bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction of Alpha Particle Beams with Fe-Based and FeNi-Based Glassy Ferromagnets
Authors: Sorescu Monica , Barb D.
Published: April 2011

Samples of Fe78B13Si9 and Fe40Ni38Mo4B18 metallic glasses were irradiated with alpha particle beams (W=2.8 MeV) using radiation doses of 1016 and 1017 cm-2. Irradiation-induced effects on the magnetic texture and phase composition of alloy samples were studied by Mössbauer spectroscopy. Related morphological changes and resultant crystalline precipitates were characterized by scanning electron microscopy. The evolution of phases and microstructure during the radiation-induced amorphous-to-crystalline transformation was found to depend on the particle flux and sample composition. The lowest radiation dose employed was found to be more effective in inducing amorphous-to-crystalline transformations in both ferromagnetic alloys studied. In addition, the FeNi-based amorphous system investigated was found to be more stable than the Fe-based metallic glass, exposed to the same particle-beam irradiation conditions. By stimulating unconventional pathways for the crystallization process, the interaction of alpha particle beams with glassy ferromagnets offers unique opportunities to understand the fundamentals of nucleation and growth in amorphous magnets.
Dependence on Collision Time of Particle Ejection of Atom-Bombarded Single-Crystal Surfaces
Authors: Chang Che-Chen , Wang Shi-Wei
Published: April 2011

Ejection properties of particles emitted from a keV-atom-bombarded Ag{100} surface are calculated using classical dynamics to model the energy dissipation process. The ejection behavior of the sputtered particles depends strongly on the time interval between the instant of the primary impact on the surface and the moment when the emitting surface atom passes the cutoff boundary of the interaction potential. Both the sputtered neutrals and ions have a similar collision-time distribution. Most particles eject from the surface within 350 fsec after the primary impact. The sputter intensity maximized at around 145 fsec. For particles leaving the surface after -100 fsec of the primary impact, the preferred azimuths of ejection are not sensitive to the collision time. The angular distribution of sputtered particles is less dependent of the collision time than of the ejection energy. The angular anisotropy is also significantly enhanced at high collision times. The results find applications in the characterization and imaging of material surfaces.
Optical Switching of Coherent VO2 Precipitates Embedded in Sapphire
Authors: Gea L. A. , Boatner L. A. , Budai J. D. , Zuhr R. A.
Published: April 2011

In this work, we report the formation of a new type of active or “smart” surface that is produced by ion implantation and thermal processing. By co-implanting vanadium and oxygen into a single-crystal sapphire substrate and annealing the system under appropriate conditions, it was possible to form buried precipitates of vanadium dioxide that were crystallographically oriented with respect to the host AI2O3 lattice. The implanted VO2 precipitate system undergoes a structural phase transition that is accompanied by large variations in the optical transmission which are comparable to those observed for thin films of VO2 deposited on sapphire. Co-implantation with oxygen was found to be necessary to ensure good optical switching behavior.
Scanning Tunneling Microscopy and Atomic Force Microscopy of Au Implanted in Highly Oriented Pyrolytic Graphite
Authors: Tung Y S. , Ueda A. , Henderson D.O. , Mu R. , Gu Z. , White C.W. , Zuhr R. A. , Zhu Jane G.
Published: April 2011

Surfaces of highly oriented pyrolytic graphite implanted with gold were studied by both constant current STM. constant force, and tapping mode AFM. Gold colloids were observed by both constant current STM and tapping mode AFM. The surfaces can be modified by applying currents of +4 V and 1 nA. In addition, pyramidal and faceted structures were observed on sample surfaces suggesting the presence of diamond microcrystals.
Modification of Magnetron Sputtered A-Si1-Xcx:H Films by Implantation of sn+
Authors: Tzenov N. , Dimova-Malinovska D. , Tsvetkova T.
Published: April 2011

Implantation of Sn+ into a-Si1.xCx:H films deposited by RF magnetron sputtering of silicon and graphite was carried out in order to obtain optical contrast in the layers. The expected optical effect which is an absorption edge shift to the lower photon energies accompanied by a considerable increase of the absorption coefficient was observed even for the lowest dose - 1015cm-2. This effect is more pronounced with increase of the dose. Infrared (IR) and photoelectron spectroscopy (XPS) measurements was used to study the bond configurations of implanted films. These measurements reveal that ion implantation introduces an additional disorder in the films as well as leads to their chemical modification, which could be related to the changes of the optical properties.
A Novel Etching Method of Single Crystalline A12o3 Film on Si and Sapphire Using Si Ion Implantation
Authors: Kim H. , Ishida M. , Nakamura T.
Published: April 2011

A new etching method for a single crystalline ΑI2O3(100) film grown on Si(100) by LPCVD and a sapphire wafer is established for the first time using Si ion-implantation and buffered hydrofluoric acid (HF+H2O) chemical etchant to develop many applications of the SOI structure. Line and space patterns of resist were transferred to sharp A12O3 and Si patterns. An etching of 0.1 2/μm-thick-Al2O3 films on Si substrates and sapphire wafers was observed very clearly. The etch rate is lOOÂ/min under implanted conditions of 80kV and 3×1015 cm-2.The implanted ΑI2O3 surfaces are investigated by SIMS and XPS. The change from AI2O3 to Al2O3 SiO2 (aluminosilicate), which can be easily etched HF+H2O, is considered to be a main reason, though bonds broken by implantation are also effective for this etching.
Development and Demonstration of a Two-Dimensional, Accurate and Computationally-Efficient Model for Boron Implantation into Single-Crystal Silicon Through Overlying Oxide Layers
Authors: Morris S. , Lim D. , Yang S.-H. , Tian S. , Parab K. , Tasch A. F.
Published: April 2011

