bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Implantation and Annealing Effects in Silicon Carbide
Authors: Heera V. , Skorupa W.
Published: September 2012

SiC is a promising semiconductor material for high-power/high-frequency and hightemperature electronic applications. For selective doping of SiC ion implantation is the only possible process. However, relatively little is known about ion implantation and annealing effects in SiC. Compared to ion implantation into Si there is a number of specific features which have to be considered for successful ion beam processing of SiC. A brief review is given on some aspects of ion implantation in and annealing of SiC. The ion implantation effects in SiC are discussed in direct comparison to Si. The following issues are addressed: ion ranges, radiation damage, amorphization, high temperature implantation, ion beim induced crystallization and surface erosion.
Effects of Ion Bombardment on Chemical Interactions at SiC Surface and AI/SiC Interfaces
Authors: Beck Heather L. , Lee Moon-H. , Ohuchi Fumio S.
Published: September 2012

An investigation into the SiC surface and its interaction with aluminum, in particular, focusing on the effect of ion bombardment and adsorption of oxygen, is described. Stoichiometric and carbon rich and SiC surfaces were produced and analyzed “in situ” by Auger electron spectroscopy and x-ray photoelectron spectroscopy. Cubic SiC shows preferential sputtering under Ar ion bombardment, leading to carbon rich surface, whereas high temperature annealing also causes carbon rich surface. Activity of these surfaces was compared with oxygen and aluminum adsorption. Stoichiometrically sputtered surface showed vastly increased oxygen affinity, whereas carbon-rich sputtered surfaces did not. Aluminum deposition caused significant Al-C interaction for the stoichometric ion-bombarded surface. Aluminum carbide was induced catalytically upon heating in the presence of oxygen. Carbon-rich surfaces had, however, no significant interactions with as-deposited Al due to strong surface C-C bonds.
Growth of Patterned SiC by Ion Modification and Annealing of C60 Films on Silicon
Authors: Moro L. , Paul A. , Lorents D. C. , Malhotra R. , Wu K. J. , Subramoney S.
Published: September 2012

Irradiation of vapor-deposited C60 films with a KeV ion beam (Ar+ or Ga+) transforms the surface layer of C60 into a non-volatile carbon film. During the subsequent annealing at 900°C, the modified C60 layer confines the underlying C60 on the silicon surface, allowing the formation of SiC. With this method, patterned SiC structures on silicon with the high lateral resolution possible with ion beams are fabricated
Formation of a Buried Soft Layer in Sic for ”Compliant Substrate” by Ion Implantation
Authors: Lioubtchenko M. , Hunn J. , Suvkhanov A. , Parikh N. , Bray D.
Published: September 2012

Radiation damage and its removal have been studied in ion implanted 6H-SiC by Rutherford backscattering/Channeling (RBS). We have implanted Ga and Ti at 800°C using doses of 1 × 1016 to 2× 1017 cm−2. The implanted samples have been subsequently annealed at 1050°C, and then at 1400°C for 30 sec to study the removal of damage produced during implantation. The energies of implanted species have been chosen to obtain 20 – 40 nmn projected ranges to form a buried metallic or graphitic layer. No significant damage removal has been observed after 1050°C anneal, however 1400°C annealing of 40 and 120 keV Ga implanted samples (fluence 2 × 1016 cm−2) resulted in significantly less damage as can be observed from RBS/Channeling data. In the case of Ti implanted samples annealing led to an appreciable increase in the channeled backscattering yield, which might be due to the formation of some new phase (e.g. TiSi or TiSi2 ) and may be related to distortions of the existing lattice.
Modeling of Dislocation Loop Growth and Transient Enhanced Diffusion in Silicon for Amorphizing Implants
Authors: Gencer Alp H. , Dunham Scott T.
Published: September 2012

It has been observed that dislocation loops form and grow during annealing of silicon wafers implanted at doses above the amorphization threshold. Dislocation loops can act to store interstitials for prolonged periods of anneals, sustaining an interstitial super-saturation and thus causing substantial transient enhanced diffusion (TED). We have developed a comprehensive model which, in combination with a model and parameters for s{311} defects from previous work, accounts for the formation and evolution of dislocation loops during ion implant annealing, as well as giving the correct TED behavior.
Transient Enhanced Diffusion of Dopants in Preamorphised Si Layers
Authors: Claverie A. , Bonafos C. , Omri M. , Mauduit B. De , Assayag G. Ben , Martinez A. , Alquier D. , Mathiot D.
Published: September 2012

Transient Enhanced Diffusion (TED) of dopants in Si is the consequence of the evolution, upon annealing, of a large supersaturation of Si self-interstitial atoms left after ion bombardment. In the case of amorphizing implants, this supersaturation is located just beneath the c/a interface and evolves through the nucleation and growth of End-Of-Range (EOR) defects.

