Kinetic Control of CaF2 on Si(111) Growth Morphology

1993 ◽  
Vol 312 ◽  
Author(s):  
J. D. Denlinger ◽  
Eli Rotenberg ◽  
U. Hessingert ◽  
M. Leskovar ◽  
Marjorie A. Olmstead
Keyword(s):  
Photoelectron Spectroscopy ◽  
Molecular Beam ◽  
Layer Growth ◽  
Layer By Layer ◽  
X Ray ◽  
Photoelectron Diffraction ◽  
Triple Layer ◽  
Growth Modes ◽  
Level Shifts

AbstractThin (0.5 to 8 triple layer) CaF2 on Si(111) films were grown using molecular beam epitaxy (MBE) and characterized using an in situ combination of x-ray photoelectron spectroscopy (XPS) and componentresolved x-ray photoelectron diffraction (XPD). We identified surface, bulk-like, and interface F and Ca core-level shifts and used the XPS shifts and XPD modulations to identify the growth modes as a function of the kinetic parameters of CaF2 flux and Si temperature. We identify 3 distinct regimes: (i) for high temperatures and flux we find a complete reacted F-Ca-Si layer, overlaid by 2 layer high islands which coalesce, followed by layer-by-layer growth, (ii) for high temperature and low flux, we find the reacted F-Ca-Si layer to be partially covered with thick islands, and (iii) for low temperatures we find an incompletely occupied F-Ca-Si layer followed by layer-by-layer growth. In all cases we find the buried interface to be structurally identical to the unburied F-Ca-Si layer

Synthesis and Characterization of Zn Oxide Hexagonal Nano-Pole Films on Quartz Glass Substrate

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Jie Chen ◽  
Jun Wang
Keyword(s):  
Growth Mechanism ◽  
Quartz Glass ◽  
Photoelectron Spectroscopy ◽  
Glass Substrate ◽  
Sol Gel ◽  
Layer Growth ◽  
Layer By Layer ◽  
Quartz Glass Substrate ◽  
Wurtzite Phase ◽  
X Ray

Hexagon-shaped Zn oxide nano-pole films with terraces and steps have been successfully fabricated by means of a combined approach involving sol-gel process, high-temperature heat treatment, and the hydrothermal method. The surface chemistry and morphological features of the films were characterized by means of x-ray photoelectron spectroscopy and scanning electron microcopy. All the diffraction peaks in x-ray diffraction pattern match with those of the hexagonal wurtzite phase of Zn oxide. Transmittance measurements show that the optical transmittance of the sample synthesized at 520°C on quartz glass substrate is the highest, reaching about 65% in the visible-light region. Based on the detailed structural characterization and the nucleation-growth kinetics, we find that the whole crystallization process of wurtzite Zn oxide nano-poles includes nanocatalysis and layer-by-layer growth mechanism. The present study provides an important understanding of the growth mechanism for nano-pole synthesis of Zn oxide and related materials.

Surfactant-Mediated Growth of Ge/Si(001) Interface Studied by XPD

1998 ◽  
Vol 05 (01) ◽  
pp. 157-161 ◽  
Author(s):  
R. Gunnella ◽  
P. Castrucci ◽  
N. Pinto ◽  
P. Cucculelli ◽  
I. Davoli ◽  
...  
Keyword(s):  
High Temperature ◽  
Auger Electron ◽  
Layer Growth ◽  
Layer By Layer ◽  
Growth Morphology ◽  
High Quality ◽  
X Ray ◽  
Photoelectron Diffraction ◽  
Quality Degradation ◽  
Cap Layer

The influence of Sb as a surfactant on the formation of Si/Ge interface is studied by means of XPD (X-ray photoelectron diffraction) and AED (Auger electron diffraction) from Ge and Si core levels. The technique employed is particularly suitable for checking the film tetragonal distortion, the growth morphology and the sharpness of the interface. We found a layer by layer growth mode for 3 ML of Ge on Si(001) and related values of strain of the film close to the value predicted by the elastic theory which enforces the use of such a surfactant to obtain high quality and sharp heterostructures. In addition, studying the influence of 3 ML of the Si cap layer on the 3 ML Ge, we obtain no indication of Ge segregation into the Si cap layer. Finally, evidences of quality degradation after high temperature (T > 600° C ) annealing are shown.

An In-Situ Oblique-Incidence Optical Reflectance Difference Study of Co Electrodeposition on a Polycrystalline Au(111) Surface

2002 ◽  
Vol 721 ◽  
Author(s):  
J. Gray ◽  
W. Schwarzacher ◽  
X.D. Zhu
Keyword(s):  
Oblique Incidence ◽  
Three Dimensional ◽  
Oscillatory Behavior ◽  
Layer Growth ◽  
Deposition Condition ◽  
Layer By Layer ◽  
Optical Reflectance ◽  
Growth Modes ◽  
Highly Sensitive

AbstractWe studied submonolayer and multilayer deposition of Co on Au(111) using in-situ oblique-incidence optical reflectance difference (OI-RD). We show that the optical technique is highly sensitive and accurate in determining the electrodeposited film thickness and growth mode. We found that the optically determined thickness of the ultrathin Co film is in very good agreement with that deduced from the integration of the anodic current during cyclic voltammetry (CV). From a weak oscillatory behavior of the optical reflectance difference signal, it seems that the growth of electrodeposited Co on Au(111) under pulsed deposition condition proceeds by a combination of three dimensional island and quasi layer-by-layer growth modes.

