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Epitaxy
Kinds of Epitaxy Terms modified by Epitaxy Selected AbstractsInterdiffusion phenomena in InGaAs/GaAs superlattice structuresCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2010B. Sar, kavak Abstract We have studied structural properties of InGaAs/GaAs superlattice sample prepared by Molecular Beam Epitaxy (MBE) using high resolution X-ray diffractometer (HRXRD). Increasing strain relaxation and defect generations are observed with the increasing Rapid Thermal Annealing (RTA) temperature up to 775 °C. The higher temperatures bring out relaxation mechanisms; interdiffusion and favored migration. The defect structure and the defects which are observed with the increasing annealing temperature were analyzed. Firstly, the in-plane and out-of-plane strains after the annealing of sample were found. Secondly, the structural defect properties such as the parallel X-ray strain, perpendicular X-ray strain, misfit, degree of relaxation, x composition, tilt angles and dislocation that are obtained from X-ray diffraction (XRD) analysis were carried out at every temperature. As a result, we observed that the asymmetric peaks especially in asymmetric (224) plane was affected more than symmetric and asymmetric planes with lower polar or inclination angles due to c-direction at low temperature. These structural properties exhibit different unfavorable behaviors for every reflection direction at the increasing temperatures. The reason is the relaxation which is caused by spatially inhomogeneous strain distribution with the increasing annealing temperature. In the InGaAs superlattice samples, this process enhances preferential migration of In atoms along the growth direction. Further increase in the annealing temperature leads to the deterioration of the abrupt interfaces in the superlattice and degradation in its structural properties. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Bulk growth of gallium nitride: challenges and difficultiesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2007M. Bockowski Abstract The present status of the GaN bulk growth by High Pressure Solution (HPS) method and combination of HPS and Hydride Vapor Phase Epitaxy (HVPE) methods is reviewed. Up to now the spontaneous high pressure solution growth of GaN results in crystals having habit of hexagonal platelets of surface area of 3 cm2 or needles with length up to 1 cm. Recently, the platelets and needles have been used as seeds for the HVPE growth. On the other hand, the LPE technique under pressure with pressure-grown GaN (hp-GaN), GaN/sapphire template, patterned GaN/sapphire template and free standing HVPE GaN as seeds has been examined and developed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Controlled Nucleation of GaN Nanowires Grown with Molecular Beam EpitaxyADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Kris A. Bertness Abstract The location of GaN nanowires is controlled with essentially perfect selectivity using patterned SiNx prior to molecular beam epitaxy growth. Nanowire growth is uniform within mask openings and absent on the mask surface for over 95% of the usable area of a 76 mm diameter substrate. The diameters of the resulting nanowires are controlled by the size of the mask openings. Openings of approximately 500 nm or less produce single nanowires with symmetrically faceted tips. [source] Perfect Bi4Ti3O12 Single-Crystal Films via Flux-Mediated Epitaxy,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2006R. Takahashi Abstract Excellent crystallinity of material films and atomic control of their surface/interface, sufficient for the realization of their optimal physical properties, are technological premises for modern functional-device applications. Bi4Ti3O12 and related compounds attract much interest as highly insulating, ferroelectric materials for use in ferroelectric random-access memories. However, it has been difficult thus far for Bi4Ti3O12 films to satisfy such requirements when formed using vapor-phase epitaxy, owing to the high volatility of Bi in a vacuum. Here, we demonstrate that flux-mediated epitaxy is one of the most promising and widely applicable concepts to overcome this inevitable problem. The key point of this process is the appropriate selection of a multi-component flux system. A combinatorial approach has led to the successful discovery of the novel flux composition of Bi,Cu,O for Bi4Ti3O12 single-crystal film growth. The perfect single-crystal nature of the stoichiometric Bi4Ti3O12 film formed has been verified through its giant grain size and electric properties, equivalent to those of bulk single crystals. This demonstration has broad implications, opening up the possibility of preparing stoichiometric single-crystal oxide films