bluuebunny/crossref_metadata_2025 huggingface dataset:
Divacancy Annealing in Silicon Monitored by Differential Calorimetry and Infrared Absorption Spectroscopy
Authors: Roorda Sjoerd
Published: March 2011

Annealing of divacancies in crystalline Si has been characterized by differential scanning and isothermal calorimetry and infrared absorption spectroscopy. Si discs of 0.1 mm thickness have been implanted with 3.4 MeV protons. Scanning calorimetry shows a relatively sharp peak centered around 425 K and a broader feature ranging from 450 to 620 K. The isothermal heat release at 620 K exhibits a single exponential rather than a bimolecular decay. As the annealing progresses, a decrease in infrared absorption at 1.8 µm is observed which is directly related to the annealing of divacancies.
Formation and Thermal Stability of End-of-Range Defects in Ge Implanted Silicon
Authors: Seibt M. , Imschweiler J. , Hefner H.-A.
Published: March 2011

By means of transmission electron microscopy we have studied the redissolution of extended end-of-range defects during high temperature rapid thermal annealing. We find, that after the transformation of initially present {113} stacking faults into energetically more favorable structures, each type of end-of-range defect establishes its individual redissolution rate with {111} faulted loops being the most stable configuration.
Extended Defects in Fe-Implanted InP After Thermal Annealing
Authors: Frigeri C. , Bocchi C. , Carnera A. , Gasparotto A. , Gambacorti N. , Longo F.
Published: March 2011

The recovery of the implant-induced damage and the defects present after thermal annealing at 650 °C in Fe-implanted InP have been investigated by TEM, RBS and X-ray diffractometry as a function of the annealing time that was varied betweeen 0.5 and 2 h. The near-surface damaged layer was removed only for annealing times ≥ 1.5 h. The annealed samples contained stacking fault tetrahedra of vacancy type, extrinsic dislocation loops and microdefects. These extended defects were mostly localized in a band corresponding to the region of transition between amorphous top layer and crystalline substrate as was detected in the as-implanted sample. Stacking fault tetrahedra and loops have also been observed before and beyond this band, respectively. Such defects could be due to either shear strains at the recrystallization front or implant-induced point defects.
Solid-Phase Epitaxial Crystallisation of GexSi1-x Alloy Layers
Authors: Elliman Robert G. , Wong Wah-Chung , KringhØj Per
Published: March 2011

Thermally-induced solid-phase epitaxial crystallisation (SPEC) and ion-beam-induced epitaxial crystallisation (IBIEC) of amorphous GexSi1-x alloy layers is examined for three different starting structures: a) strain-relaxed alloy layers of uniform composition, b) strained alloy layers of uniform composition, and c) Ge implanted Si layers. Thermal annealing experiments show that the activation energy for strain-relaxed alloys is higher than that expected from a simple extrapolation between the activation energies of Si and Ge, and exceeds that of Si for x ≤ 0.3. Experiments on thin strained layers show that MBE grown strained layers which are stable during annealing at 1100°C for 60 s are also fully strained after SPEC, whereas layers which relax during annealing at 1100°C also relax during SPEC. Experiments on ion-implanted GeχSiι_x structures show that fully strained Si/GexSi1-x /Si heterostructures can be fabricated for ion fluences below a critical fluence, and as for uniform alloy layers that this critical fluence is accurately predicted by equilibrium theory. Strain relaxation during SPEC of uniform alloys and implanted structures is shown to be correlated with a sudden reduction in crystallisation velocity which is believed to be caused by stress-induced roughening or faceting of the crystalline/amorphous interface. IBIEC of thick (800 nm) implanted layers is shown to be limited by competition from ion-beam induced random crystallisation, while thin (120 nm) uniform alloys and implanted structures are shown to crystallise ephaxially and to exhibit similar behaviour to thermally annealed samples under certain conditions.
Ion Beam Induced Epitaxial Crystallization of Single Crystalline 6H-SiC
Authors: Heera V. , Kögler R. , Skorupa W. , Glaser E.
Published: March 2011

For the first time, ion beam induced epitaxial crystallization (IBIEC) has been found in SiC. The effect of 300 keV Si+ irradiation through an amorphous surface layer in single crystalline 6H-SiC at 477±5°C has been investigated by RBS/C and XTEM. A shrinkage of the amorphous layer was found after ion irradiation at this temperature which is caused by both an ion dose independent thermal regrowth of about 20 nm and an additional ion beam induced epitaxial crystallization with a rate of about 1.5 nm/ 1016 cm-2.
Density Reduction: A Mechanism for Amorphization at High Ion Doses
Authors: Specht E.D. , Walko D.A. , Zinkle S.J.
Published: March 2011

At cryogenic temperatures, the accumulation of vacancy-interstitial pairs in Al2O3 from atomic displacements associated with ion implantation produces amorphization. At room temperature, these pairs recombine, and amorphization occurs only at high doses. X-ray reflectivity measurements show that amorphization of the surface of Al2O3 implanted at room temperature with 160 keV Cr+ ions is preceded by a progressive reduction in near-surface density. Monte Carlo simulations show that this density reduction can be accounted for by high-energy-transfer collisions which knock atoms deep into the target, leaving widely separated vacancies and interstitials, which do not recombine. Electron microscopy shows that at least some of these vacancies condense into voids. We propose that this reduction in near-surface density can lead to amorphization at high doses. We present simple approximations for the density reduction expected for different ions and targets.
Electron Energy Dependence of Amorphization in Zr3Fe
Authors: Motta A.T. , Howe L.M. , Okamoto P.R.
Published: March 2011

