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Ion implantation for deterministic single atom devices
Here, we demonstrate a capability of deterministic doping at the single atom level using a combination of direct write focused ion beam and solid-state ion detectors. The focused ion beam system can position a single ion to within 35 nm of a targeted location and the detection system is sensitive to single low energy heavy ions. This platform can be used to deterministically fabricate single atom devices in materials where the nanostructure and ion detectors can be integrated, including donor-based qubits in Si and color centers in diamond.
Implantation of 30 keV Helium into Graphene-Coated Tungsten
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Radiation impacts on toxicity of cobalt–chromium (CoCr) implant debris
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Dynamical implantation of objects in the Kuiper Belt
Several models have been suggested in the past to describe the dynamical formation of hot Kuiper Belt objects (hereafter Hot Classicals or HCs for short). Here, we discuss a dynamical mechanism that allows orbits to evolve from the primordial planetesimal disk at ≲ 35 AU to reach the orbital region now occupied by HCs. We performed three different sets of numerical simulations to illustrate this mechanism. Two of these simulations were based on modern theories for the early evolution of the solar system (the Nice and jumping-Jupiter models). The third simulation was performed with the purpose of increasing the resolution at 41-46 AU. The common aspect of these simulations is that Neptune scatters planetesimals from ≲ 35 AU to >40 AU and then undergoes a long phase of slow residual migration. Our results show that to reach an HC orbit, a scattered planetesimal needs to be captured in a mean motion resonance (MMR) with Neptune where the perihelion distance rises due to the Kozai resonance (which occurs in MMRs even for moderate inclinations). Finally, while Neptune is still migrating, the planetesimal is released from the MMR on a stable HC orbit. We show that the orbital distribution of HCs expected from this process provides a reasonable match to observations. The capture efficiency and the mass deposited into the HC region appears to be sensitive to the maximum eccentricity reached by Neptune during the planetary instability phase. Additional work will be needed to resolve this dependency in detail.
Experimental studies on the formation of D{sub 2}O and D{sub 2}O{sub 2} by implantation of energetic D{sup +} ions into oxygen ices
The formation of water (H{sub 2}O) in the interstellar medium is intrinsically linked to grain-surface chemistry; thought to involve reactions between atomic (or molecular) hydrogen with atomic oxygen (O), molecular oxygen (O{sub 2}), and ozone (O{sub 3}). Laboratory precedent suggests that H{sub 2}O is produced efficiently when O{sub 2} ices are exposed to H atoms (∼100 K). This leads to the sequential generation of the hydroxyperoxyl radical (HO{sub 2}), then hydrogen peroxide (H{sub 2}O{sub 2}), and finally H{sub 2}O and a hydroxyl radical (OH); despite a barrier of ∼2300 K for the last step. Recent detection of the four involved species toward ρ Oph A supports this general scenario; however, the precise formation mechanism remains undetermined. Here, solid O{sub 2} ice held at 12 K is exposed to a monoenergetic beam of 5 keV D{sup +} ions. Products formed during the irradiation period are monitored through FTIR spectroscopy. O{sub 3} is observed through seven archetypal absorptions. Three additional bands found at 2583, 2707, and 1195 cm {sup –1} correspond to matrix isolated DO{sub 2} (ν{sub 1}) and D{sub 2}O{sub 2} (ν{sub 1}, ν{sub 5}), and D{sub 2}O (ν{sub 2}), respectively. During subsequent warming, the O{sub 2} ice sublimates, revealing a broad band at 2472 cm{sup –1} characteristic of amorphous D{sub 2}O (ν{sub 1}, ν{sub 3}). Sublimating D{sub 2}, D{sub 2}O, D{sub 2}O{sub 2}, and O{sub 3} products were confirmed through their subsequent detection via quadrupole mass spectrometry. Reaction schemes based on both thermally accessible and suprathermally induced chemistries were developed to fit the observed temporal profiles are used to elucidate possible reaction pathways for the formation of D{sub 2}-water. Several alternative schemes to the hydrogenation pathway (O{sub 2}→HO{sub 2}→H{sub 2}O{sub 2}→H{sub 2}O) were identified; their astrophysical implications are briefly discussed.
Implantation of energetic D{sup +} ions into carbon dioxide ices and implications for our solar system: formation of D{sub 2}O and D{sub 2}CO{sub 3}
Carbon dioxide (CO{sub 2}) ices were irradiated with energetic D{sup +} ions to simulate the exposure of oxygen-bearing solar system ices to energetic protons from the solar wind and magnetospheric sources. The formation of species was observed online and in situ by exploiting FTIR spectroscopy. Molecular products include ozone (O{sub 3}), carbon oxides (CO{sub 3}(C {sub 2v}, D {sub 3h}), CO{sub 4}, CO{sub 5}, CO{sub 6}), D2-water (D{sub 2}O), and D2-carbonic acid (D{sub 2}CO{sub 3}). Species released into the gas phase were sampled via a quadrupole mass spectrometer, and possible minor contributions from D2-formaldehyde (D{sub 2}CO), D4-methanol (CD{sub 3}OD), and D2-formic acid (DCOOD) were additionally identified. The feasibility of several reaction networks was investigated by determining their ability to fit the observed temporal column densities of 10 key species that were quantified during the irradiation period. Directly relevant to the CO{sub 2}-bearing ices of comets, icy satellites in the outer solar system, and the ice caps on Mars, this work illustrates for the first time that D2-water is formed as a product of the exposure of CO{sub 2} ices to D{sup +} ions. These findings provide strong support for water formation from oxygen-bearing materials via non-thermal hydrogen atoms, and predict reaction pathways that are likely to be unfolding on the surfaces of asteroids and the Moon.
Model development of plasma implanted hydrogenic diffusion and trapping in ion beam damaged tungsten
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Transport spectroscopy of low disorder silicon tunnel barriers with and without Sb implants
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Probing magnetic order and disorder in the one-dimensional molecular spin chains CuF2(pyz) and [Ln(hfac)(3)(boaDTDA)](n) (Ln = Sm, La) using implanted muons.
We present the results of muon-spin relaxation (mu+SR) measurements on antiferromagnetic and ferromagnetic spin chains. In antiferromagnetic CuF2(pyz) we identify a transition to long range magnetic order taking place at T-N = 0.6(1) K, allowing us to estimate a ratio with the intrachain exchange of T-N/vertical bar J vertical bar approximate to 0.1 and the ratio of interchain to intrachain exchange coupling as vertical bar J'/J vertical bar approximate to 0.05. The ferromagnetic chain [Sm(hfac)(3)(boaDTDA)](n) undergoes an ordering transition at T-c = 2.8(1) K, seen via a broad freezing of dynamic fluctuations on the muon (microsecond) timescale and implying T-c/vertical bar J vertical bar approximate to 0.6. The ordered radical moment continues to fluctuate on this timescale down to 0.3 K, while the Sm moments remain disordered. In contrast, the radical spins in [La(hfac)(3)(boaDTDA)](n) remain magnetically disordered down to T = 0.1 K suggesting T-c/vertical bar J vertical bar < 0.17.
Strain Doping: Reversible Single-Axis Control of a Complex Oxide Lattice via Helium Implantation
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Formation window of gas bubble superlattice in molybdenum under ion implantation
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Lab-on-a-Fish: Wireless, Miniaturized, Fully Integrated, Implantable Biotelemetric Tag for Real-Time In Vivo Monitoring of Aquatic Animals
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