We report the enhancement of grain growth in 50 nm-thick Ge films during Ge ion bombardment, or self-implantation, at 500-600 ° C. Conventional and cross-sectional transmission electron microscopy (TEM) indicate that normal grains grow to a columnar structure at considerably lower temperatures than during ordinary thermal annealing. Furthermore, self-implantation-enhanced normal grain growth is found to be very weakly dependent on temperature. The time dependence and temperature dependence of grain growth during self-implantation were compared with data for thermal annealing experiments and suggest that the enhancement results from elastic collisions between ions and atoms located at the grain boundaries.

We demonstrate that non-normal incidence ion bombardment applied during thin film growth has a pronounced alignment effect on crystallographic orientation. Restricted fiber texture is achieved in Nb films deposited at room temperature onto amorphous silica substrates with simultaneous 200 eV Ar+ ion bombardment at 20 degrees from glancing angle. Xray pole figure measurements and transmission electron diffraction show that the alignment direction is a channeling direction for the incident ions between (110) planes. The degree of alignment increases linearly with the fraction resputtered by the ion beam. Recommendations are given for optimizing this ion beam orientation effect.

The amorphous(a)-to-crystalline (c) phase transition has been studied in electron(e-) and/or ion irradiated silicon (Si). The irradiations were performed in i n the Argonne High Voltage Microscope-Tandem Facility The irradia ion of Si, at <10 K, with 1-MeV e- to a fluence of 14 dpa failed to induce the c-to-a transition. Whereas an irradiation, at <10 K, with 1.0 or 1.5-MeV Kr+ ions induced the c-to-a transition by a fluence of ≈0.37 dpa. Alternatively a dual irradiation, at 10 K, with 1.0-MeV e and 1.0 or 1.5-MeV Kr+ to a Kr+ fluence of 1.5 dpa -- where the ratio of the displacement rates for e- to ions was ≈0.5--resulted in the Si specimen retaining a degree of crystallinity. These results are discussed in terms of the degree of dispersion of point defects in the primary state of radiation damage and the mobilities of point defects.

The solid phase epitaxial regrowth of silicon implanted with a group V dopant, such as antimony, results in excellent incorporation of the dopant atoms into silicon lattice sites. However, annealing at higher temperatures or longer times results in transient dopant precipitation with a diffusion coefficient up to five orders of magnitude above that of tracer diffusion and with a reduced activation energy.

This precipitation is accompanied by the nucleation of dislocation loops that are interstitial in nature, and the transient ceases as the dislocation loops develop. It is believed that Si interstitials are trapped in a stable defect complex during the implantation process.

Although they survive SPE these complexes dissolve at higher temperatures and release a large supply of interstitials which serve to promote dopant migration via an interstitialcy mechanism until they condense to form the observed dislocation loops. By following the Sb implantation with an implantation of B to an equivalent concentration profile the loop formation is efficiently suppressed. For higher B concentrations the Sb precipitation is no longer observed. Results for As implantation are similar to Sb except that As precipitates can not be directly observed. Calculations of the dopant and interstitial concentration depth distributions were also performed.

We have studied the native oxide of silicon (110) and the changes roduced by MeV ion bombardment using transmission ion channeling of 5.9 MeV 9Be, and Elastic Recoil Detection Analysis (ERDA). Transmission channeling was used to measure interfacial nonregistered Si and adsorbed C and 0. ERDA was used to measure the surface concentration of H. MeV ions were found to cause an increase in the interfacial nonregistered silicon which saturates at approximately one monolayer. Rapid desorption of hydrogen was observed. The effect of 2 keV electrons on the silicon native oxide was also studied by Auger Electron Spectroscopy.