This paper reports the results from a study conducted to determine the effect of electron energy on the dose-to-amorphization of Zr3Fe at 23-30 K. Zr3Fe samples were irradiated in the HVEM at Argonne National Laboratory, at energies ranging from 200 to 900 keV. Amorphization occurred at electron energies from 900 keV down to 250 keV. Three distinct regions were observed: between 900 and 700 keV amorphization occurred at a constant low dose of ~ 4 × 1021 e cm-2; a higher plateau at 1022 was observed between 600 and 400 keV, and finally there was a sharp increase in the dose-to-amorphization below 400 keV, so that at 250 keV the necessary dose was an order of magnitude higher than that at 900 keV. In the region below 400 keV there was evidence of a dependence of the dose-to-amorphization on the orientation of the sample with respect to the electron beam. The results can be analyzed in terms of a composite displacement cross section dominated at high energies by displacements of Zr and Fe atoms, by displacements of Fe atoms at intermediate energies and of secondary displacements of lattice atoms by recoil impurities at low energies.
MeV Boron Implantation and Masking
Authors: Lavine James P. , Filo A. J. , Losee D. L. , Guidash P. A. , Lee S.-T. , Braunstein G. H. , Kosman S. L. , Kyan H.
Published: March 2011

Boron depth distributions are reported for MeV implants into silicon through a variety of masking materials. Silicon is implanted with boron through a 0.1-µm-thick layer of thermally grown silicon dioxide. Secondary ion mass spectrometry (SIMS) shows the projected ranges agree within 10% with data reported in the literature and with results from the computer program TRIM. Silicon dioxide, photoresist, and metal layers are used to mask the high-energy boron implants. The SIMS results indicate that TRIM overestimates the energy loss of MeV boron ions as they pass through photoresist and/or silicon dioxide.
Thermally Stable Oxygen and Nitrogen Implant Isolation of C-Doped Al0.35Ga0.65As
Authors: Zolper J. C. , Sherwin M. E. , Baca A. G. , Schneider R. P.
Published: March 2011

Oxygen and nitrogen ion implantation have been applied, for the first time, to C-doped Al0.35Ga0.65As layers produce high resistivity regions (ps ≥ 1×1010 Ω/□) that are stable after annealing at 900 ºC. A dose threshold for stable compensation for both O and N ions was found above 8×1013 cm-2 for samples doped at 2×1018 cm-3. Although O implantation has been reported to form stable compensation in Si-doped and Be-doped AlGaAs, the ability of nitrogen implantation to produce thermally stable compensation has not been previously reported and may be due to a C-N complex. The existence of this C-N complex is supported by results for O- and N-implants into C-doped GaAs where N formed thermally stable compensation but O did not. Sheet resistance data versus anneal temperature and estimates of the depth of the defect levels are reported. This result will have application to heterojunction bipolar transistors and complementary heterostructure field effect transistor technologies that employ C-doped AlGaAs or GaAs layers along with high temperature post-isolation processing.
Erbium Ion Implantation for Optical Doping
Authors: Polman A.
Published: March 2011

Erbium is a rare-earth ion which, when incorporated in a solid in the trivalent state, shows characteristic intra-4f emission at 15 µm, an important telecommunication wavelength. A review is given of recent work in the area ofEr ion implantation into soda-lime silicate and AI2O3 optical waveguide films, LiNbO3 and silicon. Structural and optical characteristics are discussed and future challenges for this exciting new field are described.
Studies of Dislocation Formation in Annealed Self-Ion Irradiated Silicon
Authors: Goldberg R. D. , Simpson T. W. , Mitchell I. V. , Schultz. P. J.
Published: March 2011

Variable energy positron annihilation and Rutherford backscattering spectroscopy have been used to investigate the evolution of secondary defects during the annealing of self-ion irradiated silicon. Evidence supporting the existence of both vacancy- and interstitially-based defects after high temperature anneals is presented. Dopant type and irradiation temperature have both been shown to influence the structure of the defects whose onset can be manipulated via the implantation flux.
Erbium Implantation in Silicon: A Way Towards Si-Based Optoelectronics
Authors: Priolo F. , Franzó G. , Coffa S. , Polman A. , Bellani V. , Carnera A. , Spinella C.
Published: March 2011

In this paper our recent work on erbium implantation for optical doping of silicon is reviewed. It is shown that O co-implantation plays a key role both in providing Er with the appropriate chemical surrounding and in allowing the incorporation of high Er concentrations in thick Si layers without the formation of twins and/or precipitates. The luminescence intensity in Er and O co-implanted samples shows a much weaker temperature dependence (a decrease by a factor of 30 from 77K to 300K) than in samples without O (a decrease by 3 orders of magnitude in the same temperature range). This allowed us to observe room temperature photo- and electro-luminescence in Er and O co-doped samples. The temperature dependence of the luminescence in these samples has been determined to be due to non-radiative de-excitation processes. These data are reported and discussed.
Nanosize Metal Alloy Particle Formation in AG and CU Sequentially Implanted Silica
Authors: Zuhr R. A. , Magruder R. H. , Anderson A. , Wittig J. E.
Published: March 2011

A series of high purity silica samples were sequentially implanted with Ag and Cu ions at energies such that the depth distributions for each of the ions overlapped. The samples were characterized by RBS, TEM and optical spectroscopy. The optical response was found to be dependent on the order of sequential implantation, as well as the relative concentration of the implanted elements. The changes in the optical response are attributed to composition changes of the metal colloids that are formed as a result of alloying of the sequentially implanted metal ions, as well as to changes in the size the colloids.
Fluorine-Enhanced Si:Er Light Emission
Authors: Ren F.Y.G. , Michel J. , Jacobson D.C. , Poate J.M. , Kimerling L.C.
Published: March 2011

