bluuebunny/crossref_metadata_2025_split huggingface dataset:
MOVPE Growth and optical characterization of high-quality ZnSe-ZnS superlattices using a novel zinc adduct precursor
Authors: Briot O. , Blasio M. Di , Cloitre T. , Briot N. , Bigenwald P. , Gil B. , Averous M. , Aulombard R. L. , Smith L. M. , Rushworth S. A. , Jones A.C. 
Published: April 2011

ABSTRACTA novel zinc precursor adduct tetramethylmethylene diamine: dimethylzinc (TMMD:DMZn) has been used to grow ZnSe-ZnS strained layer superlattices by low pressure MOVPE at 300'C. The use of this new precursor leads to improved material purity and lower homogeneous gas phase premature reaction than in the case of dimethylzinc. Optical characterization has been made between liquid helium and room temperature. The 2K photoluminescence lines range between 2.85 eV and 3.15 eV. The 2K photoluminescence is characterized by a linewidth at half maximum ranging from 13-45 meV. Additional reflectivity and photoreflectance experiments have been carried out to measure light-hole excitons. A variational calculation of the Rydberg energies has been performed using a sophisticated trial function. The experimental data is in agreement with the theoretical value when a small conduction band offset is used.
Van der Waals Epitaxy of GaSe on GaAs(111)
Authors: Rumaner L. E. , Ohuchi F.S. 
Published: April 2011

ABSTRACTAlthough heteroepitaxy of lattice-matched and lattice-mismatched materials leading to artificially structured materials has resulted in impressive performance in various electronics devices, material combinations are usually limited by lattice matching constraints. A new concept for fabricating material systems using the atomically abrupt and low dimensional nature of layered materials, called van der Waals epitaxy (VDWE), has been developed. GaSe (Eg = 2.1 eV) has been deposited on the three dimensional surface of GaAs (111) using a molecular beam deposition system. GaSe was evaporated from a single Knudsen source, impinging on a heated substrate. Even with a lattice mismatch of 6% between the substrate and the growing film, good quality single crystal films were grown as determined by RHEED. The films have further been analyzed using a complementary combination of XPS and X-ray reflectivity.
Photoluminescence Spectroscopy and Rutherford Backscattering Channeling Evaluation of Various Capping Techniques for Rapid Thermal Annealing of Ion-Implanted ZnSe
Authors: Allen E.L. , Zach F.X. , Yu K.M. , Bourret E.D. 
Published: April 2011

ABSTRACTWe report on the effectiveness of proximity caps and PECVD Si3N4 caps during annealing of implanted ZnSe films. OMVPE ZnSe films were grown using diisopropylselenide (DIPSe) and diethylzinc (DEZn) precursors, then ion-implanted with 1 × 1014 cm−2 N (33 keV) or Ne (45 keV) at room temperature and liquid nitrogen temperature, and rapid thermal annealed at temperatures between 200°C and 850°C. Rutherford backscattering spectrometry in the channeling orientation was used to investigate damage recovery, and photoluminescence spectroscopy was used to investigate crystal quality and the formation of point defects. Low temperature implants were found to have better luminescence properties than room temperature implants, and results show that annealing time and temperature may be more important than capping material in determining the optical properties. The effects of various caps, implant and annealing temperature are discussed in terms of their effect on the photoluminescence spectra.
Epitaxial Growth and Characterization of the Ordered Vacancy Compound CuIn3Se5 on GaAs (100) Fabricated by Molecular Beam Epitaxy
Authors: Nelson Art J. , Bode M. , Horner G. , Sinha K. , Moreland John 
Published: April 2011

ABSTRACTEpitaxial growth of the ordered vacancy compound (OVC) CuIn3Se5 has been achieved on GaAs (100) by molecular beam epitaxy (MBE) from Cu2Se and In2Se3 sources. Electron probe microanalysis and X-ray diffraction have confirmed the composition for the 1-3-5 OVC phase and that the film is single crystal Culn3Se5 (100). Transmission electron microscopy (TEM) characterization of the material also showed it to be single crystalline. Structural defects in the layer consisted mainly of stacking faults. Photoluminescence (PL) measurements performed at 7.5 K indicate that the bandgap is 1.28 eV. Raman spectra reveal a strong polarized peak at 152 cm−1, which is believed to arise from the totally symmetric vibration of the Se atoms in the lattice. Atomic force microscopy reveals faceting in a preferred (100) orientation.
GaAs/AlGaAs Multiquantum Well Infrared Detector Array with 6.0 μm Response Width
Authors: Li Jin-Min , Zheng Hai-Qun , Zeng Yi-Ping , Kong Mei-Ying 
Published: April 2011

