bluuebunny/crossref_metadata_2025 huggingface dataset:
Germanium Redistribution Phenomena in the Synthesis of SiGe Layers
Authors: Patel C. J. , Butcher J. B.
Published: September 2012

A unique germanium redistribution phenomenon occurs in the synthesis of SiGe by 74Ge+ ion implantation. A number of silicon samples were implanted with 74Ge+ ion using a range of substrate temperatures (R.T. to 600°C) with different germanium fluences (1.5 × 1016 cm-2 to 4 × 1016 cm-2) and implantation energies (100keV – 18OKeV). Samples were germanium profiled using Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS).The experimental results show that the peak range of the germanium implant increases progressively above 150°C and a shift of 40nm in the peak germanium range was measured for a sample implanted at 600°C. The ‘hot’ implants have an extended tail profile contrary to the Debye model for root-mean-square deviations of the lattice atoms from their equilibrium sites which should ideally contribute to dechanneling. The data suggest strongly that dynamic annealing related diffusion (DARD) processes exist, whereby mobile non-equilibrium point defects influence diffusion to take place at the elevated implantation temperature. The SIMS spectra of samples implanted with high Ge fluences at elevated temperature show “uphill” diffusion.
Formation of Buried Layers of (SiC)1-x(AINT)x in 6H-SiC Using Ion-Beam Synthesis
Authors: Yankov R. A. , Hatzopoulos N. , Fukarek W. , Voelskow M. , Heera V. , Pezoldt J. , Skorupa W.
Published: September 2012

Solid solutions of SiC and III-V compound semiconductors are recognized as promising materials for novel semiconductor applications. This paper reports on experiments which explore the possibility of synthesizing thin buried layers of (SiC)l-x(AIN)x having composition of about x = 0.2 by co-implanting N+ and Al+ ions into 6H-SiC wafers maintained at temperatures in the range 200 - 800°C. Structural and compositional evaluation of as-implanted samples was carried out using a combination of Rutherford backscattering/channelling spectrometry and infrared reflectance spectroscopy. It is shown that the structures are highly sensitive to the substrate temperature. The use of sufficiently high temperatures (400 - 800°C) enables the crystallinity of the host material as well as relatively low damage levels to be maintained during implantation. The formation of AI-N bonds within the implanted layers is also confirmed over the temperature range studied.
Ion Beam Synthesis of SiC/Si Heterostructures by Mevva Implantation
Authors: Wong S. P. , Ho L. C. , Chen Dihu , Guo W. S. , Yan H. , Kwok R. W. M.
Published: September 2012

Ion beam synthesis of SiC/Si heterostructures was performed by MEVVA (metal vapor vacuum arc) implantation under various implantation and annealing conditions. The implanted SiC/Si heterostructures were characterized by various techniques. Carbon redistribution in overstoichiometrically implanted samples during annealing to form a stoichiometric SiC layer has been observed for the first time. The FTIR spectra were found to be composed of two components, one attributed to amorphous SiC and the other to β-SiC. It was also found that there are critical dose and critical energy at which the crystalline fraction increases abruptly. Other results on electrical and optical characterization are also presented and discussed
Conductive Tungsten-Based Layers Synthesized by Ion Implantation into 6H-Silicon Carbide
Authors: Weishart H. , Schoneich J. , Voelskow M. , Skorupa W.
Published: September 2012

We studied high dose implantation of tungsten into 6H-silicon carbide in order to synthesize an electrically conductive layer. Implantation was performed at 200 keV with a dose of 1.2x 1017 WIcm 2 at temperatures between 200°C and 400°C. The influence of implantation temperature on the distribution of W in SiC was investigated and compared to results obtained earlier from room temperature (RT) and 500°C implants. Rutherford backscattering spectrometry (RBS) was employed to study the structure and composition of the implanted layers. Implantation at temperatures between RT and 300°C did not influence the depth distribution of C, Si and W. The W depth profile shows a conventional Gaussian shape. Implanting at higher temperatures led to a more confined W rich layer in the SiC. This confinement is explained by Ostwald ripening which is enabled during implantation at temperatures above 300°C. The depth of the implantation induced damage decreases slightly with increasing implantation temperature, except for 400°C implantation. The amount of damage, however, is significantly reduced only for implantation at 500°C.
SiC Precipitate Formation During High Dose Carbon Implantation into Silicon
Authors: Lindner J. K. N. , Volz K. , Stritzker B.
Published: September 2012

The formation of SiC precipitates during the high-dose implantation of carbon ions into Si(100) is studied by means of TEM for implantation conditions, which are suitable for the ion beam synthesis of buried SiC layers in silicon. It is observed that in crystalline silicon nm-sized epitaxially oriented 3C-SiC precipitates are formed which are almost identical in size, nearly independent of the depth and dose (4 - 9 x 1017 C+/cm2 ). With increasing dose, it is mainly the density of precipitates which increases. Amorphization of the silicon host lattice leads to depth intervals with a strongly decreased density of oriented crystalline SiC precipitates. The irradiation induced formatLion of larger randomly oriented SiC crystallites is observed to occur in amorphized regions after prolonged implantation. Both the irradiation induced destruction and formation of SiC precipitates contribute to the generation of a nearly box-shaped precipitate density distribution at doses near the stoichiometry dose.
Quantum Transport in Ion Beam Synthesized Cobalt Disilicide Wires
Authors: Lenssen D. , Mesters S. , Mesters S.
Published: September 2012

