Ion induced nanopatterns on semiconductors: formation and application


Ion induced nanopatterns on semiconductors: formation and application

Keller, A.; Roßbach, S.; Facsko, S.; Möller, W.

It is well known that under certain conditions, low and medium energy (typically 0.1 – 100 keV) ion sputtering can induce the formation of self-organized patterns on the irradiated surface [1]. Periodic ripple patterns and hexagonally ordered dot arrays form for oblique and normal ion incidence, respectively. The periodicity of the patterns depends on the sputtering conditions and ranges from some ten nanometres up to several microns. These structures were found on a large variety of materials, such as semiconductors, metals, and insulating surfaces [2]. The first attempt to describe the formation process was made by Bradley and Harper and led to a continuum model based on sputter theory [3].
In this framework, the patterns result from the interplay between curvature dependent sputter yield and diffusion.
To investigate the process of pattern formation, semiconductor surfaces are eroded by sub-keV Ar ions. The topography of the sputtered surfaces is studied by ex-situ atomic force microscopy (AFM).
Off-normal ion erosion of Si creates ripple patterns with a wavelength ranging from 20 nm to 60 nm and amplitude of approximately 2 nm. By means of normal incidence bombardment, well ordered dot arrays are fabricated on GaSb. These arrays exhibit hexagonal symmetry and a periodicity of the order of 40 nm. The amplitude is of the same magnitude as the periodicity. The formation process will be discussed in detail and recent results of our studies on pattern evolution and the influence of boundary conditions are presented.
As a promising application, erosion induced surface patterns can be used as templates in further processes such as molecular beam epitaxy or sputter deposition. The morphological anisotropy of the surface can influence the process significantly. Recent findings of investigations on ripple induced anisotropies in metallic thin films are presented.

[1]M. Navez, D. Chaperot and C. Sella, C. R. Acad. Sci. 254, 240 (1962)
[2]U. Valbusa, C. Boragno and F. Buatier de Mongeot, J. Phys.: Condens. Matter 14, 8153 (2002)
[3]R. Bradley and J. Harper, J. Vac. Sci. Technol. A 6, 2390 (1988)

  • Lecture (Conference)
    16th International Workshop on Inelastic Ion-Surface Collisions, 17.-22.09.2006, Hernstein, Österreich

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