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Focused Ga + ion milling of lightly Si-doped, n-type Ga 2 O 3 was performed with 2–30 kV ions at normal incidence and beam currents that were a function of beam voltage, 65 nA for 30 kV, 26 nA for 10 kV, 13 nA for 5 kV, and 7.1 nA for 2 kV, to keep the milling depth constant at 100 nm. Approximate milling rates were 15, 6, 2.75, and 1.5 μm 3 /s for 30, 10, 5, and 2 kV, respectively. The electrical effects of the ion damage were characterized by Schottky barrier height and diode ideality factor on vertical rectifier structures comprising 10 μm epitaxial n-Ga 2 O 3 on n + Ga 2 O 3 substrates, while the structural damage was imaged by transmission electron microscopy. The reverse bias leakage was largely unaffected even by milling at 30 kV beam energy, while the forward current-voltage characteristics showed significant deterioration at 5 kV, with an increase in the ideality factor from 1.25 to 2.25. The I–V characteristics no longer showed rectification for the 30 kV condition. Subsequent annealing up to 400 °C produced substantial recovery of the I–V characteristics for all beam energies and was sufficient to restore the initial ideality factor completely for beam energies up to 5 kV. Even the 30 kV-exposed rectifiers showed a recovery of the ideality factor to 1.8. The surface morphology of the ion-milled Ga 2 O 3 was smooth even at 30 kV ion energy, with no evidence for preferential sputtering of the oxygen. The surface region was not amorphized by extended ion milling (35 min) at 5 kV with the samples held at 25 °C, as determined by electron diffraction patterns, and significant recovery of the lattice order was observed after annealing at 400 °C.
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This content will become publicly available on March 17, 2026
Quantifying Patterned Features on Material Surfaces Created using Ga Ion Beam in FIB-SEM
Abstract We introduced and applied a set of parameters to quantify surface modifications and pattern resolutions made by a Ga ion beam in a focused ion beam instrument using two material systems, Si and SrTiO3. A combination of top-view scanning electron microscopy and cross-sectional scanning transmission electron microscopy imaging and energy-dispersive X-ray spectroscopy was used to study the structure, composition and measure dimensions of the patterned lines. The total ion dose was identified as the key parameter governing the line characteristics, which can be controlled by the degree of overlap among adjacent spots, beam dwell time at each spot, and number of beam passes for given beam size and current. At higher ion doses (>1015 ions/cm2), the Ga ions remove part of the material in the exposed area creating “channels” surrounded with amorphized regions, whereas at lower ion doses only amorphization occurs, creating “ridges” on the wafer surface. To pattern lines with similar sizes, an order of magnitude different ion doses was required for Si and SrTiO3 indicating strong material dependence. Quantification revealed that lines as fine as 10 nm can be reproducibly patterned and characterized on the surfaces of materials.
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- PAR ID:
- 10589261
- Publisher / Repository:
- Oxford
- Date Published:
- Journal Name:
- Microscopy and Microanalysis
- Volume:
- 31
- Issue:
- 2
- ISSN:
- 1431-9276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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