Orion nanofab he ne ion microscope

Helium ion exposures were performed with a Zeiss ORION NanoFab He/Ne ion microscope. An accelerating voltage of 25 keV was used for all exposures. Beam currents were varied from 0.3–6.0 pA in order to enable a large range of exposure doses (1 × 10¹²–1 × 10¹⁷ion/cm²). All patterns in this study were exposed with a constant 1 μs dwell time, whereas the pixel spacing was varied with the desired dose. For low dose exposures (<1 × 10¹⁴ions/cm²), larger pixel spacing (4–40 nm) with beam defocus was utilized to supply a uniform dose to the pattering area. For higher doses (>1 × 10¹⁴ion/cm²), a pixel spacing of 2 nm was used. Patterns were generated using Fibics NPVE pattern generating software and hardware scan controller.

Scanning helium ion microscopy and lithography on single layer graphene was performed using a Zeiss ORION Nanofab He/Ne ion microscope, operating at an accelerating voltage of 30 kV and a beam current of 4.2 pA. All the graphene devices were fabricated using the ion microscope’s built-in patterning software and imported bitmaps. Each milled area was exposed to the He⁺/Ne⁺ beam at a field of view and pixel spacing that yielded a fluence of ~1 × 10¹⁹ ions/cm² for He⁺ beam and ~5 × 10¹⁷ ions/cm² for the Ne⁺ beam. Subsequent high-resolution images were acquired at the same field of view using a 50 μs dwell time.
Scanning electron microscopy secondary electron images of the exact same graphene devices were obtained using a Zeiss MERLIN VP SEM equipped with an in-lens detector operating at 3 kV.