A Scanning Tunneling Microscopy Study of Mbe-Grown GAAS(001)-Faceted Surfaces

1992 ◽  
Vol 283 ◽  
Author(s):  
R. Maboudian ◽  
V. Bressler-Hill ◽  
X.-S. Wang ◽  
K. Pond ◽  
P. M. Petroff ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Molecular Beam ◽  
Microscopy Study ◽  
High Energy ◽  
Scanning Tunneling ◽  
Rheed Pattern ◽  
Tunneling Microscopy ◽  
Local Ordering ◽  
The Difference ◽  
Stm Images

ABSTRACTScanning tunneling microscopy (STM) and reflection high-energy diffraction (RHEED) have been employed to investigate the morphology of faceted GaAs(001) surfaces grown by molecular beam epitaxy (MBE). The RHEED pattern monitored during the growth indicates that the faceting corresponds to (711)A planes. The STM images obtained on these surfaces reveal predominantly a (2×4) local ordering, although unusual (2×3) and (2×6) structures have also been observed. The atom-resolved imaging of the (2×4) structure indicates that the unit cell consists of two As dimers and two missing dimers, identical to the structure obtained on the flat As-rich GaAs(001)-(2×4) surface. Furthermore, islands on the surface are found to be anisotropie, with a shape anisotropy of about 4:1 for step A to step B. The anisotropy is explained in terms of the difference in step edge reactivity.

Self-Assembled InAs Islands on (AI,Ga)As, an In Situ Scanning Tunneling Microscopy Study

1999 ◽  
Vol 571 ◽  
Author(s):  
P. Ballet ◽  
J.B. Smathers ◽  
G.J. Salamo
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Molecular Beam ◽  
Three Dimensional ◽  
Microscopy Study ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Self Organized ◽  
Scanning Tunneling Microscopy Study ◽  
Island Density

ABSTRACTWe report an in-situ molecular beam epitaxy – scanning tunneling microscopy study of three dimensional (3D) self organized InAs islands on (AI,Ga)As surfaces. The influence of the presence of Al atoms on the roughness of the starting surface and on the island density is shown by investigating several Al compositions. We emphasize the case of InAs/AlAs and point out the major differences between this system and the widely studied InAs/GaAs system.

Growth of Laser Ablated YBa2Cu3O7−δ Films as Examined by Rheed and Scanning Tunneling Microscopy

1992 ◽  
Vol 285 ◽  
Author(s):  
Stephen E. Russek ◽  
Alexana Roshko ◽  
Steven C. Sanders ◽  
David A. Rudman ◽  
J. W. Ekin ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Scanning Tunneling Microscopy ◽  
Three Dimensional ◽  
High Energy ◽  
Spiral Growth ◽  
Scanning Tunneling ◽  
Initial Growth ◽  
Rheed Pattern ◽  
Island Growth ◽  
Tunneling Microscopy

ABSTRACTUsing scanning tunneling microscopy (STM) and reflection high energy electron diffraction (RHEED) we have examined the growth morphology, surface structure, and surface degradation of laser ablated YBa2Cu3O7−δ thin films. Films from 5 nm to ltm thick were studied. The films were deposited on MgO and LaAlO3 substrates using two different excimer laser ablation systems. Both island nucleated and spiral growth morphologies were observed depending on the substrate material and deposition rate used. The initial growth mechanism observed for a 5–10 nm thick film is replicated through different growth layers up to thicknesses of 200 run. Beyond 200 rnm, the films show some a-axis grains and other outgrowths. The thinnest films (5–10 nm) show considerable surface roughness on the order of 3–4 nm. For both growth mechanisms the ledge width remains approximately constant (∼ 30 nm) and the surface roughness increases as the film thickness increases. The films with spiral growth have streaked RHEED patterns despite having considerable surface roughness, while the films with island growth have more of a three dimensional diffraction pattern. RHEED patterns were obtained after the film surfaces were degraded by exposure to air, KOH developer, a Br-methanol etch, and a shallow ion mill. Exposure to air and KOH developer caused only moderate degradation of the RHEED pattern whereas a shallow (I nm deep) 300 V ion mill completely destroyed the RHEED pattern.

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