In Situ STM Observation of the Spiral Growth in the Epitaxial Fe Films on MgO(001)

1999 ◽  
Vol 580 ◽  
Author(s):  
Agus Subagyo ◽  
Kazuhisa Sueoka ◽  
Koichi Mukasa
Keyword(s):  
Film Thickness ◽  
Growth Temperature ◽  
Critical Thickness ◽  
Growth Mode ◽  
Spiral Growth ◽  
Scanning Tunneling ◽  
Mode Transition ◽  
Tunneling Microscopy ◽  
Atomically Flat

AbstractWe reported a scanning tunneling microscopy(STM) observation on the growth mode transition from 2D-nucleation to spiral growth in the epitaxial Fe films on MgO(001). As the growth temperature is increased to above 493 K, a temperature region where the Schwoebel barrier is overcome, the Fe films grow in a 2D-nucleation and growth mode formed atomically flat films. The 2D-nucleation transformed into a spiral growth as increasing film thickness. At a growth temperature of 493 K, the transition of 2D nucleation to the spiral growth was observed at a film thickness of 75 Å. The critical thickness of the emergence of growth transition decreased as the growth temperature is increased.

Epitaxial YBa2Cu3O7−x Thin Films: Scanning Tunneling Microscope Study of the Initial Stages of Epitaxial Growth, Growth Mechanism, and Effects of Substrate Temperature

1991 ◽  
Vol 237 ◽  
Author(s):  
Shen Zhu ◽  
Douglas H. Lowndes ◽  
X.-Y. Zheng ◽  
David P. Norton ◽  
R. J. Warmack
Keyword(s):  
Film Thickness ◽  
Growth Mechanism ◽  
Growth Temperature ◽  
Lattice Mismatch ◽  
Unit Cell ◽  
Growth Mode ◽  
Spiral Growth ◽  
Scanning Tunneling ◽  
Growth Stages ◽  
Island Growth

ABSTRACTThe surface microstructure of epitaxial YBa2Cu3O7−x films grown by pulsed laser ablation on (001) MgO and SrTiO3 substrates has been studied at various growth stages, ranging in thickness from eight c-axis perpendicular unit cells to ∼220 nm. On MgO (lattice mismatch ∼9%) even the thinnest films grow unit cell-by-unit cell by an island growth mechanism. However, on SrTi03 (mismatch ∼1%), a transition from a layer-like growth mode to island growth is observed as the film thickness increases. Islands with clear spiral growth structures are observed in even the thinnest films on MgO, but for films grown on SrTiO3 the spiral growth features are found only for film thicknesses slightly greater than the critical thickness for the switch to an island growth mode. The islands consist of stacks of atomically flat terraces whose step heights are multiples of the c-axis lattice parameter. The island density decreases significantly with increasing film thickness, while their diameters range from 50–400 nm, increasing with growth temperature. The terraced island grain morphology causes a surface roughness of from 10 to 30 nm (depending on growth temperature) in films ∼200 nm thick.

Ge-Quantum Dots on SI(001) Tailored by Carbon Predeposition

1998 ◽  
Vol 533 ◽  
Author(s):  
O. Leifeld ◽  
D. Grützmacher ◽  
B. Müller ◽  
K. Kern
Keyword(s):  
Surface Roughness ◽  
Critical Thickness ◽  
Carbon Deposition ◽  
Compressive Strain ◽  
Second Step ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Island Nucleation ◽  
Facet Formation

AbstractThe morphology of Si(001) after carbon deposition of 0.05 to 0.11 monolayers (ML) was investigated in situ by ultrahigh vacuum scanning tunneling microscopy (UHV-STM). The carbon induces a c(4×4)-reconstruction of the surface. In addition, carbon increases the surface roughness compared to clean Si(001) (2×1). In a second step, the influence of the carbon induced restructuring on Ge-island nucleation was investigated. The 3D-growth sets in at considerably lower Ge coverage compared to the clean Si(001) (2×1) surface. This leads to a high density of small though irregularly shaped dots, consisting of stepped terraces, already at 2.5 ML Ge. Increasing the Ge-coverage beyond the critical thickness for facet formation, the dots show { 105 }- facets well known from Ge-clusters on bare Si(001) (2×1). However, they are flat on top with a (001)-facet showing the typical buckled Ge rows and missing dimers. This indicates that the compressive strain is not fully relaxed in these hut clusters.

