Medium-range order has been observed in ion-implanted amorphous silicon,suggesting a paracrystalline structure for this material. The origin of aparacrystalline structure may be due to an energy spike phenomenon. Toevaluate the influence of energy spikes on a particular process, we haveattempted to calculate the characteristic energy in a spike. However, theobserved depth dependence of amorphous structures in as-implanted silicon ispuzzling. To explain this, we simulated the depth distribution of cascadeevents in a particular energy range. We found a great increase of pointdefect concentration and cascade events as the depth increases. This resultcould explain the experimental depth dependence.

Cathodoluminescence (CL) Microanalysis (spectroscopy and microscopy)provides unique high sensitivity, high spatial resolution information aboutthe defect structure and distribution of defects in wide band gap materialsand therefore is an ideal technique with which to investigate themicrostructural processes induced by irradiation. CL microanalyticaltechniques allow the in situ monitoring and post irradiation assessment ofelectron irradiation induced damage. Changes in the defect structure andsurface topography of electron irradiated silicon dioxide polymorphs andrelated silicates including pure crystal quartz, pure silica glasses, pureamorphous fused quartz and alkali-borosilicate glasses, have beeninvestigated and compared using CL microanalysis and Scanning ProbeMicroscopy (SPM) techniques. CL and SPM evidence shows all specimens aresensitive to electron irradiation. CL evidence is consistent with theproduction and micro-segregation of irradiation induced defects. Theobserved damage is highly correlated with the electron irradiation inducedchanges in the surface topography of the investigated specimens.

We report the results of comparison of radiation-induced defects (1 MeVelectrons) in n+-p-p+ Si diodes doped with gallium orboron ranging in concentration from 8 × 1014 to 5 × 1016 cm−3, together with the impact of oxygen onradiation –induced defects. Present results provide evidence for new defectsstates in addition to those previously reported in gallium- and boron-dopedSi. The combined boron and gallium data provide enough information to gainvaluable insight into the role of the dopants on radiation-induced defectsin Si. The interesting new future of our results is that the gallium appearsto strongly suppress the radiation induced defect, especially hole level EV+0.36 eV, which is thought to act as a recombination center.Similarly the dominant electron level at EC-0.18 eV in B-doped Si(which act as a donor) has not been observed in Ga-doped CZ-grown Si.

Photon absorption (PA), Positron Beam Analysis (PBA) and Neutron DepthProfiling (NDP) is applied to study the relation between photon absorptionbehavior and the precipitates formed by ion implantation and thermalannealing. Monocrystals of MgO(100) were implanted with 1.0×10166Li ions cm−2 at an energy of 30 keV. The samples werethermally annealed in air in steps up to 1200 K. After each step Dopplerbroadening Positron Beam Analysis (PBA) was applied to monitor the depthprofile of the implantation defects. The evolution of the depth profile oflithium was followed with the aid of NDP. During the annealing there ishardly any change in the location of the lithium implantation peak at 150 nm(peak concentration 2 at. %). Only after annealing to 1200 K the majority ofthe lithium has left the crystal and optical absorption effects havedisappeared. During annealing at 750 K an absorption band develops between400 and 600 nm; at 950 K the maximum absorption is centered at 450 nmcorresponding to Mie absorption and scattering by lithium nanoclusters.Positron beam analysis shows a considerable increase of annihilations withlow momentum electrons in the implanted zone. A positron method formeasuring electron momentum distributions (2D-ACAR) coupled to an intensepositron beam gave evidence for the presence of semi-coherent metalliclithium inclusions.

Bombardment of slightly rough, planar surfaces with an energetic gas-clusterion beam (GCIB) is known to result in a decrease in roughness. We reportcomparison of measured surface evolution with simulations based on a simplephenomenological model. The model consists of a continuum rate equation forthe surface height undergoing multiple cluster impacts. With suitableassumptions the main features observed in the evolution of an initiallynonplanar surface can be simulated. Qualitatively, both experiment andsimulation show that sharp features and asperities are rapidly eroded.Examples are given of initial surfaces that are either randomly rough andscratched, or very smooth with added nanoscale engineered features. Bothtypes of surfaces show smoothing in microscopy evaluations of the GCIB andin the simulations, thereby identifying impact-transient surface diffusionas the primary cluster smoothing mechanism.

