Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Ion Beam Synthesis of Nanoclusters and Nanowires by FIB

Bischoff, L.

During the last decades, the focused ion beam (FIB) became a very useful and versatile tool in microelectronics industry, as well as in the field of basic and applied research and derived an exceedingly importance with the development of the nano-technology. For special purposes like writing ion implantation for doping or ion beam synthesis (IBS) in the µm- as well as in the nm-range without any lithographic steps ion species other than gallium become more and more relevant. Therefore mass separated FIB systems equipped with alloy liquid metal ion sources (LMIS) play an increasing role.
A Co-FIB obtained from a Co36Nd64 alloy LMIS was applied for the IBS at elevated sample temperatures and subsequent annealing for the fabrication CoSi2 nano-structures down to 20 nm on Si(111) and Si(100) substrates. The combination of FIB implantation (top-down approach) and self organization processes during IBS (bottom-up approach) can provide a spatial reduction of the FIB implanted structures. A second investigated process is the defect induced formation of CoSi2 nanoparticles and nanowires using other ions than cobalt in the FIB, focused down to a spot diameter less than 30 nm at room temperature. The source for Co atoms for the NW growth was a 10 nm thin Co film evaporated onto the rear side of the wafer. The FIB irradiation of Nd, Ga, Si and Au ions and doses of 1015-1017 cm-2 creates a broad spectrum of defects in the substrate. Subsequent annealing leads amongst others to the formation of rod-like extended {311}-defects, which act as a prime source of transient enhanced diffusion of impurities in silicon. Also these defects can dissolve and form other rod-like defects always aligned to the (110) direction with a diameter of 10 – 20 nm and a length of some hundred nm. The heat treatment (1000°C, 30 min, N2) leads to a gettering of cobalt atoms in these defects followed by a CoSi2 formation through Ostwald ripening which stabilizes the origin of the defect rods. The obtained crystalline CoSi2 nanowires showed a diameter of 10 – 30 nm and a length up to some ten micrometer always aligned along the (110) orientations independent of the FIB writing direction with respect to the wafer orientation. These structures were studied by SEM/EDX and AFM analysis as well as by electrical characterization after contacting with W-pads, fabricated by FIB MO-CVD [1].
Furthermore, the high resolution mass separated Rossendorf FIB system, equipped with a CANION 31Mplus column (Orsay Physics) and a Ga liquid metal ion source (LMIS) as well as with different alloy LMIS (CoNd, AuSi, etc.) was used to fabricate other nanostructures.

[1] C. Akhmadaliev, B. Schmidt and L. Bischoff, Appl. Phys. Lett. 89 (2006) 223129

Keywords: Focused Ion Beam; nanostructures; nanowires; CoSi2

  • Lecture (others)
    Indian Association for the Cultivation of Science, 01.10.2007, Kolkatta, India

Publ.-Id: 10557