Submicrometer cobalt disilicide wires in Si(100) were fabricated by ion beam synthesis. We implanted cobalt ions through the openings of an implant mask made by direct electron beam writing. The formation of the wires was achieved by rapid thermal annealing at temperatures up to 1100°C for 10s. The produced wires have thicknesses of about 85 nm and widths depending on the widths of the implant mask which were varied between 1 μm and 100 nm. These wires were characterized by means of cross-section transmission electron microscopy and magnetoresistance measurements at low temperatures. The results can be well explained by weak localization with strong spirn-orbit scattering and superconducting fluctuation (Maki-Thompson) corrections.
Microstructural Observation of Focused Ion Beam Modification of Ni Silicide/Si Thin Films
Authors: Tanaka Miyoko , Furuya Kazuo , Saito Tetsuya
Published: September 2012

Focused ion beam (FIB) irradiation of a thin Ni2Si layer deposited on a Si substrate was carried out and studied using an in-situ transmission electron microscope (in-situ TEM). Square areas on sides of 4 by 4 and 9 by 9 μm were patterned at room temperature with a 25keV Ga+-FIB attached to the TEM. The structural changes of the films indicate a uniform milling; sputtering of the Ni2Si layer and the damage introducing to the Si substrate. Annealing at 673 K results in the change of the Ni2Si layer into an epitaxial NiSi2 layer outside the FIB irradiated area, but several precipitates appear around the treated area. Precipitates was analyzed by energy dispersive X-ray spectroscopy (EDS). Larger amount of Ni than the surrounding matrix was found in precipitates. Selected area diffraction (SAD) patterns of the precipitates and the corresponding dark field images imply the formation of a Ni rich silicide. The relation between the FIB tail and the precipitation is indicated.
Ab Initio Pseudopotential Calculations of Carbon Impurities in SI
Authors: Zhu Jing , Rubia T. Diaz De La , Mailhiot Christian
Published: September 2012

Ab initio planewave pseudopotential method is used to study carbon diffusion and pairing in crystalline silicon. The calculation is performed with a 40 Ry planewave cutoff and 2×2×2 special k-point sampling with a supercell of 64 atoms. It is found that substitutional carbon attracts interstitial Si forming a <001> C interstitial with a large binding energy of 1.45 eV. The interstitial carbon is mobile and can migrate with a migration energy of 0.5 eV. The interstitial carbon can bind further to another substitutional carbon forming a substitutional carbon-interstitutional carbon pair with a binding energy of 1.0 eV. This model is used to understand the effect of high C concentration on the transient enhanced diffusion in Si.
Synthesis of Soi Materials Using Plasma Immersion Ion Implantation
Authors: Chu Paul K.
Published: September 2012

As the dimensions of integrated circuits shrink towards the deep sub-micromeLer regime, silicon-on-insulator is regarded to be more favorable than silicon substrates. The biggest drawback of SOI is cost which will become more critical for next generation 300-nm silicon wafers. Plasma immersion ion implantation (PIII) provides a viable alternative for the fabrication of SOI wafers as the processing time is very short and independent of wafer size. Pill is being employed to synthesize two types of SOI materials, SPIMOX (Separation by Plasma IMplantation of OXygen) and bonded SOL. In SPIMOX fabrication, both oxygen and water plasmas have been attempted and the results indicate that a discrete buried oxide layer can indeed be formed. In the case of wafer bonding, PIII is utilized for smart-cutting, a process in which implanted hydrogen or helium causes the bonded wafer to crack along the plane thereby making one side of the wafer recyclable. This article reviews the work done and current status of SOI fabrication by PIII.
Thermal Stability of Cu Films on Tin/Ti/Si(100) by Partially Ionized Beam Deposition
Authors: Jang H. G. , Kim K. H. , Choi D. J. , Han S. , Choi S. C. , Choi W. K. , Jung H-J. , Koh S. K.
Published: September 2012

Cu thin films with a thickness around 850 Å were prepared on Ti45N55/Ti/Si(100) substrates at room temperature by partially ionized beam deposition (PIBD) with an ion energy of 3 keV at pressure of 8×10−7-1 x 10−6 Torr. The Cu/Ti45N55/Ti/Si samples were annealed at 8×10−6-1 × 10−5 Torr with annealing temperature of 500 to 700 °C for 30 min.. Thermal stability of the PIB-Cu films was investigated with Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), Scanning electron microscopy (SEM), and X-ray diffraction (XRD). The as deposited Cu films had a (111) texture and there was no change of phase in annealed Cu films regardless of annealing temperature. Grain size of the annealed Cu films increased with annealing temperature. SEM studies show no hillock and no voiding on the Cu film surface up to annealing temperature of 700 °C. For PIB-Cu/Ti45N55/Ti/Si samples, all the layers were intact and there was no indication of interdiffusion by conventional depth profiling techniques (RBS, AES) up to 700 °C in vacuum for 30 minutes.
Optical Properties of Multi-Component Cadmium-Silver Nanocluster Composites Formed in Silica by Sequential Ion Implantation
Authors: Zuhr R. A. , Magruder R. H. , Anderson T. S.
Published: September 2012

The formation and optical properties of nanometer dimension metal colloid composites formed by the sequential implantation of Cd then Ag and by single element implantations of Cd and Ag in silica were characterized by transmission electron microscopy (TEM) and optical spectroscopy. A nominal dose of 6×1016 ions/cm2 as determined by current integration was used for both ion species. The doses used for the sequential implantations were a 1 to 1 ratio of Cd to Ag. Sequential implantations of Cd and Ag led to the formation of both multi-component metal nanoclusters and elemental nanoclusters. The electron diffraction measurements indicated that the polycrystalline particles of Ag5Cd8 and elemental Ag were formed. The optical response was consistent with results expected from effective medium theory.
Formation of Silver Metal Nanoclusters in MgO by MeV Ag Implantation
Authors: Ila D. , Wu Z. , Zimmerman R. L. , Sarkisov S. , Qian Y. , Poker D. B. , Hensley D. K.
Published: September 2012

