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

Published online by Cambridge University Press:  01 January 1992

Stephen E. Russek ,
Alexana Roshko ,
Steven C. Sanders ,
David A. Rudman ,
J. W. Ekin  and
John Moreland
Stephen E. Russek
Affiliation:
Electromagnetic Technology Division, National Institute of Standards and Technology, Boulder, Colorado, 80303
Alexana Roshko
Affiliation:
Electromagnetic Technology Division, National Institute of Standards and Technology, Boulder, Colorado, 80303
Steven C. Sanders
Affiliation:
Electromagnetic Technology Division, National Institute of Standards and Technology, Boulder, Colorado, 80303
David A. Rudman
Affiliation:
Electromagnetic Technology Division, National Institute of Standards and Technology, Boulder, Colorado, 80303
J. W. Ekin
Affiliation:
Electromagnetic Technology Division, National Institute of Standards and Technology, Boulder, Colorado, 80303
John Moreland
Affiliation:
Electromagnetic Technology Division, National Institute of Standards and Technology, Boulder, Colorado, 80303
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Abstract

Using 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.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 285: Symposium I – Laser Ablation in Materials Processing–Fundamentals and Applications , 1992 , 305
Copyright
Copyright © Materials Research Society 1993

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References

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