In Situ Initial Growth Studies of SrTiO3 on SrTiO3 by Time Resolved High Pressure RHEED

In Situ Initial Growth Studies of (Sr, Ca)CuO2 ON SrTiO3 by High Pressure Rheed

MRS Proceedings ◽

10.1557/proc-502-255 ◽

1997 ◽

Vol 502 ◽

Cited By ~ 2

Author(s):

Gertjan Koster ◽

Guus J. H. M. Runders ◽

Dave H. A. Blank ◽

Horst Rogalla

Keyword(s):

High Pressure ◽

Pulsed Laser ◽

High Energy ◽

Initial Growth ◽

Force Microscopy ◽

Atomic Force ◽

Growth Studies ◽

Layer Structures ◽

First Results

ABSTRACTThe initial growth of pulsed laser deposited SrCuO2 (SCO) and CaCuO2 (CCO) on SrTiO3 has been studied using high pressure Reflection High Energy Electron Diffraction (RHEED) and Atomic Force Microscopy (AFM). For this, we developed a Pulsed Laser Deposition (PLD)- RHEED system, with the possibility to study the growth and to monitor the growth rates, in situ, at typical PLD pressures (10–50 Pa). In case of depositing oxide materials, high oxygen pressures are desired. Moreover, crystallinity can be improved using higher oxygen pressures and therefore higher temperatures. With this technique we are able to obtain atomically flat films, a first step towards multi-layer structures.In this paper we present the initial growth studies of SCO and first results incorporating CCO layers in a SCO matrix.

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Interface and Luminescence Properties of Pulsed Laser Deposited MgxZn1-xO/ZnO Quantum Wells with Strong Confinement

MRS Proceedings ◽

10.1557/proc-0957-k07-23 ◽

2006 ◽

Vol 957 ◽

Cited By ~ 5

Author(s):

Susanne Heitsch ◽

Gregor Zimmermann ◽

Alexander Müller ◽

Jörg Lenzner ◽

Holger Hochmuth ◽

...

Keyword(s):

Quantum Wells ◽

Stark Effect ◽

Pulsed Laser ◽

Energy Shift ◽

High Energy ◽

Interface Roughness ◽

Force Microscopy ◽

Quantum Confined Stark Effect ◽

Barrier Layers ◽

Atomic Force

ABSTRACTMgxZn1-xO/ZnO/MgxZn1-xO quantum wells (QWs) (0.12 ≤ x ≤ 0.15) have been grown on a-plane sapphire substrates by pulsed laser deposition. The nominal ZnO well layer thickness lies between 1.2 nm and 6 nm. Atomic force microscopy (AFM) investigations at ZnO/MgxZn1−xO heterostructures show the film-like structure of the ZnO layers. Their root mean square surface roughness of ∼ 0.5 nm gives information about the interface roughness in the QWs. AFM results from the MgxZn1−xO barrier layers show the same surface structure and roughness. We confirmed the lateral homogeneity of the Mg distribution in the MgxZn1−xO barrier layers by scanning cathodoluminescence measurements. The QWs show a bright and laterally homogeneous luminescence, suggesting good crystalline quality of the ZnO wells. The measured QW photoluminescence energies agree well with calculated values and display the presence of the quantum-confined Stark effect. As a result of quantum confinement a high-energy shift of the ZnO excitonic photoluminescence of 222 meV is observed in the thinnest QW.

