Abstract
Isolated pyramids, 30–80 nm wide and 3–20 nm tall, form during sputter-annealing cycles on the Ge (110) surface. Pyramids have four walls with {19 13 1} faceting and a steep mound at the apex. We used scanning tunneling microscopy (STM) under ultrahigh vacuum conditions to periodically image the surface at ion energies between 100 eV and 500 eV and incremental total flux. Pyramids are seen using Ar+ between 200 eV and 400 eV, and require Ag to be present on the sample or sample holder. We suspect that the pyramids are initiated by Ag co-sputtered onto the surface. Growth of pyramids is due to the gathering of step edges with (16 × 2) reconstruction around the pyramid base during layer-by-layer removal of the substrate, and conversion to {19 13 1} faceting. The absence of pyramids using Ar+ energies above 400 eV is likely due to surface damage that is insufficiently annealed.
Highlights
Surface features formed through ion bombardment depend on many parameters, including sputter ion type, fluence, flux, energy, and incident angle; sample type, orientation, and temperature; as well as sample cleanliness and the presence and type of contaminants and defects
The methods of formation reported in the literature are varied, including dot and ripple patterns [1], faceted ripples [2], pyramids [3], positive-growth whiskers and cones [4], vacancy accumulation of pits [5], and many patterns that rely on an interplay of roughening and smoothing during high-energy ion bombardment [1,6,7,8]
All sample preparation and measurements were performed in an ultrahigh vacuum system consisting of three principal chambers housing a low-energy electron microscope (LEEM, Elmitec Elektronenmikroskopie GmbH, Clausthal-Zellerfeld, Germany), an scanning tunneling microscopy (STM)
Summary
Surface features formed through ion bombardment depend on many parameters, including sputter ion type, fluence, flux, energy, and incident angle; sample type, orientation, and temperature; as well as sample cleanliness and the presence and type of contaminants and defects. The methods of formation reported in the literature are varied, including dot and ripple patterns [1], faceted ripples [2], pyramids [3], positive-growth whiskers and cones [4], vacancy accumulation of pits [5], and many patterns that rely on an interplay of roughening and smoothing during high-energy ion bombardment [1,6,7,8]. This paper discusses the formation of isolated pyramids with {19 13 1} faceted sides that form during sputter-annealing cleaning cycles performed on the Ge (110) surface.
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