bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion Beam Synthesis of IrSi3 by 1-MeV Ir Ion Implantation into Si(111)
Authors: Sjoreen T. P. , Hinneberg H.-J. 
Published: March 2011

ABSTRACTThe 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

ABSTRACTBombardment 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

ABSTRACTAmorphous 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

ABSTRACTThis 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

ABSTRACTWe 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

ABSTRACTDiamond-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

ABSTRACTReactive 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

ABSTRACTDiamondlike 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

ABSTRACTRecently, 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

ABSTRACTDry 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

ABSTRACTBeams 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

ABSTRACTThe 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

ABSTRACTThermally 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

ABSTRACTThis 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTPlasma 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

ABSTRACTUnsized, 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

ABSTRACTAs 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

ABSTRACTCarbon 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.