An erbium-fluorine complex is 100 times more effective than an erbium-oxygen complex in generating light emission at 1.54 µm in Si:Er. The luminescence light intensity is linearly proportional to the total retained F atoms in Si after heat treatment. F enhancement in light emission in Si:Er is eventually limited by the damage associated with high dose F implantation. The optimum annealing temperature to achieve the maximum intensity is found to decrease slightly from 1000ºC to 800ºC as the initial F implanted concentration increases. The Si:Er heat treatment process and the optimum processing window are determined by the interaction of three different processes: damage recovery/complex formation, F out-diffusion and Er-F complex dissociation.
Characterization and Applicatons of Arsenic-Implanted Mocvd-Grown GaAs Structures
Authors: Namavar Fereydoon , Kalkhoran N. , Cremins A. , Vernon S.
Published: March 2011

Arsenic precipitates can be formed in GaAs using arsenic implantation and annealing, thereby producing very high resistivity (surface or buried) GaAs layers. Arsenic-implanted materials are similar to low-temperature (LT) GaAs:As buffer layers grown by molecular beam epitaxy (MBE) which are used for eliminating side- and backgating problems in GaAs circuits. Arsenic implantation is not only a simple and economical technique for device isolation but also can improve the quality of individual devices. Through surface passivation, arsenic implantation can reduce gate-to-drain leakage in and enhance the breakdown voltage of GaAs-based metal semiconductor field-effect transistors (MESFETs) and high electron mobility transistors (HEMTs). High resistivity thin surface layers may be used as gate insulators for GaAs-based metal insulator semiconductor (MIS) FETs, leading to the development of a novel GaAs-based complementary metal insulator semiconductor (CMIS) technology like advanced Si-based complementary metal oxide semiconductor (CMOS) technology but with higher radiation hardness and operational speed.
The Tribological Properties for Pulsed W+C and Mo+C Dual Implanted H13 Steel
Authors: Tonghe Zhang , Fuzhong Wei , Jun Chen , huixing Zhang , Xioji Zhang
Published: March 2011

The tribological properties for pulsed W+C and Mo+C dual implanted H13 steel are given in this paper. The pulsed ion of W, Mo and C were implanted at 40KV to dose of (3~12)×1017/cm2 with ion flux from 25 to 100µA/cm2 using MEVVA implanter. The results show that the wear resistance life and hardness of the dual implanted H13 steel increase 2~3 times. The comparison of dual implantation with single implantation shows that the dual implantation is better. The tribological properties of W+C dual implanted H13 steel is better than Mo+C dual implanted H13 steel. The TEM and X-ray diffraction analysis show that the super high hardening dispersed phases of MoC, MoCx, WC and W2C were formed during ion implanting. The iron compounds of tungsten and molybdenum and iron carbides were obtained also. That is, the strengthening effect in H13 steel of phases MoC and WC is better than FeMo, Fe3Mo2, Fe2W and Fe7W6.
Large Scale Ion Beam Equipment and Processing - Review of Ammtra Project -
Authors: Matsuda Koji
Published: March 2011

An R&D project of large scale ion beam equipment and processing is being carried out from 1986 till 1994. The project includes R&D of five ion beam systems and three material processes for surface modification. The five equipment R&D projects are:

(1)High current metal ion beam system,

(2)Integrated high current ion beam system,

(3)Ionized multiple beam system with high deposition rate,

(4)High energy ion beam system,

(5)Gas-phase focused ion beam system.

The three materials processing R&D projects are:

(1)Glass surface modification,

(2)Metal surface modification,

(3)Low scattering multilayer film deposition. This paper reviews recent progress on development of the project. This work was conducted in the program: ’Advanced Material Processing and Machining System’ consigned to AMMTRA from the New Energy and Industrial Technology Development Organization, which is carried out under the Industrial Science and Technology Frontier Program enforced by the Agency of Industrial Science and Technology of Japan.
In-Situ Control of Wafer Charge Neutralization During High Current Ion Implants
Authors: Shauly E.N. , Koltin E. , Munin I. , Avrahamov Y.
Published: March 2011

Ion implantation in semiconductor devices frequently leads to a substantial wafer surface charge build up. Control of this charge during high current implantation is a major process issue, as it may affect the yield and reliability of thin dielectric layers. In addition, the charge build up may affect the ion beam resulting in a non-uniform implant and a reduction in device yield. Control of a specific machine parameter, that will give the charge condition of the ion implanter will enable to neutralize the charge build up.

