Influence of the substrate temperature and deposition flux in the growth of a Bi thin film on the ten-fold decagonal Al-Ni-Co surface

Abstract

We compare the growth of a Bi thin film on the ten-fold surface of the decagonal Al-Ni-Co quasicrystal at different substrate temperatures and fluxes using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The growth at 29 K leads to the formation of a quasicrystalline monolayer, consistent with the results obtained at 300 K. Further deposition at low temperature produces pseudocubic islands with {100} surface orientation. The islands have two or four atomic layer heights. Both STM and LEED measurements reveal that there is a transition from the pseudocubic {100} film to the hexagonal {0001} surface orientation at coverage () 4 5 5 6 ML. The hexagonal domains are oriented along the high symmetry directions of the substrate. Growth at room temperature with different fluxes results in different island-height distributions. High flux predominantly produces islands of uniform fourlayer high islands, whereas low flux yields islands of varying heights, yielding a rough film morphology. The two-layer high islands are found to be more stable at low temperature than at room temperature.

Thin Film Growth on Quasicrystalline Surfaces

“…LEED indicates that the islands are randomly aligned with respect to the surface plane. Above a critical coverage, the pseudo‐cubic {100} islands transform into the hexagonal {0001} surface orientation,54, 56 which is the natural cleavage plane of bulk Bi 57. In contrast to randomly oriented pseudo‐cubic islands, the hexagonal islands are aligned along the five high symmetry directions of the substrate 54.…”

“…In contrast to randomly oriented pseudo‐cubic islands, the hexagonal islands are aligned along the five high symmetry directions of the substrate 54. 56 Higher deposition flux results in higher island density and produces pseudo‐cubic islands with shared domain boundaries, which prevent transformation to the hexagonal structure 54…”

“…The distribution of the island heights on d ‐Al‐Ni‐Co depends on growth temperature and deposition flux. High flux or low substrate temperature yields islands of uniform height of 4 L on d ‐Al‐Ni‐Co 56…”

The memory of surfaces: epitaxial growth on quasi-crystals

“…A recent quantitative analysis by X-ray photoemission spectroscopy (XPS) of Bi/i-Al-Pd-Mn has confirmed the growth and the stability of the islands [34]. The Bi islands exhibit specific heights (the so-called 'magic heights'), which correspond to the stacking of four atomic layers (4L) or multiples of this height [24,30,32,33,36] (figure 5a). Here, coverage is quoted in units of monolayer equivalent (MLE), where the calibration is fixed by the deposition of the first ML.…”

“…High flux or low substrate temperature yield islands of uniform height of 4L [36]. The observation of the magic heights is believed to be due to quantum size effects [24].…”