bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical Reaction Between Polymers (Pc, Pmma, and Pet) and Oxygen Gas During Ar+ Irradiation
Authors: Park Sung-Chul , Jung Hyung-Jin , Koh Seok-Keun
Published: April 2011

A surface of PC, PMMA, and PET samples irradiated with Ar+ ion of 1 keV energy with and without oxygen environment was investigated by contact angle measurement and x-ray photoelectron spectroscopy (XPS) spectra. Contact angle of water droplets on the irradiated surface of the polymers decreased and remained almost constant with increasing Ar+ irradiation without oxygen. However, when the polymers were irradiated under oxygen environment, the contact angle markedly decreased with increasing ion dose upto 1016 ions/cm2. XPS results show that, after Ar+ irradiation under oxygen, hydrophilic groups were developed on PC, PMMA, and PET. The peak ratio (O/C) of PET irradiated without oxygen decreased with increasing ion dose, whereas that of PET irradiated under oxygen increased with ion dose upto 1016 ions/cm2
Nanocrystals and Quantum Dots Formed by High-Dose Ion Implantation
Authors: White C.W. , Budai J. D. , Zhu J. G. , Withrow S. P. , Hembree D. M. , Henderson D.O. , Ueda A. , Tung Y.S. , Mu R.
Published: April 2011

Ion implantation and thermal annealing have been used to produce a wide range of nanocrystals and quantum dots in amorphous (SiO2) and crystalline (AI2O3) matrices. Nanocrystals of metals (Au), elemental semiconductors (Si and Ge), and even compound semiconductors (SiGe, CdSe, CdS) have been produced. In amophous matrices, the nanocrystals are randomly oriented, but in crystalline matrices they are three dimensionally aligned. Evidence for photoluminescence and quantum confinement effects are presented.
Silver Cluster Formation in Implanted A12O3 Single Crystals
Authors: Freire F.L. , Broil N. , Mariotto G.
Published: April 2011

Single crystals of sapphire were implanted at room temperature with 300 keV-Ag+. The metal precipitate was characterized by a multitechnique approach including RBS, optical absorption and Raman spectroscopy. RBS measurements were used to determine the depth-profiles of the implanted ions. Ag depth profiles, derived from RBS are in good agreement with the results predicted by Monte Carlo simulations. Linear absorption spectroscopy has been used to characterize the effects of the ion fluence on the optical properties of the metal colloids in the UV-Vis region. The broad absorption band due to the surface plasmon resonance shows an appreciable red-shift when the fluence of bombarding ions increases. Raman scattering from acoustic vibrations of the silver clusters progressively shifts toward the laser frequency with increasing implantation dose. From low-frequency Raman spectra an evaluation of the average size of metal aggregates was derived.
Atomic Scale Simulations of Arsenic Ion Implantation and Annealing in Silicon
Authors: Caturla M.-J. , Díaz de la Rubia T. , Jaraiz M. , Gilmer G.H.
Published: April 2011

We present results of multiple-time-scale simulations of 5, 10 and 15 keV low temperature ion implantation of arsenic on silicon (100), followed by high temperature anneals. The simulations start with a molecular dynamics (MD) calculation of the primary state of damage after l0ps. The results are then coupled to a kinetic Monte Carlo (MC) simulation of bulk defect diffusion and clustering. Dose accumulation is achieved considering that at low temperatures the damage produced in the lattice is stable. After the desired dose is accumulated, the system is annealed at 800 °C for several seconds. The results provide information on the evolution for the damage microstructure over macroscopic length and time scales and affords direct comparison to experimental results. We discuss the database of inputs to the MC model and how it affects the diffusion process.
Short-Time Hydrogen Passivation of Poly-Si CMOS Thin film Transistors by High Dose Rate Plasma Ion Implantation
Authors: Qin Shu , Bernstein James D. , Zhou Yuanzhong , Liu Wei , Chan Chung , King Tsu-Jae
Published: April 2011

Plasma ion implantation (PII) hydrogenation has been developed for defect passivation in polycrystalline silicon (poly-Si) thin film transistors (TFTs). A high dose rate PII process using a microwave multipolar bucket (MMB) plasma source and a 12.5 kHz pulse generator achieves saturation of device parameter improvement in 5 minutes, which is much shorter than other hydrogenation methods investigated thus far. These results have been achieved in one sixth the implant time of our previous PII experiments and are in good agreement with our process simulation.
Effect of Hydrogenation on the Electrical and Optical Properties of GaSb
Authors: Dutta P.S. , Bhat H.L. , Kumar Vikram
Published: April 2011

The effect of hydrogen plasma treatment on the optical and electrical properties of Gallium Antimonide bulk single crystals is presented. Plasma exposure gives rise to a layer of defects on the surface. These defects introduce multiple trap levels in the band gap from which a slow emission of carriers is observed during the capacitance - voltage measurements. On removal of the defect layer by controlled etching, the effects of hydrogen passivation are seen. The results of optical measurements indicate that passivation of shallow acceptors is more efficient than that of the donors and in general the passivation efficiency depends on the doping level. Passivation of deep levels and extended defects like grain boundaries and dislocations has also been observed. The thermal stability of the passivated deep level and extended defects is higher than that of the shallow level.
Low-Temperature (< 100°C) Growth of Ain by Ion Beam Assisted Deposition+
Authors: Karimy H. , Tobin E. , Bricault R. , Cremins-Costa A. , Colter P. , Perry D. , Namavar F.
Published: April 2011

During the past few years, there has been growing interest in aluminum nitride (A1N) thin films because of their excellent optical, electrical, chemical, mechanical and high-temperature properties. Ion beam assisted deposition (IBAD) was used to deposit A1N films on flat and curved substrates, including Si, SIMOX, sapphire, quartz, aluminum, stainless steel, and carbon, at temperatures substantially below 100°C. The objective was to enhance the physical and mechanical properties of A1N film by controlling the crystal size and structures.