In this study, Disk Current Monitoring (DCM) is shown to be a reliable method for monitoring the Electron Shower (ES) performance in real time. A correlation was found between DCM level and yields, and between DCM level and breakdown voltage, as well as different maintenance activities regarding me ES. A simple 5 steps method is described to achieve a reliable, real time charge monitor, to insure operation within the “High Yield Range”.
Ion Implantation Monitoring of GaAs Using Thermal Waves
Authors: Garcia R. , Jaquez E. J. , Culbertson R.J. , D'Acosta C. , Jasper C.
Published: March 2011

Laser modulated thermoreflectivity, also called thermal wave technology, has been used in recent years to monitor ion implantation dose by monitoring the damage due to implantation. The thermal properties which are affected by lattice perturbations and other crystal imperfections are tracked by this technique. A gauge capability study was performed on the Thermawave TP300 for monitoring ion implantation of GaAs wafers. The results are presented. In order to determine the sensitivity of the technique to changes in dose, a matrix of GaAs and Si wafers was measured. During this study a downward trend was observed in the repeatability of our results. It is shown that damage to a sample during implantation will relax to a certain degree at room temperature. This damage relaxation can take up to 80 hours at room temperature and can be observed using thermal waves. It is shown that “hot wafer decay” follows a logarithmic decay which is indicative of a diffusion process. At 180°C the decay lasts less than 1 minute which indicates that the defects causing this phenomenon have a low activation energy.
Ion Beam Synthesis of IrSi3 by 1-MeV Ir Ion Implantation into Si(111)
Authors: Sjoreen T. P. , Hinneberg H.-J.
Published: March 2011

The formation of a Si/IrSi3/Si heterostructure by 1-MeV Ir ion implantation and subsequent annealing has been studied for different doses (0.1-2.25 × 1017 Ir/cm2), substrate temperatures (450°-600°C) and annealing temperatures (1000°-1200°C) using Rutherford backscattering spectrometry, ion channeling and cross-sectional transmission electron microscopy. The heterostructure formation is observed to depend strongly on the processing conditions. The best structure, nearly continuous and precipitate-free, is obtained by implanting 1.8-2.0 × 1017 Ir/cm2 at a substrate temperature of 550°C and annealing at 1100°C for 5 h. A stoichiometric IrSi3 layer can also be produced by furnace annealing at 1150°C for 1 h or by rapid-thermal-annealing at 1200°C for 3 min. Other substrate temperatures generally lead to a structure with a discontinuous IrSi3 layer frequently interrupted by large surface precipitates or islands. The origin of these islands, as well as the dependence of the heterostructure on processing parameters, is discussed.
Ultrathin Nitride Films Grown Under Low-Energy Ion Bombardment
Authors: Ren Zhong-Min , Ying Zhi-Feng , Xiong Xia-Xing , He Mao-Qi , DU Yuan-Cheng , Chen Liang-Yao , Li Fu-Ming
Published: March 2011

Bombardment of silicon surfaces by low-energy nitrogen ions has been investigated as a possible process for growing films of silicon nitride at relatively low temperature(<500°C). Broad ion beams of energy 300–1200eV have been used to grow ultrathin silicon nitride films. Film thickness and chemical states are analyzed using ellipsometery, X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy(AES). As a result, thicknesses dependence on ion energy, substrate temperature and implantation time have been investigated. The thicknesses of films obtained appear to increase with ion energy in the range from 300 to 1200eV, and with time of bombardment. The thicknesses are also observed to vary slightly with substrate temperature. The growth mechanism has also been investigated and discussed. The average activation energy of nitridation rates is about 3.5meV which indicates nonthermal process kinetics, compared to an activation energy of 0.2–0.6eV for thermal nitridation. AES results show that the atomic ratio [N]/[Si] is about 1.5, larger than that of pure Si3N4. All the analyses show that silicon nitride films of about 60Å thickness have been grown on silicon by low-energy ion beam nitridation.
Adhesion and Tribological Behavior of Si-DLC Coatings on Steel Processed by Ion Beam-Assisted Deposition
Authors: Fountzoulas C. G. , Kattamis T. Z. , Chen M.
Published: March 2011

Amorphous silicon-containing diamond-like carbon (Si-DLC) films were processed by Ar+ ion beam-assisted deposition (IBAD) on AISI 4130, 17-7 PH, 440-C, and 4340 alloy steel specimens, as well as Cr-preplated and TiN-precoated-Cr-preplated 4340 steel specimens. Coating thicknesses ranging from 1.8 to 4.31 µm were obtained, and increased with increasing beam current density and appeared to depend on the composition of the steel substrate. Microhardness values were slightly lower for the coating on Cr-preplated 4340 steel (1,017 KHN) and substantially higher for the coating on TiN-precoated 4340 steel (1,825 KHN). The cohesion and adhesion failure loads increased with increasing coating thickness and underlying layer hardness. The adhesion failure load of the coating on TiN-precoated-Cr-preplated 4340 steel exceeded those on other substrates. The friction coefficient of the coating surface was lower for the Cr-preplated 4340 specimen and substantially lower for the TiN-precoated-Cr-preplated substrate. Wear resistance seemed to be practically the same for coated 4340 or 17-7 PH steel substrates (3.16 × 10-6 to 8.60 × 10-6 mm3 N-1m-1).
Ion Beam-Assisted Deposition of Boron Nitride from a Condensed Layer of Diborane and Ammonia at 78 K
Authors: Kroczynski R. J. , Strongin D. R. , Ruckman M. W. , Strongin M.
Published: March 2011

This paper examines the ion beam-assisted deposition (IBAD) of thin boron nitride films using cryogenically condensed precursors. Low energy (1100 eV) argon and (2000 eV) deuterated ammonia beams with currents of 600-850 nA were used to mix and initiate reactions in frozen (90 K) layers of diborane (B2H6) and ammonia (NH3) or only B2H6, respectively. The resulting film is shown to be an amorphous BN coating approximately 30 Å thick.
Characterization of Doped Diamondlike Carbon Films and Multilayers
Authors: hofsäss H.C. , Biegel J. , Ronning C. , Downing R.G. , Lamaze G.P.
Published: March 2011