For this reason, we discuss here the relation between TED and EOR defects. Modelling of the behavior of these defects upon annealing allows one to understand why and how they affect dopant diffusion. This is possible through the development of the Ostwald ripening theory applied to extrinsic dislocation loops. This theory is shown to be readily able to quantitatively describe the evolution of the defect population (density, size) upon annealing and gives access to the variations of the mean supersaturation of Si self-interstitial atoms between the loops and responsible for TED. This initial supersaturation is, before annealing, at least 5 decades larger than the equilibrium value and exponentially decays with time upon annealing with activation energies that are the same than the ones observed for TED. It is shown that this time decay is precisely at the origin of the transient enhancement of boron diffusivity through the interstitial component of boron diffusion. Side experiments shed light on the effect of the proximity of a free surface on the thermal behavior of EOR defects and allow us to quantitatively describe the space and time evolutions of boron diffusivity upon annealing of preamorphised Si layers.
Effect of Argon Ion Bombardment on the Stability of Narrow Cobalt Silicide/Polysilicon Structure
Authors: Maa Jer-Shen , Peng Chien-Hsiung
Published: September 2012

The stability of cobalt silicide formed on narrow polysilicon line degraded rapidly with shrinkage of linewidth as shown by the increase of sheet resistance after annealing. Stability was improved by adding a titanium interlayer under cobalt with or without a Ti or TiN cap layer. The stability was affected by silicide thickness and substrate doping. In best cases an increase of sheet resistance after annealing was still observed. Adding an Ar ion bombardment step improved the thermal stability drastically. This structure did not show any sheet resistance change after a 30 min annealing at 850°C, either with or without interlayer or cap layer.
Plasma Ion Implantation for Flat Panel Displays
Authors: Chan Chung , Qin Shu , Zhou Yuanzhong , Liu Wei , Wu Shuichi , Vai Mankuan Michael , Bursuc Ionel , Shao Jiqun , Denholm Stuart
Published: September 2012

Development of ion doping and hydrogenation equipment using plasma ion implantation (PII) is being studied. It is shown that low energy, high throughput operation could eliminate problems associated with etching, charging, cooling, and contamination. The applications of a new plasma source and neural network implementation optimization are also reported.
N-Type Doping by Plasma Ion Implantation Using a PH3 SDS System
Authors: Qin Shu , Zhou Yuanzhong , Warner Keith , Chan Chung , Shao Jiqun , Denholm Stuart
Published: September 2012

PH3 SDS (safe delivery system) gas was used for the first time in P11 doping experiments to fabricate n+p junctions and NMOS devices. Two gas recipes (PH3 diluted in H2 and He) were investigated. Under lower pressure, a minimum etching effect was observed. A 4x1015/cm2 phosphorus dose and a 22 Ω/□ sheet resistance were achieved in 4 seconds. Very low contamination level was involved. An anomalous tail of P profile in Si substrate was observed using SIMS measurements.
Investigations of Plasma Immersion Ion Implantation Hydrogenation for Poly-Si Tfts Using an Inductively Coupled Plasma Source
Authors: Zhou Yuanzhong , Qin Shu , Chan Chung
Published: September 2012

A plasma immersion ion implantation (PIII) hydrogenation process using an inductively-coupled plasma (ICP) source is implemented for defect passivation in polycrystalline silicon (poly-Si) thin film transistors (TFT's). Device parameter improvement saturates in 4 minutes, which is considerably shorter than for other reported hydrogenation methods. Stress test indicates that the devices hydrogenated by this novel technique have much better long-term reliability. The hydrogenation effects on two types of trap states are analyzed the current-voltage characteristics of the devices. The densities of deep states and tail states are significantly reduced after short time hydrogenation.
Growth of Low-Temperature Polycrystalline Si Film by Direct Negative Si Ion Beams
Authors: Sohn M. H. , Kim D. , Ahn Y. O. , Kim S. I.
Published: September 2012

Polycrystalline Si (Poly-Si) films were successfully grown at temperature less than 500 °C by using a direct Si ion beam deposition technique. In this process, the ion beam energy of Si- is directly coupled to the formation of the films. High substrate temperature (>600 °C), normally required for conventional CVD techniques, has been a major barrier for the Poly-Si Thin Film Transistor Liquid Crystal Display (TFT LCD) which uses a glass substrate. Thus, the ability to produce Poly-Si film below the glass transition temperature and to control the grain size will make this direct Si- ion beam deposition process a potential alternative technique for future TFT LCD. The grain size dependence on the ion beam energy and substrate temperature was investigated using a Transmission Electron Microscope (TEM). The grain size could be controlled from 0.1 μm to 1 μm at ion beam energies from 10 to 50 eV with a substrate temperature less than 500 °C. The resistivity of the as-deposited film was of the order of 100 Ωcm due to in-situ doping effect.
Growth of Ge1-xCx Alloys on Si by Combined Low-Energy Ion Beam and Molecular Beam Epitaxy Method
Authors: Shibata H. , Kimura S. , Fons P. , Yamada A. , Makita Y. , Obara A. , Kobayashi N. , Takahashi H. , Katsumata H. , Tanabe J. , Uekusa S.
Published: September 2012

A combined ion beam and molecular beam epitaxy (CIBMBE) method was applied for the deposition of a Ge1-xCx alloy on Si(100) using a low-energy ( 50 – 100 eV ) C+ ion beam and a Ge molecular beam. Metastable Ge1-xCx solid solutions were formed up to x = 0.047, and the CIBMBE method was shown to have a very high potential to grow metastable Ge1-x,Cx alloys. It was also revealed that the sticking coefficient of C+ ions into Ge was ∼28% for Ei, = 100 eV and ∼18% for Ei = 50 eV. Structural characterization suggests that the deposited films are single crystals grown epitaxially on the substrate with twins on {111} planes. Characterization of lattice dynamics using Raman spectroscopy suggested that the deposited layers have a small amount of ion irradiation damage.
Combined Ion-Beam and Laser-Beam Synthesis of Silver Oxide Nanoclusters in Soda-Lime Glass
Authors: Haglund R. F. , Osborne D. H. , Gonella F. , Mazzoldi P. , Battaglin G.
Published: September 2012

