AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS-TuP

Paper SS-TuP13
Surface Morphology of Ge(111) and Ge(001) Etched by keV Xe Ions

Tuesday, October 26, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: J.C. Kim, University of Illinois, Urbana-Champaign
Authors: J.C. Kim, University of Illinois, Urbana-Champaign
D.G. Cahill, University of Illinois, Urbana-Champaign
R.S. Averback, University of Illinois, Urbana-Champaign
Correspondent: Click to Email
In situ scanning tunneling microscopy (STM) was used to study the surface morphology and defects created by keV Xe@super +@ ion etching of Ge(111) and Ge(001). Starting surfaces were prepared by etching single crystal Ge wafers at ~ 510 @super o@C by 5 keV Xe@super +@ ions with ion flux of 2.7 x 10@super 13@ ions cm@super -2@s@super -1@ and fluence of 5 x 10@super 16@ ions cm@super -2@; the samples were subsequently cooled and etched at lower temperatures with various ion fluences and ion energies, and imaged at room temperature. Ge(111) and Ge(001) surfaces remain crystalline after being etched at T @>=@ 295 @super o@C. Crater-like surface features, which were not observed on the starting surfaces and will be called pits, were observed on both Ge(111) and Ge(001) surfaces etched at 295 @super o@C and 325 @super o@C. These pits are ~ 200 Å in diameter and are surrounded by closely spaced steps. Pits were observed on the Ge surfaces etched by Xe@super +@ ions with energies as low as 650 eV. Etching of a Ge(111) buffer layer, which was grown at ~ 365 @super o@C with the thickness of 1000 Å in an in situ MBE chamber, at 295 @super o@ was performed to examine the interaction of 5 keV Xe@super +@ ions with the surface prepared without etching at high temperature and revealed no pits. These results that pits were observed following 650 eV Xe@super +@ ion etching and not observed following etching of an MBE buffer layer suggest that these large surface features are not the result of the individual surface cascades as has been observed for 20 keV Ga ions. The pits initially grow in size and number and eventually disappear after the samples were etched for approximately one hour, leading to different surface roughening morphologies at 295 @super o@C and 325 @super o@C. Rutherford backscattering spectroscopy (RBS) data show that Xe atoms are implanted below the starting surface, subsequent ion etching at lower temperatures causes a broadening of Xe peak in RBS spectra. Our data suggest that interaction of bulk defects, e.g. Xe bubbles or vacancy clusters, with surface can have a strong influence on the evolution of surface morphology during ion etching at keV energies.