Nanopatterned Si(001) Substrates as Templates for Quantum Dot Growth

2003 ◽  
Vol 775 ◽  
Author(s):  
A. Ney ◽  
C. Pampuch ◽  
J. J. Schulz ◽  
L. Perepelittchenko ◽  
R. Koch
Keyword(s):  
Temperature Treatment ◽  
Growth Mode ◽  
Scanning Tunneling ◽  
Island Growth ◽  
Tunneling Microscopy ◽  
Preparation Conditions ◽  
Low Temperature Treatment ◽  
Reconstructed Surface ◽  
Atomically Flat ◽  
Microscopy Images

AbstractIt has been shown recently, that the formation of GeSi quantum dots on Si(001) is strongly affected by the surface properties of the substrate. With an increasing number of missing dimer vacancies the growth mode can even change from a Stranski-Krastanow to a kinetic 3D island growth mode. Here we report on atomically resolved scanning tunneling microscopy images of Si(001) after different preparation procedures, namely the conventional high temperature procedure employed for commercial wafers, and Shiraki-type samples which require only low temperature treatment. The latter method yields an atomically flat Si(001) (2 × 1) surface, however, with a defect (ad- and missing dimers) concentration depending on the respective preparation conditions. Furthermore, repeated flashing occasionally yields a (2 × n) reconstructed surface consisting of well-ordered self-assembled trenches of missing dimers, similar to the ones discussed controversially in the previous literature. From our results we can clearly exclude contaminants to be involved.

Scanning Tunneung Microscope Studies of Initial Epitaxial Growth of YBa2Cu3O7-δ Thin Films

1992 ◽  
Vol 263 ◽  
Author(s):  
Xiang-Yang Zheng ◽  
D. H. Lowndes ◽  
Shen Zhu ◽  
R. J. Warmack
Keyword(s):  
Thin Films ◽  
Epitaxial Growth ◽  
Growth Temperature ◽  
Lattice Mismatch ◽  
Growth Mode ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Weber Type ◽  
Film Substrate ◽  
Miscut Angle

ABSTRACTThe initial stages of epitaxial growth of laser ablated YBa2Cu3O7-δ (YBCO) thin films on (001) SrTiO3, LaAlO3, and MgO substrates, and on slightly miscut LaA1O3 and SrTiO3, have been studied with scanning tunneling microscopy (STM). Surface images show that the initial YBCO growth mode can be either of the Stranski- Krastanov or the Volmer-Weber type, depending on the film-substrate lattice mismatch and the growth temperature. A small substrate miscut angle is found to strongly influence the growth mode of YBCO films. Screw dislocation-mediated growth is suppressed, and films grown at 800°C on (001) LaAlO3 substrates with miscut angle of 2.0° along <100> or <110> directions were found to consist of tilted platelets that are epitaxially aligned with the substrate crystal lattice.

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).

Spin-Polarized Scanning Tunneling Spectroscopy of Self-Organized Nanoscale Co Islands on Au(111) Surfaces

2008 ◽  
Vol 8 (7) ◽  
pp. 3616-3620 ◽  
Author(s):  
K. Schouteden ◽  
D. A. Muzychenko ◽  
C. Van Haesendonck
Keyword(s):  
Substrate Surface ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Self Organized ◽  
Spin Polarized ◽  
Magnetization Orientation ◽  
Atomically Flat

Magnetic monolayer and bilayer Co islands of only a few nanometer in size were grown by atomic deposition on atomically flat Au(111) films. The islands were studied in situ by scanning tunneling microscopy (STM) and spectroscopy at low temperatures. Spin-resolved tunneling spectroscopy, using an STM tip with a magnetic coating, revealed that the Co islands exhibit a net magnetization perpendicular to the substrate surface due to the presence of spin-polarized d-states. A random distribution of islands with either upward or downward pointing magnetization was observed, without any specific correlation of magnetization orientation with island size or island height.

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