c is 7.53 K for Al-40 vol. % Si. The dose dependences of T c , Δ T c and R 0 reflect the mixing process and suggest that disorder might be the reason for T c enhancement.

Amorphization of Fe-Zr and Co-Zr by ion beam mixing and other techniques

By ion beam mixing, investigations of the amorphization of Fe100−x Zrχ and C100−χ Zrχ thin films with 5 < χ < 80 have been carried out at temperatures down to 25 K. Transmission-electron microscopy was used to characterize the films. The results are compared with data obtained by the corresponding techniques of melt-spinning, vapour deposition and solid-state reaction. In the light of this comparison, various ion beam mixing amorphization mechanisms are discussed.

Ion induced metastable phases

We have investigated the formation of crystalline, metastable phases in metallic alloy systems by use of ion beam mixing techniques. Equilibrium phases with two atoms/cell such as CsCl structures or solid solutions can be formed as well as metastable amorphous alloys. Al-based alloys Al/Pd, Al/Fe and Al/Zr represent examples of systems which exhibit different behavior under irradiation. Extended solid solutions and CsCl structures are formed in Pd/Al. Both Al/Fe and Al/Zr at compositions of 80 at.% Al form amorphous alloys under room temperature irradiation and transform to metastable structures under elevated temperature ion irradiation or thermal annealing. Al 80 Fe 20 transforms to the quasicrystalline icosahedral phase and Al 80 Zr 20 to an ordered cubic. Both systems transform to the stable phase Al 3 M when annealed at 400°C. Further, irradiation of multilayer structures at 200°C results in a direct transformation to the metastable phase.

Ion beam mixing of Au–Ge and Au–Ge–Ni deposited on GaAs

We have investigated the feasibility of applying ion beam mixing techniques to the fabrication of Ohmic contacts in GaAs. The approach has been to deposit alternating layers of Au, Ge and Au, Ge, Ni with e-beam evaporation on GaAs and then to irradiate these layers with energetic Si+ ions. Mixing has been studied by employing Rutherford backscattering, Auger electron spectroscopy, and cross-sectional transmission electron microscopy (X-TEM). Differing amounts of mixing have been achieved for Au–Ge layers by using 125 keV Si+ at doses in the range of 1×1015 to 1×1016 cm−2. The kinetics of mixing is greatly reduced in the case of Au–Ge–Ni layers. Ni layers in between Au–Ge layers seem to act as inhibitors for ion beam mixing. It has been observed by X-TEM that a band of dislocation loops is produced in GaAs at a depth of about 600 Å from the interface although computer simulation of range and damage indicate shorter penetration distances. Even at an incident ion energy low enough so that no direct penetration across the interface takes place, dislocation loops are found to be present. Contacts in the presence of a damaged region at the interface showed non-Ohmic behavior. However, selected Au–Ge contacts fabricated with low energy and low dose irradiation showed Ohmic behavior with resistivity ∼10−4 Ω cm2 after annealing at 340 °C for 5 min. Ion beam mixed metallizations showed remarkable improvement in surface morphology after annealing compared to conventionally alloyed contacts.

Metal-oxide-semiconductor field-effect transistors fabricated using self-aligned silicide technology

N- and p-channel metal-oxide-semiconductor field-effect transistors have been fabricated with self-aligned WSi2 source, WSi2 drain, and WSi2/polycrystalline-silicon gate. Ion beam mixing and rapid thermal annealing techniques were employed to form smooth WSi2 films selectively on the device area and to simultaneously form shallow source and drain p-n junctions. Good electrical characteristics were obtained for both n- and p-channel devices, which have a gate length of 1.5 μm.