Experimental results, as obtained by Rutherford backscattering spectroscopy (RBS) show the formation of stoichiometric A1N. Plan-view/cross-sectional transmission electron microscopy (TEM), clearly demonstrated the formation of a smooth, uniform A1N film. Electron diffraction and dark field TEM studies clearly show the growth of A1N crystallites with cubic and/or hexagonal structures and dimensions of 30 to 100A. The films are transparent and have good adhesion to all substrates. In addition to excellent high temperature (up to 1050°C measured) and chemical stability (shown through a variety of acid tests), these films have demonstrated extreme hardness, greater than two times that of bulk AIN.
Growth and Structure of Thin Films by High-Intensity Pulsed Ion-Beam Deposition
Authors: Ivanov YU.F. , Matvienko V.M. , Potyomkin A.V. , Remnev G.E. , Zakoutayev A.N.
Published: April 2011

The high-intensity pulsed ion-beam (HIPIB)/solid interaction results in the generation of an ablated plasma ( ∼1020 cm-3; ∼1 eV) which can be used to advantage for the deposition of thin films. Presented are the results of investigation on the deposition by HIPIB of thin films of high-melting metals, i.e. W, Ta, Mo, Nb, as well as of Al and Cu. The kinetics of the layer-by-layer film growth has been studied using transmission electron microscopy (TEM), transmission electron diffraction (TED) and reflection ellipsometry. The experiments were performed on a TEMP-2 supercurrent accelerator (ion energy 500 keV; ion current density at the target 200 A/cm ; power density (0.7 – 1.5) 108 W/cm2; pulse duration 60 ns; pulse repetition rate 8-10 min-1). The deposition of the films was carried out at room temperature at a high rate of 0.6 – 4.0 mm/s using (100)Si, (001)NaCl, glass and glass ceramic substrates.
The Ionization Degree of Ar Atoms Single Scattered from Pure Metal and Alloy Surfaces
Authors: Abdulkasimov F.B. , Ferleger V.Kh.
Published: April 2011

A procedure of deflection of backscattered neutral atoms with low energy E° = (250÷3000) eV based on neutral ionization by electron impact has been developed. The ionization degrees η+of Ar atoms single scattered at the angle θ=138° from V and VI period metal polycrystal surfaces as well inelastic energy losses Q have been measured. It has been found that both η+ and Q changed nonmonotonically within each period. It has been shown that for the elements of the same group under otherwise equal conditions η+ at the scattering from V period elements appeared to be always higher than those for the VI period. It has been established that at scattering from MoRe alloy surface η+ in peaks of single scattering from Mo and Re the metal target values coincided with corresponding values measured for pure Mo and Re metal targets. Using the results obtained one could draw some conclusions about the dependence of the charge state on the target structure.
Ion Sources for Ion Beam Assisted Thin Film Deposmon
Authors: Svadkovsk Igor V. , Dostanko Anatoly P.
Published: April 2011

Two types of the ion sources for ion beam assisted deposition using inert gases, oxygen or nitrogen are reported. Their design and operational features are presented. Each of them has the properties of two existing main types of the gridless Hall sources: an end-Hall source and the anode-layer version a closed-drift ion source. Basic distinction of the developed sources is the extended range of ion energies in high-current beam for optimization of deposition, cleaning and etching processes.
The Gas Field Ion Source for Finely Focused Ion Beam Systems
Authors: Thompson W. , Armstrong A. , Etchin S. , Percival R. , Saxonis A.
Published: April 2011

The Gas Field Ion Source, GFIS, promises a 109A/(cm2 str) brightness, small beam sizes, and inert gas ion species. If this performance could be demonstrated on a commercial system, the GFIS might replace the liquid metal ion source as the standard source for FIB applications. Recent work at the Max-Planck-Institut für Kernphysik (MPI-K) in Heidelberg, Germany has shown that a GFIS with a ‘Super Tipped’ emitter can be reliably fabricated and can be run with stable helium beam current for more than 200 hours. However, this GFIS source must operate in a bakable UHV chamber, at cryogenic temperatures, and at high voltages with low vibration. A GFIS is now being integrated with high resolution ion optics and a vacuum chamber designed for studying GFIS image quality and ion induced chemistry.
On the Influence of Illumination During Ion Damage Defect Anneal of Silicon
Authors: Tanabe A. , Ashok S.
Published: April 2011

An exploratory deep level transient spectroscopy (DLTS) study on the possible role of illumination during thermal annealing has been carried out on Si with extended defects generated by Ar implantation and electron cyclotron resonance (ECR) hydrogen plasma. Experiments with rapid thermal anneal (RTA) using quartz-halogen lamps show only a minor role for illumination on anneal of defects generated by Ar ion damage as well as thermal generation of defects under post-hydrogenation anneal. However, significant differences are evident relative to conventional furnace anneal and it appears likely that recombination-assisted defect reactions may be quite significant in Si processing when high intensity sources such as arc lamps are adapted in RTA systems.
Anomalous Leakage Current Reduction by Ramping Rate Control in Mev Implantation
Authors: Hamada K. , Nishio N. , Saito S.
Published: April 2011