Nanoclusters of Ag metal in MgO(100) single crystals was formed by implantation of 1.5 MeV silver ions at fluences of 6 x 1016 ion/cm2 and at 1.2 x 1017 ion/cm2, and subsequent annealing at temperatures between 600°C to 1100°C. The formation of the Ag metallic clusters was confirmed using optical absorption spectrophotometry by the absorption band at 430 nm. This is in agreement with the theoretical prediction using Mie's theory, with calculated average nanocluster size about 3 nm. Using ion channeling we confirmed that the orientation of the Ag nanoclusters was in the same direction of the host crystal. Using Z-scan we found the nonlinear refractive index of Ag implanted MgO to be 4.9 x 10-8 esu.
Non-Linear Optical Response of Metallic and Emiconducting Nanocrystals in Fused Silica
Authors: Elliman R. G. , Luther-Davies B. , Samoc M. , Dowd A.
Published: September 2012

The linear and nonlinear optical properties of Ge-implanted fused-silica were examined and compared with Au- and Si-implanted samples. Samples as-implanted with 1.0 MeV Ge ions to a fluence of 3x1017 Ge.cm-2 exhibited relatively large non-linearities, |n2| ≤5x10-12 cm2/W, and fast relaxation times, ∼lps. In contrast, samples implanted with comparable fluences of Au ions exhibited smaller non-linearities, |n2| ∼1x10-13 cm2/W, and slower response times, ≥ 10ps. The non-linearity for Ge was much larger than that for samples as-implanted with Si.
Linear and Nonlinear Optical Properties of Metal Nanoclustersilica Composites Formed by Implantation of Sb in High Purity Silica
Authors: Magruder R. H. , Weeks R. A. , Anderson T. S. , Zuhr R. A.
Published: September 2012

The linear and nonlinear optical properties of a series of Sb nanometer dimension metal colloids in silica were measured. The colloids were fabricated by the implantation of Sb in silica with nominal doses of 3, 6 and 9x1016 ions/cm2 at 320 keV. The linear optical response was measured from 200 to 900 nm. The nonlinear optical properties were measured using the z-scan technique at wavelengths of 596 and 617 nm. The results are compared to linear and nonlinear properties of a sample implanted with 6x1016 Ag ions/cm 2. Both absorption and the nonlinear index of refraction increase with increasing volume fraction for the Sb implanted samples. The lower linear absorption and comparable nonlinear index of refraction for the Sb colloid-glass composites may be better for devices than composites using metal colloids that have a surface plasmon resonance.
Carbon Implanted in Optical Grade Fused Silica: Annealing Effects in Reducing and Oxidizing Atmospheres
Authors: Tung Y. S. , Mu R. , Ueda A. , Henderson D. O. , Wang P. W. , White C. W. , Zhu Jane G. , Zuhr R. A.
Published: September 2012

Carbon is implanted into fused silica with doses of 1, 3, 6, 10×1016 ions/cm2. Infrared spectroscopy has identified the formation of CO and CO2 molecules in the implanted glasses. The relationships among concentrations of carbon dioxide, carbon monoxide and carbon doses are established by the infrared measurements. Annealing under different atmospheres have dramatic effects on CO and CO2 concentrations.
Excitation and De-Excitation Processes in Er Implanted Light Emitting Si Devices
Authors: Franzo' G. , Coffa S. , Priolo F.
Published: September 2012

In this paper we show that room temperature electroluminescence at 1.54 μm can be obtained in Er and O co-doped Si diodes, fabricated by ion implantation, under both forward and reverse bias conditions. This electroluminescence is particularly strong under reverse bias at the breakdown, when Er is excited through impact with hot carriers. This last mechanism is shown to occur with a cross section of 6×10-17 cm2. The measured decay lifetime of Er ions during pumping is 100 μs at room temperature and this allows to obtain a high internal quantum efficiency. However, when the diode is shut off, the decay lifetime becomes shorter and in particular it is less than 1.2 μs (that is the time response of our system). These results can be explained by the presence of Auger nonradiative de-excitation processes that are inhibited within the depletion region during pumping and set in when, at the shut off, the Er ions are immediately embedded within the heavily doped region (∼1019/cm3) of the device. The long lifetime (100 μs) during pumping and the very fast decay time (≤ 12 μs) at the diode shut off allow us to obtain, in our diode and under reverse bias, both a high efficiency (> 10-4) and a fast modulation (≥ 80 kHz) of the 1.54 μm emission.
Optical Properties and Surface Roughness of Ion Implanted Single Crystal Sapphire
Authors: Demaree J. D. , Kirkpatrick S. R. , Kirkpatrick A. R. , Hirvonen J. K.
Published: September 2012