ABSTRACTlO×16 GaAs/AlGaAs quantum well infrared detector arrays with peak responsivity at 9.3μm have been achieved with front-side normal illumination based on a waveguide of doubly periodic grating coupler. The detector array with a wideband response from 4.2μm to 10.3μm is demonstrated by optimizing the quantum well structures and device processes. A peak detectivity D*λ =2.9×1010 cmHz1/2 /W and high a responsivity Rp=0.37A/W have been obtained at λp=9.3μm and T=77K. The dark current densities of the detectors in the array were smaller than 6.2×10−6 A/cm2 with the detectors biased (Vb=3.2V) for maximum detectivity.
A Study of the Surface Texture of Polycrystalline Phosphor Films Using Atomic Force Microscopy
Authors: Revay R. , Schneir J. , Brower D. , Villarrubia J. , Fu J. , Cline J. , Hsieh T. J. , Wong-Ng W. 
Published: April 2011

ABSTRACTStimulable phosphor thin films are being investigated for use as optical data storage media. We have successfully applied atomic force microscopy (AFM) to the measurement of the surface texture of these films. Determination of the surface texture of the films is important for evaluating the effect of surface quality on optical scatter. In other thin film material systems it has been found that the surface “bumps” revealed by AFM correspond to grains in the film. This is not the case for the stimulable phosphor films used in our study. We have determined the grain size of our phosphor films by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The grain size from TEM and XRD does not correlate with the size of the AFM surface “bumps.” For example, in two of the five films studied, the XRD derived grain size varies by a factor of two but the size of the surface “bumps” remains the same. We conclude that the texture of the film surface is not directly determined by the grain size of the phosphor material.
Nanocrystalline Microstructures by Thin-Film Synthesis Methods
Authors: Libera M. , Smith D. A. 
Published: April 2011

ABSTRACTNanostructured materials are being extensively studied because their ∼1–100nm grain size can dramatically affect properties. Most nanocrystalline synthesis methods produce particulate or flake. The process of consolidation also allows coarsening, contamination, and the introduction of porosity. The effect of nanocrystallinity on mechanical properties must be deconvoluted from these extrinsic artifacts. Most synthesis routes also produce small quantities of material. Reproducibly making enough specimens to explore more than a few properties is thus difficult. This paper describes thin-film processes to produce nanostructured materials. Thin-film deposition can easily produce many specimens, free from extrinsic artifacts, with identical composition and processing history. Many methods are now well established to study a variety of thin-film mechanical properties. We show examples of nanostructured films generated by controlling deposition and/or post-deposition processing.
Toward Realizing the Structure-Property Link in Polycrystalline Thin Films
Authors: Nichols C. S. 
Published: April 2011

ABSTRACTMany materials for engineering applications are used in polycrystalline form and contain grain boundaries with a range of structures and properties. However, most research on grain boundaries to date has focussed exclusively on symmetric coincidence site lattice interfaces. To go beyond descriptions for these simple interfaces and thence to an aggregate of grains and grain boundaries in a polycrystal will require a new approach. Here we discuss two models for properties of polycrystalline materials, including their advantages and drawbacks, and indicate the microstructural variables available to optimize properties.
Stability of Ruthenium-Silica Bilayer Structures
Authors: Weng-Sieh Zara , Nguyen Tai. D. , Gronsky Ronald 
Published: April 2011

ABSTRACTThe microstructural evolution of ruthenium-silicon dioxide bilayer structures upon annealing is studied using transmission electron microscopy. SiO2/Ru/SiO2 structures, with thicknesses of 2/1/2 nm, 4/2/4 nm, 8/4/8 nm, and 20/10/20 nm, are formed by magnetron sputtering and annealed at 300 or 600°C. As-deposited films have grain sizes on the order of the Ru film thickness. After annealing at 600°C, significant grain growth is observed for all thicknesses, such that the final grain sizes are approximately 3 to 20x greater than the original film thickness. The largest increase in the average Ru grain size is observed for the 2 nm thick ruthenium film possibly due to the coalescence of Ru grains. The coalescence of the Ru particles in the 1 and 2 nm thick films results in the formation of lamellar Ru grains, which disrupts the contiguity of the Ru film. In all other cases, the increase in grain size is attributed to normal grain growth, but the formation of anomalous spherical grains is also observed.
Monocrystalline and Polycrystalline Thin Films Formed by Cobalt Ion Implantation in the Organic Substrate (Polyester)
Authors: Stepanov A. L. , Khaibullin R. I. , Abdullin S. N. , Osin Yu. N. , Khaibullin I. B. 
Published: April 2011