A 2-D model for boron implantation into (100) silicon through overlying oxide layers has been developed and implemented into the process simulator FLOOPS. This model is both accurate and computationally efficient and shows explicit dependencies on all of the key implant parameters: energy, dose, tilt and rotation angles, oxide layer thickness, mask height, mask edge orientation, and rotation of the wafer during implantation.
Surface Effects During Ion Beam Processing of Materials
Authors: Averback R.S. , Ghaly Mai , Zhu H.
Published: April 2011

Microstructural changes of surfaces during ion implantation have been investigated on the atomic level by molecular dynamics computer simulations. Unlike past surface studies, which have been focused on the problem of sputtering, the current work examines the effects of collective materials response on surface topography. Collective behavior has been noted for the crystal interior in the context of thermal spikes, but we show here that it can lead to far more dramatic consequences at the surface. The investigation includes implantation in several metals, but emphasizing Pt, Si and Ge. In addition, the study includes the first simulations of implantations of a metallic glass, CuTi, and amorphous Si.
Structuring of Conducting Polymers by Ion Implantation
Authors: Edinger Klaus , Schiestel Stefanie , Wolf Gerhard K.
Published: April 2011

Conducting polypyrrole polymer films have been modified by ion implantation. The resulting cross linking leads to changes in resistivity and electrochemical behaviour. By ion implantation through masks or with a focused ion beam lateral structures can be produced which can be imaged by scanning electron microscopy and optical absorption. The implanted polypyrrole layers can be removed by electrochemical treatment while not implanted regions can be electroplated. Therefore in combination with electrochemical treatment three dimensional structures have been generated and were investigated by atomic force microscopy. In order to study structures in the submicrometer range implantation experiments with a focused ion beam were performed and the minimal line widths were investigated by scanning electron microscopy.
Improving Adhesion of Polytetrafluoroethylene to Aluminum, Copper, and an Adhesive by Ar+ Irradiation with and without Oxygen Environment
Authors: Koh Seok-Keun , Park Sung-Chul , Choi Chang-Kyu , Song Seok-Kyun , Jung Hyung-Jin , Pae Kook D.
Published: April 2011

A surface of thin square PTFE samples (1×1×0.2 cm3) was irradiated with Ar+ ion at 1 keV with varying ion dose from 5 x 1014 to 1 x 1017 ions/cm2 with and without oxygen environment. The chemical structure of the surface was examined by XPS. The high resolution XPS spectra showed decreased intensity of the Fls peak and formation of the Ol s peak when irradiated with O2 environment. The Ols peak reached the maximum height at the ion dose of 1 x l015 ions/cm2. The increase of the Ols peak may be attributed to the reaction of oxygen atoms and the free radicals created by Ar+ bombardment. Adhesion tests were conducted on 2000 Å thick Al or Cu film which was evaporated on the irradiated and unirradiated PTFE samples with and without O2 environment. Full detachment of the metal films was observed when PTFE samples were not modified. With regard to the Al film, partial detachment of the film occurred when PTFE was irradiated without O2 environment, regardless of ion dose. No detachment of the film occurred when PTFE was irradiated with O2 environment with the ion dose exceeding 1 x 1016 ions/cm2. As to the Cu film, partial detachment was observed with or without O2 environment when the ion dose was 5 x 1014 ions/cm2. No detachment occurred with or without O2 environment when the ion dose was 1 x 1015 ions/cm2 or greater. The adhesion of an adhesive (Crystal Bond) to the irradiated PTFE samples was found to increase significantly with increasing ion dose up to 1 x 1016 ions/cm2 in tensile tests. It appears that three separate mechanisms are at work in improving adhesion of Cu/PTFE and Al/PTFE system. The first is the surface roughness of PTFE caused by Ar+ bombardment, the second is the chemical changes on the PTFE surface, and the third is a change of the interface between the metal and PTFE. The wettability of the PTFE surface was also determined by dropping water droplets on the modified surfaces. The contact angle between water droplets and the irradiated surface of PTFE samples decreased with ion dose up to 1 x 1015ions/cm2, increased at higher dose, and finally increased to the extent that no wetting was possible at 1 x 1017 ions/cm2. The PTFE samples irradiated with Ar+ without O2 gas environment had lower contact angle than those with O2, even though the samples with O2 developed hydrophilic groups on the irradiated surface. This result on wettability is not consistent with our earlier results on PMMA and PC and is due to the unusually
high level of surface roughness of PTFE caused by Ar+ bombardment.
Changes of Wettability and Surface Energy of Polymer by keV Ar+ Ion Irradiation
Authors: Cho Jun-Sik , Choi Won-Kook , Yoon Ki Hyun , Jung Hyung-Jin , Koh Seok-Keun
Published: April 2011

Surface modification of polycarbonate(PC) was performed to improve the wettability by Ar+ ion irradiation with 1 keV energy in oxygen environment. The ion dose ranged from 5 x 1014 to 5 x 1016 ions/cm2 and oxygen flow rate was also varied from 0 to 6 sccm(ml/min.). Contact angle was not much decreased from 78° to 48° for water and from 63° to 32° for formamide by Ar+ ion irradiation without oxygen gas, but largely reduced to 12° for water and to 8° for formamide as Ar+ ion irradiation with 4 seem oxygen gas. Surface energy of modified PC surface which was irradiated with oxygen gas was more increased than that of PC surface irradiated without oxygen gas. It is evident that the increase of surface energy for PC modified with oxygen gas is due to hydrophilic group which result from the chemical reaction between PC surface and oxygen gas. From X-ray photoelectron spectroscopy(XPS) analysis, the newly formed hydrophilic group is identified as hydrophilic C=0 bond, and atomic force microscope(AFM), it is found that the root mean square of surface roughness is changed from 14 Å to 22 ∼ 26 Å for Ar+ ion irradiation only and 26 ∼ 30 Å for Ar+ ion irradiation with 4 seem oxygen gas. Therefore wettability of PC surface is much more affected by newly formed hydrophilic group than surface roughness in keV energy Ar+ ion irradiation.
The Role of Glass Structure in the Formation of Implanted Gold Nanoclusters for Enhanced Nonlinear Optical Properties
Authors: Arnold G.W. , Battaglin G. , Boscolo-Boscoletto A. , Mazzoldi P. , Meneghini C.
Published: April 2011