It has been shown that metal ion implantation can harden single crystal sapphire and introduce compressive stresses at the surface, which may lead to an increase in the fracture toughness of the material. This may significantly affect the usefulness of this material as a shatter-resistant optical window in missile applications. In this study, we have examined the extent to which sapphire can be implanted without severely degrading its optical quality by ion beam defect production. Optically-polished single-crystal c-axis sapphire was implanted with 150 keV Cr+, Ti+, and Si+ ions to doses of 0.3 – 3.0 × 1017 ions/cm2 at both room temperature and at 800 °C, to measure the optical effect of in situ annealing. Rutherford backscattering spectrometry showed evidence of implant species migration only in the case of Ti implanted at high temperatures; all other implant profiles were Gaussian. The optical transmittance of the sapphire was examined using visible spectrum transmission and Fourier Transform Infrared Spectroscopy. Si implantation resulted in a 10 % reduction in infrared transmittance at the highest ion dose, but this was reduced to 6 % when the implantation was done at high temperature. Both Cr and Ti implantation reduced the sapphire IR transmittance (by 16 % and 42 %, respectively) , but the effect of implantation temperature on transmittance was different. High temperature during implantation increased the transmittance of Cr-implanted samples, but further darkened Ti-implanted samples. Photon tunneling and atomic force microscopy showed that both Ti and Cr implantation roughened the surface of the material.
Violet Luminescence from Ge+-Implanted SiO2 Film on Si Substrate
Authors: Bao Xi-Mao , Gao Ting , Yan Feng , Tong Song
Published: September 2012

The SiO2 films thermally grown on crystalline Si were implanted with Ge ions at 60 keV with doses of l×1015 cm-2 and l×1016 cm-2, followed by thermal annealing at various temperatures. Under an ultraviolet excitation of 240 nm, the films exhibit intense violet luminescence with a peak at 396 nm. This peak is ascribed to the T1 → S0 transition in GeO formed during implantation and annealing. After 1100°C annealing, Ge clusters were formed in an SiO2 matrix and a PL peak at 840 nm, due to the quantum confinement effect, which was measured at low temperature (77 K).
Surface Modification of Polymer by Ion Assisted Reaction in Reactive Gases Environment
Authors: Koh S. K. , Choi S. C. , Choi W. K. , Jung H. J. , Hu H. H.
Published: September 2012

Wettable surface of polymers (advanced wetting angle ∼10° and surface energy ∼ 60 ∼ 70 erg/cm2) have been accomplished by the ion assisted reaction, in which energetic ions are irradiated on polymer with blowing oxygen gas. The energies of ions are varied from 0.5 to 1.5 keV, doses 1014 to 1017 ions/cm2, and blowing rate of oxygen 0 ∼ 8 ml/min. The wetting angles are increased when the wettable polymers were exposed in air, but are remained in pure water. Improvement of surface energy is mainly due to the polar force. Surface analysis shows hydrophilic functional groups such as C=O, (C=O)-O, C-O, etc., are formed without surface damage after the ion assisted reaction treatment. Comparisons between the conventional surface treatments and the ion assisted reaction are described in term of physical bombardment, surface damage, functional group, and chain mobility in polymer.
Plasma Immersion Ion Implantation Modification of Surface Properties of Polymer Material
Authors: Husein Imad F. , Zhou Yuanzhong , Qin Shu , Chan Chung , Kleiman Jacob I. , Marchev Krassimir
Published: September 2012

The use of plasma immersion ion implantation (PIII) as a novel method for the treatment of polymer surfaces is investigated. The effect of PIII treatment on the coefficient of friction, contact angle modification, and surface energy of silicone and EPDM (ethylene-propylene-diene monomer) rubber are investigated as a function of pulse voltage, treatment time, and gas species. Low energy (0 - 8 keV) and high dose (∼1017 - 1018 ions/cm2) implantation of N2, Ar, and CF4 is performed using an inductively coupled plasma source (ICP) at low pressure (0.2 mTorr). PIII treatment reduces the coefficient of friction (μ) of silicone rubber from μ = 0.464 to the range μ = 0.176 – 0.274, and μ of EPDM rubber decreases from 0.9 to the range μ = 0.27 – 0.416 depending on processing conditions. The contact angle of water and diiodomethylene decreases after implantation and increases at higher doses for both silicone and EPDM rubber.
Surface Modification of Polytetrafluoroethylene by Ar+ Irradiation for Improving Adhesion to other Materials
Authors: Koh S. K. , Park S. C. , Seok J. W. , Choi S. C. , Choi W. K. , Jung H. J.
Published: September 2012

Ion Irradiation on polytetrafluoroethylene(PTFE) has been carried out to improve adhesion to metal and to adhesive cement. Argon ion was irradiated on the polymer, and amount of Ar+ was changed from 1014 ions/cm2 to l×1017 ions/cm2 at 1 keV, and 4 ml/min of oxygen gas was flowed near the polymer surface during the ion irradiation. Wetting angle was changed from 100 degree to 70 – 150 degree depending on the ion beam condition. The changes of wetting angle and effects of Ar+ irradiation in oxygen environment were explained in a view of surface morphology due to the ion beam irradiation onto PTFE and formation of hydrophilic group due to a reaction between irradiated polymer chain and the blown oxygen. Strongly enhanced adhesions were explained by interlock mechanism, formation of electron acceptor groups on the modified PTFE, and interfacial chemical reaction between the irradiated surface and the deposited materials.
Tunneling Current Change of Graphite Surface by Single Ion Irradiation
Authors: Ogiso H. , Mizutani W. , Nakano S. , Tokumoto H. , Yamanaka K.
Published: September 2012

We discuss changes in electronic structure and the topography of a graphite surface undergoing by a single ion impact. Protrusion-like regions (PLRs) found in a scanning tunneling microscope image disappeared in the same view of a noncontact atomic force microscope image. We measured tunneling current versus voltage characteristics to determine the density-of-states change in PLRs. We found that the density of states at the Fermi level of PLRs was greater than that of the intact surface. We therefore concluded that the PLRs were not actual topographical changes, but originated from electronic structural changes in semimetal to metal transition.
Quantitative Analysis of Chemically-Enhanced Sputtering during Ion Beam Deposition of Carbon Nitride Thin Films
Authors: Hofsäss H. , Ronning C. , Feldermann H. , Sebastian M.
Published: September 2012