Self-assembled quantum dots (QDs) have attracted significant attentionbecause of their potential applications in novel semiconductor devices. Inthis work, we investigated radiation effects induced by 1.0 MeV proton ionbeams on InAs self-assembled quantum dots. In particular, we emphasized theeffects of lattice environments of QDs on their luminescence emission afterion beam irradiation. Photoluminescence (PL) spectroscopy was used tocharacterize the optical properties of QDs subjected to proton irradiationand post-irradiation annealing. Compared to the single-layer QDs grown inGaAs films, the QDs embedded in an AlAs/GaAs superlattice exhibited muchhigher PL degradation resistance to proton beam bombardment, e.g., at thehighest dose (1.0×1014 cm−2) used in this work, adifference of ~ 20-fold in PL intensity was found between the QDs configuredin these two different lattice structures. After thermal annealing ofirradiated QD samples, ion beam enhanced blueshift of PL was observed to bemuch more pronounced for the single-layer QDs. We discuss mechanisms thatmay result in the differences in optical response to ion beams between QDswith different lattice surroundings.

Epitaxial thin film liftoff using the ion-slicing method has been applied to SrTiO3 single crystals. Rutherford backscattering spectrometryalong with channeling (RBS/C) has been used to investigate the relativedisorder as a function of temperature from the samples that were irradiatedby 40 KeV hydrogen ions to a fluence of 5.0×1016 H+/cm2. Hydrogen profiles were also measured as afunction of annealing temperature to understand the role of hydrogen in theion slicing process. Film cleavage occurred during or after annealing at 570K, and cleaved film has been successfully transferred to a silicon substrateusing ceramic adhesive.

The sputter-erosion of hcp Co (0001) single crystal with Ar+ ionsin the 100 to 700 eV energy range was investigated using in-situ time-resolved x-ray scattering. At temperaturesabove 300°C the surface remains relatively smooth, erosion evolving througha layer-by-layer or step flow mechanism. In this regime the ions have asmoothening effect on the surface and the resulting roughness decreases withincreasing ion energy. Below 300°C the surface develops a pattern of moundsor pits with a characteristic wavelength. The time, ion energy andtemperature dependence of this wavelength were studied in detail. EpitaxialCo thin films thermally evaporated on sapphire were also sputtered throughin order to synthesize self-assembled arrays of Co nanoclusters with anarrow size distribution. The degree of local order within the Co dot arrayswas examined using atomic force microscopy.

In this work we report the structural and optical properties of ionimplanted GaN. Potential acceptors such as Ca and Er were used as dopants.Ion implantation was carried out with the substrate at room temperature and550 °C, respectively. The lattice site location of the dopants was studiedby Rutherford backscattering/channeling combined with particle induced X-rayemission. Angular scans along both [0001] and [1011] directions show that50% of the Er ions implanted at 550 °C occupy substitutional or nearsubstitutional Ga sites after annealing. For Ca we found only a fraction of30% located in displaced Ga sites along the [0001] direction. The opticalproperties of the ion implanted GaN films have been studied byphotoluminescence measurements. Er- related luminescence near 1.54 µm isobserved under below band gap excitation at liquid helium temperature. Thespectra of the annealed samples consist of multiline structures with thesharpest lines found in GaN until now. The green and red emissions were alsoobserved in the Er doped samples after annealing.

Ion bombardment during thin film growth is known to cause structural andmorphological changes in the deposited films and thus affecting the filmproperties. These effects can be due to the variation in the bombarding ionflux or their energy. We have deposited titanium nitride films by twodistinctly different methods, viz. Electron Cyclotron Resonance (ECR) plasmasputtering and bias assisted reactive magnetron sputtering. The formerrepresents low energy (typically less than 30 eV) but high density plasma (1011cm−3), whereas, in the latter case the ionenergy is controlled by varying the bias to the substrate (typically a fewhundred volts) but the ion flux is low (109cm−3). Thedeposited titanium nitride films are characterized for their structure,grain size, surface roughness and electrical resistivity.