Various silicate glasses (fused silica, soda-lime, Na- and K-borosilicates, lithia-alumina silicate, and Pyrex®) were implanted with 8 x 1015 285 keV Au/cm2. Colloid growth was monitored as a function of annealing and N implantation (2 x 1017 35 keV N/cm2). Annealing to 1040 °C for fused silica and to 600 °C for the other glasses resulted in Au aggregation and optical absorption. Radiation damage removal is associated with the fused silica annealing; the aggregation of Au at lower temperatures for the other glasses is expected because of the lower glass transition temperature. Phase-seption in the alkali-borosilicates may be important because of grain-boundary diffusion. N implantation did not significantly affect nanocluster growth.
Waveguide Formation in Silica by Implantation with Si, P and Geions
Authors: Leech Patrick W. , Ridgway Mark C.
Published: April 2011

Low loss channel waveguides have been formed in substrates of fused silica and silica-on-silicon by the implantation of 5 MeV Si, P and Ge ions. The silica-on-silicon substrates comprised an upper core layer which was doped with either 3 or 7% Ge. Annealing of the implanted silica-on-silicon waveguides has defined a narrow range of temperature (500 - 600°C) over which the loss coefficient, α, was at a minimum of 0.10 - 0.20 dB/cm at wavelengths of λ = 1300 and 1550 nm. For the fused silica substrates, a similar minimum loss ( 0.10 - 0.20 dB/cm) was measured at 1300 nm. However, at λ = 1550 nm the value of α was significantly increased because of an absorption edge in the fused silica (Suprasil-2) at -1500 nm. The results show that the optical loss characteristics of the waveguides were essentially independent of the ion species.
Proton Induced Defect Formation in Quartz Glasses
Authors: Gulamova R.R. , Gasanov E.M. , Alimov R.
Published: April 2011

The contributions of ionization energy losses and elastic collisions to radiation induced defect formation along the proton track were considered in quartz glasses irradiated by protons with different energies. It is shown that on a larger part of the proton track the color and luminescence center formation by means of recharging of the native defects is due to the ionization energy losses. Generation of structural defects like displaced atoms and their vacancies by elastic collisions with protons and recoil atoms dominates for proton energies < 5 MeV. At proton energies 10 MeV the color and luminescence center formation due to ionization energy losses prevails, and generation of the alumina-alkaline centers, causing an increase of the optical absorption at 550 nm and the thermoluminescence peak at 360 C and a band at 460 nm, occurs. At the proton energies Ep 10 MeV generation of the displaced atoms and their vacancies by elastic collisions dominates, leading to an increase of the E'-centers and to the destruction and transformation of the alumina-alkaline centers.
Synthesis and Properties of GaAs Nanocrystals in Sio2 Formed by Ion Implantation
Authors: Zhu Jane G. , White C. W. , Wallis D. J. , Budai J. D. , Withrow S. P.
Published: April 2011

GaAs nanocrystals have been formed by the sequential ion implantation method. The sequence of Ga and As ion implantation (i.e., Ga + As or As + Ga) is found to affect the size distributions of GaAs nanocrystals significantly. The nanocrystal sizes are much bigger in the samples with Ga implanted first than those with As implanted first. This phenomenon is explained by the different diffusion behaviors of Ga and As species. Different precipitate regions have been observed in the samples implanted with Ga first and then As. Optical absorption measurements show that Ga particles have already formed in the as-implanted stage.
Carbon Nitride Formation by Plasma Assisted Ion Beam Deposition
Authors: Tompa G.S. , Murzin I.H. , Kim S.I. , Ahn Y.O , Gallois B. , Fischer T.E. , Forsythe E.W.
Published: April 2011

Theoretical works have indicated that carbon nitride, in a β-C4N4 phase, would have optical and mechanical properties comparable to or exceeding those of diamond. In this effort, the formation of carbon nitride thin films was investigated using a Plasma Assisted Ion Beam Deposition (PAIBD). In this technique, a C- ion beam combined with a N2 or NH3 RF plasma source is used to synthesize carbon nitride films. These films were investigated as a function of both C- ion beam energy and the power of the plasma source. The C- ion energy was found to be a key parameter in the formation of carbon nitride. The films were evaluated by a variety of diagnostic techniques including Raman, AES, XRD and FTIR. Analysis confirms high nitrogen concentration in the synthesized films and the major portion of carbon being single bonds in the sp3 bond configuration, which is a characteristic of the tetrahedral -C3N4 phase. Tribology tests confirmed that the friction coefficient and the wear rate are comparable to diamond. The results show that the higher C- ion beam energy (-150 eV) forms insulating films with the highest single bond percentages in the range studied. We believe beam energy control is critical to the types of bonds formed.
In-Situ Hvem Studies of Radiation-Induced Segregation In Ni-Al Alloys During Simultaneous Irradiation with Electrons and Ions
Authors: Giacobbe M. J. , Lam N. Q. , Okamoto P. R. , Stubbins J. F.
Published: April 2011