The sputter losses during growth of carbon nitride thin films using mass selected ion beam deposition of C+ and N+ ions with energies between 20 eV and 500 eV are studied. Depending on the ion energy 35 – 100 % of C+ but only 3 – 35 % of N+ ions are incorporated in the films. Thus the films are always strongly nitrogen-deficient. To suppress the preferential loss of nitrogen we introduce the concept of continuously growing surface protective layers. Starting from a diamond-like carbon film as substrate, carbon nitride films are deposited using 100 eV 12C+ and 1 keV 14N+ ions, so that the growing films are always covered with a 1–2 rm thick protective layer of amorphous carbon. In this case we observe an increased nitrogen incorporation yielding to films with average film composition of C2N.
Pulsed Laser Deposition of Diamond-Like Carbon Thin Films: Ablation Dynamics and Growth
Authors: Yang Peidong , Zhang Z. John , Hu Jiangtao , Lieber Charles M.
Published: September 2012

Thin films of diamond-like carbon have been grown by pulsed laser deposition using a Nd:YAG laser at 532 nm. Time-of-flight mass spectroscopy was used to investigate the effects of laser power density and background gas pressure on the plume characteristics including the species in the plume and the kinetic energy distribution of each species. We found that with increasing laser power density (1) the relative amount of C+ ions increases, (2) the kinetic energy distributions of C+ get broader and can be deconvoluted into fast and slow components, and (3) the kinetic energy of the fast component of C+ ions increases from several to 40 eV. The resistivity and the local carbon bonding in films grown under these same conditions were also characterized. It was found that there is direct correlation between the characteristics of fast part of C+ ions in the plume and the diamond-like properties of the thin films. Under optimal growth conditions diamond-like carbon films with a large fraction of sp3 bonding can be prepared, although the maximum fraction appears to saturate at 70%. The implications of these results are discussed.
Mechanical and Tribological Properties of Chromium-Nitrogen Films Deposited by Ion Beam Assisted Deposition
Authors: Tobin E. J. , Namavar F. , Karimy H. F. , Colerico-Stenstrom C. , Bricault R. J. , Haupt Justus , Hirvonen J.-P. , Ayer R.
Published: September 2012

Mechanical and tribological properties of chromium-nitrogen films deposited by ion beam assisted deposition (IBAD) were investigated. The films were deposited reactively, i.e., via chromium evaporation with concurrent nitrogen ion beam bombardment, on stainless steel substrates at low deposition temperatures (<200°C). Two primary deposition regimes, with differing Cr/N atom-to-ion arrival ratios, were investigated: approximately 0.8–1.0 and 2.5–3.0. Rutherford Backscattering Spectroscopic analysis showed the lower arrival ratio films to be essentially stoichiometric CrN, whereas films deposited at higher arrival ratios were Cr-rich with Cr/N ratios of about 3:1. Both films were fine grained polycrystalline (typically 5–20 nanometer crystal dimension). The stoichiometric films were approximately two times harder than the Cr-rich films., based on nanohardness indentation measurements, and possessed higher residual stress levels. Both film types substantially improved the wear resistance of stainless steel disks, based on the results of ball-ondisk wear tests against ruby balls. The best performance was obtained with Cr-rich films, which exhibited a very low wear rate and lower friction than either the stoichiometric film or the uncoated steel.
Effects of Aluminum Implantation on the Oxidation Behavior of Silicon Nitride in a Sodium Nitrate-Oxygen Gas Mixture
Authors: Cheong Y. , Du H. , Withrow S. P.
Published: September 2012

The role of aluminum in negating the adverse effect of alkali species on the oxidation resistance of Si3N4 ceramics was investigated by exposing unimplanted and aluminum-implanted (1 and 5 at.%) Si3N4 samples to a sodium nitrate (95 ppm)-dry oxygen gas mixture at 1. atm and at 900°1100°C. Oxidation of unimplanted Si3N4 was rapid and linear with an activation energy of 57 kJ/mol. In contrast, samples implanted with aluminum exhibited a considerably reduced oxide growth which was parabolic in nature with activation energies of 103–112 kJ/mol. The morphological characteristics of the oxide layer also showed marked improvement as the aluminum concentration increased.
Surface Microchemistry Associated with Particle Bombardment on Ni(111)
Authors: Yang Jiun-Chan , Hwang Hsin-Yen , Chang Che-Chen
Published: September 2012

The influence of particle bombardment on surface reactivity is examined by using the reaction of CO on the Ni(111) surface as a model system. Thermal desorption studies shows that a large amount of residual CO may be deposited on the surface during ion bombardment. An appreciable amount of oxygen can be produced on the surface by collision-induced CO dissociation. A new dlesorption state of CO is also formed. The activation energy for CO desorption from this new state is estimated to be about 90 kJ/mol, which corresponds to a decrease of the C-Ni bond energy of 25 – 30 kJ/mol as the sample evolves from a smooth to a damaged state. The dipole-dipole repulsion is present between CO molecules adsorbed on the ion-bombarded surface, which causes CO to desorb at a lower temperature for higher CO exposures. Under similar bombardment conditions, the sticking probability of CO on the bombarded surface decreases with decreasing momentum of the impinging particle.
The Influence of Cerium Ion Implantation on Early-Stage Oxidation Kinetics of Nickel
Authors: Czerwinski F. , Szpunar J. A.
Published: September 2012