The formation of nanovoids in Si(100) and MgO(100) by 3He ionimplantation has been studied. Contrary to Si in which the voids aregenerally almost spherical, in MgO nearly perfectly rectangular nanosizevoids are created. Recently, the 2D-ACAR setup at the Delft PositronResearch Center has been coupled to the intense reactor-basedvariable-energy positron beam POSH. This allows a new method of monitoringthin layers containing nanovoids or defects by depth-selectivehigh-resolution positron beam analysis. The 2D-ACAR spectra of Si with aburied layer of nanocavities reveal the presence of two additionalcomponents, the first related to para-positronium (p-Ps) formation in thenanovoids, and a second one most likely related to unsaturated Si-bonds atthe internal surface of the voids. The positronium is present in excitedkinetic states with an average energy of 0.3 eV. Refilling of the cavitiesby means of low dose 3He implantation (1×1014 cm−2) followed by annealing reduces the formation of Ps andthe width of the Ps peak in the ACAR spectrum. This width reduction is dueto collisions of Ps with He atoms in the voids. In MgO, p-Ps formed with aninitial energy of ~3 eV shows a final average energy of 1.6 eV atannihilation due to collisions with the cavity walls. Possibilities of thisnew, non-destructive method of monitoring the sizes of cavities and theevolution of nanovoid layers will be discussed.

Ion implantation, specified by parameters like ion energy, ion fluence, ionflux and sub-strate temperature, has become a well-established tool tosynthesize buried low-dimensional nanostructures. In general, in ion beamsynthesis the evolution of nanostructures is determined by the competitionbetween ballistic and thermodynamic effects. A kinetic 3D latticeMonte-Carlo model is introduced, which allows for a proper incorporation ofcollisional mixing and phase separation within supersaturatedsolid-solutions. It is shown, that for both the ballistically andthermodynamically dominated regimes, the Gibbs-Thomson relation is the keyingredient in understanding nanocluster evolution. Various aspects ofprecipitate evolution during implantation, formation of ordered arrays ofnanophase domains by focused ion implantation and compound nanoclustersynthesis are discussed.

The 1.5 µm luminescence from Si:Er is known to strongly depend on impurities(e.g. carbon) in silicon. In this work, we investigate the effect of carbonco-doping on the lattice location of Er atoms in Si by Rutherfordbackscattering(RBS)/channeling techniques. A float-zone (FZ) Si (100) waferwas first amorphized to a depth of ~ 0. 3 µm by Si ions implanted to a doseof ~ 1×1015cm2 at liquid nitrogen temperature. Carbonions were then implanted into the amorphous silicon, which wasrecrystallized via solid phase epitaxial growth (SPEG) at 600°C following Cimplant. Finally Er ions were implanted into the C-doped and C-free Sicrystals, with the substrate temperature at 25°C and 300°C respectively. TheRBS/channeling results show that the Er redistribution and Si crystallinityare strongly affected by C co-doping. The incorporation of C into Si cansignificantly suppress Er surface segregation, and modify the latticelocation of Er atoms in Si. We discuss these effects in terms of theformation of Er-C defect complexes.

Ion implantation followed by rapid thermal annealing is used to induce layerintermixing and thus selectively blue-shift the emission wavelength ofInP-based quantum well hetero- structures. The intermixing is greatlyenhanced over thermal intermixing due to the supersaturation of defects. Themagnitude of the observed blue-shift has been studied previously as afunction of ion fluence and ion mass: the dependence on ion mass is wellestablished, with heavier ions producing a larger shift. We show here thatchemical effects can also play a significant role in determining the inducedblue-shift. Data are presented from the implantation of the similar massions; aluminum (m~27), silicon (m~28) and phosphorus (m~31). The P- inducedblue shift displays a monotonic increase with fluence, consistent withprevious studies; however, the fluence dependence of Al- and Si-inducedblue-shifts both deviate significantly from the behaviour for P. Theseresults have important implications for attempts to scale intermixingbehaviour with ion mass.

A new method of producing a buried oxide is proposed. It involves implantinga silicon wafer with helium rather than oxygen ions and then subjecting itto high- temperature oxidation. The voids formed by helium ion implantationand subsequent annealing enhance the diffusion of oxygen atoms into thesilicon. The oxygen atoms cause thermal oxide to grow at the void/siliconinterface and transform the voids into buried oxide precipitates. Augerelectron spectroscopy revealed that the total number of oxygen atoms in theprecipitates was 9.3 × 1016 cm−2 and that the peakvalue of oxygen atom concentration in the wafer was approximately 25%.