Thick amorphous hums of Ni base alloys using high energy (MeV) ion beam mixing

This work investigates the potential for applying ion beam mixing techniques to the fabrication of amorphous metallic alloy coatings of MoNi and TiNi on metal substrates to improve their corrosion resistant properties. Alternating layers of 100 Å Mo and 70 Å Ni with total thicknesses of 1450 Å and 2900 Å were prepared by e-beam evaporation on Ni substrates. Similarly, 80 A Ti and 50 Å Ni alternate layers with total thicknesses of 900 Å and 1560 Å were deposited on Ni. A batch of alternating films of total thickness 5200 Å of TiNi with individual thicknesses of 160 Å Ti and 100 Å Ni were also prepared on Ni substrates. The thicknesses of individual films were adjusted in this way to obtain an overall composition of Ni 50Mo 50 and Ni 50Ti 50 after mixing. The films were irradiated with 1 and 2 MeV Au + and 1.5 MeV Ni + ions depending on the total thickness. The ion beam mixing and nucrostructure of these films have been studied as a function of dose using RBS and TEM. Amorphous layers have been tested for their corrosion behavior by potentiodynamic polarization techniques. Measurements carried out in nitric acid solution reveal that both NiMo and NiTi amorphous layers are more resistant to corrosive attack than the polycrystalline multiphased alloys. NiTi exhibited much superior corrosion resistant properties than NiMo.

Untersuchungen zur Ionenstrahl-induzierten Mischung des AgCu-Systems

Supersaturated metastable AgCu solid solutions were obtained by ion beam mixing of thinly deposited silver and copper layers of compositions Ag 90Cu 10, Ag 75Cu 25, Ag 60Cu 40, Ag 40Cu 60, Ag 20Cu 80 and Ag 10Cu 90. Multilayered systems of thinly deposited AgCu films of various compositions were bombarded with energetic xenon and argon ions at room temperature and at 300 °C. The alloys were studied using high voltage electron microscopy and selected area diffraction. By using ion beam mixing techniques, a continuous series of metastable solid solutions of AgCu (α' and β') was almost obtained. The lattice parameters of the ion-beam-induced alloys with 10–75 at.% Ag showed a slight positive deviation (up to 1%) with composition from Vegard's law for ideal solid solutions. The lattice parameters of alloys with 40–60 at.% Ag showed a larger deviation (up to 2.7%) with composition from Vegard's law. A pronounced increase in grain size was observed as a result of ion beam mixing. The stability of these metastable solid solutions of AgCu was investigated by annealing at temperatures up to 600 °C. Decomposition of the alloys occurred at temperatures of 50–100, 175–200 and 250–300 °C in three stages. The implantation of noble gas ions at temperatures above 300 °C leads to a eutectic mixture.

Chemical profiling and structural studies of ion-beam-mixed aluminum on silicon

The ion beam mixing technique has been applied to the production of AlSi thin alloy layers as an alternative method to thermal annealing. Both unimplanted deposited aluminum thin films on silicon substrates and films implanted with energetic xenon ions were studied by Rutherford backscattering, channeling, secondary ion mass spectroscopy, nuclear resonance profiling and scanning electron microscopy techniques. The results of these experiments indicate that (i) iintermixing between aluminum and silicon became observable when the implantation dose of energetic xenon through the interface surpassed 2 × 1016 ions cm−2; (ii) intermixing is dependent on the dose but not on the dose rate of implantation; (iii) damage to the silicon substrate extended only to the region penetrated by implanted ions; (iv) the AlSi alloy layer region is uniform in texture and no segregation can be observed. Moreover, the integrity of the alloy layer is retained for a long period of room temperature annealing.

Reduction in the thermal reaction barrier for the formation of MnBi thin films by ion-beam mixing technique

The ion-beam mixing technique involving bombardment by energetic ions such as Ar + or N 2 + followed by a low-temperature (200°C) treatment has been employed for the first time to synthesize ferromagnetic MnBi films. The formation and growth of MnBi films has been investigated as a function of ion dose and subsequent thermal treatment by observing the variation of electrical resistance with temperature and the X-ray diffraction patterns. The ion-beam-induced mixing is also confirmed by Auger depth profiling. Unlike in conventional thermal diffusion wherein not only high temperatures for synthesis of MnBi films are required, but also the formation of MnBi film at the interface is sensitively dependent on the sequence of deposition, the ion-beam mixing is very rapid and can be carried out at low temperatures. Further, it is independent of the sequence in which Mn and Bi films are deposited. The MnBi films formed using the ion-beam mixing technique are very much less sensitive to oxidation as compared to the films formed by thermal diffusion. The distinct advantages of the ion-beam mixing technique over the conventional thermal diffusion method for the formation of MnBi films used in magneto-optical memory devices are discussed.

