CHARPAN

Charged Particle Nanotech

Project

Emerging applications

In one of the first papers on CHARPAN prepared for the SMMIB 2005, the 14th International Conference on Surface Modification of Materials by Ion Beams, W. Bruenger, A. Dietzel and H. Loeschner already introduced the basic application groups^[14]:

Using the different penetration depths of ions from a plasma source, fabrication of 3D-structures in resist, like free standing grids or T-gate structures, is possible. The ion induced intermixing of magnetic multilayers has been investigated for the creation of nano dots for data storage. The intermixing efficiency is greatly increased by using heavy ions (Ar+, Xe+). The creation of ion induced nucleation centers on p-Si allows for subsequent selective electroplating of nano structures. These nucleation centers can also start metal deposition on non-conducting surfaces (glass, polymers) by electrode less deposition in super saturated metal salt solutions.

Nano/micromechanical structures, so called cantilevers, operated in static or dynamic (resonant) mode are potentially extremely versatile sensors. As a mass sensor they offer outstanding performance to measure ultra-small amounts of mass deposited on them (in the femto-gram range). J. Arcamone and his colleagues at the Instituto di Microelectronica de Barcelona not only developed a new mass sensing device based on a polysilicon double cantilever^[15], they also described the use of FIB based processes for the definition and functionalisation of nano-mechanical devices monolithically integrated into CMOS circuits^[16].

Karade, Brünger and other partners in the CHARPAN project presented a technique to fabricate polymer substrates with locally structured surfaces in the nanometer scale[17]. They used ion projection to directly modify the surface of the polymer film. By ion projection the surface of a stretched polymer is locally cross-linked and afterwards annealed above the glass transition temperature to induce surface rippling. The rippling periodicity depends on the thickness of the cross-linked surface layer, formed through hydrogen vacancies, which are generated by the ion bombardment. The number of vacancies can be controlled by the ion type, the ion current and the ion energy used. Defined structures with a ripple periodicity of 250 nm were fabricated. Thus, ion projection direct cross-linking (IPDC) offers the possibilities to generate bas-relief patterns down to the nanometer scale. The images show Polystyrene irradiated with (a) Xe+ and (b) Ar+.

Quite another application is investigated by Dan Nicolau at University of Liverpool and Monash University, Australia. Various experiments have been made to study the behaviour of bio-nano-devices on patterned surfaces ([18]and[19]). Hydrophobicity and hydrophilicity of the surface seem to play an important role for the behaviour of bacteria on structured surfaces.

The AFM images show bacterium E. coli attached to untreated hydrophobic PDMS. a) where the bacteria form extracellular polymeric substances (EPS) on UV-light treated hydrophilic PDMS surfaces, b) where E. coli cells appear in small aggregates or singular and without the formation of EPS, c) E. coli on a square structured surface, the area 1: 3 mm [UoL, MUAUS]

A group of researchers from the TECHNION (Israel) is working on an alternative ion source based on C60 fullerenes. The image shows an experimental set-up for a CNT-FET exposure experiment. The bombardment with C60 fullerene ions is at normal incidence for maximum effect. Performance of the nano-device will be measured on-line as a function of exposure conditions (impact energy, current density, total dose) [TECHNION, CSIC-CNM]

^[14] Bruenger, W.H.: "Ion Projection Surface Structuring with Noble Gas Ions at 75 keV", Surface Coatings International, Vol. 201, 19-20, 8437-8441, (2007)
^[15] Arcamone, J. et al.: "Mass measurements based on nanomechanical devices: differential measurements", ICN+T 2007, 2-6 Jul 2007
^[16] Borrisé, X. et al.: "Focused ion beam fabrication and functionalization of CMOS integrated silicon nanocantilevers", MNE 2007, 23-26 Sep 2007
^[17] Karade, Y. et al.: "Oriented nanometer surface morphologies by thermal relaxation of locally cross linked and stretched polymer samples" Microelectronic Engineering 84, 797-801 (2007)
^[18] Bakewell, D.J.G. and Nicolau, D.V: "Protein Linear Molecular Motor-Powered Nanodevices" Australian Journal of Chemistry. 60, 314-332, 2007
^[19] Nicolau, D.V.: "Surface Hydrophobicity Modulates the Operation of Actomyosin-Based Dynamic Nanodevices" Langmuir, 23, 10846-10854, 2007