The crucial problem for buried layer formation using MeV implantation is the reduction of anomalous leakage current at the phosphorus dose of lxl014/cm2. We have demonstrated that the origin of anomalous leakage current is dislocations, on {111}Si planes, elongated along the <110 direction and that these defects can be reduced by using a high ramping rate above 50°C /sec. At the low ramping rate below 10°C/sec, high leakage current above 1 nA was observed , which was caused by the extension of dislocations to the surface. On the other hand, by increasing the ramping rate above 50°C/sec, dislocations were formed around the Rp, but they did not extended to the surface and as a result, low leakage current was obtained. These results suggest that some kinds of defects can be suppressed by ramping rate.
Investigation of Lateral and Vertical Profiles Enhanced by Implantation
Authors: Mineji A. , Hamada K. , Saito S.
Published: April 2011

In shallow junction formation with junction depth below 0.1μm, enhanced diffusion control is essential. The purpose of this paper is to investigate the B enhanced diffusion by point defects, introduced by high dose implantation with amorphization. Ge ions were implanted to induce amorphization within the S/D region of pMOS. These results were compared with that of the B enhanced diffusion by point defects, induced by Si+ implant with non-amorphization. These results suggest that the B enhanced diffusion in lateral profiles is much smaller, compared with that in vertical profiles, when point defects were introduced by amorphization.
Ion Beam Mixing in Insulator Substrates
Authors: McHargue Carl J.
Published: April 2011

Ion beam mixing involving insulator substrates is reviewed with an emphasis on thermochemical considerations. Studies generally have employed the bi-layer geometry for metal/insulator or oxide/oxide combinations. There is little evidence for long-range material transport in crystalline substrates.

Recoil mixing has been detected for both metal and oxide films deposited on sapphire and irradiated at room temperature. Agglomeration of non-wetting metal films suggests that surface diffusion is induced by the ion beam. Evidence has been reported for the occurrence of chemical reactions and perhaps thermally-induced migration in amorphous aluminum oxide substrates.

Ballistic mixing is also indicated for metal films on SiC, Si3N4 and SiO2. Ion beam-induced reactions have been observed at the interfaces for systems in which the enthalpy of reaction is favorable. Chemical effects in the cascade mixing regime may determine the phases present in the mixed zone after the composition changes caused by ballistic processes.
Energetic Ion Beams in Semiconductor Processing: Summary of a Doe Panel Study
Authors: Picraux S. T. , Chason E. , Poate J. M. , Borland J. O. , Current M. I. , Diaz De La Rubia T. , Eaglesham D. J. , Holland O. W. , Law M. E. , Magee C. W. , Mayer J. W. , Melngailis J. , Tasch A. F.
Published: April 2011

The trend toward smaller dimensions in integrated circuit technology presents severe physical and engineering challenges for ion implantation. These challenges, together with the need for physically-based models at exceedingly small dimensions, are leading to a new level of understanding of fundamental defect science in silicon. Recently the DOE Council on Materials requested that our panel examine the current status and future research opportunities in the area of ion beams in semiconductor processing. Particularly interesting are the emerging approaches to defect and dopant distribution modeling, transient enhanced diffusion, high energy implantation and defect accumulation, and metal impurity gettering. These topics were explored both from the perspective of the emerging science issues and the technology challenges.
Epitaxy of PbTio3 on (100) SrTio3 and Vicinal (100) SrTio3 by Pulsed Laser Deposition
Authors: Theis C. D. , Schlom D. G.
Published: April 2011

Epitaxial PbTiO3 films have been grown on (100) SrTiO3 substrates by pulsed laser deposition. X-ray diffraction analysis indicates pure c-axis oriented PbTiO3 films with a rocking curve FWHM of 0.25° for the 002 reflection. Thicker films (˜ 2000 Å) grown on 4° miscut SrTiO3 show mixed aaxis and c-axis PbTiO3 due to twinning along {1011} planes. The [100] axis of the a-axis domains are misoriented by 3.4° - 3.8° toward <001> substrate directions with respect to the substrate normal. In contrast to growth on well-oriented (100) SrTiO3 surfaces where the four equivalent tilts of the [100] axis of the a-axis domains are equally likely, on vicinal SrTiO3 the a-axis domains are preferentially oriented (˜ 90 vol. %) in an uphill direction with respect to the miscut substrate.
Temperature Dependent Micro-Raman Scattering of Sr0.35Ba0.65TiO3Film Grown by Pulsed Laser Deposition
Authors: Sen Sampriti , Ching-Prado E. , Reynés-Figueroa A. , Katiyar R. S. , Horwitz J. S. , Knauss L. A.
Published: April 2011

A film of Sr0.35Ba0.65TiO3(SBT) has been grownin situby pulsed laser deposition on (001) LaAlO3single crystal. From X-ray diffraction studies the sample is found to be in single phase and well oriented. Raman spectrum of the SBT film shows bands around 178, 219, 296, 513, 571 and 741 cm”. The spectrum is similar to that found in SBT ceramic material, but the frequencies of the phonons are shifted. This can be explained if the film is under stress due to the presence of defects. The bands at 296 and 741cm−1correspond to the B1and A1(LO) normal modes of the BaTiO3(BT) system, and they are representative of the BT tetragonal phase, which at first glance appears to contradict earlier structural symmetry assignment for SBT(x=0.35) film at room temperature. Micro-Raman measurements from different regions of the film indicate that the SBT film is homogeneous. The bands at 296 and 741 cm−1are broader in comparison to those in BT single crystal and SBT ceramic material. Temperature dependent halfwidths of these modes suggest strong contribution of defects. Temperature dependent results are discussed in terms of anharmonic contributions involving three and four phonon processes as well as defects. Also, the orthorhombic and rhombohedral phase transitions are discussed. Finally, SEM/EDAX and FT-IR techniques have been used for the structural characterization.
The Structure and Electric Field Dependent Dielectric Properties of Annealed Sr1−xBaxTio3 Ferroelectric Thin Films
Authors: Knauss L.A. , Pond J.M. , Horwitz J.S. , Mueller C.H. , Treece R.E. , Chrisey D.B.
Published: April 2011