Ion beam deposition offers a number of interesting possibilities for creating nonlinear materials for photonic devices such as waveguides. Ion beams have been used by a number of groups to create metal and semiconductor nanocrystallites in silica and other glassy substrates in a geometry suitable for shallow channel waveguides. In this paper, we describe the use of He ion beams to initiate nucleation of Ag nanocrystallites in ion-exchanged soda-lime glass. The nanocrystallites are remarkably uniform in size, and exhibit substantial third-order optical nonlinearity. The combination of ion exchange and ion implantation has an advantage over conventional implantation techniques because it produces guiding layers deep enough (several microns) to form practical channel waveguides. In addition, we have shown that it is possible, by means of subsequent laser irradiation, to further alter the properties of the nonlinear composite material. In this particular case, irradiation by visible or infrared laser beams following ion implantation induces oxidation of the silver nanocrystallites, as documented by Auger analysis of the composite material. Furthermore, the third-order nonlinearity of the composite material changes sign, changing a self-focusing nonlinearity into one which is self-defocusing. These experiments suggest a number of possibilities for combining ion- and laser-beam irradiation to create laterally structured waveguide materials as well as nonlinear channel waveguides.
High Current Implantation of Negative Copper Ions into Silica Glasses
Authors: Kishimoto N. , Gritsyna V. T. , Kono K. , Amekura H. , Saito T.
Published: September 2012

High- current implantation of Cu- ions into silica glasses has been demonstrated using mAclass negative ion beams at 60 keV. Negative ion implantation has an advantage to alleviate specimen charging for insulating substrates and has attained high dose rates, up to 260 μA/cm2. Spherical Cu colloids form in the silica glasses without additional thermal annealing. Optical absorption and reflection of the implanted specimens vary with the current density, even at a fixed dose level. A beam- induced surface plasma may affect the high current implantation.
Optical and Structural Characterization of Zinc Implanted Silica Under Various Thermal Treatments
Authors: Mu R. , Chen Jinli , Gu Z. Y. , Ueda A. , Tung Y. -S. , Henderson D. O. , White C. W. , Zhu Jane G. , Budai John D. , Zuhr R. A.
Published: September 2012

Zinc ion implanted silica with controlled thermal annealing has been investigated. Low temperature optical measurements indicate the presence of Zn clusters in the as-implanted silica. Optical spectra of the annealed sample under a reducing environment suggest Zn cluster and Zn metal colloid formation. The absorption peak at ∼5.3 eV may be due to the surface plasma absorption of Zn metal colloids in silica. The oxidized samples (10 and 6 x 1016 ions/cm2) show an absorption peak at ∼4.3 and ∼4.8 eV, respectively and imply ZnO quantum dot formation. The blueshift in exciton absorption can be attributed to the quantum confinement effects.
Quantum-Sized Silicon Precipitates in Silicon-Implanted and Pulse-Annealed Silicon Dioxide Films: Photoluminescence and Structural Transformations
Authors: Tyschenko I. E. , Kachurin G. A. , Zhuravlev K. S. , Pazdnikov N. A. , Volodin V. A. , Gutakovsky A. K. , Leier A. F. , Fröb H. , Leo K. , Böime T. , Rebohle L. , Yankov R. A. , Skorupa W.
Published: September 2012

Strong blue, red and near-infrared photoluminescence has been observed from Si+-implanted and pulse-annealed SiO2 layers. Raman scattering and high-resolution electron microscopy analyses have revealed a correlation between the structure of the Si inclusions in the SiO2 matrix and the photoluminescence. Structural transformations in the Si-rich SiO2 layers during pulse and furnace annealing have been discussed in terms of the changes in the light emission observed experimentally. Small Si clusters, non-crystalline inclusions and nanocrystals are believed to be the light sources. The blue, red and near-infrared photoluminescence is associated with small complexes of excess Si atoms, non-crystalline Si nanoinclusions and quantum-confined Si nanocrystals, respectively.
Er-Doped Amorphous and Crystalline Al2O3 and La2O3 Films Grown with Low Energy Ions From an Ecr Plasma
Authors: Barbour J. C. , Potter B. G. , Follstaedt D. M. , Knapp J. A. , Sinclair M. B.
Published: September 2012

The effects of low energy ions from a biased electron cyclotron resonance plasma during growth of Al2O3 and La2O3 are used to modify the density and crystalline quality of these oxide films. The type of phase formed for Al2O3 is varied with the ion-assisted growth from amorphous to crystalline γA12O3. The photoluminescence (PL) properties of different Er-doped Al- and La-oxide phases are examined, and through comparison of the PL spectra, the local environment of Er in these oxide materials is discussed.
Ion Beam Damage of Polymer Surfaces: Insights from Molecular-Dynamics Simulation
Authors: Brenner D. W , Shenderova O. , Parker C. B.
Published: September 2012

Molecular-dynamics simulations are used to model the bombardment of crystalline polyethylene by carbon and rare-gas atoms with kinetic energies between 20 eV and 80 eV. The simulations predict substantial near-surface damage, including radical formation via loss of hydrogen from the chains, insertion of carbon into the polymer backbone, and chain crosslinking. For the rare gas atoms, the observed chemical dynamics are dependent on the mass of bombarding species, with the ratio of broken carbon-hydrogen to carbon-carbon bonds decreasing with increasing mass. The total number of bonds broken, however, is a linear function of kinetic energy with the lighter species having a higher slope and lower threshold energy for inducing damage.
Effects of MeV Ion Beam on Polymers
Authors: Evelyn A. L. , Ila D. , Zimmerman R. L. , Bhat K. , Poker D. B. , Hensley D. K.
Published: September 2012