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Micro Raman Spectroscopy of Silicon Nanocrystals Produced by Picosecond Pulsed Laser Ablation

MRS Proceedings ◽

10.1557/proc-738-g12.2 ◽

2002 ◽

Vol 738 ◽

Author(s):

M. H. Wu ◽

R. Mu ◽

A. Ueda ◽

D. O. Henderson ◽

B. Vlahovic

Keyword(s):

Laser Ablation ◽

Raman Spectra ◽

Silicon Nanocrystals ◽

Pulsed Laser ◽

Pulsed Laser Ablation ◽

Size Distributions ◽

Laser Plume ◽

Force Microscopy ◽

Atomic Force

ABSTRACTPulsed laser ablation has been used to produce silicon nanocrystals. Variation of the laser fluence, backing gas type and pressure result in nanocrystals with controllable size distributions. Properties of nanocrystals produced with this method also depend on the distance of the nanocrystal from the center of the laser plume. Correlated atomic force microscopy and in-situ micro-Raman measurements confirm that particle size decreases as distance from the plume center increases. Silicon peaks in the micro raman spectra taken at increasing distance from plume center show considerable differences in both center energy and width. Confocal micro raman spectra from thicker (> 10 micron) samples show little variation with depth, in contrast with porous silicon samples.

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Pathway Complexity in Supramolecular Porphyrin Self-Assembly at an Immiscible Liquid|Liquid Interface

10.26434/chemrxiv.14170202 ◽

2021 ◽

Author(s):

Iván Robayo-Molina ◽

Andrés F. Molina-Osorio ◽

Luke Guinane ◽

Syed A.M. Tofail ◽

Micheal D. Scanlon

Keyword(s):

Self Assembly ◽

Immiscible Liquid ◽

Bulk Solution ◽

Time Resolved ◽

Force Microscopy ◽

Atomic Force ◽

Aggregate Growth ◽

High Concentrations ◽

Thermodynamic Processes

Nanostructures that are inaccessible through spontaneous thermodynamic processes may be formed by supramolecular self-assembly under kinetic control. In the past decade, the dynamics of pathway complexity in self-assembly have been elucidated through kinetic models based on aggregate growth by sequential monomer association and dissociation. Immiscible liquid|liquid interfaces are an attractive platform to develop well-ordered self-assembled nanostructures, unattainable in bulk solution, due to the templating interaction of the interface with adsorbed molecules. Here, we report time-resolved in situ UV/vis spectroscopic observations of the self-assembly of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrin (ZnTPPc) at an immiscible aqueous|organic interface. We show that the kinetically favoured metastable J-type nanostructures form quickly, but then transform into stable thermodynamically favoured H-type nanostructures. Numerical modelling revealed two parallel and competing cooperative pathways leading to the different porphyrin nanostructures. These insights demonstrate that pathway complexity is not unique to self-assembly processes in bulk solution, and equally valid for interfacial self-assembly. Subsequently, the interfacial electrostatic environment was tuned using a kosmotropic anion (citrate) in order to control the influence the pathway selection. At high concentrations, interfacial nanostructure formation was forced completely down the kinetically favoured pathway and only J-type nanostructures were obtained. Furthermore, we found by atomic force microscopy (AFM) and scanning electron microscopy (SEM) that the J- and H-type nanostructures obtained at low and high citric acid concentrations, respectively, are morphologically distinct, which illustrates the pathway-dependent material properties.

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Drastic Change in the Gan Film Quality by In-Situ Controlling Surface Reconstructions In Gsmbe

MRS Proceedings ◽

10.1557/proc-482-223 ◽

1997 ◽

Vol 482 ◽

Cited By ~ 1

Author(s):

X. Q. Shen ◽

S. Tanaka ◽

S. Iwai ◽

Y. Aoyagi

Keyword(s):

Growth Conditions ◽

High Energy ◽

X Ray Diffraction ◽

X Ray ◽

Force Microscopy ◽

Gas Source ◽

Atomic Force ◽

Surface Reconstructions ◽

Gan Film

AbstractGaN growth was performed on 6H-SiC (0001) substrates by gas-source molecular beam epitaxy (GSMBE), using ammonia (NH3) as a nitrogen source. Two kinds of reflection high-energy electron diffraction (RHEED) patterns, named (1×1) and (2×2), were observed during the GaN growth depending on the growth conditions. By careful RHEED study, it was verified that the (1×1) pattern was corresponded to a H2-related nitrogen-rich surface, while (2×2) pattern was resulted from a Ga-rich surface. By x-ray diffraction (XRD), photoluminescence (PL) and atomic force microscopy (AFM) characterizations, it was found that the GaN quality changed drastically grown under different RHEED patterns. GaN film grown under the (1×1) RHEED pattern showed much better qualities than that grown under the (2×2) one.

