Morphological evolution of the fivefold surface ofi−AlPdMnquasicrystals

Abstract

Morphology of the fivefold symmetric quasicrystal surface of AlPdMn was investigated by x-ray reflectivity and by x-ray diffraction. X-ray experiments revealed two different morphologies depending on the surface preparation. Sputtering and annealing up to 900 K, under UHV conditions, produced a rough and facetted quasicrystal surface. These features were confirmed by atomic force microscopy and scanning tunnel microscopy measurements. We also observed that an annealing above 900 K induces a rapid and irreversible transition toward a flat surface.

SEM and AFM studies of a 5-fold surface of icosahedral AlPdMn

“…The AFM observations in the present work reveal clearly the cluster nature of the i-AlPdMn QC. However, the size of the clusters observed in this work is different from that reported by others [7,8,10]. For example, Cappello et al [8], observed terraces of about 10 nm in height constructed from the packing of small spheres of about 10 nm in radius.…”

“…In view of the fact that the oxide layer on the surface of the i-AlPdMn QC surface is typically less than 2 nm thick see Ref. [8]. we assume that it will not affect the surface morphology observed by either SEM or AFM.…”

“…The evolution of the composition and structure of the cleaved and subsequently heat-treated i-AlPdMn QC surfaces has been studied by Ebert et al [9,11] using scanning electron microscopy (SEM), STM and Auger electron spectroscopy (AES). Cappello et al [8] on the other hand, studied the morphological evolution of the 5-fold surface of i-AlPdMn QCs prepared by sputtering and annealing using AFM and STM [8]. During AFM and SEM observation, the sample can be investigated at large scale and any part of the surface can be probed at will, which is not always the case in STM measurements.…”

“…Second, how does the surface structure relate to the unusual properties such as low coefficient of friction and low surface energy? In the past, many techniques such as low energy electron diffraction (LEED) [1,2,4], secondary-electron imaging (SEI) [5], scanning tunneling microscopy (STM) [3,6,7] and atomic force microscopy (AFM) [8] have been employed to tackle the first problem in various ways. The studies were mostly focused on the 5-fold surface of i-AlPdMn.…”

Terrace selection during equilibration at an icosahedral quasicrystal surface

“…This array of surface morphologies includes rough surfaces, 4-9 faceted voids, 10 and smooth ͑to within a few tenths of an angstrom͒ terraces. 6,8,9,[11][12][13][14][15][16] The latter type of structure-flat terraces-is the topic of this paper.…”