bluuebunny/crossref_metadata_2025 huggingface dataset:
Defect Creation by Electronic Processes in MgO Bombarded with GeV Heavy Ions
Authors: Beranger M. , Thevenard P. , Bremer R. , Balanzat E.
Published: April 2011

To study the defect creation induced by electronic processes in refractory oxides, MgO single crystals were irradiated with high energy tin, uranium and lead ions. Optical absorption measurements showed that F-type centers (oxygen vacancies with trapped electrons) were created during irradiation. The total number of centers per unit area of bombarded sample increases linearly with irradiating fluence. The main part of the point defects was found to arise from electronic processes. The concentration of F-type centers induced by ionization increases with the electronic energy losses. Assuming a saturation of point defect concentration at high fluences, F-type center creation cross sections could be estimated. The influence of irradiation temperature and of the velocity of the bombarding ions are discussed.
Optical and Magnetic Properties of Silica Implanted with N+ and Fe+
Authors: Isobe T. , Weeks R.A. , Zuhr R.A.
Published: April 2011

Silica platelets (Corning 7940) were implanted sequentially with N at 52 keV to different doses ranging from 0 to 1.2×l017 ions cm2 and then with Fe at 160 keV to a dose of 6×10 ions cm2. The optical absorption decreased with increasing N1 dose at photon energies ranging from 1.4 eV to 6.5 eV. The relative intensity, S(0°), of the ferromagnetic resonance absorption and its resonance field, H(0°), at θ = 0° were larger than S(90°) and H,(90°) at 0 = 90°, where Θ is the angle between the applied magnetic field and the normal to the implanted surface. The maximum values of S(0°) and S(90°) were observed near the N/Fe atomic ratio of 0.2. At the similar atomic ratio, the differential relative intensity, S(0°)- S(90°), and the differential resonance field, H,(0°)-H,(90°). associated with the degree of magnetic interaction between the produced compounds, also showed maxima. We conclude that sequential ion-implantation of N1 and Fe1 into silica causes a chemical interaction to produce iron nitrides.
Materials Science Issues of Plasma Source Ion Implantation
Authors: Nastasi M. , Elmoursi A.A. , Faehl R.J. , Hamdi A.H. , Henins I. , Malaczynski G.W. , Mantese J.V. , Munson C. , Qui X. , Reass W.A. , Rej DJ. , Scheuer J.T. , Speck CE. , Walter K.C. , Wood B.P.
Published: April 2011

Ion beam processing, including ion implantation and ion beam assisted deposition (IBAD), are established surface modification techniques which have been used successfully to synthesize materials for a wide variety of tribological applications. In spite of the flexibility and promise of the technique, ion beam processing has been considered too expensive for mass production applications. However, an emerging technology, Plasma Source Ion Implantation (PSII), has the potential of overcoming these limitations to become an economically viable tool for mass industrial applications. In PSII, targets are placed directly in a plasma and then pulsed-biased to produce a non-line-of-sight process for intricate target geometries without complicated fixturing. If the bias is a relatively high negative potential (20-100kV) ion implantation will result. At lower voltages (50-1200V), deposition occurs. Potential applications for PSII are in low-value-added products such as tools used in manufacturing, orthopedic devices, and the production of wear coatings for hard disk media. This paper will focus on the technology and materials science associated with PSII.
New Developments in Metal Ion Implantation by Vacuum Arc Ion Sources and Metal Plasma Immersion
Authors: Brown I.G. , Anders A. , Anders S. , Dickinson M.R. , MacGill R.A. , Monteiro O.R. , Oks E.M. , Raoux S. , Wang Z. , Yushkov G.
Published: April 2011

Ion implantation by intense beams of metal ions can be accomplished using the dense metal plasma formed in a vacuum arc discharge embodied either in a vacuum arc ion source or in a ‘metal plasma immersion’ configuration. In the former case high energy metal ion beams are formed and implantation is done in a more-or-less conventional way, and in the latter case the substrate is immersed in the plasma and repetitively pulse-biased so as to accelerate the ions at the high voltage plasma sheath formed at the substrate. A number of advances have been made in the last few years, both in plasma technology and in the surface modification procedures, that enhance the effectiveness and versatility of the methods, including for example: controlled increase of the ion charge states produced; operation in a dual metal-gaseous ion species mode; very large area beam formation; macroparticle filtering; and the development of processing regimes for optimizing adhesion, morphology and structure. These complementary ion processing techniques provide the plasma tools for doing ion surface modification over a very wide parameter regime, from ‘pure’ ion implantation at energies approaching the MeV level, through ion mixing at energies in the ∼1 to ∼100 keV range, to IBAD-like processing at energies from a few tens of eV to a few keV. Here we review the methods, describe a number of recent developments, and outline some of the surface modification applications to which the methods have been put.
Dual Ion Beam Sputtering of Carbides for EUV Reflectance
Authors: Schwarcz Dan , Keski-Kuha R.A.M.
Published: April 2011

There is a need for thin optical coatings that can be produced at low temperatures and have a high reflectance at the extreme ultraviolet (EUV), λ < 1200 Å. Currently, the best such materials are silicon carbide (SiC) and boron carbide sputtered onto optical surfaces. The EUV reflectance of sputtered SiC, however, is not as high as that of the sputtered target materials (sintered or CVD -SiC). More significantly, the reflectance of both sputtered films degrades with time. In previous work the reflectance degradation of the SiC films has been quantified, and efforts to ameliorate it via ion-beam assisted deposition (BAD) were described. Further work on sputtered SiC films is reported, including chemical and structural analysis. In addition, the degradation behavior of sputtered boron carbide is discussed.
Depth Profiles of Medium Energy Phosphorus Implants into Silicon
Authors: Lavine J. P. , Zheng L. , Whalen P. M. , Downey D. F.
Published: April 2011