via vapor-phase epitaxy, even if volatile constituents are required. [source] Epitaxial Graphene Growth by Carbon Molecular Beam Epitaxy (CMBE)ADVANCED MATERIALS, Issue 37 2010Jeongho Park A novel growth method (carbon molecular beam epitaxy (CMBE)) has been developed to produce high-quality and large-area epitaxial graphene. This method demonstrates significantly improved controllability of the graphene growth. CMBE with C60 produces AB stacked graphene, while growth with the graphite filament results in non-Bernal stacked graphene layers with a Dirac-like electronic structure, which is similar to graphene grown by thermal decomposition on SiC (000-1). [source] An Inorganic/Organic Semiconductor "Sandwich" Structure Grown by Molecular Beam EpitaxyADVANCED MATERIALS, Issue 47 2009S. Blumstengel Preparation of ZnO/organic/ZnO "sandwich" semiconductor hybrid structures by molecular beam epitaxy is reported. Overgrowth of the organic layer becomes possible because ZnO epitaxy requires exceptionally low substrate temperatures. The molecule, a spirobifluorene derivative, withstands ZnO overgrowth without degradation of its optical properties. Excitonic coupling as well as optical gain in ZnO/organic/ZnO sandwich hybrid structures are demonstrated. [source] Thermoelectric Performance of Epitaxial Thin Films of Layered Cobalt Oxides Grown by Reactive Solid-Phase Epitaxy with Topotactic Ion-Exchange MethodsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2007Kenji Sugiura This article reviews high-quality epitaxial film growth of layered cobalt oxides by reactive solid-phase epitaxy (R-SPE) with topotactic ion-exchange methods. Epitaxial film of Na0.8CoO2 was grown on a (0001)-oriented ,-Al2O3 substrate by R-SPE using CoO film as the starting material. The Na0.8CoO2 epitaxial films were converted into high-quality epitaxial films of Sr0.32Na0.21CoO2 and [Ca2CoO3]xCoO2 by topotactic ion-exchange methods. The Sr0.32Na0.21CoO2 film exhibited better stability against moisture than that of the Na0.8CoO2 film, while it retained the good thermoelectric properties of Na0.8CoO2. The [Ca2CoO3]xCoO2 film exhibited a high electrical conductivity of 2.95 × 102 S/cm and a large Seebeck coefficient of +125 ,V/K at 300 K. [source] UV emission on a Si substrate: Optical and structural properties of ,-CuCl on Si grown using liquid phase epitaxy techniquesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009A. Cowley Abstract Considerable research is being carried out in the area of wide band gap semiconductor materials for light emission in the 300,400 nm spectral range. Current materials being used for such devices are typically based on II,VI and III-nitride compounds and variants thereof. However, one of the major obstacles to the successful fabrication of III-N devices is lattice mismatch-induced high dislocation densities for epitaxially grown layers on non-native substrates. ,-CuCl is a direct bandgap material and an ionic wide bandgap I,VII semiconductor with a room temperature free exciton binding energy of ,190 meV (compared to ,25 meV and ,60 meV for GaN and ZnO, respectively) and has a band gap of 3.4 eV (, , 366 nm). The lattice constant of ,-CuCl (0.541 nm) is closely matched to that of Si (0.543 nm). This could, in principle, lead to the development of optoelectronic systems based on CuCl grown on Si. Research towards this end has successfully yielded polycrystalline ,-CuCl on Si(100) and Si(111) using vacuum-based deposition techniques [1]. We report on developments towards achieving single crystal growth of CuCl from solution via Liquid Phase Epitaxy (LPE) based techniques. Work is being carried out using alkali halide flux compounds to depress the liquidus temperature of the CuCl below its solid phase wurtzite-zincblende transition temperature (407 °C [2]) for solution based epitaxy on Si substrates. Initial results show that the resulting KCl flux-driven deposition of CuCl onto the Si substrate has yielded superior photoluminescence (PL) and X-ray excited optical luminescence (XEOL) behavior relative to comparitively observed spectra for GaN or polycrystalline CuCl. This enhancement is believed to be caused by an interaction between the KCl and CuCl material subsequent to the deposition process, perhaps involving a reduction in Cl vacancy distributions in CuCl. This paper presents a detailed discussion of a CuCl LPE growth system as well as the characterization of deposited materials using X-ray diffraction (XRD), room temperature and low temperature PL, and XEOL. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hybrid reflections in InGaP/GaAs(001) by synchrotron radiation multiple diffractionPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2009Alan S. de Menezes Abstract Hybrid reflections (HRs) involving substrate and layer planes (SL type) [Morelhão et al., Appl. Phys. Lett. 73 (15), 2194 (1998)] observed in Chemical Beam Epitaxy (CBE) grown InGaP/GaAs(001) structures were used as a three-dimensional probe to analyze structural properties of epitaxial layers. A set of (002) rocking curves (, -scan) measured for each 15° in the azimuthal plane was arranged in a pole diagram in , for two samples with different layer thicknesses (#A , 58 nm and #B , 370 nm) and this allowed us to infer the azimuthal epilayer homogeneity in both samples. Also, it was shown the occurrence of (13) HR detected even in the thinner layer sample. Mappings of the HR diffraction condition (,:,) allowed to observe the crystal truncation rod through the elongation of HR shape along the substrate secondary reflection streak which can indicate in-plane match of layer/ substrate lattice parameters. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] First step to Si photonics: synthesis of quantum dot light-emitters on GaP substrate by MBEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2009Weiming Guo Abstract We have grown InAs and InP quantum dots (QDs) on GaP substrate by Molecular Beam Epitaxy (MBE) and analysed them by Atomic Force Microscopy (AFM) and photoluminescence (PL). AFM images confirm the formation of InAs and InP QDs. Largest InAs QDs density is obtained at a growth temperature of 450 °C and under an AsH3 flux of 0.3SCCM. The evolution of QDs shape and absence of photoluminescence indicate a likely plastic relaxation of the strain between InAs and GaP. Concerning InP/GaP QDs, their lateral size, height and density indicate good quality QDs. Photoluminescence signal has been detected for capped InP/GaP QDs until 180 K. The unchanged peak position with respect to InP coverage is attributed to the nearly constant height of the QDs. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reflectance-anisotropy study of the dynamics of molecular beam epitaxy growth of GaAs and InGaAs on GaAs (001)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2008J. Ortega-Gallegos Abstract Reflectance-Anisotropy (RA) observations during the Molecular Beam Epitaxy (MBE) growth of zincblende semiconductors films were carried out using the E1 optical transition as a probe. We follow the kinetics of the deposition of GaAs and In0.3Ga0.7As on GaAs (001) at growth rates of 0.2 and 0.25 ML/s, respectively. During growth we used a constant As4 or As2 flux pressure of 5× 10,6 Torr. Clear RA-oscillations were observed during growth with a period that nearly coincides with the growth period for a Ga-As bilayer. RHEED was used as an auxiliary technique in order to obtain a correlation between RHEED and RA oscillations. On the basis of our results, we argue that RAS oscillations are mainly associated to periodic changes in surface atomic structure. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Interfacial spin structure in epitaxial Fe/FeSn2 bilayers with exchange biasPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004F. Stromberg Abstract Fe/FeSn2 structures with epitaxial FeSn2 layers have been grown by MBE (Molecular Beam Epitaxy). Exchange bias and pinning phenomena were proved by SQUID magnetometry. In order to elucidate the spin structure at the Fe/FeSn2 interface and in some depth of the FeSn2 layer with CEMS (Conversion Electron Mössbauer Spectroscopy), 57FeSn2 tracer layers of approx. 50 Å thickness have been incorpo- rated in the base structure, the only difference being the isotopic enrichment with 57Fe. An ellipsoidal model was applied to represent the spin structure. A strong out-of-plane component of the spin structure at the interface was observed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Proceedings of the E-MRS 2003 Fall Meeting , Symposia A and CPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004Marek Godlewski This volume contains the proceedings of Symposium A: Novel Wide Bandgap Materials for Optoelectronic and Electronic Applications and Symposium C: 5th International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology at the E-MRS 2003 Fall Meeting, organized by the European Materials Research Society for the first time in Warsaw, Poland, 15,19 September 2003. Symposium A reviewed recent progress in the studies of wide bandgap materials such as nitrides and ZnO, as well as in relevant experimental techniques, whereas Symposium C was devoted to the current trends in physics and technology of MBE and MOCVD. [source] Competition of Epitaxy and Ion Beam Irradiation-Determined Texture during Ion Beam-Assisted Deposition of Gallium Nitride Films on r-Plane SapphirePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003J.W. Gerlach Abstract The nitrogen ion beam-assisted growth of wurtzitic gallium nitride thin films on the r -plane of sapphire is