Structuring magnetic and electronic materials using GFIS noble gas focused beams


Structuring magnetic and electronic materials using GFIS noble gas focused beams

Hlawacek, G.

New device concepts envisioned to solve some of the pressing problems in todays computing technology require new methodological approaches—both for manufacturing but also during initial research. In this presentation I want to highlight the potential and limitations of ion beams and in particular gas field ion sources based (GFIS) noble gas beams for this demanding development process.
In an first example I want to present results of low fluence ion beam structuring of alloys with interesting magnetic properties such as FeAl. This material undergoes a phase transition upon ion irradiation that converts the initially paramagnetic material into a ferromagnetic one. Using the highly localized irradiation possible in the helium ion microscope and low fluencies of only 1-5 Ne + per nm 2 we can locally change the properties and this create arbitrary shaped nano magnets. The fundamental properties of these electron spin controlling structures with critical dimensions as small as 20 nm can be studied by TEM holography or scanning transmission x-ray microscopy.
Other device concepts require the control of currents at the single electron level. In the second part of the talk I will present first results of the realization of a CMOS compatible single electron transistor (SET) that works at room temperature (RT). We employ a focused GFIS Ne beam to locally mix silicon into a thin silicon dioxide layer. During a subsequent thermal treatment a single silicon cluster with a diameter of only 2-3 nm forms in the oxide. The cluster is separated from the surrounding silicon by only 2 nm providing optimum tunnel distances for RT SET operation. This process is based on the small size of collision cascade in the HIM. A more CMOS compatible restriction of the mixed volume can be achieved by using broad beam irradiation and nano pillars. The first is a well established technique in semiconductor fabrication and latter can be mass fabricated using advanced lithography. In the so achieved restricted mixed volume a single cluster forms during the subsequent annealing.
Both examples highlight the flexibility of the GFIS technique and its potential for the rapid prototyping of new device concepts based on ion beam techniques.
This work has been partially funded by the European Unions Horizon 2020 Research and Innovation Program under grant agreement No. 688072 IONS4SET.

Keywords: HIM

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