Secondary ion mass spectrometry (SIMS) is used to produce depth profiles of ion-implanted phosphorus in silicon. The implant energies are 250, 500, and 750 keV, and there is a 0.06-μm thick oxide on the silicon. The experimental profiles are compared with predictions from a variety of simulation programs, most of which give larger projected ranges than the data. The silicon crystal structure needs to be included in the calculations to produce projected ranges and depth profiles that agree with the present experimental data and with data from the literature.
Controls of Crystallinity and Surface Roughness of Cu Film in Partially Ionized Beam Deposition
Authors: Koh Seok-Keun , Kim Ki-Hwan , Choi Won-Kook , Jang Hong-Gui , Yoon Young-Soo , Han Sung , Jung Hyung-Jin
Published: April 2011

Changes of crystallinity and surface roughness are discussed in terms of the average energy per deposited atom in the partially ionized beam(PIB) deposition. The average energy per deposited atom can be controlled by adjusting the ionization potential, Vi and acceleration potential, Va. The ion beam consists of a Cu ion beam and residual gas ion beam and residual gases as well as Cu particles that were ionized and accelerated to provide the film with energy required for film-growth. The relative contribution of residual gas ions and Cu ions to total average energy per deposited atom was varied with the ionization potential. At fixed ionization potentials of Vi=400 V and Vi=450 V, the average energy per deposited atom was varied in the range of 0 to 120 eV with acceleration potential Va, of 0 to 4 kV. The relative intensity ratio, 1(111)/I(200), of the Cu films increased from 6 to 37 and the root mean square(Rms) surface roughness decreased with an increase in acceleration potential at Vi=400 V. The relative intensity ratio, I(lll)/I(200), of Cu films increased up to Va=2 kV at Vi=2 kV, above which a decrease occurred, and the surface roughness of Cu films increased as a funtion of acceleration potential. The degree of preferred orientation was closely related with the average energy per deposited atom. The change of Rms roughness might be affected by ion flux, particle energy and preferred orientation.
Characterization of Defects Created in Silicon Due to Etching in Low-Pressure Plasmas Containing Fluorine and Oxygen
Authors: Buyanova I. A. , Henry A. , Monemar B. , Lindström J. L. , Lamprecht A. , Svensson B. G. , Oehrlein G. S.
Published: April 2011

Defect characterization in n-type silicon after the reactive ion etching (RIE) in low-pressure plasmas containing fluorine and oxygen is performed by using photoluminescence (PL) and deep level transient spectroscopies (DLTS). It is shown that RIE treatment results in the formation of (i) luminescence centers giving rise to the C- and G- excitonic lines and broad emission bands related to radiation-induced defect complexes and extended defects and (ii) several electron traps located at 0.16 eV, 0.26 eV, 0.43 eV and 0.58 eV below the conduction band. The addition of oxygen to the SF6 and CF4 plasma is shown to cause nonuniform stress in the near surface region. This stress is responsible for the experimentally observed splitting of the C- and G-excitonic lines, a low energy shift of the phosphorous bound exciton lines, as well as the splitting of the DLTS spectra. It is shown that the stress field is highly inhomogeneous across the wafer, and is rather related to the RIE-induced extended defects than caused by the reaction layer formed on the Si surface.
Role of Interface in Ion Mixing or Thermal Annealing Induced Amorphization in Multilayers in Some Immiscible Systems
Authors: Liu B.X. , Zhang Z.J. , Jin O. , Pan F.
Published: April 2011

Six binary metal systems were selected to study the possibility of forming amorphous alloys by ion mixing or thermal annealing in multilayered Films, i.e. the Ta-Cu, Zr-Nb, Zr-Ta, Y-Zr, Y-Mo and Y-Ta systems, featuring positive heats of formation (ΔHf) ranging from +3 to +40 kJ/mol. Firstly, the interfacial free energy consisting of a chemical and an elastic terms was calculated and added to the energetic state of the multilayers. It was found that the excess interfacial free energy increased with increasing the fraction of the interfacial atoms in the multilayers, and could raise the multilayers to an energy level intersecting with or being higher than thai of the amorphous phase possessing a typical convex shape. It is therefore possible to produce amorphous alloys in such systems, if the multilayered filins included enough fraction of the interfacial atoms. The multilayered samples were then designed and prepared accordingly and both ion mixing and thermal annealing under appropriate conditions resulted in the formation of a number of new amorphous alloys, confirming the above prediction based on the interfacial free energy concern. It is noted that the success of synthesising amorphous alloys by solid-state reaction in the immiscible systems develops a new glass forming technique, namely interface-generated spontaneous amorphization, which has a great potential to produce new and relatively thick amorphous films, e.g. a Ta72Cu28 amorphous film of 800 nm thick was obtained.
Properties of Silicon-on-Defect-Layer Material
Authors: Li Jianming , Jones K. W. , Coleman J. H. , Yi J. , Wallace R. , Anderson W. A.
Published: April 2011

