Gas cluster ion beam equipment (max. voltage 30kV) for sputtering has been developed. Cluster ion beams from gaseous materials such as Ar, O2, N2 and compound materials such as SF6, N2O, CO2 can be generated by expanding them through a Laval nozzle into a high-vacuum region. With this equipment sputtering process fundamentals have been studied. One of the unique characteristics of gas cluster ion bombardment is lateral sputtering. This is shown experimentally by measuring the angular distribution of sputtered atoms and is predicted by molecular dynamics simulation. Dependencies of sputtering yield (10-1000 times higher than for the monomer ion case) on cluster ion size and on ion beam energy for different substrate surfaces have been obtained. Examples of surface smoothing (typically less than 1 nm average roughness) on metals, semiconductors and insulators and of surface cleaning are presented.

Annealing experiments of deuterium implanted silicon have been performed while positron beam analysis was used for monitoring the cavity growth. The experiments indicate up to annealing temperature 500° C similar defect evolution for both the low dose of 1016 cm-2 as for a 3 times higher dose. At this temperature the deuterium stabilized vacancy clusters dissociate and only in the case of the high dose micro-cavities are formed. Monte Carlo simulations of vacancy cluster growth in silicon based on vacancy cluster dissociation energies, calculated with the Stillinger Weber potential, have been performed. The results indicate that for low initial defect concentrations vacancy clusters might be hindered to grow because the vacancy binding energy of the clusters does not increase monotonically with the cluster size. Only a high concentration guarantees that growth barriers will be overcome.

Radiation damage kinetics in synthetic MgTiO3 (geikielite) single crystals have been studied using the in situ ion beam facility at Los Alamos National Laboratory. The geikielite samples were irradiated at temperatures of 170, 300, and 470 K with 400 keV xenon ions and the radiation damage was sequentially measured with Rutherford backscattering using a 2 MeV He ion beam along a channeling direction. Threshold doses of 1 and 5×1015 Xe/cm2 were determined for the crystalline-to-amorphous transformation induced by Xe ion irradiation at 170 and 300 K, respectively. However, geikielite retained its crystallinity up to a dose of 2.5x1016 Xe/cm2 at the irradiation temperature of 470 K. This study has shown that MgTiO3, which has a corundum derivative structure, is another radiation resistant material that has the potential for use in radiation environments.

The enhanced diffusion of boron due to high dose arsenic implantation into silicon is studied as a function of arsenic dose. The behavior of both the type-V and end-of-range loops is investigated by transmission electron microscopy (TEM). The role of arsenic deactivation induced interstitials and type-V loops on enhanced diffusion is assessed. Reduction of the boron diffusivity is observed with increasing arsenic dose at three different temperatures. The possible explanations for this reduction are discussed.

Oriented single crystals of synthetic alpha-alumina (α-Α12O3), geikielite (MgTiO3), and natural ilmenite (FeTiO3) were irradiated with 200 keV argon ions under cryogenic conditions (100 K) to assess their damage response. Using Rutherford backscattering spectrometry combined with ion channeling techniques, it was found that ilmenite amorphized readily at doses below 5×1014, alumina amorphized at a dose of 1-2x1015, and geikielite was amorphized at -2x1015 Ar cm-2 . The radiation damage response of the ilmenite crystal may be complicated by the presence of hematite exsolution lamellae and the experimentally induced oxidation of iron. The relative radiation-resistance of geikielite holds promise for similar behavior in other Mg-Ti oxides.

The effects of cascade remnants on Freely Migrating Defects (FMD) were studied by measuring Radiation-Induced Segregation (RIS) in Cu-l%Au at 400°C during simultaneous irradiation with 1.5-MeV He and (400-800)-keV heavy ions (Ne, Ar or Cu). The large RIS observed during 1.5-MeV He-only irradiation was dramatically suppressed under simultaneous heavy ion irradiation. For Cu simultaneous irradiation, the suppression disappeared immediately after the Cu irradiation ceased, while for simultaneous inert gas (Ne or Ar) irradiation, the suppression persisted after the ion beam was turned off. These results demonstrate that the displacement cascades created by heavy ions introduce additional annihilation sites, which reduce the steady-state FMD concentrations. As the cascade remnants produced by Cu ions are thermally unstable at 400°C, the RIS suppression occurs only during simultaneous irradiation. On the other hand, the inert gas atoms which accumulate in the specimen apparently stabilize the cascade remnants, allowing the suppression to persist.

Samples of Fe78B13Si9 and Fe40Ni38Mo4B18 metallic glasses were irradiated with alpha particle beams (W=2.8 MeV) using radiation doses of 1016 and 1017 cm-2. Irradiation-induced effects on the magnetic texture and phase composition of alloy samples were studied by Mössbauer spectroscopy. Related morphological changes and resultant crystalline precipitates were characterized by scanning electron microscopy. The evolution of phases and microstructure during the radiation-induced amorphous-to-crystalline transformation was found to depend on the particle flux and sample composition. The lowest radiation dose employed was found to be more effective in inducing amorphous-to-crystalline transformations in both ferromagnetic alloys studied. In addition, the FeNi-based amorphous system investigated was found to be more stable than the Fe-based metallic glass, exposed to the same particle-beam irradiation conditions. By stimulating unconventional pathways for the crystallization process, the interaction of alpha particle beams with glassy ferromagnets offers unique opportunities to understand the fundamentals of nucleation and growth in amorphous magnets.

