AVS 62nd International Symposium & Exhibition
    Helium Ion Microscopy Focus Topic Wednesday Sessions
       Session HI-WeA

Paper HI-WeA7
Fabrication of Nanoscale Electronics with a Focused Helium Ion Beam

Wednesday, October 21, 2015, 4:20 pm, Room 210F

Session: GFIS Based Nanostructuring
Presenter: Ethan Cho, University of California, San Diego
Authors: E.Y. Cho, University of California, San Diego
M. Ma, Univeristy of California, San Diego
C. Huynh, Carl Zeiss Microscopy, LLC
R.C. Dynes, Univeristy of California, San Diego
S.A. Cybart, Univeristy of California, San Diego
Correspondent: Click to Email
Since the invention of gas field ion source focused ion beams, researchers have had access to ion sources from inert gases. In particular, the focused helium ion beam (FHB) has a sub-nanometer beam spot that allows the direct patterning of nanometer scale devices without contamination. However, preparing samples with direct patterning is time consuming, especially when milling away large volumes of material. Here we demonstrate patterning a wide range of materials through disordering the crystal structure that only requires a dose orders of magnitude less than the milling dose. Patterning graphene has been difficult due to edge formation in the reactive ion etching step. Using a lower dose to perturb and disorder the carbon atoms would locally change the characteristics of graphene without destroying the integrity of the film. For materials that are hard to grow as a multilayer such as the iron based superconductor FeAs, the properties of conventional stacked Josephson junctions are limited by the film quality. With a FHB we can induce disorder in a very narrow region that suppresses the critical temperature (TC) within this region to serve as the junction barrier. By removing the multilayer-processing the fabrication steps of these in-plane junctions are greatly simplified, and higher quality junctions are produced. Using disorder to create a lower Tc barrier also works for more metallic superconductors like MgB2. For materials that undergo a superconductor-insulator transition, as for example cuprates, we demonstrate insulating in-plane tunnel junctions and nano wires. This technique also works for magnetic manganites that are sensitive to disorder. These materials have interesting characteristics at the interface between a multiferroic and magnetic material. Extensive care during the processing phase is required to preserve the interfacial properties. We demonstrate that the interface remains intact after a junction is fabricated with FHB. Most of the materials described above are extremely sensitive to processing, but by only locally altering the properties we eliminate interfacial problems and degradation due to heat generated in removing the material. Direct patterning using disorder induced from the FHB pushes the feature size truly to the nano meter scale, simplifies the fabrication both in time and number of steps, and preserves material integrity throughout the process. This FHB has the potential to be a general technology, and therefore allows us to engineer and study the fundamental physics of a variety of phenomena.