A new silicon material, silicon-on-defect-layer (SODL), has been measured by secondary ion mass spectrometry (SIMS) and spreading resistivity (SR) measurements. SIMS data show that the buried defect-layer in SODL consists of silicon oxide due to the gettering of intrinsic oxygen by proton-implanted damage. Furthermore, SODL procedure makes a silicon wafer contain much fewer oxygen in surface-layer on the defect-layer, resulting in a purfied surface-layer. Measurements of SR indicate that the surface-layer of n-type silicon wafer was converted to p-type silicon after SODL procedure. A metal oxide semiconductor (MOS) device with a value of the electron mobility in the inversion mode of 714 cm2/(V s) was fabricated on SODL material. Like isolation function of a well in a complementary MOS (CMOS) device, the p-n junction in SODL material could play a role of isolation between the surface-layer and bulk. In addition, by reducing the implantation energy, SODL technology for making p-n junction, in which built-in field separates light-generated electrons and holes, is a candidate to make cheap solar cells by using low-quality low-cost silicon.
Cavity Nucleation and Evolution in He-Implanted Si and GaAs
Authors: Follstaedt D. M. , Myers S. M. , Petersen G. A. , Barbour J. C.
Published: April 2011

The criteria for forming stable cavities by He implantation and annealing are examined for Si and GaAs. In Si, implanting at room temperature requires a minimum of 1.6 at.% He to form a uniformly dense layer of cavities after annealing at 700°C. Near this threshold, cavities are located at dislocations and planar defects. Peak He concentrations just above 1.6 at.% produce narrow layers of cavities at the projected range. In GaAs, room-temperature implantation followed by annealing results in exfoliation of the surface layer. Cavities were formed instead by implanting Ar followed by overlapping He, both at 400°C, with additional annealing at 400°C to outgas the He. This method forms 1.5-3.5 nm cavities that are often on {111} planar defects.
High-Energy Ion-Implantation of a Moderately Deep Acceptor Hg Into Liquid Encapsulated Czochralski Grown GaAs : Formation of New Shallow Emission Bands
Authors: Harada K. , Makita Y. , Shibata H. , Lo B. , Beye A. C. , Halsalic M. P. , Kimura S. , Kobayashi N. , Iida T. , Shima T. , Obara A.
Published: April 2011

Hg (mercury) in GaAs is known to be a moderately deep acceptor impurity, having a 52 meV activation energy. Optical properties of Hg acceptors in GaAs were systematically investigated as a function of Hg concentration, [Hg]. Samples were prepared by high-energy ion-implantation of Hg+ into GaAs grown by the liquid encapsulated Czochralski (LEC) method. Heat treatment was made by furnace annealing and rapid thermal annealing. Photoluminescence measurements at 2K revealed that the Hg-related so-called “g” line is formed in addition to the well-defined conduction band-to-Hg acceptor transition, (e, Hg). Additionally, three shallow emissions are formed for net hole concentrations INA-NDI greater than 2×1017cm−3 . This is the first demonstration that even Hg in GaAs makes multiple shallow emissions due to acceptor-acceptor pairs and LEC GaAs can be used for the investigations of these emissions.
The Fabrication of Complex Membrane Structures in N-GaAs for Micromechanical Applications
Authors: Miao J. , Weiss B.L. , Hartnagel H.L. , Wilson R.J. , Ruck D.
Published: April 2011

A novel process for the fabrication of complex membrane structures in n-GaAs has been developed which utilises high energy nitrogen implantation and annealing to produce a semi-insulating etch stop layer and pulsed anodic etching for the selective removal of material. The process is versatile and can be used to produce complex, single crystal, stress-free, self-supporting membrane structures which are suitable for use as transducers operating up to ∼300°C. The semi-insulating properties of the membrane demonstrates its potential use as a substrate for electronic circuits.
Mev Ion Beam Synthesis of Well-Defined Buried 3C-Sic Layers in Silicon
Authors: Lindner J.K.N. , Götz B. , Frohnwieser A. , Stritzker B.
Published: April 2011

Well-defined, homogenous, deep-buried 3C-SiC layers have been formed in silicon by ion beam synthesis using MeV C+ ions. Layers are characterized by RBS/channeling, X-ray diffraction, x-sectional TEM and electron diffraction. The redistribution of implanted carbon atoms into a rectangular carbon depth distribution associated with a well-defined layer during the post-implantation anneal is shown to depend strongly on the existence of crystalline carbide precipitates in the as-implanted state.
Electrical and Structural Properties of Annealed Epitaxial Ceo2 Films on Si(111) Substrates
Authors: Morshed A. H. , Tomita M. , El-Masry N. , Mclarty P. , Parikh N. P. , Bedair S. M.
Published: April 2011

Epitaxial CeO2 films were grown on Si(111) substrates by laser ablation of CeO2 targets under UHV conditions. The as-grown films were found to have poor electrical properties due to the presence of a large amount of defects near the oxide-silicon interface. Improved MOS electrical characteristics were obtained by annealing in an O2 environment. This however resulted in the growth of a SiO2 layer that can be 10 nm thick at the silicon interface which will thus reduce the capacitance of the grown structure. Annealing in argon and argon followed by oxygen environments were investigated as means to reduce the defects while minimizing the intermediate SiO2 layer thickness. The annealed films were compared based on their RBS yields, breakdown voltages and capacitance-voltage characteristics. Growth and annealing conditions were optimized to achieve device quality MOS structures.
Defects and Their Origin in Thin Films of (001) Alkaline Earth Oxides
Authors: Walker F. J. , Mckee R. A. , Pennycook S. J. , Thundat T. G.
Published: April 2011