The electronic (εe) and nuclear (εa) stopping effects produced by 3.5 MeV and 5.0 MeV ion bombardment in polyvinylidine chloride (PVDC), polyethylene (PE) and polyethylene sulfide were studied and compared. To separate these effects we chose two bombardment energies and a thin film polymer stacking technique developed in house. The resulting stacked layered system consisting of each polymer was bombarded with 3.5 MeV and 5.0 MeV alpha particles. The layered system was selected such that the first few layers experience most of the effects of the electronic energy deposited and the last layer receives the effects of the nuclear stopping. The electrical conductance and the changes in the chemical structure were measured by direct resistivity measurements, Raman microprobe analysis, RBS, and FTIR. The post-irradiation characterization resolved the effects of the stopping powers on the polymer films.
Ion Beam Injected Point Defects in Crystalline Silicon: Migration, Interaction and Trapping Phenomena
Authors: Priolo F. , Privitera V. , Coffa S. , Libertino S.
Published: September 2012

Our recent work on the room temperature migration and trapping phenomena of ion beam generated point defects in crystalline Si is reviewed. It is shown that a small fraction (∼ 10−6) of the defects generated at the surface by a shallow implant is injected into the bulk. These defects undergo a long range trap-limited diffusion and interact with both impurities, dopants and preexisting defects along their path. In particular, these interactions result in dopant deactivation and/or partial annihilation of pre-existing vacancy-type defect markers. It is found that in highly pure, epitaxial Si layers, these effects extend to several microns from the surface, demonstrating a long range migration of point defects at room temperature. By a detailed analysis of the experimental evidences we have identified the Si self-interstitials as the major responsible for the observed phenomena. This allowed us to give a lower limit of 6×10−11-cm2/s for the room temperature diffusion coefficient of the Si self-interstitials. Room temperature trap-limited migration of vacancies is also detected as a broadening in the divacancy profile of as implanted samples. In this case the room temperature diffusion coefficient of vacancies has been found to be ≥3 × 10−12 cm 2/s. These data are presented and their implications discussed.
Structural and Magnetic Properties of Ion Beam Deposited Nanocrystalline Al-Co and Al-Co-O Films
Authors: Khan H. R. , Brouers F.
Published: September 2012

Nanocrystalline films of Al-Co and Al-Co-O are deposited on glass substrates using Ar and (Ar + O2) gas mixture by IB and IAB deposition techniques. The structure of the films is investigated by X-ray diffraction. Annealed (500°C/ 0.5 h / Vacuum) films show a preferred Co<111> + Al<200> crystallographic orientation. The crystallite size estimated from the line broadening of Co<111> + Al<2007gt;reflections lies between 4 and 12 nm. The value of Mx/Ms increases with decreasing Co concentration from 0.2 (74 at.%) to 0.4 (46 at.%) for IB(Ar) films, where Mr and Ms are the remanence and saturation magnetizations respectively. IB (Ar + O2) and IAB (Ar + O2) films of the same composition A154Co46Ox show different magnetic behaviour.
Alpha Particle Beam Interactions with Fe-Based and FeCo-Based Amorphous Magnets
Authors: Sorescu Monica , Barb D.
Published: September 2012

Samples of Fe78B13Si1 and Fe66Co18B15Si1 metallic glasses were irradiated with alpha particle beams (W=2.8 MeV) using radiation doses of 1016 and 1017 cm2. Irradiation-induced effects on the magnetic and structural properties of alloy samples were studied by transmission and conversion electron Mbssbauer spectroscopy. 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. Differences between bulk and surface irradiation behaviors were demonstrated.
Study of the Ion-Acoustic Effect using Focused Ion Beams
Authors: Teichert J. , Bischoff L. , Köhler B.
Published: September 2012

Acoustic waves induced by an intensity-modulated focused ion beam (FIB) have been measured. The experiments were performed with Ga+ ions of 35 keV at a current of 3 nA and variable chopping frequency up to 10 MHz. The acoustic signals were detected by means of a piezoelectric sensor with integrated pre-amplifier. In the paper the experimental setup and the results of first measurements are presented. Evidence for FIB induced acoustic waves has been found.
Growth and Mechanical and Tribological Characterization of Multi-Layer Hard Carbon Films
Authors: Ager J. , Brown I. , Monteiro O. , Knapp J. A. , Follstaedt D. M. , Nastasi M. , Walter K. C. , Maggiore C. J.
Published: September 2012

Vacuum-arc deposition is used to deposit multilayer carbon films by modulating the sample bias during deposition. The effect of varying the sublayer thickness in multilayer films consisting of alternating layers of “hard” (68.4 GPa, -100 V bias) and “soft” (27.5 GPa, -2000 V bias) was investigated. Films consisting of equal thickness layers of hard and soft material and an individual layer thickness varying from 10 to 35 nm were deposited. Mechanical property measurements were obtained by finite element modeling of nanoindentation load-displacement curves. The film hardness values were about 20% below the average of the component layers and relatively independent of the layer thickness. TEM investigation revealed deterioration of the multilayer structure when the sublayer thickness was below 15 nm due to implantation damage of the hard layers caused by the energetic C+ ions of the soft layers (-2000 V bias) deposited over them. Pin-on-disk wear tests show that the wear rate drops when sublayer thickness is decreased below 20 nm and remains constant with further decreases in the layer thickness.
Thermal Annealing Behavior of Si-DLC Ibad Coatings
Authors: Fountzoulas C. G. , Demaree J. D. , Sengupta L. C. , Hirvonen J. K.
Published: September 2012

