We report how argon bombardment induces metallic states on the surface of insulating SrTiO3 at different temperatures by combining in situ conductance measurements and model calculations. At cryogenic temperatures, ionic bombardment created a thin–but much thicker than the argon-penetration depth–steady-state oxygen-vacant layer, leading to a highly-concentric metallic state. Near room temperatures, however, significant thermal diffusion occurred and the metallic state continuously diffused into the bulk, leaving only low concentration of electron carriers on the surface. Analysis of the discrepancy between the experiments and the models also provided evidence for vacancy clustering, which seems to occur during any vacancy formation process and affects the observed conductance.
Helium ion milling of chemically-synthesized micron-sized gold flakes is performed to fabricate ultra-narrow nanoslit cavities with a varying length and width down to 5 nm. Their plasmon resonances are characterized by one-photon photoluminescence spectroscopy. The combination of fabrication based on single-crystalline gold and resonant modes with low radiative losses leads to remarkably high quality factors of up to 24. Multiple Fabry-Pérot-type resonances in the visible/near infrared spectral range are observed due to the achieved narrow slit widths and the resulting short effective wavelengths of nanoslit plasmons. These features make nanoslit cavities attractive for a range of applications such as surface-enhanced spectroscopy, ultrafast nano-optics and strong light-matter coupling.
In the vicinity of metallic nanostructures, absorption and emission rates of optical emitters can be modulated by several orders of magnitude. Control of such near-field light-matter interaction is essential for applications in biosensing, light harvesting and quantum communication and requires precise mapping of optical near-field interactions, for which single-emitter probes are promising candidates. However, currently available techniques are limited in terms of throughput, resolution and/or non-invasiveness. Here, we present an approach for the parallel mapping of optical near-field interactions with a resolution of <5 nm using surface-bound motor proteins to transport microtubules carrying single emitters (quantum dots). The deterministic motion of the quantum dots allows for the interpolation of their tracked positions, resulting in an increased spatial resolution and a suppression of localization artefacts. We apply this method to map the near-field distribution of nanoslits engraved into gold layers and find an excellent agreement with finite-difference time-domain simulations. Our technique can be readily applied to a variety of surfaces for scalable, nanometre-resolved and artefact-free near-field mapping using conventional wide-field microscopes.
Maintaining stable fluxes for multiple source elements is a challenging task when the source materials have significantly different oxygen affinities in a complex-oxide molecular-beam-epitaxy (MBE) environment. Considering that Sr is one of the most easily oxidized and widely used element in various complex oxides, we took Sr as a probe to investigate the flux stability problem in a number of different conditions. Source oxidation was less for higher flux, extended port geometry, and un-melted source shape. The extended port geometry also eliminated the flux transient after opening a source shutter as observed in the standard port. We also found that the source oxidation occurred more easily on the crucible wall than on the surface of the source material.Atomic oxygen, in spite of its stronger oxidation effectiveness, did not make any difference in source oxidation as compared to molecular oxygen in this geometry. Our results may provide a guide for solutions to the source oxidation problem in oxide-MBE system.
SrTiO3 is known to exhibit resistive memory effect either with cation-doping
or with high-temperature thermal reduction. Here, we add another scheme,
ionic-bombardment, to the list of tools to create resistive memory effect on
SrTiO3 (STO). In an Ar-bombarded STO crystal, two orders of resistance
difference was observed between the high and low resistive states, which is an
order of magnitude larger than those achieved by the conventional thermal
reduction process. One of the advantages of this new scheme is that it can be
easily combined with lithographic processes to create spatially-selective
memory effect.Comment: 14 pages, 4 figure
To investigate the enhanced light-matter interaction mediated by optical nanoantennas, there is a need for reliable quantum emitters (QE). Nanodiamonds (ND) with N-V-centers and single-walled carbon nanotubes (SWCNT) are a good choice, since they are photostable and presumably do not blink.
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