We have grown doped diamondlike carbon (DLC) thin films on Ni and Si substrates by mass separated low energy ion beam deposition. The current-voltage characteristics of these films and also a P-doped DLC / B-doped DLC diode-like device were measured. Doped DLC films show a higher electrical conductivity, which we interpret by hopping conductivity due to an increased density of localized states rather than a shift of the Fermi level. We also present first results on doping modulated DLC multilayers deposited on Si substrates. The dopant concentration profiles were analyzed by Rutherford Backscattering for63Cu dopant atoms and by neutron depth profiling for a10B doped multilayer.
Deposition of Dlc Via Intense Ion Beam Ablation
Authors: Johnston Gregory P. , Tiwari Prabhat , Rej Donald J. , Davis Harold A. , Waganaar William J. , Muenchausen Ross E. , Tallant David , Simpson Regina L. , Williams David B. , Qui Xiamei
Published: March 2011

Diamond-like carbon films were prepared by high intensity pulsed ion beam ablation of graphite targets. A 350 keV, 35 kA, 400 ns pulse width beam, consisting primarily of carbon ions and protons, was focused onto a graphite target at a fluence of 15-45 J/cm2. Films were deposited onto substrates positioned in an angular array from normal to the target to 90° off normal. Deposition rates up to 30 nm per pulse, corresponding to an instantaneous deposition rate greater than 1 mm/sec, have been observed. Electrical resistivities between 1 and 1000 ohm·cm were measured for these films. XRD scans showed that no crystalline structure developed in the films. SEM revealed that the bulk of the films contain material with feature sizes on the order of 100 nm, but micron size particles were deposited as well. Both Raman and electron energy loss spectroscopy indicated significant amounts of sp3 bonded carbon present in most of the films.
Low Temperature Epitaxial Growth of TiO2 Rutile Films by ICB Deposition and Mechanical Properties in Helium Implanted Rutile Films
Authors: Fukushima K. , Takaoka G.H. , Yamada I.
Published: March 2011

Reactive ionized cluster beam (RICB) deposition has been used to form crystalline titanium dioxide films on various substrates. Epitaxial ruble films could be formed on Al (111) and sapphire (0001) and (1120) substrates at 450 ºC and 500 ºC , respectively. We also could grow highly oriented rutile films on Si and Ge wafers and Pt (111) and (100) pdycrystal films at 400 °C . The formation of rutile films at lower substrate temperature than 500 °C has not yet been reported to be realized by other techniques.

The surface microhardness has been measured in epitaxial and polycrystal TiO2 rutile films unimplanted or implanted with 150keV He ions. The microhardness of the epitaxial films is much higher and it increases with rising dose stronger than in the case of polycrystalline films. At high doses, however, the microhardness decreases rapidly in epitaxial films. The mechanical properties of the epitaxial films are superior to those of polycrystalline films.
Effects of Nitrogen on Formation and Properties of Diamondlike Films Synthesized by Dual Ion Beam Deposition
Authors: He Xiaoming , Song Hongwei , Li Wenzhi , Cui Fuzhai , Li Hengde , Wang Yu , You Dawei
Published: March 2011

Diamondlike carbon-nitrogen films on silicon (111) wafer and tungsten carbide plates have been prepared by using dual ion beam sputtering deposition and simultaneous bombardment by N+ with energies of 100-800 eV at room temperature. These films retain their diamondlike characteristics. However, as the nitrogen content increases from 10% at to 20% at., the Auger electron spectroscopy spectra of films change obviously in fine structure and the main Cls peak of carbon atoms in the X-ray photoelectron spectroscopy spectra shifts to 285.65 eV. The maximum hardness of these films on tungsten carbide plates is about 5260 kg/mm2. The films have an amorphous structure and smooth surface. The state of nitrogen in films and its influence on the structure and properties of films are discussed.
Damage-Free Ion Beam Doping of Carbon During Molecular Beam Epitaxy of GaAs
Authors: Makita Yunosuke , Iida Tsutomu , Kimura Shinji , Winter Stefan , Yamada Akimasa , Shibata Hajime , Obara Akira , Niki Shigeru , Tsai Yushin , Uekusa Shin-ichiro
Published: March 2011

Recently, we introduced various acceptor impurities into MBE-grown ultra-pure GaAs by conventional high-energy ion implantation and found many novel shallow emissions associated with acceptor-acceptor pairs. Most of these emissions were easily quenched by extremely small amount of residual donor atoms which were unintentionally introduced during doping processes. For the interpretation of impurity effects, the usage of mass-separated atom as dopant source was strongly suggested. Along this consideration, we developed combined ion beam and molecular beam epitaxy (CIBMBE) technology, in which damage-free doping with high mass purity (M/ΔM=100) is expected to be possible. We here present the results of low-energy (100 eV) carbon ion doping using CIBMBE method. Samples were prepared asa function of growth temperature (Tg=400-700°C) and ion beam current. Net hole concentration, |NA-ND| as high as ~1×1020 cm-3 was obtained in as-grown samples. In 2K photoluminescence spectra, emissions due to acceptor-acceptor pairs exhibit specific energy shift with growing |NA-ND|. Results indicate that carbon doping can be made efficiently even at Tg as low as 500°C without any post heat treatment. These results also tell that by CIBMBE method no serious radiation damages are produced and the undesired impurity contamination can be considerably suppressed.
An Overview of Dry Etching Damage
Authors: Fonash Stephen J.
Published: March 2011