investigated. X-ray diffraction and electron microscopy reveal that the crystallographic texture of the films is very sensitive to the ion beam parameters. By carefully choosing these parameters it is possible to direct intentionally the orientation of the GaN films. [source] Zinc Oxide Microstructures: Zinc Oxide Microtowers by Vapor Phase Homoepitaxial Regrowth (Adv. Mater.ADVANCED MATERIALS, Issue 8 20098/2009) Simultaneous axial and radial epitaxies can be achieved by growing ZnO microtowers by repeating a growth cycle several times, report Zhengwei Pan and co-workers on p. 890. The as-grown ZnO microtowers display a preferential growth habit of hexagonal prism,dihexagonal pyramid. Some rare or new growth habits such as dihexagonal prism,dihexagonal pyramid, hexagonal prism,trihexagonal pyramid and dihexagonal prism,trihexagonal pyramid (as shown on the cover) have also been identified. [source] Zinc Oxide Microtowers by Vapor Phase Homoepitaxial RegrowthADVANCED MATERIALS, Issue 8 2009Zhengwei Pan Simultaneous axial and radial epitaxies can be achieved on growing ZnO microtowers through a regrowth technique of repeating the same growth circle for several times. The as-grown ZnO microtowers display a preferential growth habit of hexagonal prism,dihexagonal pyramid. The apexes of the pyramidal towers are very sharp, with a radius of curvature as small as 2 to 50 nm. [source] Analysis of epitaxial laterally overgrown silicon structures by high resolution x-ray rocking curve imagingCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2009B. Heimbrodt Abstract Spatially resolved rocking curve imaging has been used to analyze laterally overgrown silicon layers grown by liquid phase epitaxy. We were able to study both the overgrown layer as well as the strain fluctuations of the Si substrate underneath by means of a tabletop x-ray topographic setup. The strain-field analysis reveals relative changes of the lattice parameter up to 3.5×10 -6 in the silicon substrate underneath the overgrown layer in particular regions and a down bending of both wings of the epitaxial overgrown layers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth and characterisation of Zn:LiNbO3/Mg:LiNbO3 multilayer thin films grown by liquid phase epitaxyCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2006H. J. Lee Abstract 1, 3 and 5 mol% ZnO doped LiNbO3 film and 2 mol% MgO doped LiNbO3 multilayer films were grown on the LiNbO3 (001) substrate by liquid phase epitaxy (LPE) method with a Li2O-V2O5 system. We examined the optical transmission spectra of the Zn:LiNbO3 by Fourier Transform-Infrared Spectrophotometer (FT-IR). The crystallinity and the lattice mismatch between the Zn:LiNbO3 film and Mg:LiNbO3 film was confirmed by x-ray rocking curve (XRC) and observed the ZnO and MgO distribution in the cross-section of the multilayer thin films by electron probe micro analyzer (EPMA). Furthermore, the surface morphology of the films was observed using atomic force microscopy (AFM). (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Large area lateral overgrowth of mismatched InGaP on GaAs(111)B substratesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2005S. Uematsu Abstract Application of InGaAs/InGaP double-heterostructure (DH) lasers increases the band offset between the cladding layer and the active layer more than the use of conventional 1.3 µm InGaAsP/InP lasers. As a first step in realizing 1.3 µm InGaP/InGaAs/InGaP DH lasers, we proposed InGaP lattice-mismatched epitaxial lateral overgrowth (ELO) technique and successfully carried out the InGaP growth on both GaAs (100), (111)B and InP (100) substrates by liquid phase epitaxy. In this work, we grew the InGaP crystal on GaAs (111)B substrate by adjusting Ga and P composition in In solution, to obtain In0.79Ga0.21P (, = 820 nm) virtual substrate for 1.3 µm InGaAs/InGaP DH lasers. To grow the InGaP all over the lateral surface of the substrate, the growth time was extended to 6 hours. The amount of InGaP lateral growth up to 2 hours was gradually increased, but the lateral growth was saturated. The InGaP lateral width was about 250 µm at the growth time of 6 hours. We report the result that optical microscope observation, CL and X-ray rocking curve measurements and reciprocal lattice space mapping were carried out to evaluate the crystal quality of the grown InGaP layers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of InN metalorganic vapor phase epitaxy using in-situ spectroscopic ellipsometryCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005M. Drago Abstract Metalorganic vapor phase epitaxy of InN layers on sapphire was studied in-situ by spectroscopic ellipsometry (SE), ex-situ atomic force microscopy and optical microscopy. Surface morphology has been largely improved by using