The effect of implantation with 2×1016 ions/cm2 at 150 keV Ce+on the oxidation of polycrystalline high purity Ni was examined. The radiation damage and distribution of Ce implants in Ni substrate were additionally modified by post-implantation ultra-high vacuum annealing at 1073 K. Ce implants decreased the Ni oxidation rate at 973 K by approximately one order of magnitude, and this reduction was similar to that achieved by 14 nm thick CeO2 sol-gel coatings and by 4 nm thick coatings of CeO2 deposited on the same substrate by reactive sputtering. Physical damage introduced by radiation caused a slight increase in oxidation rate during the very initial stages. However, the essential improvement in the oxidation resistance was derived entirely from the chemical role of the implants. The beneficial effect of Ce was reduced when the implanted Ni substrate was vacuum-annealed prior to the oxidation.
Stress Induced Extended Ranges for Hydration and Other Phenomena in Ion Implanted Silica Glasses
Authors: Arnold G. W. , Battaglin G.
Published: September 2012

The extended ranges (2–3 times theoretical) for hydration from an ambient atmosphere or water immersion and other anomalous ranges for property changes in ion-implanted fused silica are explained on the basis of a stress corrosion model (Michalske-Bunker). The results for the hydration of implanted soda-lime glass are similar to fused silica with the added feature of compositional modification due to the near-surface removal of alkali.
Grain-Size and Impurity Effects in Low-Temperature Deposition of TiN
Authors: Kakimy H. , Namavar F. , Tobin E. , Haupt J. , Bricault R. , Hirvonen J. P. , Ayer R.
Published: September 2012

Commercially deposited titanium nitride (TIN) thin films have been available daring recent years. These TiN films possess high hardness and have good wear resistance; however, the deposition process typically requires a temperature of 500°C or higher. In many cases, due to substrate characteristics, a deposition temperature below 150°C is required in order to exploit TiN coating properties.

The objective of this work is to demonstrate that ion beam assisted deposition (IBAD) makes it possible to deposit gold-color TiN films with good adhesion onto a variety of substrates including plastics at temperatures below 150°C. These films have physical and mechanical properties as good as those produced at high temperatures. Samples have also been examined by nanohardness techniques to accurately determine the hardness of the films and relate them to process parameters and crystal sizes. Our results indicate that, by controlling the grain size of TiN, it is possible to fabricate TiN coatings at room temperature with hardness as high as 25.5 ± 1 GPa.
Competition Between Gettering by Implantation-Induced Cavities in Silicon and Internal Gettering Associated with SIO2 Precipitation
Authors: McHugo S. A. , Weber E. R. , Myers S. M. , Petersen G. A.
Published: September 2012

The gettering behavior of Cu and Fe was investigated in CZ silicon containing both internal-gettering sites in the bulk due to SiO2 precipitation and a device-side layer of cavities formed by He ion implantation and annealing. The objective was to quantify the effectiveness of impurity gettering at cavities relative to the widely used internal-gettering process. Both rapid thermal anneals and furnace anneals were used during the gettering sequences to reveal transient effects as well as the final, thermodynamically-equilibrated condition. For temperatures of 700, 800 and 850°C, the cavity gettering was observed to dominate the internal gettering as indicated both by the number of gettered atoms in the cavities and the residual solution concentration in the device region. The results are interpreted in detail by numerically solving the diffusion equation with sink-related source terms based on earlier, fundamental studies of the underlying mechanisms of internal and cavity gettering.
Diffuse X-Ray Scattering Study of Defects Created by keV Ion Implants in Si
Authors: Partyka P. J. , Averback R. S. , Nordlund K. , Robinson I. K. , Walko D. , Ehrhart P. , Rubia T. Diaz de la , Tang M.
Published: September 2012

Diffuse x-ray scattering (DXS) and computer simulation techniques were employed to investigate the defect structure produced in Si by low keV ion and MeV electron irradiations. DXS measurements were performed for keV Ga and He implants, demonstrating the ability of the technique to provide both bulk and near-surface measurements at defect concentrations of about 1000 ppm. A rigorous analysis of these results is complicated due to the complex nature of the ion damage in Si. A computer simulation framework is developed to aid in the analysis of this data. In this technique, defects are simulated and their strain fields are calculated by simply relaxing the atoms around the defect to their equilibrium positions. The diffuse scattering is then calculated from the strain field, and the results are compared to the experimental measurements. Computer simulations are presented here only for the case of electron irradiation damage and compared to published measurements.1 Application of the technique to more complicated structures is planned and should pose no serious problems in the computational framework already developed.
Modeling of Damage Evolution During Ion Implantation into Silicon: a Monte Carlo Approach
Authors: Tian S. , Morris M. , Morris S. J. , Obradovic B. , Tasch A. F.
Published: September 2012

We present for the first time a physically based ion implantation damage model which successfully predicts both the as-implanted impurity range profiles and the damage profiles for a wide range of implant conditions for arsenic, boron, phosphorus, and BF2 implants into single-crystal (100) silicon. In addition, the amorphous layer thicknesses predicted by this damage model for high dose implants are also generally in excellent agreement with experiments. This damage model explicitly simulates the defect production and its subsequent evolution into the experimentally observable profiles for the first time. The microscopic mechanisms for damage evolution are further discussed.
In Situ Optical Observation and Control of Initial Stages of GaAs Growth On Caf2 Surface Modified by Electron Beam Irradiation
Authors: Kawasaki K. , Tsutsui K.
Published: September 2012