The effect of a post deposition anneal on the structure and dielectric properties of epitaxial Sr1−x, BaxTiO3 (SBT) thin films with x = 0.35, 0.50 and 0.60 has been measured. The films were grown by pulsed laser deposition on LaAlO3(001) substrates at 750°C in 350 mTorr of oxygen. The asdeposited films were single phase, (001) oriented with 0)-scan widths for the (002) reflection between 0.160 and 0.50'. The dielectric properties of the as-deposited films exhibit a broad temperature dependence and a peak which is as much as 50 K below the peak in bulk SBT. Also, the lattice parameter, as measured by x-ray diffraction, of the as-deposited films was larger than the bulk indicating strain in the films. The as-deposited films were annealed for 8 hours at 900°C in oxygen. The dielectric properties of the annealed films were closer to that of bulk SBT and the lattice parameter was closer to the bulk lattice parameter indicating a reduction of strain. Annealing of as-deposited films also resulted in an increased dielectric tuning without increased dielectric loss.
Epitaxy and Monolayer Patterning of Solution-Derived LiNbO3 Thin Layers
Authors: Clem P.G. , Xu Z. , Payne D. A.
Published: April 2011

Integrated lithium niobate (LiNbO3) thin layers show promise for efficient electrooptic, nonlinear optic, and optical amplifier applications. Solution-derived LiNbO3 thin layers have been deposited on sapphire substrates, allowing low temperature processing, control of stoichiometry, uniform doping and heteroepitaxy. Transmission electron microscopy of the LiNbO3/substrate interface suggests the structure consists of highly oriented grains with slight rotational variance to accommodate lattice mismatch. For use of such films as devices, the ability to pattern waveguides and other structures is desired. Modification of the substrate surface with patterns of hydrophobic monolayers allows control of deposition of solution precursors. Ambient, selective deposition of (00.1) oriented LiNbO3 heteroepitaxial strip waveguides with lateral dimensions as small as 4μm is demonstrated.
Dependence of Electro-Optic Effects on the Orientations of Epitaxial LiNbO3 Films
Authors: Lee See-Hyung , Noh T. W. , Lee Jai-Hyung
Published: April 2011

Epitaxial LiNbO3 films were grown on a-cut sapphire, i.e., α-A12O3(0112), substrates by pulsed laser deposition. It is found the oxygen pressure is an important deposition parameter to influence the orientations of the LiNbO3 films. At an oxygen pressure of 10−1 torr, LiNbO3(0001) film was grown epitaxially. And, at a low oxygen pressure (i.e., 5x10−4 torr), LiNbO3(1120) film was grown epitaxially. Due to the anisotropic electro-optic (EO) constants, these films with the different orientations display large differences in their EO properties: the epitaxial LiNb3(0001) film shows little EO effects, but the LiNbO3(1120) film shows a large quadratic EO behavior with an effective coefficient of 2.38×10−5 m2/V2. The dependence of EO effects on the orientations of the epitaxial films was analyzed in terms of the linear and quadratic EO tensors of LiNbO3.
High Resolution X-Ray Diffraction Analysis of Piezoelectric LiNbO3 Films.
Authors: Shibata Yoshihiko , Kuze Naohiro , Matsui Masahiro , Kanal Masaki , Kawai Tomoji
Published: April 2011

Thin LINbO3 films are deposited on (001) sapphire and (001) LiTaO3 substrates by using pulsed excimer-laser ablation. These films are evaluated by high-resolution X-ray diffraction (HRXRD) analysis. Strained LiNbO3 films in which the a-axis is longer and the c-axis is shorter than those of LiNbO3 single crystals are deposited on the sapphire substrates. On the other hand, extremely high-quality LiNbO3 films in which the a-axis of the films is the same as that of substrates are grown on the LiTaO substrates. X-ray rocking curves for the (006) reflection showed very narrow full width at half maximum (FWHM) of 208 arcsec for the films on the sapphire substrates, and 9 arcsec for the films on LiTaO3 substrates.
Growth and Transport Properties of Tunneling Barriers in Hts Devices
Authors: Gerritsma G. J. , Verhoeven M. A. J. , Moerman R. , Blank D. H. A. , Rogalla H.
Published: April 2011

In this contribution we will discuss the charge transport of ramp-type HTS Josephson junctions with a Ga-doped PBCO barrier layer. It will be demonstrated that in these junctions charge transport takes place via tunneling processes. The Cooper pairs tunnel directly, at least for T ≤ Tc/2, whereas the quasiparticles tunnel indirectly via localized states. By substituting Cu-chain atoms with Ga-atoms the density of localized states appear to be reduced, resulting in an increase in IcRn-product. Another way to increase this product is a reduction in barrier thickness. Growth studies by AFM of PBCO barriers on ramps indicate that below about 10 nm barriers become increasingly less homogeneous, and below about 6 nm pin holes are very likely to occur. This sets a lower limit on the useful barrier thickness. Presently critical-current densities up to 104 A/cm2 at 40 K, and IlR,-products up to 10 mV at 4.2 K are easily obtained.
Nonlinear Dielectric Thin Films For Active and Electrically Tunable Microwave Devices
Authors: Findikoglu A. T. , Jia Q. X. , Reagor D. W. , Wu X. D.
Published: April 2011