nitrogen instead of hydrogen as carrier gas during sapphire nitridation. Using the sensitivity of in-situ SE with respect to roughness we established a new growth procedure with low V/III ratio (104) at high temperature (580 °C) and growth rates as high as 350 nm/h, leading to improved electronic layer properties and allowing for growth of comparably thick layers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The impact of SiC substrate treatment on the heteroepitaxial growth of GaN by plasma assisted MBECRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005A. S. Brown Abstract We report on the impact of the preparation of the Si-face 4H-SiC(0001)Si substrate using a Ga flash-off process on the epitaxial growth of GaN by plasma-assisted molecular beam epitaxy. The nucleation, as well as the resultant structural and morphological properties of GaN grown directly on 4H-SiC(0001)Si are strongly influenced by the chemical and morphological modifications of the SiC surface induced by the Ga flash-off process. Herein we describe the impact of the specific concentration of Ga incident on the surface (quantified in terms of monolayer (ML) coverage): of 0.5 ML, 1ML and 2ML. The residual oxygen at the SiC surface, unintentional SiC nitridation and the formation of cubic GaN grains during the initial nucleation stage, are all reduced when a 2 ML Ga flash is used. All of the above factors result in structural improvement of the GaN epitaxial layers. The correlation between the SiC surface modification, the initial nucleation stage, and the GaN epitaxial layer structural quality has been articulated using x-ray photoelectron spectroscopy, x-ray diffraction, atomic force microscopy and spectroscopic ellipsometry data. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Numerical modeling and investigation of liquid phase epitaxy of Hg1,xCdxTe infrared detectorsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2005K. Lin Abstract Numerical investigations have been performed for modeling the global temperature field of an industrial liquid phase epitaxy (LPE) facility and to estimate the temperature fluctuations in a Te-rich solution during the LPE growth. The numerical results agreed well with experimental data and therefore provide reliable reference points for experimenters for further improvements of the growth conditions. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A comparative study for profiling ultrathin boron layers in SiCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2003E. Basaran Abstract The carrier concentration-depth profiles of ultrathin boron layers in Si, grown by molecular beam epitaxy, are determined by the electrochemical capacitance-voltage (ECV) and the spreading resistance (SR) profiling techniques. Secondary ion mass spectrometry (SIMS) is employed as a base for the comparison of the results. It has been shown that, under carefully chosen conditions, both ECV and SR techniques are able to resolve ultrathin layers including a delta layer, however ECV match better with the results of SIMS than that of SR. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nano vanadyl-phthalocyanine crystals fabricated on KBr substrateELECTRICAL ENGINEERING IN JAPAN, Issue 2 2008Suguru Mototani Abstract Vanadyl-phthalocyanine (VOPc) thin films deposited on a KBr substrate by molecular beam epitaxy (MBE) consist of nano-VOPc crystals epitaxially grown. The nano-VOPc crystals acquire a square shape as a result of annealing at 150°C. The size of the nano-crystals is controllable by changing the conditions of MBE deposition and thermal treatment. The growth processes of nano-crystals on the KBr substrate are elucidated experimentally and are shown to be closely related to strong interaction between the VOPc molecules and the KBr substrate. Their mechanisms can be explained in terms of surface diffusion of the VOPc molecules on the KBr substrate. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(2): 41,48, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20645 [source] Sc3AlN , A New PerovskiteEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2008Carina Höglund Abstract Sc3AlN with perovskite structure has been synthesized as the first ternary phase in the Sc,Al,N system. Magnetron sputter epitaxy at 650 °C was used to grow single-crystal, stoichiometric Sc3AlN(111) thin films onto MgO(111) substrates with ScN(111) seed layers as shown by elastic recoil detection analysis, X-ray diffraction, and transmission electron microscopy. The Sc3AlN phase has a lattice parameter of 4.40 Å, which is in good agreement with the theoretically predicted 4.42 Å. Comparisons of total formation energies show that Sc3AlN is thermodynamically stable with respect to all known binary compounds. Sc3AlN(111) films of 1.75 µm thickness exhibit a nanoindentation hardness of 14.2 GPa, an elastic modulus of 249 GPa, and a room-temperature electrical resistivity of 41.2 µ, cm. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Aligned Nanofibers: Epitaxial Growth of Highly Oriented Fibers of Semiconducting Polymers with a Shish-Kebab-Like Superstructure (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Mater. Highly oriented fibers of regioregular poly(3-alkylthiophene)s with a "shish-kebab" morphology are prepared by epitaxy on long needles of 1,3,5-trichlorobenzene grown in liquid pyridine, as described on page 2759 by Brinkmann et al. The superstructure of the fibers consists of a highly oriented thread-like core several hundreds of micrometers long, the "shish", onto which lateral crystalline nanofibrils made of folded polymer chains, the "kebabs", are connected in a periodic way. [source] Fabrication and Optical Characteristics of Position-Controlled ZnO Nanotubes and ZnO/Zn0.8Mg0.2O Coaxial Nanotube Quantum Structure ArraysADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Jinkyoung Yoo Abstract The position-controlled growth and structural and optical characteristics of ZnO nanotubes and their coaxial heterostructures are reported. To control both the shape and position of ZnO nanotubes, hole-patterned SiO2 growth-mask layers on Si(111) substrates with GaN/AlN intermediate layers using conventional lithography are prepared. ZnO nanotubes are grown only on the hole patterns at 600,°C by catalyst-free metal,organic vapor-phase epitaxy. Furthermore, the position-controlled nanotube growth method allows the fabrication of artificial arrays of ZnO-based coaxial nanotube single-quantum-well structures (SQWs) on Si substrates. In situ heteroepitaxial growth of ZnO and Zn0.8Mg0.2O layers along the circumference of the ZnO nanotube enable an artificial formation of quantum-well arrays in a designed fashion. The structural and optical characteristics of the ZnO nanotubes and SQW arrays are also investigated using synchrotron radiation X-ray diffractometry and photoluminescence and cathodoluminescence spectroscopy. [source] Perfect Bi4Ti3O12 Single-Crystal Films via Flux-Mediated Epitaxy,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2006R. Takahashi Abstract Excellent crystallinity of material films and atomic control of their surface/interface, sufficient for the realization of their optimal physical properties, are technological premises for modern functional-device applications. Bi4Ti3O12 and related compounds attract much interest as highly insulating, ferroelectric materials for use in ferroelectric random-access memories. However, it has been difficult thus far for Bi4Ti3O12 films to satisfy such requirements when formed using vapor-phase epitaxy, owing to the high volatility of Bi in a vacuum. Here, we demonstrate that flux-mediated epitaxy is one of the most promising and widely applicable concepts to overcome this inevitable problem. The key point of this process is the appropriate selection of a multi-component flux system. A combinatorial approach has led to the successful discovery of the novel flux composition of Bi,Cu,O for Bi4Ti3O12 single-crystal film growth. The perfect single-crystal nature of the stoichiometric Bi4Ti3O12 film formed has been verified through its giant grain size and electric properties, equivalent to those of bulk single crystals. This demonstration has broad implications, opening up the possibility of preparing stoichiometric single-crystal oxide films via vapor-phase epitaxy, even if volatile constituents are required. [source] Epitaxial Graphene Growth by Carbon Molecular Beam Epitaxy (CMBE)ADVANCED MATERIALS, Issue 37 2010Jeongho Park A novel growth method (carbon molecular beam epitaxy (CMBE)) has been developed to produce high-quality and large-area epitaxial graphene. This method demonstrates significantly improved controllability of the graphene growth. CMBE with C60 produces AB stacked graphene, while growth with the graphite filament results in non-Bernal stacked graphene layers with a Dirac-like electronic structure, which is similar to graphene grown by thermal decomposition on SiC (000-1). [source] An Inorganic/Organic Semiconductor "Sandwich" Structure Grown by Molecular Beam EpitaxyADVANCED MATERIALS, Issue 47 2009S. Blumstengel Preparation of ZnO/organic/ZnO "sandwich" semiconductor hybrid structures by molecular beam epitaxy is reported. Overgrowth of the organic layer becomes possible because ZnO epitaxy requires exceptionally low substrate temperatures. The molecule, a spirobifluorene derivative, withstands ZnO overgrowth without degradation of its optical properties. Excitonic coupling as well as optical gain in ZnO/organic/ZnO sandwich hybrid structures are demonstrated. [source] | ||||||||||||||||||||||||||||