The effects of 75-keV Ne+ and 300-keV Ni+ bombardment on electron radiation-induced segregation (RIS) in a Ni-9at%Al alloy were investigated in-situ using the HVEM (high voltage electron microscope)/Tandem accelerator facility at Argonne National Laboratory. The radial component of defect fluxes generated by a highly-focused 900-keV electron beam was used to induce segregation of Al atoms towards the center of the electron irradiated area via the inverse-Kirkendall effect. The radial segregation rate was monitored by measuring the increase in the diameter of the Al enriched zone within which γ'-νi3αl precipitates form during irradiation. Both dual electron-ion and pre-implanted ion-electron irradiations were performed in an attempt to separate the contributions of energetic displacement cascades and implanted ions acting as defect trapping sites to RIS suppression. It was found that 75-keV Ne implantation has a retarding effect on RIS.
A Novel Rectilinear Negative Carbon Ion Beam Source for Large-Area Amorphous Diamond Like Carbon Coatings
Authors: Sohn M.H. , Ahn YO. , Ko Y.W. , Park Y. , Kim S.I.
Published: April 2011

A novel rectilinear negative carbon ion beam source for large-area coatings has been developed, based on SKION's Solid State Ion Beam Technology. The negative carbon ion beam is effectively produced by a primary cesium ion bombardment and the secondary negative carbon ion yield has been observed to be about 0.5. The ion source produces a negative carbon ion current density of 0.25 mA/cm2 at the extraction voltage of 4 kV. The ion beam energy can be independently controlled from 0 eV to 300 eV. Due to the rectilinear geometry for the production of ion beams, the scale-up of the ion beam in length direction can be easily obtained with no limit. Furthermore, the ion source uses no gas discharge to generate ion beams and does not use any hydrogen gas. The ion source can be operated in a high vacuum (<10-7 Torr), and the cesium vapors are filtered and recirculated. The ion source produces ultra-hard (50 GPa), atomically smooth (< 1 nm Ra), and hydrogen-free amorphous diamond-like-carbon (DLC) films over large areas.
Nanoscale/Multilayer Gradient Materials for Application in the Electromagnetic Gun Systems
Authors: Otooni M.A. , Brown I.G. , Anders S. , Wang Z.
Published: April 2011

Analysis of fired rails from electromagnetic railguns indicates severe surface damage occurs due to high current arcing and tribological mismatch. We have explored the behavior of several nanoscale multilayered materials as possible routes to improve the thermomechanical properties of the rail and armature materials . Structures investigated include (i) Ti-Co alloy on Ta-Cu alloy on dlc (diamond-like carbon) on stainless steel; (ii) Ti-Co alloy on Ta-Cu alloy on dlc on Cu, (iii) Ti-Co alloy on Ta-Cu on Cu; and (iv) Ti-Co on Ta-Cu alloy on Al. The alloys were all 50:50 at% and film thicknesses were in the range 400-1000 Å. The films were formed using a repetitively pulsed vacuum arc plasma deposition method with substrate biasing- and IBAD-like techniques. The surfaces were characterized by scanning electron microscopy, transmission electron microscopy, Rutherford backscattering spectroscopy, optical microscopy, microhardness measurements, arc erosion resistance and scratch resistance tests. Preliminary results show improvement in the microhardness, arc erosion resistance and scratch resistance, most especially for the dlc-coated surfaces. This kind of multilayered approach to the fabrication of electromagnetic railgun and armature surfaces could be important for future advanced Electromagnetic EM Gun systems.
Friction Change Induced by Single Mev Ion Impact Measured by Scanning Probe Microscope
Authors: Ogiso Hisato , Nakano Shizuka , Tokumoto Hiroshi , Yamanaka Kazushi
Published: April 2011

In order to evaluate the damage caused by a single MeV ion impact, we prepared highly oriented pyrolytic graphite specimens, each implanted with 3.1 MeV Au, Ag, Cu and Si ions at a dose of 2.3×1011 cm-2 (2300 μm-2). We then observed specimens by using friction force microscope, and found round regions caused by single-ion impacts on the implanted surface. The frictional force between the surface and the silicon-nitride tip increased in disordered regions. The number density of the regions differed at individual ion-implanted surface, and was about 1000 μm-2 at the Au-implanted surface, 880 μm-2 at the Ag-implanted surface, 372 μm-2 at the Cu-implanted surface, and 44 μπτ2 at the Si-implanted surface. We calculated the electronic stopping power and the probability of knock-on atom generation by the nuclear collision to determine which process affected the density. We found that the difference in the number density was closely related to that of nuclear collisions.
High Conductivity FIB Deposited Metal
Authors: Blauner P.G. , Wagner A.
Published: April 2011

The ion beam induced metal deposition processes now employed by commercial focused ion beam (FIB) tools all demonstrate less than optimal characteristics for use in circuit repair, a major application of these tools. In particular, the processes have low efficiencies, the metals produced have poor conductivity, and some form of clean up is generally required to remove excess material surrounding the repair site. The gold deposition process developed for x-ray mask repair, in contrast, exhibits efficiencies 10-50 times higher with significantly less material deposited in unwanted areas. Unfortunately, the conductivity of the gold is even poorer than that of materials now used for FIB circuit repair.

