Atmoic-Scale Control of Oxide Substrate Surface/Termination and Novel Heteroepitaxial Growth

1999 ◽  
Vol 587 ◽  
Author(s):  
Mamoru Yoshimoto ◽  
Keisuke Mizuno ◽  
Takafumi Miyahara
Keyword(s):  
Single Crystal ◽  
Sapphire Substrate ◽  
Substrate Surface ◽  
High Energy ◽  
Atomic Scale ◽  
The Novel ◽  
Heteroepitaxial Growth ◽  
Surface Termination ◽  
Oxide Substrates ◽  
Atomically Flat

AbstractAtomic-scale surface/termination of single-crystal oxide substrates were examined by coaxial impact collision ion scattering spectroscopy (CAICISS) and atomic force microscopy (AFM). CAICISS enabled us to determine the terminating atomic species and their arrangements of single crystal oxide substrates and epitaxial oxide films. Through thermal-annealing of the single crystal oxide substrates, atomically flat terrace and stepped structures were developed on the surface. The molecular layer-by-layer growth was verified by in situ monitoring of reflection high energy electron diffraction (RHEED) intensity oscillation. The atomic-scale substrate engineering made it possible to attain the novel heteroepitaxial growth such as step-decoration epitaxy resulting in the nanowire structures and diamond epitaxy on the ultrasmooth sapphire substrate. The diamond films could be grown epitaxially only on the atomically flat sapphire substrates by pulsed laser ablation of graphite. The novel application of the ultrasmooth sapphire substrate to the AFM observation stage for DNA molecules was also presented.

Wet Etching Methods for Perovskite Substrates

1999 ◽  
Vol 587 ◽  
Author(s):  
Victor Leca ◽  
Guus Rijnders ◽  
Gertjan Koster ◽  
Dave H. A. Blank ◽  
Horst Rogalla
Keyword(s):  
Ph Value ◽  
Substrate Surface ◽  
High Energy ◽  
Etching Time ◽  
Epitaxial Thin Films ◽  
Etch Pits ◽  
High Quality ◽  
Oxide Electronics ◽  
Force Microscopy ◽  
Atomically Flat

AbstractIn oxide electronics substrates with atomically flat terraces are a request for growing high-quality epitaxial thin films. In this paper results on chemical etching of some substrates with perovskite, ABO3, structure (e.g., SrTiO3, LSAT - the (LaAlO3)0.3(Sr2AlTaO6)0.35 solid solution, and NdGaO3) are presented. In order to obtain high quality substrates, different etchants (NH4F + HF, HCl + NH4Cl, and HCl + HNO3) with various pH values have been studied. From Atomic Force Microscopy (AFM), in air, we conclude that, irrespective of the etchant that has been used, a substrate surface with a BOx terminated layer and atomically flat terraces without etch pits could be obtained. The pH-value and temperature of the etchant and the etching time, however, influence significantly the surface quality. Reflection high energy electron diffraction (RHEED) patterns confirmed the AFM results.

Epitaxial Growth and Structure of Thin Single Crystal γ-Al2O3 Films on Si (111) Using e-Beam Evaporation of Sapphire in Ultra-High Vacuum

2004 ◽  
Vol 811 ◽  
Author(s):  
M. Hong ◽  
A. R. Kortan ◽  
J. Kwo ◽  
J. P. Mannaerts ◽  
S. Y. Wu
Keyword(s):  
Single Crystal ◽  
Epitaxial Growth ◽  
Substrate Surface ◽  
High Vacuum ◽  
High Energy ◽  
Electron Beam Evaporation ◽  
Ultra High Vacuum ◽  
Plane Component ◽  
High Structural Perfection ◽  
Single Crystal Sapphire

ABSTRACTWe have characterized the structure of epitaxial Al2O3 films deposited on Si (111) substrate using electron beam evaporation from a high-purity single crystal sapphire source in a molecular beam epitaxy (MBE) approach. The structural studies were carried out mainly by single crystal x-ray diffraction with the initial epitaxial growth observed by in-situ reflection high energy electron diffraction. The Al2O3 films grow in the cubic γ-phase with a very uniform thickness, and a high structural perfection. The <111> axes of the film and the Si substrate are well aligned. A mosaic scan of the Al2O3 (222) peak (with no in-plane component) finds a 0.3 degree (or 18') spread. All three unit cell vectors of the film and the substrate are parallel, but the in-plane cone scans of the {004} and {044} diffraction peaks about the surface normal find a ±3 degree film in-plane rotation with respect to the substrate surface orientation.

