A single-grid UHV-compatible ion source was used to provide partially-ionized accelerated In+ dopant beams during Si growth by molecular beam epitaxy (MBE). Indium incorporation probabilities in 800 °C MBE Si(100). as measured by secondary ion mass spectrometry, ranged from < 10−5 (the detection limit) for thermal In to values of 0.02–0.7 for In+ acceleration energies EIn, between 50 and 400 eV. Temperature-dependent Hall-effect and resistivity measurements were carried out on Si films grown at 800 °C with EIn = 200 eV. Indium was incorporated substitutionally in electrically active sites over the entire concentration range examined. 1016— 1019 cm−3, with an acceptor level ionization energy of 165 meV. The 111 meV level associated with In-C complexes and the 18 meV “supershallow” level reported for In ion-implanted Si were not observed. Roomtemperature hole mobilities μ were higher than both annealed In-ion-implanted Si and Irvin's values for bulk Si. Phonon scattering was found to dominate at temperatures between 100 and 330 K and μ varied as T−22.

Ion implantation damage and thermal annealing results are presented for single crystals of SrTiO3 and CaTiO3. The near-surface region of both of these materials can be made amorphous by low doses (∼1015/cm2 ) of heavy ions (Pb at 540 keV). During annealing, the amorphous implanted region crystallizes epitaxially on the underlying single-crystal substrate. The kinetics of this solid-phase epitaxial recrystallization process have been measured by employing ion channeling techniques.

Rutherford backscattering in the channeling alignment was used to characterize the damage produced in rutile TiO2 by oxygen ion implantation at energies of 200 and 400 keV. Backscattering g{om the dajnaged layer increases sublinearly with ion dose above 4×1015 ions/cm2. Complete amorphization was not achieved even for much higher doses and implant temperatures well below room temperature, and remnants of the original crystal lattice remain in the damaged layer. Substantial defect annealing occurs at 450 C, and essentially complete lattice recovery is observed at 750 C when the annealing takes place in a reducing environment. In an oxidizing ambient, higher annealing temperatures are required to achieve the same degree of crystal regrowth, and dechanneling actually increases at lower annealing temperatures, apparently due to the coalescence of point defects into extended defects. The optical properties of the implanted layer were also probed by ellipsometry.

At temperatures far below the glass transition temperature metallic glasses undergo plastic deformation during irradiation with a beam of fast heavy ions at energies at which electronic stopping is the dominant deceleration mechanism. This plastic deformation causes irreversible anisotropic changes in sample dimensions. Various (Fe,Co,Ni)∼8O(B,Si)∼20 glasses and the crystalline alloys Ni80Cr20 and Fe70Cr25A15 are examin? 9 for their susceptibility to this effect by irradiation below 50 K with 129Xe ions at 2.8 MeV/u. The data suggest that the excess free volume of an amorphous material is an essential parameter for the magnitude of ion-beam-induced plastic deformation.

The implantation of Ge in Si has been found to considerably increase the steam oxidation rate of Si under certain conditions. This effect has been studied for a range of implanted ion energies and doses. During steam oxidation, implanted Ge is rejected from the growing oxide and forms a thin layer between SiO2 and Si. Segregated Ge is epitaxial with the underlying Si, and leads to enhanced oxidation of the underlying Si. Evidence suggests that the Ge alters the interfacial kinetics associated with oxide formation.

Results of preliminary investigations on varying the adhesion and growth behaviour of osteoblast-like cells on silicon are presented. Significant changes in growth behaviour are obtained by implanting oxygen or by growing a thermal oxide on the surface. The objective of the work is to modify tissue adhesion to materials used as prosthetic devices.

Implantation of reactive ions at the Cu-Al2O3 or Cu-SiO2 interface has been explored as a means of producing adhesion of thin copper films on these otherwise inert substrates. The process may promote complex chemical bonding at the interface due to the presence of a reactive implanted species; it may also enhance adhesion by interface layer mixing. Thin copper films (400–800Å) were deposited on fused quartz or sapphire substrates. After implantation and, in some cases, heat treatment thick Cu stripes were added to enable peel testing of adhesion strength. The reactive ion species implanted were oxygen (100 keV), or titanium (120 keV) or chromium (80 or 160 keV), to doses ranging from 1015 to 1017 ions/cm2. In each case, the energy was chosen to place the reactive implant at the interface region. For comparison with simple ion beam mixing, a similar set of samples was implanted with krypton ions at 2 MeV to doses of 1 or 3.6 × 1016 ion/cm2. The peel strength was found to be about 0.5 gm/mm for the unimplanted Cu-sapphire samples; 1.3 gm/mm for those implanted with oxygen; 18 gm/mm for those implanted with krypton; 90 gm/mm for those implanted with chromium; and more than 200 gm/mm for the titanium implanted samples. No significant increase in adhesion was achieved for the implanted Cu-quartz samples, except for the titanium implant, which gave an average peel strength of 66 gm/mm after anneal for the dose of 5 × 1016 Ti+/cm2. Studies of the interfaces and of the peeled surfaces were made, using RBS. Changes in both chemical bonding and interface morphology appear to contribute to the phenomena of enhanced adhesion.