Dry etching can inadvertently lead to two very different types of damage -- voltage stress damage due to dielectric wearout and plasma exposure damage due to particle and photon flux impingement. Voltage stress damage due to charge-up has beem widely studied. It is often areal in distribution; hence, it can be studied even with simple capacitor structures and capacitance-voltage measurements. All plasma exposure damage has an edge-type distribution. Consequently it requires more complicated structures and measurements for its detection.
Molecular Dynamics Simulation of the Effects of Energetic Cluster Ion Impact on Solid Surface
Authors: Insepov Z. , Sosnowski M. , Takaoka G. H. , Yamada I.
Published: March 2011

Beams of energetic clusters may provide a unique tool for surface modification. Experimental data on the effects of cluster bombardment are still scarce but Molecular Dynamics Simulation may help guide the research in most promising directions. We modeled Ar cluster impact on gold surface and compared the calculated sputtering yield with the available experimental data at 30 keV. The results confirm the uniqueness of cluster impacts characterized by deposition of very high energy density at the surface.
In-Situ Characterization of Growth and Intermixing at a Heteroepitaxial Interface: Fe on Au(001)
Authors: Jiang Q. , Chan A. , He Y.-L. , Wang G.-C.
Published: March 2011

The growth and chemical intermixing of submonolayer and a few monolayer thick Fe films on a Au(001) surface was studied by High Resolution Low Energy Electron Diffraction (HRLEED) technique. Through the analysis of the energy dependent angular profiles as a function of time, we obtained the distribution of islands and distribution of spacings during submonolayer growth. The interference of electron waves from different chemical elements in terraces at different heights in the surface contributes to the background intensity and broadening in the angular profiles of diffraction beams. A subsurface Fe capped by Au islands as a result of atomic place exchange was observed at the initial stage of monolayer growth. From the energy dependent angular profiles as a function of temperature, we determine the quantitative change of inhomogeneity length (∼20 Å) at the interface of ultrathin films at elevated temperatures due to intermixing.
An Investigation of the Al/n-GaAs Diodes with High Schottky Barrier Heights
Authors: Chen C-P. , Chang Y. A. , Kuech T.F.
Published: March 2011

Thermally stable Al/n-GaAs Schottky contacts, up to annealing temperature at 500 °C for 20 seconds, have been realized by sputter deposition from an Al target to (100) n-GaAs at a base pressure ∼2×10−7 Torr. The Schottky barrier height was 0.75 eV (0.9 eV) when using the I-V (C-V) method with an ideality factor of 1.09 for the as-deposited samples. The Schottky barrier height increased to 0.97 eV (1.06 eV) with an ideality factor of 1.07 after annealing at 400 °C for 20 seconds. This barrier height, 0.97 eV, is the highest value reported for Al/n-GaAs diodes. The interfacial stability between Al and GaAs has been examined by cross section transmission electron microscopy. A (200) dark field cross section transmission electron microscopy image of the contact after annealing at 600 °C showed that the (Ga,Al)As phase formed at the interface and the enhancement of the Schottky barrier height was due to the formation of this phase.
Electrical Modelling and Characterisation of Alloyed Ohmic Contacts
Authors: Reeves Geoffrey K. , Leech Patrick W. , Harrison H. Barry
Published: March 2011

This paper briefly reviews the standard Transmission Line Model (TLM) commonly used to measure the specific contact resistance of a planar ohmic contact. It is proposed that in the case of a typical Au-Ge-Ni alloyed ohmic contact, a more realistic model would need to take into account the presence of the alloyed layer at the metal-semiconductor interface. An alternative is described which is based on three contact layers and the two interfaces between them, thus forming a Tri-Layer Transmission Line Model (TLTLM). Expressions are given for the contact resistance Rc and the contact end resistance Re of this structure, together with a current division factor, f. Values for the parameters of this model are inferred from experimentally reported values of Rc and Re for two types of contact.
Molecular Beam Epitaxy of ZnS Films on Arsenic Passivated Silicon Surfaces
Authors: Zhou Xiaochuan , Kirk Wiley P.
Published: March 2011

The crystalline quality of ZnS films grown on arsenic covered Si(100) surfaces is shown to be improved as compared to films grown on bare silicon surfaces by MBE (molecular beam epitaxy). Employing RGA (residual gas analyzer) and RHEED (reflection high energy electron diffraction) techniques, we found that a strong initial adsorption of sulfur on bare silicon surfaces led to the formation of disordered silicon-sulfide surfaces. This disordered surface initiated three-dimensional growth of ZnS and resulted in poor crystalline quality. An arsenic overlayer was found to be effective in preventing the interaction of sulfur with the silicon surface and thereby maintained surface ordering. X-ray rocking curve analysis indicated higher crystallinity in ZnS films grown on arsenic covered surfaces.
Ab Initio Molecular Dynamics Study of Al, Ga and Si Adsorption on the Si(001) Surface
Authors: Yamasaki T. , Ikeda M. , Morikawa Y. , Terakura K.
Published: March 2011

The adsorption of Al, Ga and Si on the Si(001) surface is studied by the ab initio molecular dynamics (Car-Parrinello) method based on the norm-conserving pseudopotential. In the stable structures obtained for half mono-layer coverage( ө = 1/2), these ad-atoms form dimers, but the dimer configurations are different. Al and Ga atoms form parallel dimers whose dimerization direction is parallel to that of substrate Si-dimers, while adsorbed Si atoms form (dense) orthogonal dimers. The electronic origin of the difference in the stable configurations among Al, Ga and Si ad-atoms is analyzed by calculating the local density of states (LDOS) of each atom.
TEM Studies of Plasma Deposited Tungsten and Tungsten Nitride Barriers for Thermally Stable Metallization
Authors: Lee Chang Woo , Kim Yong Tae , Min Suk-Ki , Lee Choochon , Lee Jeong Yong , Park Young Wook
Published: March 2011