We investigated the electron beam induced surface modification of CaF2(1 11) and initial stage of GaAs growth on the modified CaF2 surface by means of the surface photoabsorption technique and atomic force microscopy (AFM). The CaF2 surface was modified by 300 eV electron beam irradiation at 200°C in a As4 molecular beam. The amount of adsorbed As atoms increased with electron dose and it follows Langmuir adsorption principle and saturated at a value equivalent to I monolayer adsorption. In situ observation of GaAs growth on this modified surface clarified that the sticking coefficient of GaAs on CaF2 surface was drastically improved by the surface modification. AFM observation revealed that the surface roughness of initial growth of GaAs on modified CaF2 was improved at the growth temperature of 550°C
Surfactant-Mediated Si/Ge Epitaxial Crystal Growth
Authors: Kim Eunja , Wuk OH Chan , Lee Young Hee
Published: September 2012

We investigate the kinetic role of a surfactant in the epitaxial Si/Ge crystal growth using ab initio molecular dynamics approach. We examine the previously suggested dimer-exchange mechanisms and find that kinetics plays a crucial role in determining the exchange process. We further find that the diffusion of adatoms on an island in the presence of a surfactant is quite different from the dimer-exchange process on a flat surface.
Interface Roughness in Strained Si/SiGe Multilayers
Authors: Darhuber A. A. , Holy V. , Stangl J. , Bauer G. , NÜtzel J. , Abstreiter G.
Published: September 2012

Diffuse x-ray reflection from a SiGe/Si multilayer grown pseudomorphically on slightly miscut Si(OOl) substrates has been studied theoretically and experimentally. In the framework of the Distorted-Wave Born Approximation (DWBA), we demonstrated that the distribution of the diffusely scattered intensity gives conclusive information on both the amount and the in-plane and inter-plane correlation properties of the interface roughness. The best model for the description of the interface-morphology was found to be a combination of a two-level model and a staircase model.
Modification of the Surface Band-Bending of A Silicon CCD for Low-Energy Electron Detection
Authors: Smith Aimée L. , Yu Qiuming , Elliott S. T. , Tombrello T.A. , Nikzad Shouleh
Published: September 2012

Silicon CCDs have limited sensitivity to particles and photons with short penetration depth, due to the surface depletion caused by the inherent positive charge in the native oxide. Because of surface depletion, internally-generated electrons are trapped near the irradiated surface and therefore cannot be transported to the detection circuitry. This deleterious surface potential can be eliminated by low-temperature molecular beam epitaxial (MBE) growth of a delta-doped layer on the Si surface. This effect has been demonstrated through achievement of 100% internal quantum efficiency for UV photons detected with delta-doped CCDs.

In this paper, we will discuss the modification of the band bending near the CCD surface by low-temperature MBE and report the application of delta-doped CCDs to low-energy electron detection. We show that modification of the surface can greatly improve sensitivity to low-energy electrons. Measurements comparing the response of delta-doped CCDs with untreated CCDs were made in the 50 eV-1.5 keV energy range. For electrons with energies below 300 eV, the signal from untreated CCDs was below the detection limit for our apparatus, and data are presented only for the response of delta-doped CCDs at these energies. The effects of multiple electron hole pair (EHP) production and backscattering on the observed signals are discussed.
A Self-Organized Molecular Beam Epitaxial Growth of the InSb/AlGaSb Quantum Dots on High-Index GaAs Substrates
Authors: Yano Mitsuaki , Koike Kazuto , Inoue Masataka , Saitoh Toshiya , Yoh Kanji
Published: September 2012

In-situ organization of InSb quantum dots on Al0.5Ga0.5Sb is reported. Samples were grown on just (100), 5°off (100) towards [0-1-1],(311)A, and (311)B surfaces of GaAs by molecular beam epitaxy. The growth mechanism and characteristics of quantum dots were analyzed using reflection high-energy electron diffraction, atomic force microscopy, and photoluminescence. Observed photoluminescence peak shift towards lower energy side with InSb thickness was interpreted by the development of quantum dots. Substrate orientation effect was examined and found to be useful to increase the dot density. As a result, as high as ~3xl 09 cm-2 dot density was achieved on the (311 )B substrate whereas the typical value on the (100) was ~2xl 08 cm-2 .
Antimony Cluster Manipulation on the Si(001) Surface by Means of STM
Authors: Kravchenko I.I. , Salling C.T. , Lagally M.G.
Published: September 2012

We present results of the manipulation of antimony clusters on Si(001) by means of a scanning tunneling microscope. By adjusting tip-sample separation and pulse voltage, an antimony cluster can be removed from the sample surface without damaging it. The success rate of the removed-cluster redeposition from the tip back onto the surface is 30%. In the remainder of the attempts a square shaped structure is created that had a hillock in the center. The hillock exhibits a metallic-like I-V curve. Such a structure cannot be created without an Sb cluster previously removed from the surface and located on the tip.
Surface Morphology of Nanoscale TiSi2 Epitaxial Islands on Si(00l)
Authors: Yang Woochul , Jedema F.J. , Ade H. , Nemanich R.J
Published: September 2012