Amorphous (a-) Ge films were deposited on air-cleaved CaF2 (111) substrates at different deposition temperatures (Td). The films were irradiated with 0.9 MeV Ge or Si ions at low ion current intensity (1c) l00nA/cm2. Their structural changes were studied by Rutherford backscattering spectrometry (RBS) -channeling technique and thin film x-ray diffraction (XRD) measurement. It was found that the films were epitaxially crystallized by Ge and Si ion irradiation although they included randomly oriented grains. Ge ion irradiation was more effective for the crystallization than Si ion irradiation. However, the amount of the randomly oriented grains was slightly higher when using Ge ions. On the other hand, ion irradiation to the films prepared at high Td also exhibited higher incidence of randomly oriented grains.

Radiation effects of 2 MeV Ar+ ions on the crystallization of copper films were investigated with or without oxygen adsorption. Metal copper films of 1-5 nm thickness deposited on SrTiO3 (100) at 300K. by evaporation consisted of fine crystals with random orientation. The crystals were grown without epitaxial relationship to the substrate by ion irradiation. The epitaxial growth of copper crystals was achieved by the combined use of oxygen adsorption and ion irradiation. The epitaxial relationship between the film and the substrate was determined Cu (100) // SrTiO3( 100) and Cu [001] // SrTiO3 [001].

We have studied the ion bombardment induced amorphous-to-crystal transition in silicon using molecular dynamics techniques. The growth of small crystal seeds embedded in the amorphous phase has been monitored for several temperatures in order to get information on the effect of the thermal temperature increase introduced by the incoming ion. The role of ion-induced defects on the growth has been also studied.

Synthesis of metastable group-IV binary alloy semiconductor thin films on Si was achieved by the crystalline growth of Si1-xSnx layers using Sn ion implantation into Si(100) followed either by ion-beam-induced epitaxial crystallization (IBIEC) or solid phase epitaxial growth (SPEG). Si(100) wafers were implanted at room temperature with 110keV 120Sn ions to a dose of 1×1016 cm-2 (x=0.029 at peak concentration) and 2x1016 cm-2 (x=0.058 at peak concentration). By this process about 90nm-thick amorphous Si1-xSnx and about 30nm-thick deeper amorphous Si layers were formed. IBIEC experiments performed with 400keV Ar ions at 300–400°C have induced an epitaxial crystallization of the amorphous alloy layers up to the surface and lattice site occupation of Sn atoms for samples with the lower Sn concentration (LC). XRD analyses have revealed a partial strain compensation for the crystallized layer. Samples with the higher Sn concentration (HC) have shown an epitaxial crystallization accompanied by defects around the peak Sn concentration. SPEG experiments up to 750°C for LC samples have shown an epitaxial crystallization of the fully strained alloy layer, whereas those for HC samples up to 750°C have revealed a collapse of the epitaxial growth around the interface of the alloy layer and the Si substrate. Photoluminescence (PL) emission from both IBIEC-grown and SPEG-grown samples with the lower Sn concentration has shown similar peaks to those by ion-implanted and annealed Si samples with intense I1 or I1-related (Ar) peaks. Present results suggest that IBIEC has a feature for the non-thermal equilibrium fabrication of Si-Sn alloy semiconductors.

In this work, we report the formation of a new type of active or “smart” surface that is produced by ion implantation and thermal processing. By co-implanting vanadium and oxygen into a single-crystal sapphire substrate and annealing the system under appropriate conditions, it was possible to form buried precipitates of vanadium dioxide that were crystallographically oriented with respect to the host AI2O3 lattice. The implanted VO2 precipitate system undergoes a structural phase transition that is accompanied by large variations in the optical transmission which are comparable to those observed for thin films of VO2 deposited on sapphire. Co-implantation with oxygen was found to be necessary to ensure good optical switching behavior.

The initial nucleation stages of sp3 bonded amorphous diamond on silicon substrates have been investigated. The energy of the incident carbon ions/atoms is understood as a key parameter for the vapor phase formation of amorphous diamond like carbon coatings. SKION's solid state carbon ion source is used for this study. The ion source is UHV compatible and capable of producing a controlled energy ion beam in the energy range of 5-300 eV. In the initial stage of the deposition, carbon is found to be deposited as a silicon carbide up to a thickness of about 180Á at room temperature. Silicon is diffused to the surface and forms SiC. As the energy of the ion beam increases, the formation of silicon carbide becomes apparent. Further carbon ion bombardment then leads to the formation of an sp3 bonded amorphous diamond film. Post-annealing above 900°C leads to the formation of crystalline silicon resulting in a Si-rich SiC surface due to silicon out-diffusion.