Plasma enhanced chemical vapor deposited tungsten nitride (PECVD-W67N33) thin film has been proposed as a diffusion barrier. The resistivity and lattice constant of PECVD-W67N33 are 110-28 μΩ-cm and 4.134 Å, respectively and this film has compressive stress of 2.6 × 1010 dyne/cm2. Thermal stability of PECVD-W67N33 as a diffusion barrier reveals that the interdiffusions between Al or W and Si substrate can be prevented by N interstitial atoms in fcc-W2N grains and grain boundaries.
XPS and Sem Characterization of Pan-Based Carbon Fibers Treated in Oxygen and Nitric Oxide Plasmas
Authors: Smiley R.J. , Delgass W.N.
Published: March 2011

Unsized, type II carbon fibers were treated for 2 to 60 minutes in either an oxygen or nitric oxide gas plasma and were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS revealed plasma treatments increased both oxygen and nitrogen functionality on the fiber surface. O2 plasma treatments showed a progressive increase of fiber surface oxidation from alcohol to carboxyl species, increasing the total surface oxygen from 3 atomic % to 46% after 60 minutes. N(1s) spectra for these fibers showed a broad peak centered at ca. 400.4 eV with a shoulder at ca. 398.2 eV, which most likely is attributed to nitrogen remaining from the polyacrylonitrile (PAN) precursor material. NO treatments only increased the total surface oxygen to 33%, but introduced additional nitrogen species onto the fiber surface compared to O2 plasmas. N(ls) spectra for the NO plasma treated fibers showed, in addition to the two nitrogen species mentioned above, a higher binding energy peak at ca. 405.5 eV, which is assigned to -NO2 species. This peak increased to a maximum intensity after 5 minutes of treatment and then decreased upon further treatment, even though the total nitrogen intensity remained constant at approximately 6%. Subsequent increases in the two lower binding energy species at 400.4 eV and 398.2 eV suggest -NO2 surface species were reduced to species such as amides, nitriles, and amines. Reducing the NO plasma power levels from 25 Watts to 5 Watts resulted in the same three peaks in the N(ls) spectra but required 30 minutes for the -NO2 species to reach a maximum intensity. Scanning electron micrographs (x 10,000 magnification) of fibers treated up to 5 minutes revealed that plasma treatments did not significantly change surface morphology. Small bumps on the surface appeared after longer treatments as the plasma began etching the fiber surface, but even 60 minutes of treatment did not significantly alter the overall fiber diameters.
Stress Evolution in Thin film Niti Shape Memory Alloys
Authors: Su Quanmin , Kim Tasung , Wuttig Manfred
Published: March 2011

As a potential micro-actuator material thin film shape memory alloys (SMAs) have drawn attention because of their capability of generating strains of a few percent reversibly. In contrast to SMAs the output strain of traditional actuator material, such as quartz and PZT ferroelectrics, is limited to 100 to 1000 ppm. The authors have investigated the transformation properties and microstructures of thin Ni50Ti50 films on Si. From application point of view, the evaluation of the actuator property should come from direct measurements of the strain output of the film/substrate composite. In the film/substrate composite, the martensitic transformation strains in the SMA thin film are coupled to elastically to the substrate through interface load transfer. Interface properties thus play crucial role on the efficiency of the composite actuators. Since the capability of interface load transfer is determined by the substrate stiffness, experiments were designed to measure the strain output of NiTi/Si composite with varying substrate stiffness. The experiments indicated that the output efficiency of the martensitic transformation strain increases by a factor of 2 when the film/substrate thickness ratio increases from 1/345 to 1/70. The result is favorable for micro-actuator application since much larger film/substrate ratios can be achieved by micro-machining. The absolute value of the transformation strain is about 2 percent which can be improved if the film texture is controlled.

Another problem related to the nature of the film/substrate composite is the thermal stress arising from the difference of the thermal expansivities of the film and substrate. The as deposited films were amorphous with a growth tensile stress ranging from 0.6 GPa to 1 GPa, increasing with the substrate stiffness. The initial recrystallization of the amorphous NiS0Ti,0 film results in an increase of the tensile stress by 80 MPa; however upon completion of the recrystallization process the tensile stress was relaxed. Young’s moduli of the recrystallized austenitic NiTi films were calculated from the thermal stresses arising in the composite samples. It was found that the moduli apparently depend on the substrate thickness. This effect is tentatively interpreted to indicate a sensitivity of the mechanical properties of the film on the grain structure of the recrystallized state which in turn might depend on the constraint due to the substrate. TEM studies will clarify the situation.

It is concluded that the interface stress restrained the efficiency of the martensitic transformation. Since the NiTi film has a high (interface) yield stress, above 1 GPa, it is proposed that the actuation efficiency of the SMA can be improved by reducing the substrate stiffness while maintaining a high load transfer efficiency. If Si is used as a substrate because of its high thermal diffusivity, the actuator design must weight the mechanical actuator output against its speed.
Improved Mechanical Strengths of Epoxy Composites Obtained from Ion Beam Treated Carbon Fibers
Authors: Lin Sin-Shong , Yip Pearl W.
Published: March 2011

