Anisotropic Behaviour of Surface Roughening in Lattice Mismatched Heteroepitaxial Thin Films

1996 ◽  
Vol 436 ◽  
Author(s):  
Cengiz S. Ozkan ◽  
William D. Nix ◽  
Huajian Gao
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Lattice Mismatch ◽  
Surface Roughening ◽  
Silicon Substrates ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Annealing Experiments

AbstractHeteroepitaxial Si1-xGex. thin films deposited on silicon substrates exhibit surface roughening via surface diffusion under the effect of a compressive stress which is caused by a lattice mismatch. In these films, surface roughening can take place in the form of ridges which can be aligned along <100> or <110> directions, depending on the film thickness. In this paper, we investigate this anisotropic dependence of surface roughening and present an analysis of it. We have studied the surface roughening behaviour of 18% Ge and 22% Ge thin films subjected to controlled annealing experiments. Transmission electron microscopy and atomic force microscopy have been used to study the morphology and microstructure of the surface ridges and the dislocations that form during annealing.

Studies of Morphological Instability and Dislocation Formation in Heteroepitaxial Si1−xGex Thin Films Via Controlled Annealing Experiments

1996 ◽  
Vol 440 ◽  
Author(s):  
Cengiz S. Ozkan ◽  
William D. Nix ◽  
Huajian Gao
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Defect Formation ◽  
Lattice Mismatch ◽  
Hydrogen Atmosphere ◽  
Surface Roughening ◽  
Silicon Substrates ◽  
Transmission Electron ◽  
Annealing Experiments

AbstractHeteroepitaxial Si1−x Gex thin films deposited on silicon substrates exhibit surface roughening via surface diffusion under the effect of a compressive stress which is caused by a lattice mismatch. In these films, surface roughening takes place in the form of ridges aligned along either <100> or <110> directions depending on the film thickness and composition. In this paper, we compare the relaxation behaviour of capped and uncapped heteroepitaxial Si1−xGex thin films containing 22% Ge, with surface roughening being inhibited in films with a capping layer. Films with 50 nm thickness were deposited on bare silicon substrates in a LPCVD reactor. Annealing experiments were conducted in a Hydrogen atmosphere in the reactor chamber. Transmission electron microscopy and atomic force microscopy have been used to study the surface morphology and microstructure of these films. XRD measurements were conducted to determine the amount of relaxation in these films. In-situ transmission electron microscopy/annealing experiments have been performed on uncapped Si1−x Gex/Si structures to study the dynamics of surface roughening and defect formation in a vacuum ambient. Finally, we compare surface morphologies and defects in samples subjected to annealing in vacuum and H2 ambients.

Phase separation in SiO2–TiO2 gel and glassy films studied by atomic force microscopy and transmission electron microscopy

2001 ◽  
Vol 16 (6) ◽  
pp. 1626-1631 ◽  
Author(s):  
A. Karthikeyan ◽  
Rui M. Almeida
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Phase Separation ◽  
Sol Gel ◽  
Force Microscopy ◽  
Pure Silica ◽  
Atomic Force ◽  
Transmission Electron

An investigation of phase separation phenomena in gel and glassy thin films of silica–titania, with TiO2 contents of 20 and 40 mol%, has been carried out by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The thin films were prepared by spin coating of a precursor sol on silicon wafers. Both the TEM measurements (carried out on scrapped thin film flakes) and the AFM measurements (carried out on films coated on the silicon substrates) for samples with different heat treatments suggest that spinodal-like structural inhomogeneities occur in these samples, unlike the corresponding observations in pure silica films, which are known to be homogeneous. Changes in the microstructure of the films have been noticed with the thermal treatment, in agreement with earlier x-ray photoemission studies. The finer characteristic dimensions of the phase separated regions reveal that silica–titania samples prepared by sol-gel processing exhibit a more intimate mixing of the phases.

Defect-Engineered Graded GexSi1-x Buffers on Si (001) with Extreme Low Threading Dislocation Density

1995 ◽  
Vol 378 ◽  
Author(s):  
G. Kissinger ◽  
T. Morgenstern ◽  
G. Morgenstern ◽  
H. B. Erzgräber ◽  
H. Richter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Threading Dislocation Density

AbstractStepwise equilibrated graded GexSii-x (x≤0.2) buffers with threading dislocation densities between 102 and 103 cm−2 on the whole area of 4 inch silicon wafers were grown and studied by transmission electron microscopy, defect etching, atomic force microscopy and photoluminescence spectroscopy.

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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