We have prepared electrically tunable and active microwave devices incorporating (superconducting YBa2Cu3O7-x)/(nonlinear dielectric SrTiO3) or (normal metal Au)/(nonlinear dielectric Sr0.5Ba0.5TiO3) bilayers. The dielectric layer thickness for these samples varied between 0.5 μm and 2 μm. The top electrode layer for each sample was patterned into a coplanar waveguide device structure. We have configured these devices as voltage-tunable resonators, voltage-tunable phase shifters, voltage-tunable mixers, and voltage-tunable filters. Under dc voltage bias, these prototype devices have exhibited up to 30% resonant frequency modulation, about 1°/mm-GHz phase shift, more than 40 dB change in mixed microwave power, and finetunable symmetric filter profile with less than 2% bandwidth and more than 15% adaptive range.
Thermodynamic Stability of Binary Oxides in Contact with Silicon
Authors: Hubbard K. J. , Schloma D. G.
Published: April 2011

Using tabulated thermodynamic data, a comprehensive investigation of the thermodynamic stability of binary oxides in contact with silicon at 1000 K was conducted. Reactions between silicon and each binary oxide at 1000 K, including those involving ternary phases, were considered. Sufficient thermodynamic data exists to conclude that all binary oxides except the following are unstable in contact with silicon at 1000 K: Li20, the alkaline earth oxides (BeO, MgO, CaO, SrO, and BaO), the column IIIB oxides (Sc2O3, Y2O3, and Re2O3 where Re is a rare earth), ThO2, UO2, ZrO2, HfO2, and Al2O3. Of these remaining oxides, sufficient thermodynamic data exists to conclude that BeO, MgO, CaO, and ZrO2 are thermodynamically stable in contact with silicon at 1000 K. Our results are consistent with reported investigations of silicon/binary oxide interfaces and identify candidate materials for future investigations.
Oxide Superconductor Interfaces Studied by Spectroscopic Ellipsometry
Authors: Gibbons B. J. , Trolier-Mckinstry S. , Schlom D. G. , Eom C. B.
Published: April 2011

In the eight years since its discovery, numerous materials have been identified as being compatible with YBa2Cu3O7-δ (YBCO). Investigation of potentially compatible compounds requires a knowledge of both the chemistry and microstructure of the interface between the superconductor and the material. In this work, spectroscopic ellipsometry (SE) is being developed as a rapid and non-destructive characterization tool for investigating these interfaces. In addition, SE was used to determine reference optical data for common YBCO substrate materials. These include BaZrO3, 9.5 mol% Y2O3-ZrO2 (YSZ), NdGaO3 and LaSrGaO4.

SE measurements of epitaxial YBCO on YSZ substrates have shown that it is possible to identify the formation of the known BaZrO3 reaction layer. The modeled thickness of the reaction layer, as well as the modeled thickness of the YBCO film, are as expected. SE measurements as a function of temperature for YBCO/SrTiO3 have also been obtained. The SE data shows dramatic changes from room temperature to high temperature. This is due to the strong dependence of the dielectric function of YBCO on the oxygen content of the film.
Oxygen Diffusion Coefficients for Sr2AlTaO6: Ramifications on Htsc Multilayer Processing
Authors: Tidrow S. C. , Lareau R. T. , King L. L. H. , Eckart D. W. , Tauber A. , Wilber W. D. , Pfeffer R. L. , Finnegan R. D. , Neal Matt
Published: April 2011

We have studied the rate of oxygen diffusion through Sr2AlTaO6 (SAT), a buffer and dielectric layer used in high critical temperature superconducting (HTSC) structures. An epitaxial bilayer film of SAT on YBa2Cu3O7-δ (YBCO) was deposited onto an (001) oriented single crystal LaAlO3 substrate using the pulsed laser deposition technique. The rate of oxygen diffusion through the bilayer was investigated over the temperature range 415 to 675 °C by post deposition annealing individual sections of the bilayer in 1/3 atm of 18O enriched molecular oxygen gas. Secondary ion mass spectroscopy was used to depth profile 18O and 16O in each sample. Oxygen diffusion coefficients for SAT at 418, 510, 570 and 673 °C were determined to be roughly (0.93, 6.31, 26.6 and 75.3) × 10−16 cm2 s−1, respectively. Since these diffusion rates can limit oxygen intake into underlying YBCO films, SAT may be an inappropriate choice as a dielectric candidate for use in an HTSC multilayer device technology and will at best require development of suitable post annealing schemes to oxygenate underlying YBCO layers.
Single Variant Orientational Growth of Yba2Cu3O7-x on Vicinal (011) SrTiO3 Substrates.
Authors: Vasiliev A. L. , Linehan D. S. , Kvam E. P. , Hou L. , McElfresh M. W.
Published: April 2011

The results of a transmission electron microscopic (TEM) and X-ray microanalysis (EDS) study of Yba2Cu3O7-x (YBCO) films grown on vicinal (011) SrTiO3 substrates are presented. The YBCO films tend to be single crystalline grown in single variant orientation with c-axis =;45° from the surface. Cracks, second phase precipitates (CuO and Y2O3), and a few small YBCO grains in other orientations were revealed in the films.
Surface Analysis of YBa2 Cu30 Thin Films with Rheed-Traxs
Authors: Ogota S. , Futaki N. , Liu Z. , Kanke Y. , Morishita T.
Published: April 2011

Total Reflection Angle X-Ray Spectroscopy with Reflection High Energy Electron Diffraction (RHEED-TRAXS) is a highly sensitive method for surface analysis. Yba2Cu3O7-x films of less than 1 unit cell average coverage can be detected by its characteristic x-rays. We grew YBCO films on MgO substrates by laser-ablation with two different kinds of surface morphology; one had few particles on a flat surface and the other had many long and narrow islands on the surface which we call linear islands. We measured the take-off angle dependence of TRAXS on these films. For the YBCO films with linear islands the intensities of YLα, BaLα and CuKα x-ray lines have shoulders at the critical angles given by a theoretical formula. For the YBCO films with smooth surfaces, only the BαLa intensity had a sharp peak at the critical angle. The result suggests that a BaO layer terminates YBCO films, or that a chemical reaction occurs at the surface and Ba compounds is produced.
Defects in YBa2Cu3O7−δ Thin Films and Their Influences on Tc
Authors: Ye Jinhua , Nakamura Keikichi
Published: April 2011