ABSTRACTThe structure and phase composition of thin films formed by 40 KeV cobalt ion implantation into organic substrate (polyester) were studied by transmission electron microscopy in conjunction with electron diffraction. Varying current density and dose implantation over the range 0.3×1016 – 2.4×1017 cm-2 we obtained island-like cobalt films of different type as well as labyrinth-like structure at the highest dose value. The granulometric and morphologic parameters were derived from the micrographs of the investigated films. Both amorphous state and α-Co crystalline lattice of cobalt granules were established from electron diffraction patterns of synthesized films. Along with discontinuous films, we formed monocrystalline plates of α-phase cobalt under the determined implantation regimes and conditions. Cross-section images of synthesized films showed that films are of about 300 Å thick and buried at the depth of 150 Å from the principal surface of the polyester.
Kinetics of Interface Reactions in Polycrystalline Thin Films
Authors: Bormann Rüdiger 
Published: April 2011

ABSTRACTA quantitative description of the nucleation and growth kinetics determining the interface reactions between two phases is given. Particular focus is given to the understanding of the mechanisms causing the distinct phase selection occurring during the early stages of interface reaction. Thereby the microstructure of the parent phases and the new phases formed are also taken into account and discussed with respect to their influence on the phase selection. The conclusions are applied to the results of two model systems, Al-Ni and Zr-Ni.
High resolution studies of the solid state amorphization reaction in the ZrCo system with the atom probe/field ion microscope
Authors: Schneider Susanne , Busch Ralf , Samwer Konrad 
Published: April 2011

ABSTRACTThe atom probe/field ion microscope is introduced as a new powerful investigation device to study the early stages of the solid state amorphization reaction (SSAR). A bilayer of Zr and Co was condensed under UHV conditions on W wire tips and analyzed in a field ion microscope (FIM) combined with an atom probe (AP). The reaction of Co with Zr has been studied at room temperature. FIM pictures and AP analysis have shown that even at low temperatures an amorphous phase is formed at the Zr/Co interface and in the Zr grain boundaries. In these areas concentration profiles have been taken on a nanometer scale. Most likely, the extended solid solution of Co found in α- Zr grain boundaries causes the formation of the amorphous phase. Further, Rutherford backscattering spectrometry (RBS) suggests that even point defects and dislocations at the surface of an α- Zr single crystal are sufficient to initiate the SSAR between a polycrystalline Co layer vapour- deposited onto that single crystal.
The Earliest Stage of the Solid State Amorphization Reaction in the Zr-Co System
Authors: Busch Ralf , Gaertner Frank , Schneider Susanne , Bormann Rüdiger , Haasen Peter 
Published: April 2011

ABSTRACTBased on atom probe field ion microscopy (AP/FIM) studies, electromotive force (EMF) measurements and CALPHAD calculations we discuss the earliest stage of the solid state amorphization reaction (SSAR) in Zr/Co-layers. The AP measurements show that two amorphous phases are formed at the Zr/Co interface from the early stages of the reaction. The metastable two phase field between these amorphous phases is shown by direct measurement of the chemical potential of Zr in amorphous co-sputtered ZrCo alloys by the EMF method. The comparison between the atom probe data and the CALPHAD calculation shows that the interfaces between the different layers are far away from metastable equilibrium in the beginning of the reaction. The amorphous phase formation at the Zr/Co interface and in the hcp-Zr grain boundary is preceded by a supersaturation of the hep ZrCo solid solution that transforms polymorphically into the amorphous state.
Effects of Microstructure and Crystallography on the Magnetic Properties of CoCrPt/Cr Thin Films
Authors: Choe G. , Chung S.J. 
Published: April 2011