Amorphous, 700 nm thick, diamond-like carbon coatings containing silicon (Si-DLC), farmed by Ar+ ion beam assisted deposition (IBAD) on silicon substrates, were annealed in air at temperatures ranging from room temperature to 600°C for 30 minutes. RBS analysis showed that the composition of the films remained the same up to 200°C, but at higher temperatures the Si-DLC coatings began to oxidize at the outer surface of the coating, forming a surface layer of SiO2. After in-air annealing at 600°C the coating had been completely converted to SiO2, with no trace of carbon seen by RBS. FTIR spectra of the unannealed coatings showed a very broad mode typical of Si-DLC bonding as well as some absorption features associated with Si and SiO2. Above 200°C the transmission mode shifted to higher frequencies which may be caused by the growth of SiO2 and the decrease of the Si-DLC film thickness. The room temperature ball-on-disk friction coefficient of the coating against a 1/2′′ diameter 440 C steel ball at 1 N load ranged from 0.2 for the original coating up to 0.5 after a 100° anneal and returned to 0.2 after annealing at 200–400°C and fell to 0.12 after a 500°C exposure. The average Knoop microhardness (uncorrected for substrate effects) was 10 GPa (1,000 KHN) for coatings annealed at temperatures as high as 400°C. All coatings up to 500 °C passed the qualitative “Scotch Tape” test.
Deposition and Properties of Doped Diamondlike Carbon Films Produced by Dual-Source Vacuum Arc Plasma Immersion
Authors: Monteiro O. R. , Delplancke-Ogletree M. P. , Brown I. G. , Ager J. W.
Published: September 2012

Diamond-like carbon films with mechanical properties approaching those of diamond have been consistently produced by cathodic vacuum arc based techniques. These films have been successfully used in applications where enhanced hardness and wear resistance are required Such DLC films have two major drawbacks that prevent their application in other areas: a high level of internal stresses, which promotes failure by spallation of thick films; and the loss of mechanical properties at temperatures higher than 300°C. In this paper we describe the effect of doping elements on the room-temperature mechanical properties and on the thermal stability of DLC films upon annealing in air. The effect of the presence of W and Ti was investigated and compared to pure DLC. The films were produced by dual-source metal plasma immersion ion implantation and deposition with magnetic filtering to remove macroparticles from the plasma; dopant content was controlled by varying the relative pulse duration of the two plasma sources. Microstructural and chemical characterization of the films are presented.
Carbon Nitride Film Formation by Low Energy Positive and Negative Ion Beam Deposition
Authors: Tsubouchi N. , Horino Y. , Enders B. , Chayahara A. , Kinomura A. , Fujii K.
Published: September 2012

Using a newly developed ion beam apparatus, PANDA (Positive And Negative ions Deposition Apparatus), carbon nitride films were prepared by simultaneous deposition of mass-analyzed low energy positive and negative ions such as C2-, N+, under ultra high vacuum conditions, in the order of 10−6 Pa on silicon wafer. The ion energy was varied from 50 to 400 eV. The film properties as a function of their beam energy were evaluated by Rutherford Backscattering Spectrometry (RBS), Fourier Transform Infrared spectroscopy (FTIR) and Raman scattering. From the results, it is suggested that the C-N triple bond contents in films depends on nitrogen ion energy.
Large Area Surface Treatment by Ion Beam Technology
Authors: Wu R. L. C. , Lanter W.
Published: September 2012

An ultra high vacuum ion beam system, consisting of a 20 cm diameter Rf excilted (13.56 MHz) ion gun and a four-axis substrate scanner, has been used to modify large surfaces (up to 1000 cm2) of various materials, including; infrared windows, silicon nitride, polycrystalline diamond, 304 and 316 stainless steels, 440C and M50 steels, aluminum alloys, and polycarbonates; by depositing different chemical compositions of diamond-like carbon films. The influences of ion energy, Rf power, gas composition (H2/CH4 , Ar/CH4 and O2/CH4/H2), on the diamond-like carbon characteristics has been studied. Particular attention was focused on adhesion, environmental effects, IR(3–12 μm) transmission, coefficient of friction, and wear factors under spacelike environments of diamond-like carbon films on various substrates. A quadrupole mass spectrometer was utilized to monitor the ion beam composition for quality control and process optimization.
Evaluating Mechanical Properties of Thin Layers using Nanoindentation and Finite-Element Modeling: Implanted Metals and Deposited Layers
Authors: Knapp J. A. , Follstaedt D. M. , Barbour J. C. , Myers S. M. , Ager J. W. , Monteiro O. R. , Brown I. G.
Published: September 2012

We present a methodology based on finite-element modeling of nanoindentation data to extract reliable and accurate mechanical properties from thin, hard films and surface-modified layers on softer substrates. The method deduces the yield stress, Young's modulus, and hardness from indentations as deep as 50% of the layer thickness.
Properties of Ion Implanted Ti-6Al-4V Processed using Beamline and PSII Techniques
Authors: Walter K. C. , Williams J. M. , Woodring J. S. , Nastasi M. , Poker D. B. , Munson C. M.
Published: September 2012

