scholarly journals Surface Roughening, Columnar Growth and Intrinsic Stress Formation in Amorphous CuTi Films

1996 ◽  
Vol 441 ◽  
Author(s):  
U. v. Hulsen ◽  
P. Thiyagarajan ◽  
U. Geyer
Keyword(s):  
Electron Beam Evaporation ◽  
Intrinsic Stress ◽  
Scanning Tunneling ◽  
Surface Roughening ◽  
Growth Stages ◽  
Tunneling Microscopy ◽  
Columnar Growth ◽  
Compressive Stresses ◽  
Stress Formation

AbstractThe growth of amorphous CuTi films, prepared by electron beam evaporation, is investigated by Scanning Tunneling Microscopy (STM), Small Angle Neutron Scattering (SANS) and in situ measurements of intrinsic mechanical stresses (ISM). In early growth stages the films develop compressive stresses and, with increasing film thickness, a crossover to tensile stresses. In the same thickness range the STM investigations show a change in the growth mode. Our experiments suggest a transition from planar growth with statistical surface roughening to columnar growth.

The Growth of Amorphous CuxTi1-x Films: Relationship Between Intrinsic Stresses and Microstructure Observed by STM

1994 ◽  
Vol 356 ◽  
Author(s):  
U. Von Hülsen ◽  
U. Geyer ◽  
S. Dina ◽  
G. von Minnigerode
Keyword(s):  
Surface Topography ◽  
Film Growth ◽  
Critical Value ◽  
Metal Films ◽  
Scanning Tunneling ◽  
Growth Stages ◽  
Tunneling Microscopy ◽  
Tensile Stresses ◽  
Compressive Stresses ◽  
Ti Films

AbstractThe evolution of the surface topography of thin amorphous Cu-Ti films during the film growth is investigated by scanning tunneling microscopy. The films begin to grow with smooth surfaces until the film thickness reaches a critical value. Then, within a small thickness interval, a grainy microstructure of the film develops which looks very similar to the microstructure of polycrystalline films. Measurements of the intrinsic macroscopic stress in these films during the film growth show compressive stresses in the early growth stages. Then a change to tensile stresses accompanies the change in the surface topography within the same thickness interval. Both, the surface topography and the intrinsic stresses, are always correlated and depend on the deposition temperature and on the film composition. We discuss implications of these observations on the origin of macroscopic intrinsic tensile stresses in amorphous transition metal films.

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.

Stm Studies at Electrochemically Controlled Interfaces

1994 ◽  
Vol 332 ◽  
Author(s):  
S.M. Lindsay ◽  
J. Pan ◽  
T.W. Jing
Keyword(s):  
Electron Tunneling ◽  
Point Contact ◽  
Localized States ◽  
Scanning Tunneling ◽  
Zero Field ◽  
Tunneling Microscopy ◽  
Dna Oligomers ◽  
Synthetic Dna ◽  
Quantum Point

ABSTRACTWe use electrochemical methods to control the adsorption of molecules onto an electrode for imaging in-situ by scanning tunneling microscopy. Measurements of the barrier for electron tunneling show that the mechanism of electron transfer differs from vacuum tunneling. Barriers depend upon the direction of electron tunneling, indicating the presence of permanently aligned dipoles in the tunnel gap. We attribute a sharp dip in the barrier near zero field to induced polarization. We propose a ‘tunneling’ process consisting of two parts: One is delocalization of quantum-coherent states in parts of the molecular adlayer that hybridize strongly (interaction ≥ kT) with Bloch states in the metal. This gives rise to a quantum-point-contact conductance, Gc ≤ 2e2/h at a height zo. The other part comes from the exponential decay of the tails of localized states, G = Gc exp{−2K(z − z0)}. Because measured decay lengths, (2K‘)−1, are small (≈ 1 Å), STM contrast is dominated by the contour along which G[z0 (x,y)] = Gc. Measured changes in z0 are used to calculate images which are in reasonable agreement with observations. We illustrate this with images of synthetic DNA oligomers.

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