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.

Scanning Tunneling Microscopy and Spectroscopy of Y-Ba-Cu-O Thin Films Produced by Ion Beam Sputter-Deposition

1992 ◽  
Vol 275 ◽  
Author(s):  
R. C. Chapman ◽  
O. Aucffillo ◽  
D. J. LichtenWalner ◽  
R. P. Adu ◽  
C. N. SobleII ◽  
...  
Keyword(s):  
Thin Films ◽  
Scanning Tunneling Microscopy ◽  
Ion Beam ◽  
Sputter Deposition ◽  
Growth Mode ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Oriented Film ◽  
Oriented Films ◽  
Ion Beam Sputter Deposition

ABSTRACTIon beam sputter-deposition has been used to produce high temperature superconducting (HTSC) thin films with controlled orientation. Room temperature scanning tunneling microscopy (STM) studies of ion beam sputter-deposited Y-Ba-Cu-O thin films indicate that the growth mode depends on whether the films are a- or c-axis oriented. The c-axis oriented films appear to grow by a screw dislocation mechanism, producing layered spirals similar to those observed in films grown by plasma sputtering and laser ablation-deposition. STM images of the a-axis oriented films show a growth mode which appears to produce layered structures perpendicular to the substrate with no spirals. Scanning tunneling spectroscopy (STS) studies of the a- and c-axis oriented films tend to reflect the anisotropy of the Y-Ba-Cu-O structure. Both the c-axis and the a-axis oriented films have semiconducting characteristics, possibly due to a native oxide, with a band gap estimated to be 1.4 eV. The c-axis oriented film, however, exhibits more fine structure in its density of states. This apparent anisotropie band structure reflects the anisotropie Y-Ba-Cu-O microstructure and superconducting characteristics. Investigations with x-ray photcelectron spectroscopy (XPS) establish a substantial chemical difference between the two surfaces inferring more substantial native oxides and air-induced by-products on the a-axis oriented film.

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.

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.

A scanning tunneling microscopy and potentiometry study of epitaxial thin films of La0.7Ca0.3MnO3

2002 ◽  
Vol 738 ◽  
Author(s):  
Mandar Paranjape ◽  
K. Shantha Shankar ◽  
A.K. Raychaudhuri ◽  
N.D. Mathur ◽  
M.G. Blamire
Keyword(s):  
Thin Films ◽  
Scanning Tunneling Microscopy ◽  
Grain Boundaries ◽  
Lattice Mismatch ◽  
Local Potential ◽  
Growth Unit ◽  
Scanning Tunneling ◽  
Epitaxial Thin Films ◽  
Tunneling Microscopy

ABSTRACTTo investigate the role of grain boundaries and other growth related microstructure in manganite films, a scanning tunneling microscope is used to simultaneously probe surface topography and local potential distribution under current flow at nanometer level in films of epitaxial thin films of La0.7Ca0.3MnO3deposited on single crystal SrTiO3and NdGaO3substrate by laser ablation. We have studied two types of films strained and strain relaxed. Thin (50nm) films (strained due to lattice mismatch between substrate and the film) show step growth (unit cell steps) and have very smooth surfaces. Relatively thicker films (strain relaxed, thickness 200nm) do not have these step growths and show rather smooth well connected grains. Charge transport in these films is not uniform on the nanometer level and is accompanied by potential jumps at the internal surfaces. In particular scattering from grain boundaries results in large variations in the local potential resulting in fields as high as 104-105V/cm located near the grain boundaries. We discuss the role of local strain and strain inhomogeneties in determining the current transport in these films and their resistance and magnetoresistivity. In this paper we attempt to correlate between bulk electronic properties with microscopic electronic conduction using scanning tunneling microscopy and scanning tunneling potentiometry.

scholarly journals Strain-Relief Patterns and Kagome Lattice in Self-Assembled C60 Thin Films Grown on Cd(0001)

2021 ◽  
Vol 22 (13) ◽  
pp. 6880
Author(s):  
Zilong Wang ◽  
Minlong Tao ◽  
Daxiao Yang ◽  
Zuo Li ◽  
Mingxia Shi ◽  
...  
Keyword(s):  
Thin Films ◽  
Self Assembly ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
Kagome Lattice ◽  
Tunneling Microscopy ◽  
Kagomé Lattice ◽  
Temperature Scanning ◽  
C60 Films

We report an ultra-high vacuum low-temperature scanning tunneling microscopy (STM) study of the C60 monolayer grown on Cd(0001). Individual C60 molecules adsorbed on Cd(0001) may exhibit a bright or dim contrast in STM images. When deposited at low temperatures close to 100 K, C60 thin films present a curved structure to release strain due to dominant molecule–substrate interactions. Moreover, edge dislocation appears when two different wavy structures encounter each other, which has seldomly been observed in molecular self-assembly. When growth temperature rose, we found two forms of symmetric kagome lattice superstructures, 2 × 2 and 4 × 4, at room temperature (RT) and 310 K, respectively. The results provide new insight into the growth behavior of C60 films.

Microstructure of SrTiO3 Thin Films as Single Layer and Incorporated in Yba2Cu3O7-x/SrTiO3 Multilayers

1995 ◽  
Vol 401 ◽  
Author(s):  
L. Ryen ◽  
E. Olssoni ◽  
L. D. Madsen ◽  
C. N. L. Johnson ◽  
X. Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Lattice Mismatch ◽  
Single Layer ◽  
Transmission Electron ◽  
Tilt Boundaries ◽  
Interfacial Dislocations ◽  
The Individual ◽  
Film Substrate

AbstractEpitaxial single layer (001) SrTiO3 films and an epitaxial Yba2Cu3O7-x/SrTiO3 multilayer were dc and rf sputtered on (110)rhombohedral LaAIO3 substrates. The microstructure of the films was characterised using transmission electron microscopy. The single layer SrTiO3 films exhibited different columnar morphologies. The column boundaries were due to the lattice mismatch between film and substrate. The boundaries were associated with interfacial dislocations at the film/substrate interface, where the dislocations relaxed the strain in the a, b plane. The columns consisted of individual subgrains. These subgrains were misoriented with respect to each other, with different in-plane orientations and different tilts of the (001) planes. The subgrain boundaries were antiphase or tilt boundaries.The individual layers of the Yba2Cu3O7-x/SrTiO3 multilayer were relatively uniform. A distortion of the SrTiO3 unit cell of 0.9% in the ‘001’ direction and a Sr/Ti ratio of 0.62±0.04 was observed, both in correspondence with the single layer SrTiO3 films. Areas with different tilt of the (001)-planes were also present, within each individual SrTiO3 layer.

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