The surface of Ti-6Al-4V (Ti64) alloy has been modified using beamline implantation of boron. In separate experiments, Ti64 has been implanted with nitrogen using a plasma source ion implantation (PSII) technique utilizing either ammonia (NH 3), nitrogen (N2), or their combinations as the source of nitrogen ions. Beamline experiments have shown the hardness of the N-implanted surface saturates at a dose level of ˜4× 1017 at/cm2 at ˜10 GPa. The present work makes comparisons of hardness and tribological tests of (1) B implantation using beamline techniques, and (2) N implanted samples using ammonia and/or nitrogen gas in a PSII process. The results show that PSII using N2 or NH3 gives similar hardness as N implantation using a beamline process. The presence of H in the Ti alloy surface does not affect the hardness of the implanted surface. Boron implantation increased the surface hardness by as much as 2.5x at the highest dose level. Wear testing by a pin-on-disk method indicated that nitrogen implantation reduced the wear rate by as much as 120x, and boron implantation reduced the wear rate by 6.5x. Increased wear resistance was accompanied by a decreased coefficient of friction.
Thermomechanically Modulated Nanoscale Multilayered Materials for Application in Electromagnetic Gun Systems
Authors: Otooni M. A. , Brown I. G. , Monteiro O.
Published: September 2012

Fired rails from electromagnetic railguns show severe damage from arcing and tribological mismatch. We have fabricated and studied several different nanoscale multilayered materials as possible routes to improve the thermal transport and thermomechanical properties of the rail and armature materials. A vacuum-arc-based plasma deposition technique with wide control of ion energy was used for the film synthesis, and high-energy high-dose (energy up to ˜ 150 keV, dose up to ˜ 1 × 1017cm−2) metal ion implantation was also used. The multilayered film structures formed and investigated included sublayers of Ti, TiCo, ZrN, TaN and dlc (diamond-like carbon) in the following combinations: (i) ZrN on TiCo on TaN on dlc on a Cu substrate, (ii) ZrN on TiCo on TaN on dlc on an Al substrate, (iii) TiN on TiCo on TaN on a stainless steel substrate, and (iv) Ti on TiCo on a stainless steel substrate. Individual sublayer film thickness was in the range of 400Å-7μ. The surfaces were characterized by SEM, TEM, RBS, high energy electron diffraction, arid microhardness measurements. Significant improvements in the material surface properties were obtained for virtually all of the surface structures investigated. Here we outline the material synthesis and surface modification techniques used and the materials characterization results obtained.
Preparation of TiC and TiC/DLC Multilayers by Metal Plasma Immersion Ion Implantation and Deposition: Relationship between Composition, Microstructure and Wear Properties
Authors: Delplancke-Ogletree M. P. , Monteiro O. R. , Brown I. G.
Published: September 2012

We have used pulsed vacuum arc deposition to prepare TixCy films and multilayer structures of TixCy / diamondlike carbon (DLC) in a dual plasma source set-up. The composition of the monolithic films was controlled by varying the pulse duration of each plasma gun. During the deposition, a repetitively pulsed bias voltage was applied to the substrate in order to improve the adhesion to the substrate and between the individual layers. For the multilayers, the carbon and Ti guns were synchronously pulsed during deposition of the TixCy, and the Ti gun was not operated during the DLC deposition. Multilayers with different periodicities were synthesized. The deposited films were analyzed by various techniques including XPS, AES, TEM, EELS, and XRD to characterize the composition, bonding states, and microstructure. Special attention was given to the interface thickness in relation to the applied bias voltage. Tribological properties such as friction coefficient and wear resistance were measured, and correlated to the composition and microstructure of the films.
Al / Al-N / Ain Compositional Gradient Film Synthesized by Ion-Beam Assisted Deposition Method
Authors: Amamoto Yoshiki , Uchiyama Shingo , Watanabe Yoshihisa , Nakamura Yoshikazu
Published: September 2012

Al / AI-N / AIN compositional gradient thin film was deposited on a Si(100) substrate at room temperature by ion-beam assisted deposition method, with a diminishing ion beam current from 1.4 to 0 mA at increments of 0.3 mA in order to gradually decrease the nitrogen to aluminum ratio at the substrate. The gradual Al and AIN variation in composition was shown by the change of the Al / N atomic ratio analysed by the energy dispersive X-ray spectroscopy(EDX) and the X-ray photoelectron spectroscopy (XPS) in the cross section of the film. The formation of crystalline Al metal and AIN ceramic layer on the Si substrate was revealed by X-ray diffraction(XRD). The cross sectional image taken by high resolution transmission electron microscope (HRTEM) showed a nano-sized crystalline AI-N ceramic material and the flat interface between the Si substrate and the AIN film.
The Effect of Impurity Content and Ion Mass on the Depth Profiles of Vacancy-Type Defects in MeV Implanted Si
Authors: Libertino S. , Coffa S. , Privitera V. , Priolo F.
Published: September 2012

We used deep level transient spectroscopy to determine the concentration and depth profile of the defects introduced by MeV He and Si implants in n-type crystalline Si. We have found that only ∼ 16% of the Frenkel pairs generated by the ion escapes recombination and is stored into room temperature stable defects such as divacancies and oxygen vacancy complexes. For a light ion (He), the depth distribution of these defect complexes is strongly dependent on the O content of the substrate: it mirrors the initial distribution of I-V pairs, as calculated by TRIM (a Monte Carlo Code) when the O content is high (∼ 1018/cm3) while it can be much wider (up to 2 μm) in a highly pure (low O content) epitaxial substrate. This effect is due to a long range migration of vacancies before clustering or trapping at impurities. This migration is strongly inhibited for an ion of higher mass (such as Si) since in a denser collision cascade direct clustering is strongly favoured with respect to agglomeration of migrating defects.
A Study of the Tribological Characteristics of Titanium Nitride Film Prepared by the Dynamic Ion Beam Mixing Method for Application on Sliding Bearings
Authors: Nagasaka H. , Koizumi T.
Published: September 2012