The morphologies of nanoscale epitaxial islands of TISi2 are studied. The islands are prepared by deposition of ultrathin Ti (3-20Å) on both smooth and roughened.Si(001) substrates. The island formation is initiated by annealing to 800-1000°C. The roughened substrates are prepared by etching with atomic H produced in a plasma. The morphologies of the substrate before and after island formation are examined by atomic force microscopy (AFM). In particular, the influence of surface-roughness on both the formation of islands and the size distribution of islands is investigated. On a rough substrate islands with a lateral dimension of ~350Å and a vertical dimension of ~25Å were observed with size uniformity of ~20%. Also it was observed that the roughness of the surface reduced the island size and affected the island distribution. The results are discussed in terms of surface energy and the strain field around the islands.
Structural Defects in Thick Ingaas Layers Grown by Lpee on Partially Masked GaAs Substrates
Authors: BRYSKIEWICZ T.
Published: September 2012

Defect formation in thick InxGa1-xAs layers, 0.06 ≤ x ≤ 0.17, grown by liquid phase electroepitaxy (LPEE) on partially masked GaAs substrates has been studied. The InxGa1-xAs ingots were 6 mm in thickness and, in some cases, more than 53 mm long in one direction. Prior to the LPEE growth, a thin SiO2 layer was deposited on the (100) oriented GaAs substrate by plasma enhanced chemical vapor deposition (PECVD), and patterned by photolithography with oxide free seeding windows of different geometry. The growth of a ternary crystal from a slightly supercooled melt originated in the form of islands within the window areas and extended laterally over the SiO2 layer to result, as the growth proceeded by LPEE, in a continuous layer with no apparent boundaries between merging islands. The two main structural defects have been identified in these compositionally uniform ternary crystals: microtwins and microcracks. They were found to result from the crystal/substrate misfit stress, when insufficiently suppressed by the SiO2 layer, and/or from improper seeding window geometry. The microcrack and microtwin formation in large diameter InxGa1-xAs crystals has been suppressed by the right choice of the seeding window geometry as well as by minimizing damage to the SiO2 layer caused by the H2 atmosphere and high growth temperature.
Facet Formation in Submicron Selective Growth of Si/SiGe
Authors: Wang K. L. , Wang Dawen
Published: September 2012

The paper reviews the work in mostly Si and SiGe epitaxy and some III-V work on patterned
substrates. Results of metalorganic chemical vapor deposition (MOCVD), low pressure chemical vapor deposition (LPCVD), gas source molecular beam epitaxy (GSMBE), and solid source molecular beam epitaxy (MBE) were discussed in the context of facet formation and mass accumulation. A model was shown to explain the facet formation and its evolution in the process of growth. Further work on surface diffusion and nucleation processes as functions of temperature and other growth parameters will provide needed information for accurate modeling of the facet growth process.
GaInP Selective Area Epitaxy for Heterojunction Bipolar Transistor Applications
Authors: PARK S. H. , FU S.-L. , YU P. K. L. , ASBECK P. M.
Published: September 2012

A study of selective area epitaxy (SAE) of GalnP lattice matched to GaAs is presented. The selectively regrown GaInP is used as the emitter of a novel heterojunction bipolar transistor (HBT) device structure. Successful SAE of GalnP on both dark field (mostly covered) and light field (mostly open) SiO2 masks is compared. To characterize the critical regrown heterojunction, diodes and HBTs were fabricated and measured. It is found that a pre-growth pause of either TEGa or PH3 results in forward bias characteristics with low leakage and an ideality factor of ~1.25, indicating low interfacial defect density. Non-self aligned regrown emitter HBTs grown with a dark field mask scheme have been fabricated. Devices with an emitter area of 3x12 μm exhibit small signal current gain up to 80 with an fT and fMAX of 22 GHz and 18 GHz, respectively. To further improve the performance of these devices, a structure with a self-aligned refractory metal base contact and light field regrowth is proposed.
Selective growth of MOVPE on AlGaAs/GaAs patterned substrates for quantum nano-structures
Authors: Sakuma Makoto , Fukui Takashi , Kumakura Kazuhide , Motohisa Junichi
Published: September 2012

We propose and demonstrate a new mask material of AlGaAs native oxide for selective area metalorganic vapor phase epitaxy (MOVPE) which has several advantages over conventional SiNx or SiO2 masks. GaAs selective area growth occurs on masked substrate of AlGaAs native oxide whose Al composition is 0.4, and the wire structures with trapezoidal cross section are formed along ]100] direction on (001) GaAs substrates with line & space mask pattern. Furthermore, after annealing the selectively grown GaAs wire samples, GaAs layers can be regrown with atomically smooth surface, in which GaAs wires are perfectly buried. The results show that this novel selective area MOVPE technique using AlGaAs native oxide masks are promising for quantum nano-structure device fabrication.
Selective Epitaxial Growth of Strained Silicon-Germanium Films in Tubular Hot-Wall Low Pressure Chemical Vapor Deposition Systems
Authors: Leet I -M. , Wang W. -C. , Koh M. T. K. , Denton J.P. , Kvam E. P. , Neudeck G. W. , Takoudis C. G.
Published: September 2012

Selective epitaxial growth (SEG) of silicon-germanium (SiGe) films on patterned-oxide silicon substrates, using a tubular hot-wall low pressure chemical vapor deposition (LPCVD) system, is demonstrated in this study. This conventional system is proposed as a low cost alternative for SiGe epitaxial growth. Three process improvements needed to achieve quality growth are discussed. First, the hydrogen bake process is modified to eliminate Ge-outgassing. Secondly, a Si SEG buffer layer is deposited prior to SiGe SEG. Finally, a small flow of dichlorosilane is introduced during the temperature ramp-down period prior to SiGe SEG. The growth results are discussed in terms of growth selectivity, thickness uniformity, growth rate, defect density, SiGe film composition, and electrical properties.