MgO is used as an optical isolation layer for waveguides epitaxially grown on silicon. The crystalline perfection of MgO is a critical issue because it serves as a substrate for the single crystal, perovskite guiding layer. Imperfections in the MgO will result in imperfections in the guiding layer and lead to large optical losses for the planar waveguide structure. We show that the most common defect to form in thin films of MgO are twin boundaries between {111}-type planes. The highest density of twins is observed when (001) MgO is grown directly on silicon/MgO interlayers containing barium. Twinning is shown to accommodate the large size of barium impurities incorporated in the MgO films through the formation of internal grain boundaries and open surfaces other than the growing (001) of MgO.
Thermodynamics of Epitaxial Ferroelectric Films.
Authors: Desu S. B. , Dudkevich V. P. , Dudkevich P. V. , Zakharchenko I. N. , Kushlyan G. L.
Published: April 2011

The problem of phase transitions and physical properties of the BaTiO3-type films on the (001) single-crystal substrates of the cubic syngony was solved in the limits of the Landau- Devonshire thermodynamics. The thermoelastic film-substrate interaction caused by the difference between thermal expansion coefficients was strictly taken into consideration. The model was based on the following assumptions: 1) the film is closely conjugated with the substrate; 2) the film is sufficiently “thick”to find itself unstrained at the growth temperature Ts, ( growth stresses were compensated by misfit dislocations ), and 3) the film is sufficiently “thin, and the stresses arising at the temperatures T>Ts may be considered to be uniform.
Atomic Scale Control of Epitaxial Growth and Interface in Oxide Thin Films for Advanced Oxide Lattice Engineering
Authors: Yoshimoto M. , Maeda T. , Ohnishi T. , Lee G. H. , Koinuma H.
Published: April 2011

Advanced thin film technology based on laser MBE has enabled us to control the molecular layer-by-layer epitaxial growth and interface structure of oxide thin films in an atomic scale. Molecular layer epitaxy of oxide thin film growth was verified from in situ monitoring of intensity oscillation in reflection high energy electron diffraction (RHEED). Advanced oxide thin film technology was applied to form oxide superlattices for quantum functional oxides and to achieve lattice-matched heteroepitaxy in oxide films on silicon substrate for all epitaxial oxide/silicon hybrid devices. The key factors to develop oxide lattice engineering are discussed with respect to not only in situ monitoring of growth process using RHEED but also atomic regulation of the substrate surface by atomic force microscopy and ion scattering spectroscopy.
Epitaxial Niobate Thin Films and Their Nonlinear Optical Properties
Authors: Wessels B. W. , Nystrom M. J. , Chen J. , Studebaker D. , Marks T. J.
Published: April 2011

Ferroelectric oxide thin films show considerable potential as electro-optic and non-linear optical materials. Of particular interest are the niobates such as strontium barium niobate and potassium niobate. The growth of these epitaxial oxide films by metal-organic chemical vapor deposition (MOCVD) has been investigated. This technique has yielded epitaxial thin films with excellent non-linear optical properties. Issues concerning the epitaxy of these thin films and its relationship to their optical and nonlinear optical properties are discussed.
Hetero-Epitaxial Structures of Litao3 Thin Films
Authors: Hung L.-S.
Published: April 2011

We have grown epitaxial thin films of LiTaO3 on various substrates. LiTaO3 grows epitaxially on (111) GaAs and forms a waveguide with its underlying buffer layer of MgO, providing a desirable structure for monolithic integration. LiTaO3 grows on LiNbO3 with a buffer layer of magnesium niobate or magnesium tantalate to form an optical waveguide structure having good lattice matching and pronounced differences in refractive index. This heterostructure has the potential for reducing crystal imperfection of waveguides and improving optical confinement. We also describe a multilayer structure using an epitaxial conducting layer as a bottom electrode to grow a nonlinear optical waveguide on LiNbO3 for waveguide switching and modulation. Both light-absorbing metals and transparent metallic oxides are employed. Ion channeling and x-ray diffraction reveal high crystalline quality of the hetero-epitaxial structures. The influence of surface polarity, thermal expansion, and lattice matching on waveguiding LiTaO3 thin films is addressed.
Afm Study of CeO2 Growth on Sapphire as a Buffer Layer for YBa2Cu3O7
Authors: Denhoff M. W. , Mason B. F. , Tran H. T. , Grant P. D.
Published: April 2011

The structure of CeO2 films grown on (1102) sapphire and on YBCO thin films was investigated. The films reported on here were grown by pulsed excimer laser deposition and their surface structure was probed using atomic force microscopy. We found that CeO2 films grown on sapphire were epitaxial with a granular structure which is smooth on an atomic scale. We see evidence of a surface reconstruction on a very smooth CeO2 (100) oriented surface. At higher growth temperatures, three dimensional islands begin to form. When a CeO2 film is grown on top of a YBCO film, the growth mode is two dimensional. The steps in this layer by layer growth are a surprisingly large 2 nm. This is about equal to 4 times the CeO2 lattice constant. This step height appears to be temperature dependent.
The High Resolution Magneto-Optical Faradayeffect as a Research Tool to Investigate Details of Current and Magnetic Flux Distribution in Y-Ba-Cu-O Thin Films
Authors: Forkl A. , Kronmüller H. , Habermeier H.-U. , Leibold B.
Published: April 2011

The magneto-optical Faradayeffect [MOFE] is known to be an excellent tool for the spatially resolved analysis of the flux distribution in superconductors. We use three examples to demonstrate the power of this technique for device oriented investigations. It is shown that homogeneous Yba2Cu3O7 thin films with different shape show a flux pattern strongly depending on the geometry of the sample; model calculations for the flux distribution are in excellent agreement with the experimental results. Furthermore, we show, that crystallographic defects as well as imperfections due to pattern delineation are affecting the flux pattern on macroscopic scale. In a third example we use the MOFE to demonstrate that pulsed laser irradiation of Yba2Cu3O7 thin films with UV photons of moderate flux causes an enhancement of the critical current.
New Substrate/Buffer Layer Compounds for Epitaxial HTSC Film Growth
Authors: Tauber A. , Tidrow S. C. , Wilber W. D. , Finnegan R. D.
Published: April 2011