A compact UHV X-ray diffractometer for studying surfaces and interfaces

1998 ◽  
Vol 5 (3) ◽  
pp. 887-889
Author(s):  
Yoshikazu Fujii ◽  
Takeshi Nakamura ◽  
Mutsumi Kai ◽  
Kentaroh Yoshida
Keyword(s):  
High Vacuum ◽  
Layer Growth ◽  
Ultra High Vacuum ◽  
Layer By Layer ◽  
Crystal Surfaces ◽  
X Ray ◽  
Surfaces And Interfaces ◽  
Optical Table ◽  
Specimen Orientation

A compact ultra-high-vacuum (UHV) X-ray diffractometer for surface glancing X-ray scattering has been constructed. All the equipment, including a rotating-anode source of 18 kW and a UHV specimen chamber, is arranged on one optical table of dimensions 70 × 90 cm. The specimen chamber is 14 cm in diameter and 20 cm high and can be evacuated up to 3 × 10−8 Pa. It is equipped with two Be windows of thicknesses 0.2 and 0.4 mm. Specimen orientation in the vacuum is controlled from the outside. The specimen can be heated up to 773 K. The chamber has two evaporation cells and can be used for in situ observations of growing crystal surfaces. Using this instrument, we observed a mechanically polished Ag surface and successfully made an in situ observation of the layer-by-layer growth of a PbSe(111) surface. The instrument will be useful for preliminary experiments using laboratory sources, prior to final measurements at synchrotron radiation facilities.

Structural and Morphological Properties of Ultrathin HfO2 Dielectrics on 4H-SiC (0001)

2006 ◽  
Vol 527-529 ◽  
pp. 1075-1078 ◽  
Author(s):  
Carey M. Tanner ◽  
Jun Lu ◽  
Hans Olof Blom ◽  
Jane P. Chang
Keyword(s):  
Photoelectron Spectroscopy ◽  
Field Effect Transistors ◽  
High Energy ◽  
Oxide Semiconductor ◽  
Ex Situ ◽  
Morphological Properties ◽  
Layer By Layer ◽  
Island Growth ◽  
X Ray

The material properties of HfO2 thin films were studied to evaluate their potential as a high-κ gate dielectric in 4H-SiC power metal-oxide-semiconductor field effect transistors. Stoichiometric HfO2 films were deposited on n-type 4H-SiC (0001) by atomic layer deposition (ALD) at substrate temperatures of 250-450°C. No significant interfacial layer formation was observed by in-situ X-ray photoelectron spectroscopy (XPS) and an abrupt interface was confirmed by high-resolution transmission electron microscopy (HRTEM). A temperature-dependent transition from amorphous layer-by-layer growth to crystalline three-dimensional island growth was identified by in-situ reflection high-energy electron diffraction (RHEED) and ex-situ atomic force microscopy (AFM). X-ray diffraction (XRD) confirmed the presence of monoclinic HfO2 domains in crystallized films.

Preparation of Poly(diallydimethyl ammonium chloride) (PDDA)/Au Nanocomposite Film by In Situ Electrochemical Reduction and its Electrocatalytic Properties

2010 ◽  
Vol 123-125 ◽  
pp. 189-192
Author(s):  
Hong Wei Shi ◽  
Li Zhang ◽  
Cong Wang ◽  
Ke Ying Zhang
Keyword(s):  
Electrochemical Reduction ◽  
Ammonium Chloride ◽  
Photoelectron Spectroscopy ◽  
Self Assembly ◽  
Composite Films ◽  
Nanocomposite Films ◽  
Layer By Layer ◽  
X Ray ◽  
Assembly Technique

Nanocomposite films containing Au nanoparticles were fabricated by alternating adsorption of poly(diallydimethyl ammonium chloride) (PDDA) and HAuCl4 using layer-by-layer self-assembly technique and subsequent in situ electrochemical reduction of the AuCl4- ions. The composition and properties of the composite films were characterized by ultraviolet-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV).The UV-vis characteristic absorbances of PDDA and Au increase almost linearly with the number of bilayers, which suggests a progressive deposition with almost an equal amount of the PDDA and Au in each cycle. X-ray photoelectron spectroscopy further confirms the presence of the main components (such as PDDA and Au) of the nanocomposite films. Furthermore, the nanocomposite films also exhibit good electrocatalytic activity for the oxidation of ascorbic acid (AA), which may be used in electrochemical biosensors.