Crystallographic defects introduced in the YBa2Cu3O7−δ thin films during depositions were studied using X-ray diffraction method, and their influences on superconducting properties were also investigated by examining Tc variation of the as-grown and post-annealed thin films. It was found that there exist several kinds of defects in the as-grown thin films, such as oxygen deficiency, cation disordering, and others like lattice dislocation, stacking faults, etc.. These defects could be relaxed by heat treatment at temperatures ranging from 400 to 900 °C, resulting in Tc enhancement more or less. Quantitative understandings of the relations among annealing temperature, structural relaxation, and Tc improvement has also been reached. The kinetics of the relaxation of the defects in the YBCO films was studied further using a high-temperature X-ray diffractometer. Interesting phenomena have been observed at around 400 °C due to abnormal desorption behavior of oxygen and at higher temperatures relating to cation ordering.
Investigation of Copper Ferrite, Cu0.5Fe2.5O4, as a High Saturation Magnetization Material
Authors: Sriram D. , Snyder R. L.
Published: April 2011

The ferrite of composition Cu0.5Fe2.5O4, prepared using a conventional solid-state processing route, was soaked at different temperatures between 1200°C and 1350°C, for an hour, in air. The samples were rapidly quenched into oil. Mössbauer, resistivity and x-ray lattice parameter data were obtained for the quenched phase. The maximum saturation magnetization value, obtained at 10K, was close to 5.0μB. The characterization of the sample showed Cu+1 to be partially disordered across both A and B sites of the spinel structure, with an excess occupancy of the A-site showing that under the proper conditions the ordered high 4πMs Cu+1 phase will be stable.
Study of the Verwey Transition of Fe3O4 Films and Fe3O4/MgO Multilayers Grown by Mbe
Authors: Veerdonk R. J. M. Van De , Gijs M. A. M. , Heijden P. A. A. Van Der , Wolf R. M. , Jonge W. J. M. De
Published: April 2011

Thin magnetite (Fe3O4) films and Fe3O4/MgO multilayers have been epitaxially grown by Molecular Beam Epitaxy (MBE) on MgO(100) and MgAl2O4(100) substrates. The epitaxial growth on MgO(100) substrates, with a slightly larger bulk lattice parameter than that of magnetite, resulted in an in-plane expansion of the magnetite lattice, accompanied by a perpendicular compression. For films grown on MgAl2O4(100), with a smaller lattice parameter, the substrate misfit is relaxed by the incorporation of misfit dislocations at the interface. It is shown that the substrates have a large effect on the magnetic and electronic properties of the films.

The characteristic Verwey transition is shifted towards lower temperatures, broadened, and reduced in amplitude, more so for thinner films. This can not be quantitatively explained by substrate induced stress alone, but is more likely due to a rigid structural coupling between the magnetite film and the cubic lattice of the substrate. Hereby the orthorhombic deformation accompanying the Verwey transition may be supressed.

When growing at reduced oxygen pressure, the length scale for the rigid coupling will be reduced by the introduction of vacancies. This leads to more bulk-like resistivity and Verwey transition characteristics, but also to deviations from stoichiometry, as suggested by magnetization and Ferromagnetic Resonance (FMR) experiments.
Molecular Beam Epitaxy of Single Crystal Colossal Magneto-Resistive Material
Authors: Eckstein J. N. , Bozovic I. , Rzchowski M. , O'donnell J. , Hinaus B. , Onellion M.
Published: April 2011

We have grown films of (LaSr)MnO3 (LSMO) and (LaCa)MnO3 (LCMO) using atomic layer-by-layer molecular beam epitaxy (ALL-MBE). Depending on growth conditions, substrate lattice constant and the exact cation stoichiometry, the films are either pseudomorphic or strain relaxed. The pseudomorphic films show atomically flat surfaces, with a unit cell terrace structure that is a replica of that observed on the slightly vicinal substrates, while the strain relaxed films show bumpy surfaces correlated with a dislocation network. All films show tetragonal structure and exhibit anisotropic magnetoresistance, with a low field response, (1/R)(dR/dH) as large as 5 T−1.
Dynamics of In Cluster Growth During InP(110) Surface Dissociation Studied by in-situ Reflection Electron Microscopy
Authors: Gajdardziska-Josifovska M. , Malay M. H. , Smith David J.
Published: April 2011

Annealing effects on InP (110) surfaces were observed in situ using a modified ultrahighvacuum transmission electron microscope equipped with a specimen heating holder. Reflection electron microscopy (REM) was used to record the dynamics of nucleation and growth of liquid In clusters at 650°C, following the desorption of P from the surface. These droplets showed no preference for nucleation at surface steps, and the steps appeared stationary throughout the annealing process. Two distinct types of In cluster growth rates and shape evolutions were detected. A model was developed to decouple height and length information in the REM images. Contact angle and volume above the InP(110) surface were calculated from the dynamic data. The change of contact angle with time provides evidence for sub-surface cluster etching.
Preparation of Ultrafine Supported Clusters for Electron Microscopy Studies
Authors: Singhal A. , Gibson J. Murray
Published: April 2011