A series of compounds in the system A4MeSb13O12 where A=Ba, Sr and Me=Li, Na &K were prepared by solid state reaction at elevated temperature. A new form of Sr4NaSb3O12 was prepared. The compounds were characterized with regard to their lattice parameters, density and dielectric properties. Thin films were prepared by PLD from dense targets and epitaxial relationships identified between YBCO and these compounds.
Epitaxial Thin Films and Heterostrcutures of Copper-Oxide-Based Isotropic Metallic Oxides for Device Applications
Authors: Eom C. B.
Published: April 2011

We have grown epitaxial thin films of a new family of copper-oxide-based isotropic metallic oxides such as La6.4Sr1.6Cu8O20, La5BaCu6O13 and La6BaYCu8O20in situ by 900° off-axis sputtering. These metallic oxides are pseudo-cubic perovskites with essentially isotropic properties, which could be ideal normal metals for SNS junctions in superconducting devices. We have also grown epitaxial SNS superconducting heterostructures (c-axis YBa2Cu3O7 / La6.4Sr1.6Cu8O20 / c-axis YBa2Cu3O7) with a copper-oxide-based isotropic metallic oxide (La6.4Sr1.6Cu8O20) normal metal barrier. X-ray diffraction and cross-sectional transmission electron microscopy reveal these heterostructures to have high crystalline quality and clean interfaces. This material will facilitate fabrication of ideal SNS Josephson junctions with low boundary resistance due to its excellent chemical compatibility and lattice match with cuprate superconductors and will be useful for determining the source of interface resistance in such heterostructures.
Microstructural Study of CMR Films as a Function of Growth Temperature, As-Deposited and Annealed
Authors: Hawley M. E. , Wu X. D. , Arendt P. N. , Adams C. D. , Hundley M. F. , Heffner R. H.
Published: April 2011

The properties encompassed by the family of complex metal oxides span the spectrum from superconductors to insulating ferroelectrics. Included in this family are the new colossal magnetoresistive perovskites with potential applications in advanced high density magnetic data storage devices based on single or multilayer thin films units of these materials fabricated by vapor phase deposition (PVD) methods. The realization of this potential requires solving basic thin film materials problems requiring understanding and controlling the growth of these materials. Toward this end, we have grown La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3 on LaAlO3 single crystal substrates by pulsed laser and RF sputter deposition at temperatures from 500° C to 900° C and annealed at over 900° C for about 10 hours. The evolution of the microstructure of these films was studied by scanning probe microscopies and transmission electron microscopy (TEM).

The results of SPM characterization showed that at the lower end of the growth temperature range, the as-grown films were polygranular with grain size increasing with temperature. The 500° C as-grown films appeared to be amorphous while the 750° C film grains were layered with terrace steps often one unit cell high. In contrast, films grown at 900° C consisted of coalesced islands with some 3-D surface crystals. After annealing, all films had coalesced into very large extended layered islands. The change in microstructure was reflected in a decreased resistivity of coalesced films over their unannealed granular precursors. Previous reported work on the growth of La0.84 Sr0.16MnO3 and La0.8Sr0 2CoO3 grown demonstrated the sensitivity of the microstructure to substrate and deposition conditions. Films grown on an “accidental” vicinal surface grew by a step flow mechanism.
Epitaxial Growth and Characterization of NbxTi1−xO2 Rutile Films by Oxygen-Plasma-Assisted Molecular Beam Epitaxy
Authors: Gao Y. , Chambers S. A.
Published: April 2011

Epitaxial films of NbxTi1−xO2 rutile were grown on TiO2 (110) and (100) at 600 °C by oxygen-plasma-assisted molecular beam epitaxy using elemental Ti and Nb sources. The epitaxial films were characterized by means of reflection high-energy and low-energy electron diffraction (RHEED/LEED), x-ray photoelectron spectroscopy and diffraction (XPS/XPD), ultraviolet photoemission spectroscopy (UPS) and atomic force microscopy (AFM). The epitaxial films grow in a layer-by-layer fashion and have excellent short- and long-range structure order at x≤0.3 on TiO2(110) and at x≤0.15 on TiO2(100). However, the epitaxial films become rough and disorder at higher doping levels. Nb substitutionally incorporates at cation lattice sites, leading to NbxTi1−xO2 solid solutions. In addition, the oxidation state of Nb in the NbxTi1−xO2 films has been determined to be +4.
A Novel Technique for Determining Local Dielectric Function During Ferroelectric to Paraelectric Phase Transformation in Barium Titanate with a Transmission Eels
Authors: Katti Kalpana S , Qian Maoxu , Sarikaya Mehmet
Published: April 2011

In this work a transmission electron microscopy (TEM) technique was used in obtaining local dielectric properties calculated from optical parameters for dynamic investigation of the effect of cubic to tetragonal phase transformation in barium titanate. In order to obtain in situ local dielectric during phase transformation, Kramers-Kronig relations were applied using the transmission electron energy loss (EELS) measurements. The optical excitations in the EELS spectra were consistent with the band structure results. The Re (1/ε) (real part of the dielectric function) obtained from the energy loss data indicated a change at the phase transformation. A broadening of the valence plasmon excitation suggested an order-disorder nature to the cubic to tetragonal transformation. In situ electron energy loss near edge structure (ELNES) studies from 500–700 eV energy range near the O-K edge exhibited a pre-edge feature that is associated with the Ti-L1, edge which further indicates an order-disorder nature to the phase transformation. The significance of the results is discussed.
In-Situ Tem Studies of Recrystallization and Grain Growth in Al-Mg-Mn-Zr Alloys
Authors: Vetrano John S. , Bruemmer Steve M. , Robertson Ian M.
Published: April 2011