Titanium nitride (TiN) film for the bearings and seals used in rotating machinery has been developed by the dynamic-ion-beam-mixing (DM) process, which combines Ti vapor deposition with simultaneous nitrogen ion beam irradiation. In this study, the tribological properties of the DM-TiN film on martensitic stainless steel (SS) were investigated for application on the bearings of submerged pumps. The critical contact pressure for seizure, wear resistance and friction coefficient properties of DM-TiN film paired with cast iron were investigated under practical sliding conditions, and compared with the hard surface materials of nitriding AISI 420 SS and nitriding 41CrAlMo74 (CrAlMo) steel. The results show that DM-TiN film is superior to these nitriding steels in surface contact pressure for seizure and wear resistance.
Preparation and Characterization of Tin Oxide Films by Ion-Assisted Deposition
Authors: Choi W. K. , Cho J. S. , Song S. K. , Kim Y. T. , Yoon K. H. , Jung H.-J. , Koh S. K.
Published: September 2012

Undoped tin oxide films were grown on Si substrates by a reactive ion-assisted deposition technique in which oxygen ions were irradiated on depositing Sn particles. In order to investigate the oxidation from SnO to SnO2, the effects of initial oxygen contents and heat treatment on the final crystalline structure of tin oxide films were thoroughly examined. Oxygen to Sn metal ratio (No/Nsn) of as-deposited films were controlled from 1.1 to 1.9 by varying the relative arrival ratio (F) of oxygen ion to Sn particle from 0.025 to 0.1. Heat treatment was carried out in two different ways; one was post vacuum-annealing at 400 ∼ 600°C and the other was in-situ annealing 400 ∼ 500°C. Crystalline structure of as-deposited tin oxide films at room temperature was amorphous. After post-annealing at 400°C, only SnO phase was found below No/Nsn= 1.6 in x-ray diffraction and crystalline structure of the films comprising higher oxygen contents still appeared to be amorphous. Even though the films still showed SnO phase until Γ50 after 500°C post-annealing, however, mixed structures of SnO, SnO2, and intermediate Sn2O3/Sn3O4 were observed for the films Γ75 and Γ100 with higher oxygen contents. At 600°C annealing, perfect SnO2 phase was attained for the films having No/Nsn=1.9. On the other hand, pure polycrystalline SnO2 films could be obtained by in-situ annealing at low temperature. The values of No/Nsn and the chemical shifts with the variation of oxidation were carefully determined by the comparison of Sn MNN and O KLL Auger transitions. Surface microstructure of deposited films was also analyzed using a scanning electron microscopy (SEM) and an atomic force microscope (AFM).
Engineered Nanocrystallites for Enhanced Performance of Ceramic Coatings by Ion Beam Assisted Deposition
Authors: Namavar F. , Haupt J. , Tobin E. , Karimy H. , Trogolo J. , Colter P. , Yoganathan M. , Jollimore C. , Bricault R. , Hirvonen J. P. , Ayer R.
Published: September 2012

Typical high-temperature thin-film deposition techniques are not suitable for certain substrates such as polymers and thermally-sensitive steels. In this work, ion beam assisted deposition (IBAD) was used to deposit ceramic and metallic films at temperatures below 150°C with nanocrystalline (< 100Å diameter) grain size. Nanoindentation studies of these films have shown hardnesses 50 to 100% greater than larger-grained films and, in some cases, fracture toughness approaching that of Si3N4.

By combining chromium evaporation with nitrogen beam bombardment, hard, adherent CrN films without any porosity have been produced at low temperatures with a N/Cr arrival ratio of about 1. The grain size is typically smaller than 100Å and hardness is typically higher than 25 GPa. For a N/Cr arrival ratio slightly less than 1, we observed possible grain boundary porosity. However, even with porosity, hardness is typically 20 to 24 GPa for grain sizes smaller than 100Å. For a N/Cr arrival ratio of 1/4 we deposited elemental Cr with a grain size of 300 to 500Å and a hardness greater than that of silicon (12 GPa). Using Ar ions and a N backfill, we produced elemental Cr containing a mixture of coarse (120 to 150Å) and fine (25 to 30Å) grains. For high-temperature deposition of CrN, the grain size increases (200 to 600Å) with a noticeable decrease in hardness. Mechanical properties of CrN are greatly influenced by impurities, as well as by surface conditioning of the substrate.

TiN films having gold color and grain sizes from 50 to 1000Å have been produced at low temperatures. Nanoindentation measurements of hardness and fracture toughness indicate that impurity-free TiN (with grains smaller than 100Å) has a hardness higher than 25 GPa and a fracture toughness close to that of Si3N4, but with higher wear resistance. Mechanical properties of our TiN films are greatly influenced by impurities, particularly oxygen, although it does not influence the gold color of TiN.
Defect Diffusion During Annealing of Low-Energy Ion-Implanted Silicon
Authors: Bedrossian P. J. , Caturla M.-J. , Rubia T. Diaz De La
Published: September 2012

We present a new approach for investigating the kinetics of defect migration during annealing of low-;energy, ion-implanted silicon, employing a combination of computer simulations and atomic-resolution tunneling microscopy. Using atomically-clean Si(111)-7×7 as a sink for bulk point defects created by 5 keV Xe and Ar irradiation, we observe distinct, temperature-;dependent surface arrival rates for vacancies and interstitials. A combination of simulation tools provides a detailed description of the processes that underly the observed temperature-dependence of defect segregation, and the predictions of the simulations agree closely with the experimental observations.
Effects of Interstitial Clustering on Transient Enhanced Diffusion of Boron in Silicon
Authors: Solmi S. , Valmorri S.
Published: September 2012

