Generation of ultrasmall nanostructures in oxide layers assisted by self-organization

Abstract

We explored the structural limits of unconventional electron-beam lithography by directly writing with an electron beam into ultrathin SiO2 films. The obtained structures were analyzed by tunneling microscopy. The Auger excitation process (Knotek–Feibelman mechanism) necessary for electron-stimulated oxygen desorption allows generation of ultrasmall structures. The subsequent processing step combines thermal desorption of the remaining monoxide and simultaneous etching promoted by thermally activated silicon atoms, which turns out to be a strongly anisotropic process close to step edges. Applying this combination of processes to a regularly stepped Si(557) sample, linewidths close to the resolution of the electron microscope of 5 nm were obtained.

Generation of clean iron nanocrystals on an ultra-thin SiOx film on Si(001)

“…25 The ''activated'' sites have been suggested to be oxygen vacancies generated by electroninduced desorption of oxygen via the Knotek-Feibelman mechanism, 20,21 as has been proposed by Pfnu¨r et al for ultra-thin SiO x films. 22,23 As mentioned above a main drawback of scanning probe based lithographic methods is their low speed due to sequential processing. To overcome this disadvantage, in particular when using focused electron and ion beams, multiple beam systems (see e.g., ref.…”

Electrons as “Invisible Ink”: Fabrication of Nanostructures by Local Electron Beam Induced Activation of SiOx

“…The "activated" sites are attributed to oxygen vacancies generated by electron-induced desorption of oxygen by a Knotek-Feibelman mechanism, [18,19] as has been suggested by Pfnür et al for ultrathin SiO x films. [20] In their studies, the generation of nanostructures was achieved by electron beam assisted selective thermal desorption (EBSTD) lithography, a method introduced by Watanabe and co-workers. [21] The first processing step in EBSTD, namely, the irradiation of an ultrathin SiO x film on a Si substrate with a focused electron beam, is interpreted as a local reduction of SiO 2 to SiO.…”

Correlation of geometrical and electronic properties in metallic nanowires

“…Mobility and concentration gradient can be effectively reduced by a gradual reduction of Ti film thickness. Thus during reaction saturated silicide clusters are formed quickly in the very thin parts close to bare Si, which reduce Si mobility and stop further reaction, and the surface remains flat outside the cluster area with no significant enhancement of the step density [24]. The W wire used here as shadow mask automatically produces this gradual change of Ti film thickness during evaporation in its penumbras formed at the edges of the wire by the extension of the Pb source.…”

“…Writing into an oxide with a wide band gap has the advantage that for the necessary partial reduction of the oxide most secondary electrons are ineffective [22,23]. Thus the effective minimal linewidth can be reduced to almost the width of the primary beam of 4 nm exploiting the combination of electron beam-assisted thermal desorption, reaction of Si at kinks, and steps at elevated temperatures (EBSTD) and the highly anisotropic diffusion along step edges on a regularly stepped surface such as Si(557) [24]. The formation of such a wire-like structure of bare Si in SiO 2 is shown in Fig.…”