In this paper, an annealing step which improves the conductivity of FIB deposited Au is described. Results are presented demonstrating resistivities of 5-15 μΩ-cm while maintaining the high efficiency of the gold deposition process. The suitability of the process for use in FIB circuit repair is discussed.
The Detailed Dependence of Implanted Phosphorus Profiles in (100) Single-Crystal Si on Key Implant Parameters
Authors: Ghante V. , Lam L. M. , Morris S. , Yang S.-H. , Tasch A. F. , Kamenitsa D. , Sheng J. , Evans C. , Magee C.
Published: April 2011

The continued decrease in semiconductor device feature size has required much smaller thermal processing budgets in order to achieve the required compact doping profiles. As a result, the impurity profiles have a larger dependence on the ion implant parameters, and more attention must be given to minimizing channeling, which results in deeper implanted profiles. Thus, there is a need for a detailed understanding of the dependence of the implanted profile on the key implant parameters. Since such an understanding does not exist for phosphorus implants in silicon, a detailed study has been performed by obtaining experimental phosphorus impurity profiles for a wide range of implant energies (15 - 180 keV), doses (lx1013- 8×1015 cm–2), tilt angles (0° - 10°), and rotation angles (0° - 360°). Channeling along the <100 axial channel dominates the variations. (110) planar channeling is the next most important channeling effect, appearing at higher (5°) tilt angles, where <100 axial channeling is suppressed. (100) planar channeling is not observed at the lower energies but does manifest itself for energies of 80keV and greater. Dose dependencies play a large role beginning around lxlO14 cm-2.
Afm Study of Surface Morphology of High Dose Co Implanted Si with A Mevva Ion Source
Authors: Peng Qicai , Wong S.P. , Xu J.B. , Wilson I.H.
Published: April 2011

The surface morphology of high dose Co implanted Si has been studied by atomic force microscopy. The Co implantation was performed using a metal vapor vacuum arc (MEVVA) ion source at an extraction voltage of 60 or 70 kV to a dose of 2×l017 or 4×l017 ions cm-2 at substrate temperatures Ts ranging from 210°C to 700°C. When Ts is less than about 600°C, the surface morphology of the implanted samples shows largely similar features of densely distributed narrow asperities. However, for the sample with Ts of 700°C, the surface morphology is significantly different and shows hillocks of much larger size. It is also found that when other parameters are fixed, for Ts less than about 600°C, the root-mean-square roughness Rrms increases exponentially with 7^, from the subnanometer scale to several nanometers. But for the sample with Ts of 700°C, there is an abrupt increase in Rrms to 35 nm. The variation of the surface morphology with other parameters is also discussed.
Low Temperature Phase Transition (Pt) and Defect Formation (Df) in Silicon with Dioxide Inclusions Under X-Ray Irradiation
Authors: Makhkamov SH.M. , Abdurakhmanova S.N.
Published: April 2011

Studies of galvanomagnetic and electrical parameters of p- type Si : SiO2 in the temperature range 80 – 400 K have shown that X-ray irradiation at 80 K (Mo Ka,β and braking radiation hvmax. = 50 heV) leads to various transformations of the spectrum of electron- hole states in the band gap of such material, depending on the flux density of the X-rays. Two main processes are observed: the defect (vacancy and divacancy) formation and a charge exchange of native defects localized at the Si – SiO2 interface. The charge exchange process is rather collective and stimulated one because it is in response to an X-ray-induced ferroelectric phase transition in the SiO2- phase.
Irradiation-Induced Damage and Intermixing of GaAs-Algaas Quantum Wells
Authors: Tan H.H. , Williams J.S. , Jagadish C. , Burke P.T. , Gal M.
Published: April 2011

A comparison of ion irradiation-induced intermixing in GaAs-Al0.54Gao46As quantum well structures with H, O and As ions is investigated by low temperature photoluminescence. Very large energy shifts are observed together with good recovery of the photoluminescence intensities after annealing in samples irradiated with protons. No saturation in the energy shifts is observed in samples irradiated even up to a dose of 4.3 x 1016 cm-2. Similar large shifts with low absorption are also observed in O and As implanted samples but at a significantly lower ion dose. However, both the heavier ions show a saturation effect in the degree of intermixng at higher doses. The degree of intermixing is believed to be a delicate balance among multiple competing processes that occurs across the interface.
Dose and Doping Dependence of Damage Annealing in Fe Mev Implanted Inp
Authors: Carnera A. , Fraboni B. , Gasparotto A. , Priolo F. , Camporese A. , Rossetto G. , Frigeri C. , Cassa A.
Published: April 2011

High energy (2 MeV) ion implantation of Fe in InP has been investigated by means of Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM) and secondary ions mass spectrometry (SIMS). The implanted doses ranged between 5×l013 and 5×l014 at/cm2. Annealing in the 650–800 °C range was performed and the primary as well as secondary damage evolution has been studied. The correlations between defect structure and Fe redistribution properties have been carefully analysed. The results show the role of the primary defect structure in determining the annealing properties, both for damage recovery and Fe redistribution. The latter is also influenced by the doping of the substrate.
Enhancement of the Adhesion of Beryllium Films with Interfacial Beo to Carbon Substrates
Authors: Musket R.G. , Wirtenson G.R.
Published: April 2011

We have used 200 keV carbon ions to enhance the adhesion of 240-nm thick Be films to polished, vitreous carbon substrates. Adhesion of the as-deposited films was below that necessary to pass the scotch-tape test, but carbon ion fluences less than 1.6xl014 C/cm2 were sufficient to ensure the passage of the tape test without affecting the optical properties of the films. Adhesion failure of the as-deposited film was attributed to an inner oxide layer between the Be and the carbon. Because this oxide (-5 nm of BeO) was not measurably changed by the irradiation process, these results are consistent with adhesion enhancement occurring on the atomic scale at the interface between the inner oxide and the carbon substrate, and this conclusion was supported by Rutherford backscattering (RBS) data. Potential adhesion mechanisms are discussed with consideration of relative contributions from electronic and nuclear stopping.
Oxidic Field Effect Structures with Memory
Authors: Wolf R.M. , Cillessen J.F.M. , Giesbers J.B. , Pastoor E. , Miiller G. , Grosse-Holz K.O. , Blom P.W.M.
Published: April 2011