Carbon fibers derived from various sources are surface modified by oxygen and nitrogen ion beams generated from a low voltage ion source. The surface analyses by X-ray photoelectron spectroscopy reveal that the ion treatment produces large abundances of various surface functional groups which are dependent on impinging ion energies and irradiation times. In the oxygen beam, the hydroxyl moiety is a dominant surface functionality, but in the nitrogen beam, various moieties containing oxygen and nitrogen are observed. The transverse tensile stresses of the epoxy composites made from the ion treated fibers are found to increase two to four times. The ion beam process yields the highest adhesive strength among all surface treatment methods.
Bond Strength of Pressed Composites
Authors: Wiegand Donald A.
Published: March 2011

Composites samples containing 80% and 85% organic filler in a polymer-plastizer binder were produced by mixing, extruding, cutting, drying and pressing. Before pressing the extruded material was in some cases coated with a thin layer of graphite (= one micron) for ease in pressing. As part of a general study of these composites the compressive strength, σm, was determined as a function of temperature, strain rate and the thickness of the graphite coating. Without graphite σm increases with decreasing temperature and increasing strain rate. With graphite σm has the same behavior above approximately −10 C, but is independent of both temperature and strain rate below −10 C for a strain rate of 1.0/Sec. In addition, the low temperature value of Om decreases with increasing graphite thickness. The cracking and fracture patterns are temperature and strain rate dependent and are different with and without graphite. These results indicate that the bond produced by pressing the graphite containing material is stronger than the composite above −10 C and weaker below −10 C so that failure initiates in the composite above −10 C and in the bond below −10 C. With decreasing strain rate this transition temperature decreases. The bonding is discussed.
High Sensitivity FT-IR-Ras for Silicon Surface Study
Authors: Ohshima Hisayoshi , Urisu Tsuneo , Yamada Yoshiyasu , Hattori Tadashi
Published: March 2011

A novel configuration for Fourier-transform infrared reflection absorption spectroscopy (FT-IR-RAS) has been devised to study the nature of silicon wafer surfaces in the wide IR irradiation region (especially below 1300 cm−1) with high sensitivity. The configuration is basically similar to a conventional one of FT-IR-RAS except that a optical-flat mirror is placed on a silicon wafer surface and the IR beam is incident on the back side of the wafer with a grazing angle. The sensitivity of the novel technique was estimated by the observation of the stretching vibration absorption of the Si-Hx bond (2070-2150 cm−1) on HF/NH4F-treated Si(111) surfaces and Si-O bond (1000-1250 cm−1) of chemically oxidized layer ( ∼0.7 nm ) on Si(111) surfaces. The dependence of Si-Hx absorption peaks intensities on the composition of HF/NH4.F solutions was clearly observed. Furthermore, Si-O bond peak corresponding to the longitudinal optical phonon was also detected.
Infrared Spectra of Ultra-Thin SiO2 Grown on Si Surfaces
Authors: Yamazaki T. , Miyazaki S. , Bjorkman C. H. , Fukuda M. , Hirose M.
Published: March 2011

The structure of thin SiO2 films thermally grown on Si(100) and Si(111) surfaces has been characterized by using infrared internal reflection and x-ray photoelectron spectroscopy. It is found that the infrared absorption peak due to the LO phonon mode originating from the Si-O-Si stretching vibration shows a considerable red shift in the thickness range below 30A. This red shift is interpreted in terms of the compressive stress near the interface.
New Analytical Method of SiO2 Structure by Infrared Reflection Absorption Spectroscopy (Ir-Ras)
Authors: Ishikawa K. , Ogawa H. , Inomata C. , Fujimura S. , Mori H.
Published: March 2011

Simulation of a thin oxide RAS spectrum obtained by using the dielectric function extracted from thick oxide RAS spectra is shown to be a viable method for the comparison of oxide films of differing thickness. Bulk and near-interfacial features of thermally grown SiO2 thin films were studied by this method and it was found that the LO phonon peak at about 1255 cm−1 reflects bulk SiO2 structure and a higher reflectance between 1100 and 1200 cm−1 reflects SiO2/Si interface structure.
The Enabling Role of Surface Passivation in Visible Photoluminescence from Si Nanoparticles
Authors: Seraphin A.A. , Werwa E. , Chiu L.A. , Kolenbrander K.D.
Published: March 2011

Silicon nanocrystallites have been studied in a variety of passivating environments to study the role of surface passivation in visible light emission from the particles. Thin films of Si nanocrystallites have been deposited by a laser ablation supersonic expansion technique. The films show significant room temperature photoluminescence (PL) behavior only after processing to achieve surface passivation. Passivation effects on light emission are studied through PL emission spectroscopy on clusters in the gas phase, as well as films in a variety of passivating media. The intensity of PL emission seems to scale with the extent of surface passivation, but the specific nature of the passivating species is not critical in defining the wavelength of emitted light.
The Model for Description of Electrical Properties of Polymerization-Filled Composite Materials
Authors: Tchmutin I.A. , Ponomarenko A.T. , Shevchenko V.G.
Published: March 2011

The conductivity behavior found in polymerization-filled composites differs from that predicted by percolation theory and can be explained by a simple model predicting the existence of two characteristic values in such systems: the radius of filler particles and the distance of charge penetration into polymer matrix. Detailed mechanisms, responsible for such peculiarities in charge transfer are also discussed.
The Influence of Silicon Overlayers on the Electrical Conductivity of Very Thin Chromium Films
Authors: Aleshin Andrej N. , Schroder Klaus
Published: March 2011

The influence of silicon overlayers on the electrical conductivity of 5 nm to 10 nm thick chromium films has been studied. It was found that the deposition of silicon decreases the resistivity of Cr-film by up to 24 %. Possible mechanisms for the resistance decrease due to the silicon overlayer are discussed.