A MODEL OF STRUCTURAL DISORDER IN (Ba2Cu2O4+x)/(CaCuO2)n SUPERLATTICES

2000 ◽  
Vol 14 (25n27) ◽  
pp. 2719-2724
Author(s):  
G. PASQUINI ◽  
G. BALESTRINO ◽  
S. LAVANGA ◽  
P. G. MEDAGLIA ◽  
G. PETROCELLI ◽  
...  
Keyword(s):  
Structural Disorder ◽  
Layer Growth ◽  
Internal Stresses ◽  
Layer By Layer ◽  
Mixed Composition ◽  
X Ray ◽  
Order Of Magnitude ◽  
Random Disorder ◽  
Kinematical Approach

The structural disorder in ( Ba 2 Cu 2 O 4+x )/( CaCuO 2) n superlattices with ultrathin individual layers was investigated. Numerical simulations of x-ray spectra were carried out following a kinematical approach in a simplified model structure. The model assumes a two-dimensional layer by layer growth in which mixed composition layers can be corrugated to adjust the internal stresses due to the large mismatch between the constituent oxides. An additional random disorder is added to take into account the experimental dispersion in the amount of material deposited in each iteration. The model was successfully used to simulate x-ray spectra for samples with non integer n ranging from 2 to 16, grown in optimal conditions to obtain a superconducting behavior. The same model was used to simulate spectra of samples grown at lower pressures monitored with in-situ RHEED diagnostic. In this case, random disorder results more than one order of magnitude smaller.

Influence of pyrrole feeding ratios on physicochemical characteristics of high-performance multilayered PPy/PVC/PDA@FG-NH2 nanocomposites

2019 ◽  
Vol 33 (10) ◽  
pp. 1358-1382
Author(s):  
Asima Naz ◽  
Rabia Sattar ◽  
Muhammad Siddiq ◽  
Muhammad Abid Zia
Keyword(s):  
Conjugated Polymers ◽  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Oxidative Polymerization ◽  
Physicochemical Characteristics ◽  
Layer By Layer ◽  
X Ray ◽  
Melting And Crystallization ◽  
Scanning Electron

Nanocomposites of conjugated polymers polypyrrole (PPy) and polyvinyl chloride (PVC) as matrices and 1,4-phenylenediamine (PDA) as a linker with amine functional graphite (FG-NH2) as filler have been efficiently fabricated using in situ oxidative polymerization, and the effect of various mass ratios on physicochemical characteristics of prepared nanocomposite was investigated. The layer-by-layer oxidative polymerization of various matrices on host filler surface is confirmed by Fourier transform infrared, energy dispersive X-ray, and X-ray photoelectron spectroscopy examinations. Field emission scanning electron microscopy revealed fibrillary morphology of obtained nanocomposites. Thermal stability, glass transition temperature, and melting and crystallization temperature of the nanocomposites were increased with the incorporation of modified graphite. Brunauer–Emmett–Teller analysis explored the improved adsorption capacity (128 cm3 g−1) of the nanocomposite with higher feeding ratio of pyrrole. The influence of FG-NH2 and pyrrole on electrical conductivity performance of composites was also investigated. Functionalized graphite in the resultant PPy/PVC/PDA@FG-NH2 nanocomposites played an important role in forming conducting network in PPy matrix indicating synergistic effect between PPy and FG-NH2.

A compact molecular-beam epitaxy apparatus for in situ soft X-ray magnetic circular dichroism experiments

1998 ◽  
Vol 5 (3) ◽  
pp. 1038-1040
Author(s):  
Tsuneharu Koide ◽  
Tetsuo Shidara ◽  
Nobuo Nakajima ◽  
Hiroshi Miyauchi ◽  
Hirohito Fukutani
Keyword(s):  
Circular Dichroism ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Magnetic Circular Dichroism ◽  
Layer By Layer ◽  
X Ray ◽  
Optical Instruments ◽  
Circular Dichroïsm

An economical and easily movable molecular-beam epitaxy (MBE) apparatus which prepares magnetic ultrathin films and superlattices with atomically well controlled interfaces has been designed and constructed. Cleaning and characterization of substrates, sample deposition in a layer-by-layer fashion, and characterization of samples both during and after growth can be carried out in a single ultrahigh vacuum (UHV) chamber. This MBE apparatus is combined with UHV high-field magneto-optical instruments for in situ soft X-ray magnetic circular dichroism experiments on two-dimensional magnetic systems.

In situ X-ray photoelectron spectroscopy of Ag/Al bilayers grown by molecular beam epitaxy

2003 ◽  
Vol 256 (1-2) ◽  
pp. 201-205 ◽  
Author(s):  
D.K. Aswal ◽  
K.P. Muthe ◽  
Niraj Joshi ◽  
A.K. Debnath ◽  
S.K. Gupta ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Photoelectron Spectroscopy ◽  
Molecular Beam ◽  
X Ray
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