Two types of switching memory devices have been made by integrating a ferroelectric layer in a device. A Schottky diode consisting of a ferroelectric semiconductor and a high work function metal was found to show a bistable I-V behaviour. Experimentally an On/Off current ratio of two orders of magnitude was found in a structure consisting of a semiconducting PbTiO3 layer with a gold top contact, grown on a La0.5Sr0.5CoO3 bottom contact layer. The ferroelectric polarization parallel or antiparallel to the internal field of the diode gives rise to a change in the Schottky barrier height and depletion width. This will, depending on the polarization direction of the ferroelectric layer, enhance or diminish the tunnel probability of charge carriers through the Schottky barrier and thereby increase or decrease the current through the device. In the Ferroelectric Field Effect Transistor an insulating ferroelectric gate oxide was brought in close contact to a gated n-type Sb-doped SnO2 semiconducting channel layer. A maximum On/Off Source-Drain current (IsD) ratio at zero gate voltage of 5.7 was found. Gate pulse measurements showed retention of IsD after polarisation reversal of the ferroelectric gate oxide in both polarization directions. After more than 104 switching cycles the device shows a gradual decrease in ISD both in the On and Off state.
Structural and Ferroelectric Properties of Epitaxial La0.5Sr0.5CoO3/Ba0.4Sr0.6TiO3/La0.5Sr0.5CoO3 Thin-Film Capacitors on Silicon for Dram Applications
Authors: kung Pang-Jen , Fenner David B. , Li Qi
Published: April 2011

Epitaxial La0.5Sr0.5CoO3/Ba0.4Sr0.6Tio3/La0.5Sr0.5CoO3 heterostructures were grown (650- 750 °C) on yttria-stabilized zirconia (YSZ)-buffered silicon (100) by pulsed laser (Nd:YAG) deposition. A 15-nm-thick YBa2Cu3O7 film was deposited on the YSZ to act as a template layer for epitaxial growth of the subsequent conductive oxide and ferroelectric film layers. The Ba0.4Sr0.6TiO3 film was (h00) oriented normal to the Si-wafer surface. The temperaturedependent resistance curve measured on the La0.5Sr0.5CoO3 top electrode layer was found to indicate to some extent the film quality of the underlying layers. Hundreds of capacitors, fabricated by wet chemical etching from the as-deposited films, exhibited dc leakage current densities in the range of 0.05–0.1 μA/cm2 at 1-volt operation. By increasing the thickness of the dielectric layer, some of them were able to be tested at up to 20 volts before resistive leakage became dominant. To reduce leakage current densities and increase dielectric constants in these film capacitors for dynamic random access memory (DRAM) applications, we have made efforts to incorporate hybrid Pt/La0.5Sr0.5CoO3 bottom electrodes into capacitors. This results in improved dielectric constants (451 at 10 kHz) and P-E hysteresis characteristics (Ec = 58 kV/cm, Pr = 7.5 μC/cm2, and Pg = 25 μC/cm2).
Homoepitaxial and Heteroepitaxial Growth of Sr0.61Ba0.39Nb2O6 Thin Films by Pulsed Laser Deposition
Authors: Yeo J. S. , Youden K. E. , Huang T. F. , Hesselink L. , Harris J. S.
Published: April 2011

Epitaxial SBN:61 films have been grown on SBN:75 and MgO substrates by pulsed laser deposition. The optical loss due to absorption is greatly reduced by increasing the oxygen pressure to 1 mbar during the cooling process. In homoepitaxy, X-ray phi scans on the (221) plane of the SBN:61 films indicate that the in-plane grains are rotated 0° or ±28° with respect to single crystalline SBN:75 substrates. Cross-section and plane view high resolution TEM reveals this crystalline relations and microstructure of SBN thin films. Pr doped SBN:61 thin films show sharp transition band at 495 nm and 607 nm in room temperature photoluminescence measurement.
High Temperature Superconducting Step-Edge SNS Josephson Junctions on Silicon Substrates
Authors: Rosenthal P. A. , Cosgrove J. E. , Fenner D. B. , Vale L. R. , Ono R. H. , Rudman D. A.
Published: April 2011

We have fabricated and tested YBCO step-edge SNS Josephson junctions on silicon substrates. The silicon step edges were patterned photolithographically and reactively ion etched using an SF6 plasma. The structures were fabricated through sequential angled pulsed laser deposition of yttria stabilized zirconia, YBCO, and gold layers, followed by photolithographic patterning and ion milling. The completed devices showed resistively shunted junction (RSJ)-like current voltage characteristics and microwave induced Shapiro steps. Critical currents as large as 84 PA and resistances of order 0.5 Ω were obtained. Measurable critical currents were observed up to 76 K. We report on the fabrication and properties of these junctions.
The Influence of Weak Links and Oxygen Deficiency on Electrical Properties of Bi-2212 and Ti-2212 Hts Thin Films
Authors: Schindler Jon L. , Dimeo Frank , Duran Carolyn R. , Hinds Bruce J. , Wessels Bruce W. , Marks Tobin J. , Kannewurf Carl R.
Published: April 2011

Thin films of the Bi-2212 and T1–2212 compounds were prepared by MOCVD deposition techniques. Resistivity versus temperature and critical current density measurements were used to characterize the electrical properties. An analysis of the data based on a proposed model determined the influence of intragranular weak links. Thin film samples in both systems with near optimum oxygen doping showed a correlation between the slope and magnitude of the resistivity in the normal state. Samples with reduced oxygen content displayed a strong increase in the intragrain boundary resistance, consistent with weak link defects. The results agree with a similar analysis of YBCO samples and support a common mechanism for the development of weak links in cuprates.
The Function of Buffer Layers and Defects in Heteroepitaxial BaxSr1-xTiO3/YBa2Cu3O7-x/CeO2/Y-ZrO2/Si/Al2O3 Multilayers
Authors: Olsson E. , Boikov Yu. , Ivanov Z. G. , Vasiliev A. L. , Claeson T.
Published: April 2011