Ion beam deposition (IBD), the process whereby magnetically analyzed ions are directly deposited on single crystal substrates, has been studied for 74Ge and 30Si ions on Si(100) and Ge(100). The effects of sputtercleaning prior to deposition and substrate temperature during deposition were investigated. Three analytical techniques were systematically used to obtain information on the deposited films: (1) Rutherford backscattering combined with ion channeling, (2) cross-section TEM, and (3) Seeman-Bohlin X-ray diffraction. In the energy range explored (40–200 eV), the width of the interface between the IBD film and the substrate was found to be always less than 1 nm. Each IBD layer was highly uniform in thickness and composition for deposition temperatures from 300 K to 900 K. Without prior sputter-cleaning and annealing of the Si(100) and Ge(100) substrates, no epitaxy was observed. UHV conditions were found to be a requirement in order to grow crystalline Si films presenting bulk-like density. This was not the case for Ge films which showed bulk-like density for IBD at higher pressures. Results on the first Si/Ge superstructure grown by IBD are also shown.

A model is formulated to predict the width of an amorphous layer in Si produced by ion implantation. The dependency of the amorphous Si layer width on the ion implantation energy, dose, and temperature is computed.

We have investigated the damage which results from silicon self-implantation for the range of doses from 2E14 to 1E16 cm−2 for temperatures from 82 to 296 K for 150 and 300 keV implants. Cross-sectional TEM was used to evaluate the nature of the amorphous layer. The experimental results were correlated with computer calculated damage distributions using a Monte Carlo simulation program. The depth of amorphous-crystalline interface(s) was evaluated as a function of dose and temperature. An experimental damage energy density curve was constructed. Using the curve, a critical energy density for amorphization, Ec was calculated for the samples implanted at different temperatures. The energy was found to depend on depth and implant energy, and it increased with temperature. A study of a-c interface morphology shows no dependance on temperature within the range considered. Kinetics of dynamic annealing are discussed in conjunction with the above findings.

Diffusion, crystallization and phase separation processes in indium implanted amorphous silicon are examined for low temperature annealing (600°C). Both diffusion and crystallization are shown to be extremely sensitive to the indium concentration. Diffusion coefficients more than 10 orders of magnitude higher than tracer diffusion coefficients in crystalline silicon are measured, and amorphous to crystalline silicon transitions at temperatures as low as 350°C are reported. Phase separation is also observed.

Individual, as well as multiple doses of 27Al+, 31p+, 28Si+, and 28Si+ plus 12C+ were implanted into (100) oriented monocrystallne β-SiC films+. A critical energy of =16 eV/atom required for the amorphization of β-SiC via implantation of Al and P was determined using the TRIM84 computer program for calculation of damage-energy profiles coupled with results of RBS/ion channeling analyses. In order to recrystallize amorphized layers created by the individual implantation of all four ion species, thermal annealing at 1600, 1700, or 1800°C was employed. Characterization of the recrystallized layers was performed using XTEM. Examples of SPE regrown layers containing; 1) precipitates and dislocation loops, 2) highly faulted, microtwinned regions, and 3) random crystallites were observed.

In Ion Beam Mixing new surface alloys are produced by a combination of vacuum deposition and ion irradiation. One may wonder what the advantages are of this combination. Indeed one may ask:

- Why not just ion implantation?

- Why ion beams instead of laser or electron beams?

- Why ion mixing instead of evaporation only?

- What phases are formed and what is the stability of ion mixed phases?

In an attempt to answer these questions the role of ion beam mixing in modern materials modification will de delineated. Areas of controversy and further development will also be illustrated.

Surface layers of the icosahedral phase of Al(Mn) have been formed from thin, alternating Al/Mn layers deposited on Al or Fe surfaces by rapid electron-beam or laser melting, by ion beam mixing, and by solid-state diffusion. The electron beam and laser treatments are similar to other liquid quenching techniques used previously to form the phase, but have well defined temperature histories which allow us to place limits on the melting point of the icosahedral phase, the time needed for its nucleation from the melt, and its growth velocity. Ion beam mixing is a way of forming the icosahedral phase which is quite different from melt quenching; the phase is formed during ion beam mixing at temperatures of 100–200°C. For mixing at ≤60C an amorphous phase with icosahedral short-range order is formed; this phase can be converted to the icosahedral phase by subsequent annealing. Formation of the icosahedral phase by reacting the as-deposited layers in the solid state is a new technique not previously reported. The results presented here place new restrictions on proposed structural and thermodynamic models for the icosahedral phase.