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Preparation of (111)-Oriented Pt Electrode Films with Quasi-Monocrystal Properties on MgO/TiN Buffered Si(100) by PLD

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.280-283.823 ◽

2007 ◽

Vol 280-283 ◽

pp. 823-826 ◽

Cited By ~ 1

Author(s):

Tong Lai Chen ◽

Xiao Min Li

Keyword(s):

High Energy ◽

Layer Growth ◽

Atomic Scale ◽

Layer By Layer ◽

X Ray Diffraction ◽

Pt Electrode ◽

Force Microscopy ◽

Atomic Force

Atomic-scale smooth Pt electrode films have been deposited on MgO/TiN buffered Si (100) by the pulsed laser deposition (PLD) technique. The whole growth process of the multilayer films was monitored by using in-situ reflection high energy electron diffraction (RHEED) apparatus. The Pt/MgO/TiN/Si(100) stacked structure was also characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The HREED observations show that the growth mode of the Pt electrode film is 2D layer-by-layer growth. It is found that the (111)-oriented Pt electrode film has a crystallinity comparable to that of monocrystals. The achievement of the quasi-single-crystal Pt electrode film with an atomic-scale smooth surface is ascribed to the improved crystalline quality of the MgO film.

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In Situ Growth Studies of Artificial Layered (BA,SR,CA)CUO2 on Quasi-Ideal SrTiO3 Substrates by High Pressure Rheed

MRS Proceedings ◽

10.1557/proc-569-35 ◽

1999 ◽

Vol 569 ◽

Cited By ~ 1

Author(s):

Gertjan Koster ◽

Guus J.H.M. Rijnders ◽

Dave H.A. Blank ◽

Horst Rogalla

Keyword(s):

High Pressure ◽

Thin Film Deposition ◽

High Energy ◽

Layer Growth ◽

Film Deposition ◽

Perovskite Oxide ◽

Ex Situ ◽

Layer By Layer ◽

Substrate Surfaces

ABSTRACTThe layered structure of oxides, like the high-T, cuprates, has been topic of research for some years now. The possibility to control thin film deposition on an atomic level has made fabrication of artificial structures and junctions accessible by depositing atomic layers or molecular blocks sequentially. Perfectly smooth substrate surfaces are hereby a prerequisite.Using Pulsed Laser Deposition (PLD), different perovskite oxide materials have been deposited on SrTiO3 substrates. With in situ high pressure Reflection High Energy Electron Diffraction we studied growth at different temperatures and oxygen pressures. Ex situ XRD and AFM have been used to study the morphology after deposition.Here we applied a new approach in obtaining layer-by-layer growth implied by the way of depositing the material, almost regardless of the deposition conditions. By alternating intervals of high supersaturation depositing one unit cell layer with intervals of lower supersaturation, one is able to force a layer-by-layer growth mode, which is in principle only feasible with PLD. We applied this technique to fabricate the layered infinite structure (Ba,Sr,Ca)CuO2 with artificial layered modulation, which have been characterized by XRD and AFM.

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Pathway Complexity in Supramolecular Porphyrin Self-Assembly at an Immiscible Liquid|Liquid Interface

10.26434/chemrxiv.14170202.v1 ◽

2021 ◽

Author(s):

Iván Robayo-Molina ◽

Andrés F. Molina-Osorio ◽

Luke Guinane ◽

Syed A.M. Tofail ◽

Micheal D. Scanlon

Keyword(s):