Different aspects of interfacial interactions during the growth of epitaxial oxides are illustrated in a BaxSr1-xTiO3/YBa2Cu3O7-x/CeO2/Y-ZrO2/Si/Al2O3 heteroepitaxial multilayer. The effect of chemical interaction, interdiffusion, epitaxial strain and thermal strain are exemplified. It is shown how buffer layers can be used to compensate for otherwise detrimental interactions. Considerations necessary for annealing following the film depositions are also addressed. Even if the described structures are specific for this system, similar considerations need to be made for other oxide systems as well. The present description can provide help to identify suitable material combinations.
Investigation of Cation Disorder In ‘C’ Axis Ybco 123 Thin Films Using Raman Microscopy
Authors: Cohen L. F. , Li Y. B. , Gibson G. , MacManus-Driscoll J.
Published: April 2011

Two 123 thin films grown by e-beam evaporation have been studied using Raman microscopy. The films were grown under different conditions of temperature and oxygen partial pressure and show different levels of cation disorder as determined from the ‘c’ axis lattice parameter in combination with x-ray data. The oxygen stoichiometry in each film was changed by controlled anneals using a coulometric titration apparatus. As a result we report on the sensitivity of the 500cm−1 and 585cm−1 Raman peak to the oxygen stoichiometry and how the intensity and position of these peaks can be used to detect or confirm the presence of a small amount of cation disorder.
Epitaxial Growth of γ -Al2O3 Insulator Films on Si by Molecular Beam Epitaxy Using an Al Solid Source and N2O Gas
Authors: Wado H. , Shimizu T. , Ohtani K. , Jung Y. C. , Ishida M.
Published: April 2011

High quality crystalline γ -Al2O3 films were epitaxially grown on Si(111) substrates at growth temperatures from 750 to 900°C by molecular beam epitaxy using an Al solid source and N2O gas. Very thin γ -Al2O3 films grown at a growth temperature of 850°C showed streaky reflection high-energy electron diffraction patterns. By in situ x-ray photoelectron spectroscopy measurements, carbon contamination, as is seen in the films grown with a Al(CH3)3 source, was not detected within the measurement sensitivity. The stoichiometry of the grown film was found to be similar to that of Al2O3. Growth rates of epitaxial γ -Al2O3 layers decreased with increasing growth temperatures. The predominant growth of the γ -Al2O3(111) crystal orientation was confirmed on Si(110) and Si(100) substrates.
Growth of Epitaxial a-Axis and c-Axis Oriented Sr2RuO4 Films
Authors: Madhavan S. , Gibbons B. J. , Dabkowski A. , Dabkowska H. A. , Trolier-Mckinstry S. , Liu Ying , Schlom D. G.
Published: April 2011

Epitaxial films of Sr2RuO4 have been grown in situ by pulsed laser deposition on (100) LaAlO3 and (100) LaSrGaO4 substrates. X-ray diffraction results show that the films are single domain and grow c-axis oriented on (100) LaAlO3 and a-axis oriented on (100) LaSrGaO4 substrates. X-ray ø-scans indicate epitaxial alignment of the film and substrate in-plane axes in both cases. Resistivity versus temperature measurements reveal that the as-grown c-axis oriented films are semiconducting and the a-axis oriented films are metallic. The metallic films grown so far were found to be non-superconducting down to 50 mK.
Epitaxial Single Crystalline Ferrite Films for High Frequency Applications
Authors: Suzuki Y. , Dover R. B. Van , Korenivski V. , Werder D. , Chen C. H. , Felder R. J.
Published: April 2011

The successful growth of single crystal ferrites in thin film form is an important step towards their future incorporation into integrated circuits operating at microwave frequencies. We have successfully grown high quality single crystalline spinel ferrite thin films of (Mn, Zn)Fe2O4 and CoFe2O4 on (100) and (110) SrTiO3 and MgAl2O4 at low temperature. These ferrite films are buffered with spinel structure layers that are paramagnetic at room temperature. In contrast to ferrite films grown directly on the substrates, ferrite films grown on buffered substrates exhibit excellent crystallinity and bulk saturation magnetization values, thus indicating the importance of lattice match and structural similarity between the film and the immediately underlying layer. X-ray, RBS, AFM and TEM analysis provide a consistent picture of the structural properties of these ferrite films. We then use this technique to grow exchange-coupled bilayers of single crystalline CoFe2O4 and (Mn, Zn)Fe2O4. In these bilayers, we observe strong exchange coupling across the interface that is similar in strength to the exchange coupling in the individual layers.
The Effect of Oxygen Deposition Pressure on the Structure and Properties of Pulsed Laser Deposited LaxCa1−xMnOδ Films
Authors: Horwitz J. S. , Dorsey P. C. , Koon N. C. , Rubinstein M. , Byers J. M. , Gillespie D. J. , Osofsky M. S. , Harris V. G. , Grabowski K. S. , Knies D. L. , Donovan E. P. , Treece R. E. , Chrisey D. B.
Published: April 2011