Electrochemical and A.E.S. studies of FeCr surface alloys formed on AISI 52100 steel by ion beam mixing

FeCr surface alloys have been formed on AISI 52100 steel by ion beam mixing in order to improve localized corrosion resistance. Three implant species were considered in this work, namely: Cr +, Xe 2+ and Kr 2+. Ion implanation was carried out on Cr surface layers, of 30 and 50 nm, deposited onto 52100 steel coupons. The resulting surface alloys were chemically characterized by Auger electron spectroscopy. Electrochemical pitting studies were carried out in deaerated 0.01 M NaCl solution buffered to pH 6. Each of the surface alloys formed by the ion beam mixing technique exhibited a significantly higher resistance to localized corrosion compared to 52100 steel. The possbile influence on the localized corrosion resistance of the surface alloys of oxidation, carbide formation and sputtering, resulting from the ion implantation treatments, is discussed.

High Energy Ion Beam Mixing in Al2 O3

ABSTRACTThe ion beam mixing technique has been employed to mix metal atoms into the surface layers of Al2O3. Ion beams of Fe+ and Zr+ in the 1 to 4 MeV energy range were used to irradiate Al2O3 specimens on the surfaces of which films of chromium or zirconium had been evaporated. Some specimens were irradiated at elevated temperatures of 873 or 1173 K. Rutherford backscattering (RBS) and channeling methods were used to measure the metal atom depth profiles near the surface. Analyses of the backscattering data included binary collision calculations using the codes TRIM and MARLOWE. The significance and limitations of high energy (&gt;1 MeV) beams for ion beam mixing experiments is discussed. Evidence was found for radiation enhanced diffusion and/or solubility of zirconium and chromium in Al2O3 at 873 K.

Dynamic Recoil Mixing for the Production of Silicon Nitride Films

ABSTRACTIn Dynamic Recoil Mixing (DRM) a film of constant thickness is sputtered on to a substrate by using a broad low energy (lkeV) ion beam and is subsequently bombarded by a high energy (10 key) ion beam. During the bombardment process a dynamic balance is maintained between the backsputtering and the deposition of the film, thus providing an ‘unlimited’ source of the dopant material. In this way very high surface dopant concentrations may be achieved which otherwise cannot be reached by more conventional ion beam mixing techniques. Furthermore, by choosing reactive ion species, films of novel chemical compositions may be produced. This technique has been employed to produce silicon nitride films on polished commercial mild steel samples. Measurements of knoop hardness of these films indicate an increase of over 200% whilst the wear and friction properties have shown considerable improvement. Conventionally sputtered silicon films of similar thickness, recoil mixed silicon using argon, or implantation of 10 keV argon and nitrogen to similar doses, indicate only a modest change in tribological characteristic compared to the reactive mixed films.

Chemical Profiling and Structural Studies of Ionbeam-Mixed Aluminum on Silicon

The ion beam mixing technique has been applied to the production of Al–Si thin alloy layers as an alternative method to thermal annealing. Both unimplanted deposited aluminum thin films on silicon substrates and films implanted with energetic xenon ions were studied by Rutherford backscattering, channeling, secondary ion mass spectroscopy, nuclear resonance profiling and scanning electron microscopy techniques. The results of these experiments indicate that (i) intermixing between aluminum and silicon became observable when the implantation dose of energetic xenon through the interface surpassed 2 × 1016 ions cm−2; (ii) intermixing is dependent on the dose but not on the dose rate of implantation; (iii) damage to the silicon substrate extended only to the region penetrated by implanted ions; (iv) the Al-Si alloy layer region is uniform in texture and no segregation can be observed. Moreover, the integrity of the alloy layer is retained for a long period of room temperature annealing.