Direct writing of ferromagnetic materials by focused electron beam: a novel nanofabrication access to 3-dimensional nanomagnet logic

Abstract

Nanomagnet logic (NML) is a relatively new paradigm of computational technology, using single domain (SD) magnetic nanostructures encoding and processing the Boolean digital information. NML allows not only reducing the power consumption in logic devices compared to conventional CMOS technology, but also eliminates the stand-by power dissipation. This thesis work, for the first time, proposes the mask-less, resist-less and direct-write fabrication of nanomagnets by focused electron beam induced deposition (FEBID). In FEBID a precursor is injected in proximity of the impinging area of a focused electron beam, which is promoting the deposition of the desired material. Initially, a parameter variation study using Fe(CO)5 and Co2(CO)8 as precursor substances was executed. Such a study revealed that the use of Fe(CO)5 leads to both a high metal content and the best control over the deposit-s structure. Consequently, magnetic properties of shape engineered Fe based nanostructures were successfully investigated by magnetic force microscopy (MFM) with the aim to obtain SD nanostructures suitable as key elements for NML. The Fe nanowires obtained herein by FEBID were then used for the fabrication of advanced 2 dimensional NML arrays having specific digital logic functions, such as line processing, fan-out and NAND/NOR. In addition, since FEBID permits the deposition of vertical nanostructures, arrays of out-of-plane nanopillars and in-plane nanowires were successfully fabricated for 3 dimensional NML circuitry. Such novel approach, besides enabling an increase in packing density, provides an additional magnetic degree of freedom, which could serve, for example, to separate digital processing from input/output functionality.