We have previously reported the delay and reduction of the hydriding of uranium by implantation of oxygen. The reduced hydriding was attributed to the presence of the uranium oxide layer created near room temperature. In this paper we present results for the layers formed by implantation of 80 keV C+ to a dose of 8E17 C/cm2. The carbide layers formed were characterized by Auger electron spectroscopy, Rutherford backscattering, and glancing angle x-ray diffraction. Hydriding properties of both nonimplanted and implanted uranium were measured for 76 Torr hydrogen at 130°C. The implanted specimens had significantly longer incubation times for the start of the reaction after exposure to hydrogen and less area participating in the reaction.

The implantation temperature dependence of dopant solubility and electrical activity was investigated for Sn, Cd and Te ions in GaAs. Implantation doses of 5×1012 – 5×1015 cm−2 were performed in the temperature range from LN2 to 400°C, followed by rapid thermal annealing (950°C) or furnace annealing between 650°C and 850°C. Solubilities above 1020 cm−3 were obtained for all of the species, with a peak value of 2.5×1021 cm−3 for Te after 850°C furnace annealing. However essentially no correlation existed between dopant solubility and electrical activity or between electrical activity and the high density of defects remaining after many of the annealing cycles. This emphases the role of fine scale, point defect complexes in controlling the electrical activity of implanted dopants in GaAs.

Annealing behavior of point defects near room temperature is studied by measuring the strain relaxation of Si+ implanted GaAs. Polished semi-insulating GaAs wafers were implanted with 300keV Si+ at liquid nitrogen ( LN2 ) and room temperature (RT ). The strain profile was obtained by the X-ray Double Crystal Diffraction ( DCD) technique and kinematical fitting. The maximum strain of the samples stored at RT and elevated temperature 100°C in air, decreases with time, which indicates the reduction of point defects. Relaxation is exponential in time. At least two time constants of 0.24hrs and 24hrs are needed to fit the data, suggesting that two different processes are responsible for annealing defects. Time constants are obtained for different doses at RT and LN2 implantation temperature, and found to be insensitive to both these quantities. The activation energy for defect migration is estimated using simple diffusion model.

High energy Si implantation into GaAs is of interest for the fabrication of fully implanted monolithic microwave integrated circuits. 30Si has been implanted into LEC GaAs at energies of 1, 2, 4, and 6 MeV. We have measured atomic concentration profiles using SIMS and carrier concentration profiles using an electrolytic CV procedure. Theoretical atomic profiles have been calculated using TRIM-86. Excellent SIMS dynamic range and low background (<1014/cm3) was achieved for the profiles by the use of 30Si. The range statistics and profile shape factors: Rm, Rp, ΔRp, skewness (Y1), kurtosis (B2), and maximum Si density (Nmax) have been determined from the SIMS data by applying a Pearson IV computer fitting routine. The first two moments (Rp and ΔRp) were also obtained from the carrier profiles and the theoretical profiles. The range and standard deviation obtained from each profile have a maximum difference of only 15%, and the difference is usually less than 10%. This is less than the mutual experimental uncertainty of 17%. The samples were activated using a furnace anneal (800°C, 15 min) with a Si3N4 cap and using rapid thermal anneal (1000°C, 10s) with and without a Si3N4 cap. No redistribution of Si was observed for any of the anneal conditions within experimental error.

High resolution transmission electron microscopy techniques have been used to obtain information on the contrast, spatial distribution, size and annealing behaviour of the damaged regions produced within individual collision cascades by heavy ion (As, Sb and Bi) bombardment (10–120 KeV) of silicon with 1.0 × 1011 – 6.0 × 1011 ions cm−2. The fraction of the theoretical cascade volume occupied by a heavily damaged region steadily increased as the average deposited energy density within the cascade increased. At high energy densities, the visible damage produced in the main cascade consisted of a single, isolated damaged region. With decreasing values of (i.e. increasing ion implant energies), there was an increasing tendency for multiple damaged regions to be produced within the main cascade.

Ion-beam induced epitaxial crystallization of thin amorphous silicon layers at {100} and {110} crystalline/amorphous interfaces exhibits no orientation dependencies, whereas at a {111} crystalline/amorphous interface a weak orientation dependency relative to thermal-induced epitaxial crystallization is observed. This behavior supports an interpretation in which the thermal crystallization process is dominated by the need to form interfacial defects and/or growth sites and in the ion-beam experiment this formation process ocurrs athermally. It is thought that the observed orientation dependent regrowth on a {111} substrate relative to a {100} (or {110}) substrate is associated with the special correlated atomic sequencing which is believed to control solid-phase epitaxial crystallization at a {111) crystalline/amorphous interface.