Thin films (∼1000 Å) of LaxCa1−xMnOδ (x=0.67) were deposited onto LaA1O3 (100) substrates at of 600 and 700°C. Varying the oxygen deposition pressure between 15 and 400 mTorr systematically changed the oxygen concentrations in the as deposited films. Asdeposited films exhibited an orthorhombic structure with an oxygen pressure dependent lattice parameter. The films were highly oriented as characterized by narrow x-ray ω-scans (FWHM ≤ 0.16 −0.70°). At low pressures, the films were preferentially (202) oriented while at high pressures deposited films had a (040) preferred orientation. A 900°C anneal in flowing oxygen for a film deposited at low oxygen pressures resulted in a decrease in the lattice parameter (associated with an increase in δ) and a change in the preferred orientation from (202) to (040). The resistivity as a function of temperature (R(T)) showed a significant variation as a function of growth conditions. At 600°C, the peak in the resistivity curve (Tm) varied between 73 and 93 K for P(O2) = 15 to 400 mTorr, while at 700°C, Tm was ∼150 K. For films deposited at 600°C, the resistivity was reduced by a factor of 103 for H = 9T and Tm was shifted to 150 K. The activation energy associated with the semiconducting phase was approximately the same for all as-deposited films (∼100 meV).
Intrinsic Properties of Doped Lanthanum Manganite
Authors: Snyder G. Jeffrey , Hiskes Ron , DiCarolis Steve , Beasley M. R. , Geballe T. H.
Published: April 2011

An investigation designed to display the intrinsic properties of perovskite manganites was accomplished by comparing the behavior of bulk samples with that of thin films; the results show the "colossal magneto resistance" at very low temperatures is not an intrinsic property of the thermodynamically stable 1/3 doped material. Epitaxial 1500 Å films of perovskite La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 were grown by solid source chemical vapor deposition on LaA1O3 and post annealed in oxygen at 950°C. Crystals were prepared by LASER heated pedestal growth. The magnetic and electrical transport properties are essentially the same. Below Tc/2 the intrinsic magnetization decreases as T2 (as can be expected for itinerant electron ferromagnets) while the intrinsic resistivity increases proportional to T2. The constant and T2 coefficients of the resistivity are largely independent of magnetic field and alkaline earth element (Ca, Sr or Ba). We identify three distinct types of negative magnetoresistance. The largest effect is observed near the Curie temperature and is likely to be due to magnetic critical scattering. There is also magnetoresistance associated with the net magnetization of polycrystalline samples. The high temperature (above Tc) resistivity of La0.67Ca0.33MnO3 is consistent with small polaron hopping conductivity with a transition at 750K, while La0.67Sr0.33MnO3 does not exhibit activated conductivity until about 500K, well above Tc. The limiting low and high temperature resistivities may place a limit on the maximum possible magnetoresistance of these materials.
Semiconductive Behavior of Sb Doped SnO2 Thin Films
Authors: Grosse-Holz K.-O. , Cillessen J. F. M. , Prins M. W. J. , Blom P. W. M. , Wolf R. M. , Feiner L. F. , Waser R.
Published: April 2011

Sb doped SnO2 has been deposited on polished ceramic Al2O3 substrates by Pulsed Laser Deposition. Conductivity, charge carrier density and mobility of these thin films have been measured as a function of temperature. A model for the electrical properties of the films is proposed. Since Sb doped SnO2 is a transparent, high mobility material, it is shown that it can be used as channel material for an all-oxide thin film transparent field-effect transistor with a linear dielectric.
Heteroepitaxy of Strained and Not-Strained Ferroelectric Superlattices and their Electric Properties.
Authors: Tabata Hitoshi , Hamada Masakazu , Kawai Tomoji
Published: April 2011

Bismuth based artificial superlattices have been formed by a layer-by-layer laser deposition with in-situ monitoring of RHEED. The Bi2O2/WO6, Bi2O2/SrTa2O9, Bi2O2/SrTa2O9 /SrTiO3 and Bi2O2/SrTa2O9/BaTiO3 are constructed epitaxially by a single, double and triple perovskite layers sandwiched by Bi2O2 layers, respectively. The dielectric constant increases with increasing the number of perovskite layers. And the D-E hysteresis loop (ferroelectric properties) appears along the c-axis direction in odd perovskite layers (n=l and 3). We have also formed the SrTiO3/BiWO6/SrTiO3 multi layers. With this combination, the STO layers are isolated by the BWO layers. The dimensionality of STO layer can be controlled by changing the thickness of BWO layers. Below the BWO thickness of 500 Å, the εr increases monotonously with decreasing the BWO thickness. Therefore, the the coulomb force, which is in proportion to inverse of the distance, plays an essential role for the dielectric constant. The formation of “artificially constructed ferroelectric films” by a layer-by-layer deposition method will be discussed ad an essential approach to elucidate the mechanism of ferroelectricity.
Si(001) Homoepitaxial Growth
Authors: Tromp R. M. , Theis W. , Bartelt N. C.
Published: April 2011

Epitaxial growth is generally treated as a far-from-equilibrium process, dominated by kinetic restraints rather than thermodynamic driving forces. In this paper we show that homoepitaxial growth, at temperatures exceeding ∼500°C, is a process that can be approached very well from a thermodynamic equilibrium viewpoint, augmented with classical homogeneous nucleation theory.
Brownian Motion and Coarsening of Domain Boundaries on (7×7)-Si(111)
Authors: Atala Pita , Phaneuf R. J. , Barteltl N. C. , Swiech W. , Bauer E.
Published: April 2011

We have used low-energy electron microscopy to investigate the real-time motion of (7×7) out-of-phase domain boundaries in the (7×7) reconstruction on vicinal Si(111), just below the phase transition temperature. As a function of time, the domain boundaries wander and coalesce in one-dimension, parallel to the step edges. We have established that the motion is consistent with the statistical problem of a random walk in the presence of absorbing barriers and have measured the diffusion coefficient for domain boundary wandering. The average distance between domain boundaries becomes large as they coarsen, consequently energetic interactions are not significant in determining their arrangement on this surface.