Self Assembly ◽

Immiscible Liquid ◽

Bulk Solution ◽

Time Resolved ◽

Force Microscopy ◽

Atomic Force ◽

Aggregate Growth ◽

High Concentrations ◽

Thermodynamic Processes

Nanostructures that are inaccessible through spontaneous thermodynamic processes may be formed by supramolecular self-assembly under kinetic control. In the past decade, the dynamics of pathway complexity in self-assembly have been elucidated through kinetic models based on aggregate growth by sequential monomer association and dissociation. Immiscible liquid|liquid interfaces are an attractive platform to develop well-ordered self-assembled nanostructures, unattainable in bulk solution, due to the templating interaction of the interface with adsorbed molecules. Here, we report time-resolved in situ UV/vis spectroscopic observations of the self-assembly of zinc(II) meso-tetrakis(4-carboxyphenyl)porphyrin (ZnTPPc) at an immiscible aqueous|organic interface. We show that the kinetically favoured metastable J-type nanostructures form quickly, but then transform into stable thermodynamically favoured H-type nanostructures. Numerical modelling revealed two parallel and competing cooperative pathways leading to the different porphyrin nanostructures. These insights demonstrate that pathway complexity is not unique to self-assembly processes in bulk solution, and equally valid for interfacial self-assembly. Subsequently, the interfacial electrostatic environment was tuned using a kosmotropic anion (citrate) in order to control the influence the pathway selection. At high concentrations, interfacial nanostructure formation was forced completely down the kinetically favoured pathway and only J-type nanostructures were obtained. Furthermore, we found by atomic force microscopy (AFM) and scanning electron microscopy (SEM) that the J- and H-type nanostructures obtained at low and high citric acid concentrations, respectively, are morphologically distinct, which illustrates the pathway-dependent material properties.

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Compliance at the GaSb/GaP Interface by Misfit Dislocations Array

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.324.85 ◽

2011 ◽

Vol 324 ◽

pp. 85-88

Author(s):

Salim El Kazzi ◽

Ludovic Desplanque ◽

Christophe Coinon ◽

Yi Wang ◽

Pierrre Ruterana ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

High Energy ◽

Misfit Dislocations ◽

Initial Growth ◽

Electron Diffraction Analysis ◽

High Energy Electron ◽

Force Microscopy ◽

Atomic Force ◽

Transmission Electron

We study the initial growth of 10 monolayers (MLs) of GaSb on a (001) GaP substrate. Transmission electron microscopy and reflection high energy electron diffraction analysis show that an Sb-rich GaP surface promotes the formation of a 90° misfit dislocation array at the epi-substrate interface. Using atomic force microscopy, we investigate the influence of the growth temperature and the growth rate on the formation and the shape of GaSb islands.

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MBE Growth of IV-VI Nanowires on a Self-organized Template

MRS Proceedings ◽

10.1557/proc-1258-p04-56 ◽

2010 ◽

Vol 1258 ◽

Author(s):

Lee Andrew Elizondo ◽

Patrick McCann ◽

Joel Keay ◽

Matthew Johnson

Keyword(s):

Quantum Wires ◽

High Energy ◽

Ex Situ ◽

Mbe Growth ◽

One Dimensional ◽

Force Microscopy ◽

Self Organized ◽

Atomic Force ◽

Low Dimensional

AbstractWe present the experimental results for the first known molecular beam epitaxy (MBE) growth of quasi-one-dimensional PbSe wires on technologically relevant silicon.In this work, we describe the growth and characterization of low-dimensional IV-VI semiconductors as they evolve from one-dimensional dot/dot-chains to one-dimensional structures on a self-organized template epitaxially grown on Si(110). In situ and ex situ characterization were performed at various stages throughout growth by reflection high energy electron diffraction, scanning electron microscopy, and non-contact atomic force microscopy. Initial growths resulted in some preferential alignment of the PbSe dot-chains parallel to the self-organized template in the [-110] direction. By reducing the substrate temperature and increasing the supplemental Se flux, the morphology of dot-chains extend into lengthened one-dimensional structures. This is an important milestone in the fabrication of PbSe quantum wires on technologically relevant silicon.

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