Recrystallization and grain growth studies of Al-Mg-Mn-Zr alloys have been carried out in-situ in the transmission electron microscope. Nucleation sites were primarily on large (>I μm diameter) eutectic constituent particles. The sub-micron A16Mn dispersoids were observed to be effective as nuclei if present in clusters, and were effective at retarding grain boundary migration and dislocation motion. The smaller A13Zr precipitates seemed to have little effect on nucleation and growth, but were effective in pinning dislocations. These results have been analyzed in terms of precipitate size and shape in both the as-cold-worked microstructure and during recrystallization. The implications on the microstructural refinement of these alloys for improved superplastic properties will be discussed.
Electronic Irradiation Effect on Bi-Mo-O Catalysts Observed in a Hrtem Study
Authors: Avalos-Borja M. , Galvan D. H. , Ning X. G.
Published: April 2011

We studied by high resolution transmission electron microscopy (HRTEM) unsupported bismuth-molybdenum-oxide catalysts. The microscope utilized was a JEOL 4000 EX electron microscope with a resolution better than 0.19 nm (point to point). The image simulation were performed on a personal computer with the aid of a commercial program. With the aid of image simulation it is possible to identify γ-Bi2MoO6 and X-Mo4O11 phases, among several other possibilities that fit the interplanar spacings and angles.

A very important aspect, thermal instability, was proved indirectly in the microscope, by the changes of the particles under the electron beam irradiation at 400 kV. After several minutes of irradiation, the amorphous surface layer was totally reconstructed to crystalline phases.

The fact that we observe many phases in this sample, is certainly deleterious to the catalytic properties, since not all of them are active. Also the sensitivity to the beam indicates that minimum exposure microscopy has to be applied in order to prevent unecessary complications for phase identification.
In-Situ Tem Study of Crystallisation of Amorphous SbOx Films
Authors: Nayak R. , Petford-Long A. K. , Doole R. C. , Afonso C. N.
Published: April 2011

Amorphous d.c. sputtered SbOx films (0.19< x<2.0) have been found to be fast crystallising materials sensitive to nano- and pico-second laser pulses, and have potential applications as optical data-storage media. They were crystallised in-situ in a JEOL 4000EX TEM, and the crystallisation recorded onto video tape. The crystallisation of the SbO0.37 films occurred by random nucleation followed by growth until coalescence. In contrast the crystallisation of the SbO0.533 films occurred by surface crystallisation across the whole film followed by bulk crystallisation through the film, during which contrast in the TEM increased steadily. Analysing the video frames in an image processing package enabled kinetic parameters such as transformation index and activation energy to be extracted. High resolution transmission electron microscopy showed the crystalline phase to contain nano-crystallites approximately 10 nm in size in a less-ordered matrix.
An in Situ Stm Study of Cu and Ni Electrodeposition
Authors: Moffat T. P.
Published: April 2011

An STM study has been initiated to investigate the various processes associated with electrodeposition of Cu-Ni multilayers on Cu (100). The substrates were prepared by electropolishing in phosphoric acid followed by immersion in 10 mmol/l HCl. A (√2×√) R°45 adlattice of oxidatively adsorbed chlorine is formed under these conditions. The adlayer stabilizes the surface steps in the 〈100〉 direction which corresponds to the close packed direction of the chloride adlattice. In dilute mmo1/1 solutions of cuprous ion, reduction occurs under mass transport control with the electrocrystallization reaction proceeding by step flow in the 〈100〉 direction. At more negative potentials chloride is reductively desorbed. Coincident with desorption the highly kinked metal steps become frizzy and move towards adopting the close packed 〈110〉 orientation of the metal lattice. Preliminary experiments on heteroepitaxial nickel deposition reveal regions where electrocrystallization on Cu(100) occurs via step flow in the 〈110〉 direction.
In Situ Observation of an Electrochemical Etching Reaction in Silicon
Authors: Ross Frances M. , Searson Peter C.
Published: April 2011

We describe a TEM specimen holder which has been designed and constructed in order to observe the process of electrochemical pore formation in silicon. The holder incorporates electrical feedthroughs and a sealed reservoir for the electrolyte and it accepts lithographically patterned silicon specimens. We present ex situ observations of progressive pore propagation and show dynamic, in situ observations of electrolyte movement within the pores.
Strain Measurement in Two-Dimensional Nanoscale Si Gratings by High Resolution X-Ray Diffraction
Authors: Tanaka So , Umbach Christopher C. , Shen Qun , Blakely Jack M.
Published: April 2011

The strain induced by thermal oxidation in a cylindrical silicon (Si) structure has been studied by high resolution synchrotron x-ray diffraction. The strain in the structure studied is expected to display some of the features that exist in three-dimensional non-planar surfaces in electronic devices. The sample consisted of a 2-dimensional array, with period of 300nm, of approximately cylindrical pillars covered with a thin thermal oxide (thickness ∼6nm). These showed a tensile strain of 3.7×10-4 at room temperature. This strain can be relaxed elastically by chemical removal of the oxide. Process simulation indicates the importance of both the contribution due to interface stress during the oxide growth and stress due to differential thermal contraction during the cooldown. Significant differences exist between the strain in such cylindrical pillars and in a flat wafer.
Formation of Intensive Photoluminescence in Porous Silicon
Authors: Makara V. A. , Boltovets M. S. , Vakulenko O. V. , Datsenko O. I. , Rudenko O. V.
Published: April 2011

