An official website of the United States government
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.
more »
« less
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.
more »
« less
- 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
More Like this
-
-
This research reports the development of 3D carbon nanostructures that can provide unique capabilities for manufacturing carbon nanotube (CNT) electronic components, electrochemical probes, biosensors, and tissue scaffolds. The shaped CNT arrays were grown on patterned catalytic substrate by chemical vapor deposition (CVD) method. The new fabrication process for catalyst patterning based on combination of nanoimprint lithography (NIL), magnetron sputtering, and reactive etching techniques was studied. The optimal process parameters for each technique were evaluated. The catalyst was made by deposition of Fe and Co nanoparticles over an alumina support layer on a Si/SiO2 substrate. The metal particles were deposited using direct current (DC) magnetron sputtering technique, with a particle ranging from 6 nm to 12 nm and density from 70 to 1000 particles/micron. The Alumina layer was deposited by radio frequency (RF) and reactive pulsed DC sputtering, and the effect of sputtering parameters on surface roughness was studied. The pattern was developed by thermal NIL using Si master-molds with PMMA and NRX1025 polymers as thermal resists. Catalyst patterns of lines, dots, and holes ranging from 70 nm to 500 nm were produced and characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Vertically aligned CNTs were successfully grown on patterned catalyst and their quality was evaluated by SEM and micro-Raman. The results confirm that the new fabrication process has the ability to control the size and shape of CNT arrays with superior quality.more » « less
-
We report the growth and optical characterization of single-crystal BiFe1−xMnxO3 thin films directly on SrTiO3/Si(001) substrates using molecular beam epitaxy. X-ray diffraction confirmed epitaxial growth, film crystallinity, and sharp interface quality. Scanning electron microscopy and energy dispersive X-ray spectroscopy verified uniform film morphology and successful Mn incorporation. Spectroscopic ellipsometry revealed a systematic bandgap reduction with increasing Mn concentration, from 2.7 eV in BiFeO3 to 2.58 eV in BiFe0.74Mn0.26O3, consistent with previous reports on Mn-doped BiFeO3. These findings highlight the potential of BiFe1₋xMnxO3 films for bandgap engineering, advancing their integration into silicon-compatible multifunctional optoelectronic and photovoltaic applications.more » « less
-
Abstract Controlled fabrication of nanopores in 2D materials offer the means to create robust membranes needed for ion transport and nanofiltration. Techniques for creating nanopores have relied upon either plasma etching or direct irradiation; however, aberration‐corrected scanning transmission electron microscopy (STEM) offers the advantage of combining a sub‐Å sized electron beam for atomic manipulation along with atomic resolution imaging. Here, a method for automated nanopore fabrication is utilized with real‐time atomic visualization to enhance the mechanistic understanding of beam‐induced transformations. Additionally, an electron beam simulation technique, Electron‐Beam Simulator (E‐BeamSim) is developed to observe the atomic movements and interactions resulting from electron beam irradiation. Using the MXene Ti3C2Tx, the influence of temperature on nanopore fabrication is explored by tracking atomic transformations and find that at room temperature the electron beam irradiation induces random displacement and results in titanium pileups at the nanopore edge, which is confirmed by E‐BeamSim. At elevated temperatures, after removal of the surface functional groups and with the increased mobility of atoms results in atomic transformations that lead to the selective removal of atoms layer by layer. This work can lead to the development of defect engineering techniques within functionalized MXene layers and other 2D materials.more » « less
-
The energy and beam current dependence of Ga + focused ion beam milling damage on the sidewall of vertical rectifiers fabricated on n-type Ga 2 O 3 was investigated with 5–30 kV ions and beam currents from 1.3–20 nA. The sidewall damage was introduced by etching a mesa along one edge of existing Ga 2 O 3 rectifiers. We employed on-state resistance, forward and reverse leakage current, Schottky barrier height, and diode ideality factor from the vertical rectifiers as potential measures of the extent of the ion-induced sidewall damage. Rectifiers of different diameters were exposed to the ion beams and the “zero-area” parameters extracted by extrapolating to zero area and normalizing for milling depth. Forward currents degraded with exposure to any of our beam conductions, while reverse current was unaffected. On-state resistance was found to be most sensitive of the device parameters to Ga + beam energy and current. Beam current was the most important parameter in creating sidewall damage. Use of subsequent lower beam energies and currents after an initial 30 kV mill sequence was able to reduce residual damage effects but not to the point of initial lower beam current exposures.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1093/mam/ozaf001