In this paper, we discuss the sintering/fragmentation behavior of novel oganometallic rhenium compounds (candidates as catalyst materials) under high energy electron beam irradiation. The technique used was quantitative electron microscopy based on high angle annular dark field (HAADF) imaging in a scanning transmission electron microscope (STEM). Using this approach, we examine elastically-scattered electron intensity from graphite-supported rhenium clusters, and look for mass quantization. The emphasis in this article is not on the imaging technique, but on various sample preparation techniques, materials and synthesis issues of supports and of deposition of very small isolated clusters.
Hvem in situ Study of High-Temperature Deformation of Ceramic and Metallic Materials
Authors: Messerschmidt U. , Baither D. , Bartsch M. , Baufeld B. , Häuβler D. , Haushälter R. , Wollgarten M.
Published: April 2011

A high-temperature straining stage was designed for the Halle HVEM. Electron bombardment is used to heat the specimen grips. At present the stage is operated at a maximum temperature of 1250 °C, but somewhat higher temperatures should also be possible. Details of the stage are described and results are presented on several materials. In yttria fully-stabilized (cubic) zirconia, the different slip behaviour on cube and octahedral planes is demonstrated at a specimen temperature of about 1150 °C. While the dislocations move very jerkily on the (primary) cube planes, their motion is more smooth on the octahedral planes suggesting the action of the Peierls mechanism. In t' zirconia, the switching of tetragonal domains was recorded during ferroelastic deformation. The same process was first observed for tetragonal precipitates in partially stabilized zirconia. In γ TiAl, at the temperature of the flow stress anomaly (about 650 °c), the so-called ordinary dislocations move in a viscous manner, in contrast to the room temperature behaviour, where glide seems to be controlled by localized obstacles. Over a wide temperature range in NiAl single crystals, moving dislocations show a discontinuous dependence of the curvature on the dislocation orientation, well agreeing with calculations of the line tension using anisotropic elasticity. Direct experimental proof of dislocation motion during plastic deformation of quasicrystals is first given for A1PdMn single quasicrystals. Dislocations smoothly move on planes orthogonal to threefold and fivefold directions.
1/60 Sec. Time-Resolved High-Resolution Electron Microscopy of Surface-Diffusion of Tungsten Atoms on MgO (001) Surfaces
Authors: Tanaka N. , Kimata H. , Kizuka T.
Published: April 2011

Surface diffusion process of tungsten(W)-atoms on MgO (001) surfaces was studied by high-resolution electron microscopy (HREM) in the time resolution of 1/60 s. The W-atoms were prepared on single crystalline MgO (001) films at 300°C by vacuumdeposition of WO3 or W-metal. Analysis of the recorded images revealed individual jump-process of the W-atoms in the substrate temperature from R.T. to 400°C, and gave the barrier potential (Ed) and the pre-exponential factor (D0). The diffusion processes on terraces and along steps were also compared in viewpoint of the jump length.
In Situ High Voltage Electron Microscopy Observations of Deformation and Fracture in Multilayered Materials
Authors: Wall M. A. , Barbee T. W. , Weihs T. P.
Published: April 2011

A novel, in situ transmission electron microcopy technique for the direct observation of deformation and fracture in multilayered materials oriented in cross-section is reviewed. Cross-sectional tensile specimens were prepared from thick, free-standing, Cu/Zr and Al/Ti multilayered foils. These tensile specimens contain a micro-gauge section, thus predetermining the location at which dislocation activity and crack nucleation and growth can be observed at high magnifications in the transmission electron microscope. The results from these experiments are unique and cannot be realized by any other technique. These observations will aid us in our understanding of the micromechanisms of deformation and fracture in multilayered materials.
Controlled Environment [Ecell] Tem for Dynamic In-Situ Reaction Studies with Hrem Lattice Imaging
Authors: Boyes E D , Gai P L , Hanna L G
Published: April 2011

With a controlled environment electron microscope it is possible to remove the effect of another atmosphere, such air, to which the sample may have become exposed; to study in considerable detail the continuous development of a series of microstructures in a dynamic process, to identify important intermediate phases and defects in them which may only be metastable under specific reaction conditions of atmosphere and temperature, and to establish whether they are the origin, or merely the consequence, of the reaction. In this paper we report the extensive modification of a high resolution transmission electron microscope (Philips CM30T HRTEM) to add facilities for dynamic in-situ gas-solid reaction studies in a controlled atmosphere of gas or vapor at pressures of 0–50mbar which replaces the regular high vacuum TEM environment. The new environmental cell (ECELL) capability is combined with the original 0.23nm TEM resolution, STEM (BF/ADF) imaging and chemical and crystallographic analyses. Regular specimen holders are used; including hot stages capable of temperatures >1000°C. The full TEM resolution has been demonstrated at temperatures above 700°C and with limited (mbar) amounts of gas flowing through the integral 4-aperture differentially pumped ECELL (and with the additional pumps for the system operating). The ECELL system can be used to preserve, or if necessary to recreate, a continuous chain of evidence in a chemical reaction process.
Mimicking the Real World and Exploring New Ones with In-Situ Electron Microscopy
Authors: Howie A.
Published: April 2011

Recent progress with in-situ observations by electron microscopy is briefly surveyed by referring to developments in instrumentation for reflection and low energy electron imaging as well as for high resolution transmission imaging and spectroscopy. New opportunities have been opened up by environmental microscopy. With increased levels of illumination intensity, the ever present question of beam-induced effects is of mounting concern particularly in studies of non-metallic materials.
Stress Distributions in Free Standing Quantum Well Dots and Wires
Authors: Gippius N. A. , Tikhodeev S. G. , Steffen R. , Koch T. , Forchel A.
Published: April 2011

