Room temperature deposition of self-assembled Al nanoclusters on stepped sapphire (0001) surface and subsequent nitridation

B. Qi*, B. Agnarsson, S. Ólafsson, H. P. Gíslason, M. Göthelid

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Self-assembled growth and nitridation of ultrathin Al nanoclusters on a stepped sapphire (0001) surface were studied by high-resolution X-ray photoemission spectroscopy, atomic force microscopy and low-energy electron diffraction (LEED). Upon room temperature deposition, in the coverage range of ∼ 0.79 to 2.3 monolayer (ML), Al nanoclusters were uniformly nucleated over the entire surface of defect-free atomically smooth terraces as well as step edges. Subsequent nitridation at elevated temperatures by ammonia did not alter the morphology of the nanoclusters. The global morphology of the stepped sapphire (0001) surface such as terrace width, step height and facet orientation had no obvious influence on the nucleation morphology of the nanoclusters in the given Al coverage range. However, local structural defects at the joints of short facets and step edges played a noticeable role on the local morphology of the nanoclusters and subsequently the nitridation chemistry. The Al nanoclusters were uniformly nitridated from surface and downwards through the 3D structures. The LEED pattern indicated a certain degree of crystallinity on the nitridated surface at a nominal Al coverage less than 2 ML, whereas at 2.3 ML Al coverage, the nitridated surface became amorphous. Thus there is a critical coverage for good surface order.

Original languageEnglish
Pages (from-to)64-73
Number of pages10
JournalThin Solid Films
Issue number1
Publication statusPublished - 31 Oct 2011

Bibliographical note

Funding Information:
The work was financially supported by the Icelandic Research Fund . The authors are also grateful to the technical support and valuable instructions from Dr A. Preobrajenski at Max-lab and the financial support of European LIght Sources Activities (ELIS) operated at Max-lab.

Other keywords

  • Aluminum
  • Atomic force microscopy
  • Atomic steps
  • c-plane sapphire
  • Nanoclusters
  • Nitridation
  • X-ray photoemission spectroscopy


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