Recent progress in the growth of thin epitaxial silicides on silicon has resulted in films of very high quality with especially smooth interfaces. Using a completely different technique, high dose implantation followed by annealing, we have succeeded in creating buried single-crystal layers of CoSi2, NiSi2, and CrSi2 in crystalline silicon. The CoSi2 and NiSi2 layers grow in both the (100) and (111) orientations--those in (111) have better crystallinity, but those in (100) are of higher electrical quality. The CrSi2, on the other hand, only grows in the (111) orientation where its hexagonal structure has an almost perfect lattice match to silicon. We call this new internal growth process “mesotaxy” by analogy with epitaxy which refers to single-crystal growth on surfaces.

We report preliminary results from an ongoing study of iron nitride grains formed in high purity iron under nitrogen ion bombardment. Under various implantation conditions, different iron nitride phases grow large enough to produce sharp x-ray diffraction lines. We have used these lines to examine the influence of target temperature during implantation. Between 200°C and 400°C increasing target temperature, which enhances dopant mobility, reduces the retained dose of nitrogen and restricts the formation of nitride phases. Over this temperature range, however, increasing vacancy mobility favors the growth of nitride grains and x-ray line breadth data suggests an optimum temperature for growth of Fe4N grains.

Experiments concerning the behavior of grain size in Co80Cr20 alloy thin films upon ion irradiation were conducted. The alloy films of 80 nm thick were prepared by magnetron sputtering on cleaved NaCl crystal substrates, and then irradiated by 300 keV argon or xenon ions to a wide range of doses. The irradiated samples, before and after annealing, were examined by transmission electron microscope (TEM). It was found that the initial grain size with the dimension of 20 nm remained unchanged when the dose was less than 1×1016Ar/cm2, but rapidly reduced to the scale of 5 nm at a dose of 5×1016Ar/cm2. It is thought that this is due to a polymorphic transformation of an HCP to a BCC structure in the alloy films. After 30 min. anneals at 200° C, it was observed that the grain growth rate was a function of ion dose, and that there exists a critical fluence yielding a maximum grain growth rate. The possible mechanisms for the observations in this study are discussed.

We have examined the microstructure and the transport properties of nitrogen-implanted silicon-on-insulator wafers, as well as the performance of integrated-circuit transistors fabricated in this material. The insulating regions were fabricated in silicon by the unpatterned implantation of 4×1017 /cm2, 300 keV nitrogen dimers followed by annealing at 1473 K for 5 hours. For these parameters, the buried nitrogen-implanted layer crystallized into α-silicon nitride, and contains ≈20% excess silicon in the form of silicon inclusions of 5–15 nm diameter. The surface silicon layers are characterized by low-mobility, p-type conduction. The buried dielectric has a resistivity of approximately 108 Ωcm. Functional p-channel, integrated circuit transistors have been fabricated in n-type epitaxial silicon grown over the buried-nitride wafers. These transistors devices are similar in performance to those fabricated in bulk silicon,(hole mobilities in inversion layers of 140 cm2/V-s), and demonstrate the suitability of the buried nitride process for integrated circuit applications.

High quality Silicon-On-Insulator, with a dislocation density lower than 105cm−2, has been formed by high temperature annealing of high-dose oxygen implanted silicon. In the as-implanted state, oxygen was found to form precipitates in the top silicon film. In the upper region these precipitates were found to order into a superlattice of simple cubic symmetry. Near the interface with the buried oxide film the precipitates are larger and no ordering occurs in that region. Contrary to implants without precipitate ordering where dislocations are observed across the entire layer thickness of the top silicon film, dislocations are now only found near the buried oxide. The precipitate ordering appears to prevent the dislocations to climb to the surface. High temperature annealing results in precipitate growth in this region whereas they dissolve elsewhere. These growing precipitates pin the dislocations and elimination of precipitates and dislocations occurs simultaneously, resulting in good quality SOI material.

High dose oxygen ion implantation into silicon is an established method to form buried insulating layers. The material produced by standard processing techniques typically exhibits buried layers which are a few hundred nanome ers thick with a threading dislocation defect density on the order of 108/cm2. Unusual structures can be obtained by using repetitive cycles of partial doses of ions followed by annealing and possibly epitaxial growth. Both low and high doses may be used, the former intended to provide decreased defect density and the latter to increase the thickness of the buried layer above the theoretical maximum for higher voltage isolation. The material properties resulting from several variations of this technique are described and characterized.

We have studied buried oxide formation as a function of implantation and annealing conditions. The layers appear to form via a nucleation and growth process, so the quality of the oxide and the perfection of the overlying crystalline Si layer depend more strongly on the substrate temperature during implantation than on the annealing temperature. Since it is easier to observe the layer formation process in a thin (<1000Å) layer, we concentrated on sub-stoichiometric doses and chose substrate temperatures below 400°C to stay in a homogeneous nucleation regime. Then we varied the annealing temperature from 1150°C to 1407°C. Modeling the coalescence of the oxide layer as a thermally-activated process yields activation energies of approximately 6 eV, suggesting that crystalline damage removal may be the bottleneck for this substrate temperature regime.