Ion implantation was used to form high densities (~1019 /cm3) of small oxide precipitates in Ni in order toinvestigate the strength mechanism produced by such highly refinedstructures. Nanometer-size precipitates of Al2O3 andNiO are found to block dislocation motion in the Ni matrix, producing yieldstrengths up to 4.6 GPa, more than twice that of hardened bearing steel.Dispersion strengthening theory, developed for micrometer-size precipitatesand spacings, was found to account quantitatively for the yield strengthsproduced by nanometer-size oxides as well. Nanoindentation plusfinite-element modeling was used to quantify the mechanical properties ofimplanted metal layers, and was extended to examination of amorphous Silayers formed by self-ion implantation. The amorphous phase was found tohave a yield strength of 4.45 ± 0.20 GPa, Young's modulus of 144 ± 7 GPa,and hardness of 10.3 ± 0.4 GPa. The modulus and hardness are reduced by 10%and 15%, respectively, from those of crystalline Si.

Single crystalline samples of bismuth tellurite (Bi2TeO5) were implanted with 800 keV Au+ions to a fluence of 1×1016 cm-2 atroom temperature. The samples were subjected to heat treatments in twodifferent ambients (air and high vacuum) at temperatures ranging from 400 -700°C in a conventional furnace. Strong absorption maxima in the range from600 - 630 nm in the optical absorption spectra and an intense blue-greencolor in the samples were observed for annealings performed in air attemperatures between 500 and 700°C indicating the formation of goldcolloids. The average radii of the Au clusters formed were estimated to bein the range of 3-4 nm. Samples annealed under vacuum showed distinctchanges in color for different annealing temperatures. Studies using theRBS/channeling technique indicate that no full recrystallization of thesamples was achieved under both annealing regimes although heat treatmentunder vacuum provides a significantly better lattice recovery than for airambient.

Boron is the most important p-type dopant in Si and it is essential that,especially for low energy implantation, both as-implanted B distributionsand those produced by annealing should be characterized in very great detailto obtain the required process control for advanced device applications.While secondary ion mass spectrometry (SIMS) is ordinarily employed for thispurpose, in the present studies implant concentration profiles have beendetermined by direct B imaging with approximately nanometer depth andlateral resolution using energy-filtered imaging in the transmissionelectron microscopy. The as-implanted B impurity profile is correlated withtheoretical expectations: differences with respect to the results of SIMSmeasurements are discussed. Changes in the B distribution and clusteringthat occur after annealing of the implanted layers are also described.

Secondary Ion Mass Spectrometry (SIMS) with Gas Cluster Ion Beams (GCIB) wasstudied with experiments and molecular dynamics (MD) simulations to achievea high-resolution depth profiling. For this purpose, it is important toprevent both ion-mixing and the surface roughening due to energetic ions. Asthe Ar cluster ion beam shows surface smoothing effects and highsecondary-ion yield in the low-energy regime, the cluster ion beam would besuitable for the primary ion beam of SIMS. From MD simulations of Ar clusterion impact on a Si substrate, the ion-mixing is heavier than for Ar monomerions at the same energy per atom, because the energy density at the impactpoint by clusters is extremely high. However, the sputtering yields with Arcluster ions are one or two orders of magnitude higher than that with Armonomer ions at the same energy per atom. Comparing at the ion energy wherethe ion-mixing depths are the same by both cluster and monomer ion impacts,cluster ions show almost ten times higher sputtering yield than Ar monomerions. Preliminary experiment was done with a conventional SIMS detector anda mass resolution of several nm was achieved with Ar cluster ions as aprimary ion beam.

The evolution of the mean size and the size distribution of Au nanoclusters(NCs) under high-energy ion irradiation has been studied. Au NCs weresynthesized in a 480 nm thick SiO2 layer by 330 keV Au+ implantation and subsequent annealing at T = 1000 °C for1h in dry O2. XTEM images show a 70 nm thick layer of Au NCs,being centered at the projected ion range Rp(330keV) = 100 nm,having a mean NC size of 5 nm at Rp, and resembling the broadLifshiz-Slyozov-Wagner (LSW) size distribution of diffusion controlledOstwald ripening. Post-irradiation of the Au NCs by 4.5 MeV gold ions wasused in order to tailor their size and size distribution. The high-energy Au+ irradiations were performed at 190...210 °C with a fluenceof (0.5...1.0)×1016 cm-2. By the post-irradiation nogold was deposited into the SiO2 layer, the Au+ ionscome to rest in the (001)Si substrate at Rp(4.5MeV) = 1[.proportional]m. XTEM images of the post-irradiated Au NCs show a strongdecrease of their mean size as well as the width of their size distribution.The observed NC evolution under ion irradiation agrees with recenttheoretical predictions and kinetic Monte-Carlo simulations.