New surface modification processes have been demonstrated using gas cluster ion irradiations because of their unique interaction between cluster ions and surface atoms. For example, high quality ITO films could be obtained by O2 cluster ion assisted deposition at room temperature. It is necessary to understand the role of cluster ion bombardment during film formation for the further developments of this technology. Variable Temperature Scanning Tunneling Microscope (VT-STM) in Ultra High Vacuum (UHV) allows us to study ion bombardment effects on surfaces and nucleation growth at various temperatures.

The irradiation effects between Ar cluster ion and Xe monomer ion were compared. When a Si(111) surface with Ge deposited to a few Å was annealed to 400°C, it was observed that many islands of Ge were formed. The surface with the Ge islands was irradiated by these ions. In the STM image of cluster-irradiated surface, large craters with diameter of about 100 Å were observed, while only small traces with diameter of about 20 Å were observed in monomer-irradiated surface. The number of Ge atoms displaced by one Ar cluster ion impact was much larger than that by one Xe ion impact. This result indicates that Ar cluster ion impacts can enhance the physical modification of Ge islands. When the sample irradiated with Ar cluster was annealed at 600°C, the hole remained, but the outer rim of the crater disappeared and the surface structure was reconstructed at the site of the rim. The depth of damage region in the target became shallower with decrease of the impact energy. These results indicate that low damage and useful surface modification can be realized using the cluster ion beam.

Focused Ion Beam (FIB) technology allows to process various materials within a lateral range below 100 nm. The feasibility to mechanically sputter as well as to direct-write nanostructures and the fact that Ga-ions are utilized is unique for this method. The focused Ga-ions are used to locally induce a chemical vapor deposition of volatile precursor molecules adsorbed on a surface. Local deposition of metals and dielectrics has been achieved on a sub-µm scale utilizing a focused ion beam. This method is highly suitable for advanced microelectronic semiconductor fabrication. However, material specifications are narrow for these tailor-made applications. The effect of the Ga-ions implanted into the material both during sputtering and deposition has been realized as a key parameter for the function of FIB processed microelectronic devices. For Si-based semiconductors Ga can be used as dopant intentionally implanted into a Si substrate to locally modify the conductivity of Si. The results of locally confined ion irradiation on the surface roughness of a Si surface have been exploited by atomic force microscopy (AFM). Both local sputter depletion of the sample surface as well as sub-µm deposition of selected metals or dielectrics by ion-induced chemical vapor deposition (CVD) has been examined. The penetration depth and the distribution of Ga ions during the deposition process have been studied by simulation and experimentally by profiling with secondary ion mass spectroscopy (SIMS). Transmission Electron Microscopy (TEM) of cross-sections of the ion processed materials has revealed amorphisation of the crystalline substrate. For focused ion beam assisted deposition the effects of ion irradiation on the interface to the substrate and the local efficiency of the deposition are illustrated and discussed. The prospects of focused ion beam processing for modification of microelectronic devices in the sub-µm range and the limitations are demonstrated by the examples shown.

The structural and magnetic properties of nano-sized particles of transition metals (Co and Ni) implanted into amorphous SiO2 are investigated. The SiO2 substrates used were as grown on a silicon (100) wafer under wet O2 atmosphere. The metals were implanted as singly charged atoms energized to 30 or 160 keV. Transmission Electron microscopy (TEM) observations and X-ray absorption spectroscopy (XAS) show that M+ implantation results in the formation of metallic nanoparticles at the vicinity of the surface whereas oxide particles (< 1 nm) are formed in a deeper region. After thermal treatment under hydrogen, TEM evidences the disappearance of the oxide region and an increase in the size of the metallic particle. XAS shows that cobalt and nickel are entirely in the metallic form and saturation magnetization becomes close to the theoretical value.

Erbium atoms were implanted into p-type Si (111) wafers at an extraction voltage of 60 kV to doses ranging from 5×1016 to 2×1017 cm−2 using a metal vapour vacuum arc (MEVVA) ion source. The implantation was performed with beam current densities from 3 to 26 µA/cm2 corresponding to substrate temperatures ranging from 85 to 245°C. The characterization of the as-implanted and annealed samples was performed using Rutherford backscattering spectrometry, atomic force microscopy and x-ray diffraction. To determine the sputtering yield, masked implantation experiments were performed so that the thickness of the sputtered layer at different substrate temperatures can be obtained directly by an α-step surface profiler. The results showed that ErSi2-xwas directly formed by MEVVA implantation when the substrate temperature was higher than about 160°C. The effects of the implant dose and the beam current density on the retained dose, the sputtering yield and the surface morphology of the implanted samples were also studied.

Crystallization of spatially isolated amorphous zones in Si, Ge, GaP, InP and GaAs was stimulated thermally and by irradiation with electrons and photons. The amorphous zones were created by a 50 keV Xe+ implantation. Significant thermal crystallization occurred at temperatures greater than 425 K, 375 K and 200 K in Si, Ge and GaAs, respectively. Electrons with energies between 25 and 300 keV stimulated crystallization in all materials at temperatures between 90 K and room temperature. For electron energies above the displacement threshold, the crystallization rate decreased as the electron energy decreased. As the electron energy was decreased below approximately 100 keV, the crystallization rate unexpectedly increased. The crystallization rate was independent of temperature for all electron irradiations. Irradiation with a 532 nm green laser (hv= 2.33 eV) caused crystallization in Si (Eg = 1.11 eV) and Ge (Eg = 0.67 eV) at a rate comparable to a thermal anneal at 425 K and 375 K, respectively, and caused minimal crystallization in GaP (Eg = 2.26 eV). The electron and photon irradiation results are consistent with the model that crystallization is controlled by defects (dangling bonds and kinks) created by electronic excitation at the amorphous-crystalline interface.

Diamond-based semiconductor devices offer the promise of operation at high temperatures and under extreme radiation conditions. An essential step in the drive towards operational diamond-based electronic devices is the ability to controllably and reproducibly dope the diamond. Ion implantation is the method of choice for such doping because it offers precise control of the dopant concentration and spatially selective doping is achievable using standard masking techniques. However, compared to silicon, the doping of diamond is complicated by the tendency of the diamond to relax to graphite upon thermal annealing. Furthermore, even if graphitization can be avoided, the compensation of dopants by residual defects has proved in the past to be a limiting factor in obtaining very high mobility material. In this paper, we present a scheme for the effective doping of diamond using MeV ion-implantation. For MeV ion- implantation the doped layer is deeply buried under a cap of undamaged diamond, and so the scheme includes a method using pulsed laser irradiation for making electrical contact to the buried layer. We show that a boron doped layer fabricated by the MeV implantation scheme has, after suitable annealing and removal of these compensating/trapping defects, very high mobility and low compensation ratio. In fact, its electrical properties are quite similar to those of natural boron-doped type IIb diamond.