Atomic Scale Engineering of SrTiO3 Single Crystal Surfaces and Bicrystal Boundaries for Epitaxial Growth of Oxide Thin Films

1997 ◽  
Vol 474 ◽  
Author(s):  
Q. D. Jiang ◽  
J. Zegenhagen
Keyword(s):  
Thin Films ◽  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Atomic Scale ◽  
Spiral Growth ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Annealing Procedure ◽  
Atomically Flat

ABSTRACTWe introduce a new annealing procedure to prepare well defined surfaces of SrTiO3 single crystal and bicrystal substrates. Annealing SrTiO3 (001) substrates in oxygen and then in ultra high vacuum produces a uniformly TiO2-terminated, atomically flat and ordered SrTiO3 (001) surfaces, as revealed by Auger electron spectroscopy, low energy electron diffraction, and high resolution scanning tunneling microscopy. Applying this annealing procedure to slightly off-cut (∼1.2°) SrTiO3 (001) surfaces has a strong influence on the resulting step structure. Particular annealing procedures can be used to tailor the structure and morphology of the surface and of bicrystal boundaries down to the atomic level. For example, steps of SrTiO3 (001) surfaces can be adjusted to a height of one, two, or multiple times the unit-cell size of STO (aSTO=0.3905 nm). Atomically flat SrTiO3 (001) substrates were used for deposition of SmBa2Cu3O7-δ (SBCO) thin films. The thickness (in a range from 10 nm to 200 nm) dependency of the surface morphology of SmBa2Cu3O7-δ films was investigated with UHV-STM. No spiral growth was observed. Surfaces of all films exhibit stacks of flat terraces which are frequently separated by steps, smaller than the c-axis length cSBCO of SBCO (cSBCO=1.17 nm).

Heteroepitaxial growth of lanthanum aluminate films derived from mixed metal nitrates

1997 ◽  
Vol 12 (5) ◽  
pp. 1306-1314 ◽  
Author(s):  
Man Fai Ng ◽  
Michael J. Cima
Keyword(s):  
Thin Films ◽  
Single Crystal ◽  
Linear Growth ◽  
Substrate Surface ◽  
Single Crystal Substrate ◽  
Second Phase ◽  
Heteroepitaxial Growth ◽  
Lanthanum Aluminate ◽  
Metal Nitrates ◽  
Linear Growth Model

Epitaxial lanthanum aluminate (LaAlO3) thin films were deposited on single-crystal substrates by pyrolysis of spin-on mixed nitrate precursors. The films are epitaxial without any second phase. TEM micrographs show that all of these films have pores with sizes ranging from 5 to 30 nm. Grain boundaries are not observed. Selected area diffraction shows that the films are single-crystal-like, despite the porosity. All the films are smooth and crack-free. The precursors first decompose into an amorphous mixture. Heterogeneous nucleation occurs on the lattice-matched, single-crystal substrate surface. The epitaxial films grow upward and consume the amorphous regions. The crystallization temperature of LaAlO3 is lower for thin films than for bulk samples due to nucleation on the substrate. The crystallization of LaAlO3 does not exhibit linear growth kinetics. The Johnson–Mehl–Avrami exponent of growth is between 1.4 and 1.5. This deviation from the linear growth model (n = 1) can be attributed to continuous nucleation on the substrate/film interface.

Experiments on REM and SREM using a Tem/Stem Microscope with a Configurable Angle-Resolving Detector

1990 ◽  
Vol 48 (1) ◽  
pp. 338-339
Author(s):  
H. Banzhof ◽  
I. Daberkow
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Crystal Surface ◽  
High Energy ◽  
Contrast Effects ◽  
Atomic Steps ◽  
Single Crystal Surfaces ◽  
Platinum Single Crystal ◽  
Reflection Electron Microscopy ◽  
Beam Reflection

A Philips EM 420 electron microscope equipped with a field emission gun and an external STEM unit was used to compare images of single crystal surfaces taken by conventional reflection electron microscopy (REM) and scanning reflection electron microscopy (SREM). In addition an angle-resolving detector system developed by Daberkow and Herrmann was used to record SREM images with the detector shape adjusted to different details of the convergent beam reflection high energy electron diffraction (CBRHEED) pattern.Platinum single crystal spheres with smooth facets, prepared by melting a thin Pt wire in an oxyhydrogen flame, served as objects. Fig. 1 gives a conventional REM image of a (111)Pt single crystal surface, while Fig. 2 shows a SREM record of the same area. Both images were taken with the (555) reflection near the azimuth. A comparison shows that the contrast effects of atomic steps are similar for both techniques, although the depth of focus of the SREM image is reduced as a result of the large illuminating aperture. But differences are observed at the lengthened images of small depressions and protrusions formed by atomic steps, which give a symmetrical contrast profile in the REM image, while an asymmetric black-white contrast is observed in the SREM micrograph. Furthermore the irregular structures which may be seen in the middle of Fig. 2 are not visible in the REM image, although it was taken after the SREM record.