ABSTRACTThe effects of grain morphology and crystallography on the magnetic properties of CoCrPt/Cr thin films were investigated as a function of sputtering parameters of CoCrPt thin films. Cross sectional TEM exhibited strong separation of Co grains with increasing argon sputtering pressure, resulting in reduced exchange coupling and increased coercivity. Most Co grains sputtered at high pressure were separated by 10 to 20 Å thick boundaries, possibly due to the enhanced scattering of argon ions by sputtering particles and thus the observed higher content of Pt in the deposited films. The application of substrate bias greatly decreased the Co grain separation and the nonmagnetic grain boundary disappeared by -200 V bias sputtering, resulting in increased exchange coupling. The bias sputtered CoCrPt thin films decreased their grain size and increased epitaxial growth on Cr layer and also (1010) texture. The magnetic field required to saturate the film increased significantly with increasing substrate bias, possibly due to the induced residual stress in the bias sputtered films.
HCP-FCC Phase Transition in Co-Ni Alloys Studied With Magneto-Optical Kerr Spectroscopy
Authors: Carl A. , Weller D. , Savoy R. , Hillebrands B. 
Published: April 2011

ABSTRACTWe have studied 100nm thick electron beam evaporated Co1-xNix alloy films in the composition range 0 ≤ x ≥ 1 using magneto-optical spectroscopy and magnetic anisotropy measurements. For films with x ≈ 0.2 we have also investigated the dependence of these quantities on the growth temperature, which was varied in the range 27 ≤ TG ≥ 408°C. Both as function of the Ni content x and the growth temperature TG we observe the anticipated hcp → fcc phase transition, e.g. by monitoring the magneto-crystalline anisotropy constant Ku, 1, which changes continuously from values of ≈ 0.3MJ/m3 for Co rich hcp alloys (0 ≤ x ≥ 0.25) to ≈ -0.05MJ/m3 for Ni rich fcc alloy films, in good agreement with bulk literature data. The new and most striking result, however, is observed in the polar magneto-optical Kerr and ellipticity spectra, which were measured in the photon energy range 0.8 ≤ hv ≥ 5.5eV. Changes by up to about 40% in Kerr rotation for films of constant composition and magnetization are observed when the structure changes from hcp → fcc. This demonstrates the sensitivity of magneto-optical effects to structural changes, making Kerr spectroscopy a useful electronic and physical structure probe.
Giant Magnetoresistance in As-Sputter-Deposited Au/NiFe Multilayer Thin Films
Authors: Lee W. Y. , Gorman G. , Savoy R. 
Published: April 2011

ABSTRACTGiant magnetoresistance with low saturation fields (Hs’s) is reported in Au and permalloy (Ni0.82Fe0.18) or Co-doped permalloy multilayer thin films as-deposited on Ta-overcoated Si and glass substrates. A ΔR/R as high as 4.0% with ≈25 Oe Hs was observed at 295 K for the film consisting of 10 layers of 24 Å Au/13 Å Ni0.82Fe0.18 deposited on a 3 Å Ta-overcoated glass at 50 °C. A Hs value as low as ≈20 Oe with a 15% smaller ΔR/R has been observed for the films with a thicker (e.g., 50 Å) Ta underlayer. Magnetic hysteresis loops of these films indicate the presence of antiferromagnetic exchange coupling between the Ni0.82Fe0.18 layers. This exchange coupling is much smaller for the multilayer films without the Ta underlayer, resulting in a 6x smaller ΔR/R and lOx larger Hs observed for these films. Results of x-ray diffraction analysis indicate stronger (111) texturing for the multilayer films with a Ta underlayer, consistent with the stronger antiferromagnetic coupling between the the Ni0.82Fe0.18 layers in the film. The addition of 2–10 % Co moderately increases the ΔR/R value, but also increases substantially the Hs (up to ≈200 Oe).
Characterization of Sol-Gel Derived (Pb,Ba)(Zr,Ti,Nb)O3 Thin Films for Optical Waveguide Development
Authors: Baude P. F. , Wright J. S. , Ye C. , Francis L. F. , Polla D. L. 
Published: April 2011

ABSTRACT(PbBa)(ZrTiNb)03 thin films and powders have been prepared using the sol-gel technique. Solutions were synthesized in 2-methoxyethanol based upon our previous PZT solution preparation. Three different approaches were used for incorporating barium into PZT alkoxide solutions. Thermal analysis and x-ray diffraction results indicated that barium methoxypropoxide gave the best results. PBZTN (71% Pb and 71% Zr) was deposited onto sapphire substrates as well as oxidized silicon substrates. Optical transmission measurements showed greater than 80% transmission for wavelengths longer than 400 nm. Films with thickness of 3000 Å on sapphire exhibited a refractive index of 2.19 at λ=633 nm.
Texture Variations in Sol-Gel Derived PZT Films on Substrates with Platinum Metallization
Authors: Gardeniers J.G.E. , Elwenspoek M. , Cobianu C. 
Published: April 2011