Photoluminescence (PL) spectra of porous silicon (PS) samples are studied. Effect of mechanical stresses in substrate on PL intensity is shown. The quantum yield (QY) of PS luminescence is estimated by comparing PL spectra of PS and rhodamine 6G.
Restoration of Porous Silicon Luminescence in Water Vapour
Authors: Brodin M. S. , Bykov V. N. , Dan'ko D. B. , Fedorovich R. D. , Kipen' A. A. , Kiyayev O. E. , Naumovets G. A. , Yanushevskii N. I.
Published: April 2011

Influence of different adsorbates on recovery of porous Si luminescence was in situ investigated for samples preheated under ultra-high vacuum conditions. Exposure to simple adsorbates (O2, H2, N2 up to a pressure of 10-3 to 10-1 Torr), long exposure to air at the atmosphere pressure, or immersion into distilled water fail to recover the red luminescence. On the other hand, we found that the red luminescence can be recovered by adsorption of water vapour onto the sample surface.

The red luminescence of as-prepared porous Si can be caused by water molecules (together with possible impurities) adsorbed in the pores. The immense surface of the pores provides a large number of emitting sites. The porous Si layer can filter for the emitted light, cutting off the wave region shorter than yellow. The combination of these two factors (emission and filtering) can result in the visible red-orange luminescence of porous Si.
On the Origin of Visible Luminescence from SIO2 Films Containing Ge Nanocrystals
Authors: Min K. S. , Shcheglov K. V. , Yang C. M. , Camata R. P. , Atwater Harry A. , Brongersma M. L. , Polman A.
Published: April 2011

Synthesis of Ge nanocrystals in SiO2 is carried out by precipitation from a supersaturated solid solution of Ge in SiO2 made by Ge ion implantation. The SiO2films containing Ge nanocrystals show intense visible photoluminescence at room temperature that is very similar in spectral features to that of SiO2 containing Ge nanocrystals synthesized by other methods, such as co-sputtering and hydrothermal reduction. The dependence of the measured peak luminescence energy on the nanocrystal diameter shows a poor correlation compared to the calculated sizedependent exciton energy for Ge ‘quantum dot’ states. The measured luminescence lifetimes are much shorter than those predicted by calculated radiative decay rates for the observed size range. The photoluminescence spectra show only a weak temperature dependence. In addition, very similar photoluminescence spectra have also been observed from Xe+-implanted SiO2with damage profiles similar to Ge+-implanted SiO2. Furthermore, the luminescence has been shown to be reversibly quenched by deuterium. These results indicate that the process responsible for visible photoluminescence is not the radiative recombination of excitons in Ge ‘quantum dots’ but is instead related to luminescent radiative defect centers in the matrix or at the nanocrystal/matrix interface.
Electrical Characteristics and Temperature Effects of Electroluminescing Silicon Nanocrystals
Authors: Forsythe E. W , Whittaker E. A. , Morton D. , Khan B. A. , Sywe B. S. , Lu Y. , Liangt S. , Gorla C. , Tompart G. S.
Published: April 2011

The white electroluminescence (EL) demonstrated from Si nanocrystals in a wider bandgap amorphous oxide matrix based structure has exciting opportunities in electroptic applications as well as novel LEDs. In this report, we review the electroluminescent properties of the devices for rapid thermally annealed samples at anneal temperatures ranging from 875°C to 1025°C. Depending upon the anneal conditions the EL spectra has shown two distinct spectral features; a strong emission peak at 380nm with a width of 50nm, and a broader features centered above 800nm,. Further, the I-V characteristics and corresponding EL spectra have been measured for sample temperatures ranging from 317K to 240K. In addition, Raman scattering estimated the mean particle sizes of the Si nanocrystals of 6.5nm and 8nm as well as provide insight to the nature of the amorphous matrix. The novel light emission from our devices demonstrates an exciting opportunity for Si nanocrystal (and nanocrystals in general) technology in a wide variety of applications.
Incorporation of Nitrogen Atoms at Si/SiO2 Interfaces of Field Effect Transistors (FETs) to Improve Device Reliability
Authors: Lucovsky G. , Lee D. R. , Jing Z. , Whitten J. L. , Parker C. , Hauser J. R.
Published: April 2011

Incorporation of N-atoms at the Si-Si02 interface in field effect transistors, FETs, with ultrathin dielectrics (≤ 5.5 nm) improves device reliability. Four aspects of our recent research on nitrided Si-Si02 interfaces are discussed in this paper: i) the low-temperature/low-thermal budget process by which interface chemistry is controlled, and optimized; ii) the use of on-line and off-line diagnostics to determine the spatial confinement and concentration of interfacial N-atom incorporation; iii) comparisons of device properties for non-nitrided and nitrided interfaces; and iv) the proposal of an atom-scale model for the role that interfacial N-atoms play in improving device reliability.
Characterization of Mos Structures with Ultra-Thin Tunneling Oxynitride
Authors: Fujioka H. , Wann C. , Park D. , Hu C.
Published: April 2011