A simulation model for Boron diffusion which takes into account the aggregation of the excess interstitials in clusters, and subsequently, the dissolution of these defects, is proposed. The interstitial supersaturation and generation rate are determined according to the classical theory of nucleation and growth of particles, in analogy with the precipitation of a new phase in heavily doped silicon. The clusters are considered as precipitates formed by interstitial Si atoms. The B diffusion is modelled on the basis of the dopant-interstitial pair diffusion mechanism. The clusters dissolution during annealing maintains nearly constant, for a long period, the interstitial supersaturation and the related enhancement of the boron diffusion. This gives a good account of the diffusion results over a large range of experimental conditions. Furthermore, this approach describes most of the behavior of the transient enhanced diffusion (TED), like the temperature dependence of the level of the B diffusion enhancement, the dependence of the duration of the phenomenon on implanted dose, and the scarce dependence on the damage distribution in depth. The results of the simulations are compared with experimental data on the kinetics of interstitial cluster dissolution and of B TED.
Formation of ZnSe/GaAs Heterovalent Heterostructures by Movpe
Authors: Funato Mitsuru , Aoki Satoshi , Fujita Shizυo , Fujita Shigeo
Published: September 2012

ZnSe/GaAs (001) heterovalent heteгostructures are fabricated by metalorganic vapor phase epitaxy. During the growth, both GaAs and ZnSe surfaces are kept atomically flat to achieve precise control of the interface formation. Interface composition, Ga/As, are controlled by means of either Zn or Se treatment of a GaAs surface, and then ZnSe growth follows. Consequently, it is revealed by X-ray photoemission spectroscopy (XPS) that artificial control of Ga/As from 1.0 to 2.8 leads to the variation of valence band offsets from 0.6 to 1.1 eV. Based on the electron counting model and layer-attenuation model, it is proposed that the As plane just below the interface consists of As, anti-site Ga and As vacancy.
Atomic Hydrogen Assisted Growth of Si-Ge Heterostructures on (001) Si
Authors: Baribeau J.-M. , Lockwood D.J. , Rolfe S.J. , Syme R.W.G. , Labbé H.J.
Published: September 2012

A study of the interface chemical and physical abruptness of Si-Ge heterostructures grown on (001) Si by molecular beam epitaxy under atomic hydrogen exposure is reported. Atomic hydrogen (AH) was produced by the dissociation of molecular hydrogen interacting with a hot tungsten filament. Secondary-ion mass spectroscopy (SIMS) of structures made of alternating Ge (0.5 nm)/Si (40 nm) layers demonstrated that AH can effectively suppress Ge surface segregation. The segregation length was reduced from 1.5 nm to about 0.5 nm in films grown at a hydrogen partial pressure of −5 × 10-3 Pa and cell temperature of 2140 °C with an estimated cracking efficiency of ~5%. However, the high hydrogen background pressure had detrimental effects on the physical sharpness of the interfaces. This was evidenced by comparing the interface quality of Si/Ge atomic layer superlattices grown with and without AH exposure. X-ray reflectivity and Raman spectroscopy revealed a significant increase of the interface roughness, although the periodic character and the good crystallinity of the structures were preserved.
Surface Reactions During the Deposition of Ge from Chemical Sources on Ge(100)-(2×1)
Authors: Michael Greenlief C. , Chen Jihong
Published: September 2012

The adsorption and decomposition of diethylgermane, triethylgermane, and digermane on the Ge(100) surface are investigated with the intent of elucidating the surface processes leading to the deposition of epitaxial Ge films. Room temperature adsorption of diethylgermane or triethylgermane leads to the formation of surface germanium hydrides and ethyl groups. The ethyl groups decompose at higher temperatures and form ethylene via a β-hydride elimination reaction. Isotopic labeling experiments are used to confirm this reaction step. This is in contrast to the Si(100) surface where both α- and β-hydride elimination is observed for the decomposition of surface ethyl groups. The adsorption and reaction of digermane with the Ge surface is also determined to help provide a comparison with the ethylgermanes. Low energy electron diffraction is used to evaluate the quality of the deposited germanium films.
Physics and Control of Si/Ge Heterointerfaces
Authors: Fukatsu S. , Usami N. , Sunamura H. , Shiraki Y. , Ito R.
Published: September 2012

We describe physics and control of Si/SiGe heterointerfaces. A clear distinction will be made between the vertical and lateral effects of the Si/SiGe interface from the viewpoint of interface engineering. Ge surface segregation during nonequilibrium MBE growth and surfactant-mediated-growth are highlighted as prominent examples for the vertical effects while interface microroughness is addressed for the lateral effects. The influence of the interface effects on radiative recombination of indirect excitons is described in the context of SiGe-based optoelectronic applications.
Growth of ZnSe-Based Compounds on Ge-Terminated GaAs Surface
Authors: Saitoh T. , Tsujimura A. , Nishikawa T. , Watakabe A. , Sasai Y.
Published: September 2012

Growth of ZnSe-based compounds on the GaAs surface terminated by ultra-thin Ge epitaxial layer was carried out by molecular beam epitaxy and the influence of Ge layer on the growth of ZnSe was investigated. When the thickness of Ge layer was 1 atomic layer (AL), 2-dimensional growth occurred in the initial stage of ZnSe layer growth and anti-phase boundary (APB) free ZnSe layer was obtained. For Ge layer thickness of 10 AL, ZnSe grew 3-dimensionally and APBs were generated in the ZnSe layer. The crystalline quality of ZnMgSSe layer was also strongly influenced by the thickness of Ge layer. These phenomena were identified to be due to the transition of Ge surface structure from single domain to double domain with increasing Ge layer thickness.