Single-Layer MoS2 Grown on Atomically Flat SrTiO3 Single Crystal for Enhanced Trionic Luminescence

ACS Nano ◽  
2021 ◽  
Author(s):  
Chenxi Huang ◽  
Jun Fu ◽  
Miaomiao Xiang ◽  
Jiefu Zhang ◽  
Hualing Zeng ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Layer ◽  
Atomically Flat

scholarly journals Redox-driven atomic-scale changes in mixed catalysts: VOX/WOX/α-TiO2 (110)

RSC Advances ◽  
2014 ◽  
Vol 4 (110) ◽  
pp. 64608-64616 ◽  
Author(s):  
Z. Feng ◽  
M. E. McBriarty ◽  
A. U. Mane ◽  
J. Lu ◽  
P. C. Stair ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Surface ◽  
Oxide Catalysts ◽  
Atomic Scale ◽  
Redox Behavior ◽  
Single Crystal Surface ◽  
Tungsten Oxides ◽  
Mixed Monolayer ◽  
X Ray

X-ray study of vanadium–tungsten mixed-monolayer-oxide catalysts grown on the rutile α-TiO2 (110) single crystal surface shows redox behavior not observed for lone supported vanadium or tungsten oxides.

scholarly journals In-Situ Diagnostics at High Pressures: Ellipsometric and Rheed Studies of the Growth of Yba2Cu3O7

1997 ◽  
Vol 502 ◽  
Author(s):  
Dave H. A. Blank ◽  
Horst Rogalla
Keyword(s):  
Thin Films ◽  
High Pressures ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Complex Oxide ◽  
High Energy ◽  
Diagnostic Tools ◽  
Heteroepitaxial Growth ◽  
Deposition Parameters

ABSTRACTPulsed Laser and Sputter Deposition are used for the fabrication of complex oxide thin films at relatively high oxygen pressures (up to 0.5 mBar). This high pressure hampers the application of a number of in-situ diagnostic tools. One of the exceptions is ellipsometry. Using this technique we studied in-situ the growth of off-axis sputtered Yba2Cu3O6+x thin films on (001) SrTiO3 as a function of the deposition parameters. Furthermore, the oxidation process from O(6) to O(7) has been studied by performing spectroscopic ellipsometry during isobaric cooling procedures.Another suitable in-situ monitoring technique for the growth of thin films is Reflection High Energy Electron Diffraction (RHEED). In general this is a (high) vacuum technique. Here, we present an RHEED-system in which we can observe clear diffraction patterns up to a deposition pressure of 0.5 mBar. The system has been used for in-situ monitoring of the heteroepitaxial growth of YBa2Cu3 06+x on SrTiO3 by pulsed laser deposition.

X-Ray-Optical Multilayer Structures Studied Using High Resolution Electron Microscopy.

1986 ◽  
Vol 77 ◽  
Author(s):  
Mary Beth Stearns ◽  
Amanda K. Petford-Long ◽  
C.-H. Chang ◽  
D. G. Stearns ◽  
N. M. Ceglio ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Substrate Surface ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Degree Of Crystallinity ◽  
Multilayer Systems ◽  
Layer Width ◽  
X Ray ◽  
Resolution Electron

ABSTRACTThe technique of high resolution electron microscopy has been used to examine the structure of several multilayer systems (MLS) on an atomic scale. Mo/Si multilayers, in use in a number of x-ray optical element applications, and Mo/Si multilayers, of interest because of their magnetic properties, have been imaged in cross-section. Layer thicknesses, flatness and smoothness have been analysed: the layer width can vary by up to 0.6nm from the average value, and the layer flatness depends on the quality of the substrate surface for amorphous MLS, and on the details of the crystalline growth for the crystalline materials. The degree of crystallinity and the crystal orientation within the layers have also been investigated. In both cases, the high-Z layers are predominantly crystalline and the Si layers appear amorphous. Amorphous interfacial regions are visible between the Mo and Si layers, and crystalline cobalt suicide interfacial regions between the Co and Si layers. Using the structural measurements obtained from the HREM results, theoretical x-ray reflectivity behaviour has been calculated. It fits the experimental data very well.

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