Multilayered Al84Mn16 films ion irradiated with Xe at room temperature transform into an amorphous phase. Subsequent Xe ion irradiation at 150C transforms the amorphous to the quasicrystalline phase. The quasicrystalline structure may be formed in the composition range of 91 atomic % Al to 80 atomic % Al.

The effect of ion beam mixing of nickel-aluminum alloys with 500 keV krypton ions has been investigated over a range of temperature, composition, ion dose, and post-irradiation thermal treatments. Samples were formed by aternate evaporation of layers of aluminum and nickel. A portion of these samples was subsequently annealed to form intermetallic compunds. Irradiations were performed at both room temperature and 80 K using the 2 MV ion accelerator at Argonne National Laboratory. Phase transformations were observed during both in situ irradiations in the High Voltage Electron Microscope(HVEM) at Argonne and also in subsequent analysis of an array of irradiated samples. Electron diffraction indicates the presence of metastable crystalline structures not present in the conventional nickel-aluminum phase diagram. Transformations occur at doses as low as 5×1014 cm−2 and continue to develop as the irradiation progresses up to 2×l016 cm−2. Layer mixing is followed through Rutherford Backscattering analysis. Samples are also checked with x-rays and Electron Energy Loss Spectroscopy (EELS). A thermodynamic argument is presented to explain the phase transformations in terms of movements on a free energy diagram. This analysis explains the interesting paradox concerning the radiation hardness of the NiAl[l] phase and the amorphous structure of mixed Ni-50% Al layers[2].

We report preliminary results of a study on silicide formation by means of high dose transition metal implants into Si (100) single crystals.

100 keV Cr+, Fe+, Co+ and Ni+ were implanted at room temperature. For the Cr+, Fe+ and Ni+ implants, no silicide formation was observed after implantation. However, both Rutherford Backscattering Spectrometry (RBS) and X-Ray Diffraction (XRD) results clearly indicated the existence of CrSi2 after the Cr-Si samples were annealed 4 hours at 550°C. In the case of the Fe+ and Ni+ implants, FeSi2 and NiSi2 were identified by XRD after annealing the implanted samples half an hour at 400°C. A layer of CoSi of about 1000 Å was observed in the as implanted Co-Si samples by both RBS and XRD.

Ni+ ions accelerated to 150 keV were implanted at 350°C. A much broader distribution and higher retention of Ni was obtained in this case, showing evidence of long range atomic diffusion. NiSi and polycrystalline silicon were observed by XRD in the as implanted samples.

The possibility of high dose ion implantation as a suitable technique for producing transition metal silicides is discussed.

Pulsed laser annealing and ion beam mixing have been used as surface modification techniques to enhance the physical properties of polycrystalline α-SiC. Thin Ni overlayers (20 nm - 100 nm) were evaporated onto the SiC surface. The specimens were subsequently irradiated with pulses of a ruby or krypton fluoride (KrF) excimer laser or bombarded with high energy Xe+ or Si+ ions. Both processes are non-equilibrium methods and each has been shown to induce unique microstructural changes at the SiC surface which are not attainable by conventional thermal treatments. Under particular (and optimum) processing conditions, these changes considerably increased the mechanical properties of the SiC; following laser irradiation, the fracture strength of the SiC was increased by as much as 50%, but after ion beam mixing, no strength increase was observed.

High resolution cross-section transmission electron microscopy (X-TEM), scanning electron microscopy (SEM), and Rutherford backscattering techniques were used to characterize the extent of mixing between the Ni and the SiC as a result of the surface modification.

Nickel single crystals implanted with La, 0 and La + 0, up to about 9 a/o concentrations were irradiated with spatially homogenised ruby laser pulses (16 ns FWHM) up to 3.7 J/cm2 in vacuum (s~ 10−2 Torr). Phase changes, defect structure and solute migration were studied before and after laser melt quenching using RBS/channeling, TEM and SEM techniques.