Hard amorphous hydrogenated carbon films deposited by self-bias glow discharge were implanted at room temperature with 70 keV-nitrogen ions at fluences between 2.0 and 9.0×1016 N/cm2. The implanted samples were analyzed by Raman spectroscopy, SIMS and positron annihilation spectroscopy (Doppler broadening technique with the determination of the parameter S. For samples implanted with 2.0x1016 N/cm2 the S parameter follows the vacancies depth profile predicted by Monte Carlo simulation. For higher fluences we observed a reduction in the measured value of S. This result is discussed in terms of both hydrogen loss and structural modifications(increase of disorder at local scale and of the number of graphitic domains) induced in the carbon film by ion implantation.

Surfaces of highly oriented pyrolytic graphite implanted with gold were studied by both constant current STM. constant force, and tapping mode AFM. Gold colloids were observed by both constant current STM and tapping mode AFM. The surfaces can be modified by applying currents of +4 V and 1 nA. In addition, pyramidal and faceted structures were observed on sample surfaces suggesting the presence of diamond microcrystals.

The diffusion of aluminum in silicon carbide during high-temperature A1+ ion implantation was studied using secondary ion mass spectrometry (SIMS). Transmission electron microscopy (TEM) has been used to determine the microstructure of the implanted sample. A 6H-SiC wafer was implanted at a temperature of 1800 °C with 40 keV Al ions to a dose of 2 x 1016 cm-2. It was established that an Al step-like profile starts at the interface between the crystal region and the damaged layer. The radiation enhanced diffusion coefficient of Al at the interface was determined to be Di = 2.8 x 10-12 cm2/s, about two orders of magnitude higher than the thermally activated diffusion coefficient. The Si vacancy-rich near-surface layer formed by this implantation condition is believed to play a significant role in enhanced Al diffusion.

Implantation of Sn+ into a-Si1.xCx:H films deposited by RF magnetron sputtering of silicon and graphite was carried out in order to obtain optical contrast in the layers. The expected optical effect which is an absorption edge shift to the lower photon energies accompanied by a considerable increase of the absorption coefficient was observed even for the lowest dose - 1015cm-2. This effect is more pronounced with increase of the dose. Infrared (IR) and photoelectron spectroscopy (XPS) measurements was used to study the bond configurations of implanted films. These measurements reveal that ion implantation introduces an additional disorder in the films as well as leads to their chemical modification, which could be related to the changes of the optical properties.

Oxynitrides (SiOxNy) have been used as gate insulators for submicron devices [1]. The present work reports the oxynitride formation at SiO2/Si structure by N2+ implantation at low energies. Si substrates were implanted with N2+ ion beams (energy = 5.6 keV and dose =1×10 ions/cm2), annealed at 950°C for 30 min in N2 ambient, oxidized at 950°C in O2 + 1% TCE environment and annealed at 950°C for 30 min in N2. After these process steps, the oxynitride formation was investigated by FTIR, SIMS and ellipsometric analysis. These physical characterizations revealed the presence of Si-0 and Si-N bonds. The film thicknesses and refractive indexes were 7 nm and 1.62, respectively. The dielectric constant = 4.39 and effective charge density = 7xl010 cm–2 were determined by C-V, indicating that the SiOxNy films formed are suitable gate insulators for MOS devices.

Carbon nitride (CNX) films were prepared by nitrogen ion implantation into carbon films (a-C) deposited on Si substrates by the anodic vacuum arc. Plasma Immersion Ion Implantation (PIII) and Ion Beam (IB) implantation methods were used. X-ray Photoelectron Spectroscopy (XPS) C Is and N Is spectra of all CNX films indicate the formation of carbon-nitrogen bonds. The bonds are associated with the C 1s peaks at 286.6 eV and 285.6 eV , and the N 1s peaks at 399.1 eV and 400.6 eV. Raman spectra show that the structure of the implanted films (CNX) becomes more amorphous as the two broad peaks at 1577 cm-1 (G line) and 1350 cm-1 (D line) observed in the a-C films disappear and a broad asymmetric peak around 1500 cm-1 is formed. The interfacial tension between the a-C films and the substrate , obtained from the contact angle measurements, decreased by more than half after nitrogen implantation.

Ar ions with 1 keV energy was irradiated on aluminum nitride in an O2 environment to increase the bonding strength with Cu and also on alumina in an N2 environment to increase the bending strength. Cu(1000 Å) films were deposited by ion-beam sputter on Ar+ irradiated/unirradiated A1N surfaces and the change of the bond strength was investigated by a scratch test. For the study of chemical structural change on the Ar+ irradiated A1N surface, Cu(50Å) were deposited on an A1N substrate and XPS depth profile analysis was performed. Cu films deposited on Ar+ irradiated A1N under an O2 environment showed the bond strength of 30 Newton by a scratch test. On the basis of Cu3p, A12p near core levels and OI s, N1 s core level spectra, it was found that the improvement of bond strength of Cu films on the AlN surface resulted from the formation of intermediate layers such as copper oxide and aluminum oxynitride. The bending strength of polycrystalline alumina irradiated by Ar ions in an N2 environment was also increased.