We present a theoretical model for calculation of stress distributions in semiconductor nanostructures such as lattice-mismatched InGaAs/GaAs quantum well wires and dots. The model is based on a linear elastic deformation approximation, and assumes dislocation-free interfaces with an additional condition of continuous interatomic distance on the interfaces. The distributions of stress tensor components and the resulting effective potentials for electronhole pairs are calculated. The comparison of our model with the experimental data on the exciton spectra in free standing strained InGaAs/GaAs quantum well wires is also presented.
Three-Dimensional Epitaxy: Thermodynamic Stability Range of Coherent Germanium Nanocrystallites in Silicon Host
Authors: Balasubramanian S. , Ceder G. , Kolenbrander K. D.
Published: April 2011

We study the stability range for a coherent interface between Ge quantum dots and an epitaxial Si shell. The critical radius at which coherency is lost is evaluated as a function of Si shell thickness and Ge nanocrystallite radius by comparing the energy of the system in the coherent and incoherent state. We find that the system is coherent up to a Ge nanocrystallite radius of about 100 Å, irrespective of the Si shell thickness. Nanocrystallites of radii larger than 270 Å lose coherency by the generation of perfect dislocation loops. In nanocrystallites of intermediate radii ( between 100 Å and 270 Å), the coherency is lost by the introduction of partial dislocation loops enclosing a stacking fault. As the shell thickness decreases, the critical radius increases.
Photovoltaic and Electroluminescent Properties of Stainetched Porous Silicon Based Heterojunctions
Authors: Dimova-Malinovska D. , Tzolov M. , Kamenova M. , Tzenov N. , Sendova-Vassileva M. , Nesheva D.
Published: April 2011

The results of photoelectric properties and electroluminescent studies of structures ZnO/porous Si/p-type c-Si/Al and ZnO/porous Si/p-n c-Si junction/Al are presented. Porous Si is prepared by stain etching of c-Si covered with thin Al film. The transparent ZnO film allows light emission through the top surface of the device under forward electrical bias. Photocurrent is observed under reverse bias and a photovoltaic effect is measured on the p-n junction PS device. The model based on injection of minority carriers through a narrow energy barrier into the porous Si and the presence of the barrier at the interface porous Si/c-Si is suggested for describing the electrical, photoelectric and luminescent properties of the structures.
Micro Structural Investigation of Porous Silicon Depth Profile by Direct Surface Force Microscopy
Authors: Chang D. C. , Baranauskas V. , Doi I. , Prohaska T.
Published: April 2011

We propose a method for studies in deph profile of porous silicon (PS) using atomic force microscopy (AFM) to remove PS layers from the surface. The abrasion were made aplying forces between 10-11 to 10-13 N with the AFM liquid cell measuring method. These range of forces is enough to remove very thin PS layers of the surface at each scan the equipment makes. With this method we can make studies and see the PS diferences in depth profile made by different process or different manufacturing conditions.
Linear Polarization of Porous Si Photoluminescence
Authors: Gippius N. A. , Tikhodeev S. G. , Efros Al. L. , Rosen M. , Kovalev D. , Chorin M. Ben , Diener J. , Koch F.
Published: April 2011

We demonstrate experimentally that linear polarization of porous Si photoluminescence depends significantly on the excitation geometry and describe this effect within the framework of a dielectric model in which porous Si is considered as an aggregate of slightly deformed, elongated and flattened, dielectric elliptical Si nanocrystals with preferred orientation in the [100] direction. The theoretical best-fit analysis of the experimental data allows us to get certain information concerning the shapes and orientation of the ellipsoids.
Room Temperature Emission from Erbium Nanoparticles Embedded in a Silicon Matrix
Authors: Thilderkvist A. , Michel J. , Ngiam S.-T. , Kimerling L. C. , Kolenbrander K. D.
Published: April 2011

Strong room temperature photoluminescence emission from thin films of Er nanoparticles embedded in a matrix of silicon is reported. The Er nanoparticles were produced by a pulsed laser ablation supersonic expansion technique. After a heat treatment at 500°C in an Ar-atmosphere, intense Er-related luminescence appears at λ = 1.54 gim, characteristic of intra-4f emission from Er3÷. Only a 50% reduction in photoluminescence intensity is observed as the temperature increases from 4 K to 300 K. A photocarrier mediated process is responsible for the excitation of the optically active Er-centers.
Investigation of Local Structures Around Luminescent Centers in Doped Nanocrystal Phosphors
Authors: Soo Y. L. , Huang S. W. , Ming Z. H. , Kao Y. H. , Goldburt E. , Hodel R. , Kulkarni B. , Bhargava R.
Published: April 2011

Extended x-ray absorption fine structure (EXAFS) technique has been employed to investigate the local structures around luminescent centers in nanocrystals of Mn-doped ZnS and Tb-doped Y2O3. Size-dependent local structural changes around Mn luminescent centers have been found in Mn-doped nanocrystals of ZnS by using Mn K-edge EXAFS. Local structures around Tb investigated by Tb Li-edge EXAFS also show substantial differences between bulk and nanocrystal samples. This structural information is useful for understanding the novel optical properties of doped nanocrystals.
Persistent Spectral Hole-Burning of CuCI Semiconductor Quantum dots
Authors: Okamoto Shinji , Masumoto Yasuaki
Published: April 2011

Persistent spectral hole-burning (PSHB) phenomena of semiconductor quantum dots enable to perform the precise, high-resolution spectroscopy for the quantum dots of a certain size. We succeeded in the observation of the higher-excited states of excitons in CuCI quantum dots by means of the PSHB phenomena. Moreover, the exciton-state-splitting is observed and in agreement with the theoretical results on the assumption of platelet quantumdots.