Both La and La + 0 implants produced a buried amorphous layer on top of a polycrystalline layer above the single crystal matrix. 0 implants did not produce an amorphous phase, but a buried layer containing polycrystalline Ni, metastable hcp Ni particles and a dense dislocation network was formed. Pulsed laser melt quenching of these implanted metastable phases lead to a variety of new phases - all crystalline.

The characteristics of A112Mo formed in aluminum annealed after implantation with selected maximum molybdenum concentrations were examined by analytical electron microscopy techniques. The A112MO was isolated as the only precipitate in the microstructure for maximum as-implanted molybdenum concentrations up to 11 atomic percent. The morphology of the A112MO can be selected by choosing the maximum as-implanted molybdenum level over the same concentration range. A predominantly lamellar A112MO precipitate structure formed when aluminum was annealed at 550°C after implantation with maximum molybdenum concentrations in the range of 3.3 - 4.4 at.%. The orientation of the body centered cubic (bcc) A112Mo precipitate with respect to the face centered cubic (fcc) matrix can be expressed as (123)p || (002)m and [301]p || [310]m. An explanation for the experimentally observed orientation relationship was developed based on the characteristic relationships between the bcc A112MO precipitate and the fcc matrix. A continuous film of A112MO formed in the surface modified region when aluminum was annealed after implantation with maximum molybdenum concentrations in the approximate range of 8-11 at.%. The microstructure of the A112Mo film was found to depend on the annealing temperature. A granular film formed after annealing at 550°C whereas a mottled film formed after annealing at 400°C. Sequential annealing experiments revealed that the mottled film transforms to a granular film which indicates the mottled film is metastable.

A kinetic model has been developed to investigate the synergistic effects of radiation-enhanced diffusion, radiation-induced segregation and preferential sputtering on the spatial redistribution of implanted solutes during implantation at elevated temperatures. Sample calculations were performed for Al+ and Si+ ions implanted into Ni. With the present model, the influence of various implantation parameters on the evolution of implant concentration profiles could be examined in detail.

The microstructure of Fe implanted with up to 50 at.% C was found to consist of hexagonal iron carbide precipitates oriented with respect to the Fe matrix. For higher C concentrations, an amorphous phase forms. This concentration dependence is explained in terms of the lattice structure of the iron carbide. In Ti-implanted Fe, substitutional Ti was found in the bcc Fe lattice for concentrations ≤ 15 at.% Ti. The work of others suggests that amorphous phases form for ≥ 33 at.% Ti. These results are discussed in terms of concentration boundaries of the ternary Fe(Ti,C) amorphous phase.

Ion beam alloying methods are currently being used to form metastable alloys [1], both for fundamental investigations of such alloys as well as for potential use to improve physical properties of components [2]. An important consideration in metal alloys is what phase will form upon implantation; one aspect of this question is to determine when amorphous phases will form. Rules are currently being advanced to predict alloy systems which will yield amorphous phases. By using ion irradiation and ion beam mixing as well as ion implantation, such rules can be evaluated over entire composition ranges.

To gain insight into amorphous phase formation, we have studied Fe alloys implanted with C, Ti and Ti + C. The Fe(C) alloys exhibit compound precipitation and amorphous phase formation; the precipitation and the concentrations at which the amorphous phase appears can be accounted for by considerations of the structure of the hexagonal carbide which forms. Based on conventional uses of the Fe(C) system, such alloys may be useful for improving mechanical properties by implanting C into ferrous components. Iron implanted with Ti is examined to a limited extent here, but by including ion irradiation studies by others [3], a more complete characterization of Fe(Ti) alloys is obtained. The microstructures of Fe(C) and Fe(Ti) are examined along with the known composition limits of amorphous Fe(Ti,C) alloys, which are important for their improved mechanical properties [2]. Taken together, a more complete determination of amorphous phase formation in this ternary system is obtained.