ABSTRACTMetalorganic precursor solutions of composition Zr : Ti = 0.53 : 0.47 were used to spin-cast PZT layers on sputtered Pt films. After annealing at temperatures of 550 °C - 800 °C, the PZT films of tetragonal perovskite structure reproducibly showed different textures and surface morphologies, depending on whether or not a Ti layer was used as an adhesion layer for the Pt film. The texture differences were found to be independent of annealing treatment. It is argued that the observed texture differences are caused by a change in Pt-PZT interface composition, resulting from the diffusion of Ti into the Pt film during annealing; X-ray diffraction of an annealed Pt/Ti/SiO2/Si film combination provided evidence for a compound Pt3Ti. Annealing at 850 °C caused severe diffusion of Ti from the metal layer into the PZT film, leading to a tetragonal PZT layer with lattice constants corresponding to a Zr : Ti ratio of 30 : 70.
Growth and Characterization of Ba0.5Sr0.5TiO3 Thin Films on Si (100) By 90° Off-Axis Sputtering
Authors: Hou S. Y. , Kwo J. , Watts R. K. , Werder D. J. , Shmulovich J. , O'Bryan H. M. 
Published: April 2011

ABSTRACTWe have studied BaxSr1-xTiO3 (BST) thin films (x=0.5) grown on Si (100) with and without a Pt/Ta barrier layer using 90° off-axis RF sputtering. The growth conditions were optimized according to film crystallinity, stoichiometry, and dielectric properties. Polycrystalline BST films with strong (100) texture were obtained via growth on Si (100). The measured dielectric constant from these films was low, presumably because of the parasitic effect of native oxide at BST/Si interface as revealed by TEM. On the other hand, BST films grown on Si with Pt/Ta barrier layers have crystallinity inferior to that on bare Si as determined by X-ray diffraction. Nevertheless, the best BST films on Pt/Ta layers still have good dielectric properties with dielectric constant exceeding 330, leakage current density < 1×10−6 A/cm2 (±1 V), and loss tangent 0.05 at 1 MHz.
Preparation and Property Characterization of Oriented PLZT Thin Films Processed Using Sol-Gel Method
Authors: Sung Yoon Dae , Jung Kim Chang , Sung Lee Joon , Gi Choi Chaun , Jong Lee Won , No Kwangsoo 
Published: April 2011

ABSTRACTHighly preferentially oriented lead lathanum zirconate titanate(PLZT) thin films were fabricated on various substrates using the spin coating of metal organic solutions having the composition of (9/50/50) and (10/0/100). The substrates used in this study were SrTiO3(100), MgO(100), r-plane sapphire, PLT-coated glass, and Pt/Ti/MgO substrates. The films were heat-treated at 600°C and 700°C using the direct insertion method. The phases and the orientation of the PLZT thin films were examined using X-ray diffraction(XRD). Pole figure and X-ray rocking curves were measured to study the film orientation. The films were grown with (100), (110), and (001) plane being parallel to the surfaces of SrTiO3, sapphire, and Pt/Ti/MgO, respectively. The dielectric and optical properties of both the oriented films and the noncrystalline films were measured and discussed.
RuO2 Thin Films as Bottom Electrodes for High Dielectric Constant Materials
Authors: Yoshikawa K. , Kimura T. , Noshiro H. , Ohtani S. , Yamada M. , Furumura Y. 
Published: April 2011

ABSTRACTRuthenium dioxide (RuO2) thin films are evaluated as bottom electrode for dielectric SrTiO3. It was found that a RuO2 (50nm) / Ru (20nm) barrier layer on a Si substrate is effective as an oxygen barrier layer and as a metal diffusion barrier layer for sputter deposited SrTiO3 films at substrate temperature of 450°C. To test suitability for high temperature processes, RuO2/Ru electrodes were annealed in air at 600°C. 100nm-thiick RuO2 was sufficient to prevent oxygen diffusion. After annealing in the same condition, the leakage current of sputter deposited SrTiO3 (150nm) on RuO2(50nm) / Ru(50nm) was 7.6 × 10 −9 (A/cm2) at 2V.