Characteristics of ultrathin silicon oxynitride (15–25Å) and its interface with Si have been investigated. Oxynitride films with thickness down to 15Å can be grown reproducibly in a conventional furnace. The leakage currents through these films can be well explained by the direct tunneling mechanism and can be fit by the same equation as that for pure oxide. This result indicates that incorporation of nitrogen atoms does not seriously affect the basic properties of the film and its interface such as the effective mass and the barrier height. A p-type poly gate MOS structure with 22Å oxynitride has also been fabricated successfully without boron penetration even using BF2+ ion implantation and a conventional furnace. Since the leakage current thorough oxynitride with this thickness is acceptable for circuit operation, thickness of the gate insulator in the dual poly-Si process can be scaled down at least to 22Å.
Study of Periodic Surface Nanostructures Using Coherent Grating X-Ray Diffraction (Cgxd)
Authors: Shen Qun
Published: April 2011

It is shown that an x-ray interference phenomenon, Coherent Grating X-ray Diffraction (CGXD), can be used to study lateral nanostructure arrays on crystal surfaces and interfaces. Compared to Fraunhofer grating diffraction of visible light, x-ray grating diffraction contains information not only about geometric profiles of a surface, but also about the internal crystalline structures and lattice strain distributions in grating features. Grating diffraction patterns can also be measured in a white-beam Laue method using highly collimated polychromatic synchrotron radiation. This provides a way for parallel data collection and is useful in in-situ studies of structural evolution of nanostructure arrays.
A New Technique for Depth Profiling on a Nanometer Scale
Authors: Schwenke H. , Knoth J. , Günther R. , Wiener G. , Bormann R.
Published: April 2011

A new technique is presented for the determination of concentration depth profiles. Surface atoms are sputtered by an ion beam and deposited on a clean silicon wafer. The wafer is rotated behind a slit in step with the sputtering progress. In this way the depth profile of the sample is transferred into a lateral distribution of the sputtered atoms on the target wafer. Subsequently the wafer is scanned by Total Reflection X-ray Fluorescence Spectrometry (TXRF) which is capable of detecting traces of metallic impurities on wafers down to 10-4 of an atomic monolayer. The sequence of ion-beam sputtering, deposition of the sputtered atoms and TXRF analysis results in an excellent depth resolution in the case of areal structures. Using an ion source of the Kaufmann type, an extrapolated perpendicular resolution better than 0.1 nm was obtained for a 1500 mm2 surface. For a surface area of 3 mm2 a depth resolution of 1 nm is expected. 1.4 nm was actually measured to be the width of a coherent Ti/Al-interface within a layered structure.
The Uniformity of Surface Passivation After (NH4)2S Treatment Studied by Near-Field Scanning Optical Microscopy
Authors: Liu Jutong , Kuech T. F.
Published: April 2011

We have achieved spatially resolved room temperature photoluminescence (PL) from MOVPE GaAs (001) surfaces by Near-Field Scanning Optical Microscopy (NSOM). The PL intensity variation was related to the change of surface state density. Using this technique, the uniformity of surface passivation after (NH 4)2S treatment has been studied. We have performed the topography, reflection and PL measurements by NSOM as well as the topography measurements by Atomic Force Microscopy (AFM) on the as grown, etched and sulfur passivated GaAs samples. The uniformity of GaAs with a thin Al0 65Ga0.35As cap layer has also been studied and compared with the (NH 4)2S treatment. We found the sub-micron scale variations in PL intensity which were not correlated to the topographic features. Theoretical modeling has been used to obtain semi-quantitative analysis of the experimental results.
Reduction of Lateral Dimension on InGaAs/GaAs Multilayers on Non-(111) V-Grooved GaAs(100) Substrate by Chemical Beam Epitaxy
Authors: Kim Sung-Bock , Ro Jeong-Rae , Park Seong-Ju , Lee El-Hang
Published: April 2011

We have found that the lateral dimension of InGaAs and GaAs multiple layers can be effectively controlled on non-( 111) V-grooved GaAs substrates by chemical beam epitaxy using triethylgallium and trimethylindium coupled with precracked arsine or unprecracked monoethylarsine. We suggest that this effect is due to the efficient migration of adatoms from (111) to non-(111) planes. This is an improved method which overcomes the difficulty that has been associated with the method of using only (111) V-grooves in which the lateral dimension is controlled by the differences in the growth rates between (111) and (100) planes. In case of InGaAs and GaAs epilayers, the anisotropy factors of growth rate were less than 0.1 at optimum growth temperature. Photoluminescence peak originated from InGaAs/GaAs quantum wire was significantly distinct from other peaks, suggesting an effective reduction of InGaAs lateral dimension.
Facet Evolution and Selective Growth of GaAs/AlGaAs Lateral Structure Grown by Growth–Interrupted Chemical Beam Epitaxy Using Unprecracked Monoethylarsine
Authors: Ro Jeong-Rae , Kim Sung-Bock , Park Seong-Ju , Lee Jihwa , Lee El-Hang
Published: April 2011

Facet evolution and selective area epitaxy of GaAs/AIGaAs ridge and V-groove structure grown on non-planar GaAs(100) substrate by chemical beam epitaxy(CBE) have been investigated for nanostructure applications. To enhance the crystallographic selectivity and to study the new facet evolution on patterned substrate, GaAs and AlGaAs epilayer were grown by growth-interruption mode and continuous mode, respectively. High selectivity of GaAs layer was observed to depend on the various crystallographic planes even at low growth temperature. This was attributed to the efficient Ga surface migration and desorption during the growth-interruption periods. The growth-interruption method was found to be very efficient in improving the morphology of faceted surfaces. We demonstrated that the formation of (111) V-groove and (411) ridge GaAs structures which were surrounded by AlGaAs layer to show the potential implication of this method for the formation of quantum wires.