Optical size control in growth of gallium nanoparticles

We report that a low level of optical excitation provides a substantial influence on the size distribution of gallium nanoparticles grown from the atomic beam on a cryogenic substrate, thus providing a new way of achieving tailored films of nanoparticles with given characteristics. The growth experiments, performed in situ in the vacuum chamber of a scanning electron microscope (SEM) equipped with an inverted effusion cell, revealed that the median diameter of the nanoparticles decreases with increasing irradiating optical power, with 0.1, 0.2 and 0.4 mW average power resulting in 70, 50 and 45 nm particles, respectively

Phase-change memory functionality in gallium nanoparticles

We report that the structural phase of gallium nanoparticles can be switched by optical excitation and read via their cathodoluminescence (CL) when excited by a scanning electron beam. This opens a new paradigm in developing high-density phase change optical memory elements. A film of gallium nanoparticles was sputtered at the end face of an optical fiber, through which the reflectivity at 195 K was monitored by a 1.31 µm laser. By launching a single pulse from a 1.55 µm laser (17 mW, 1 µs) to the sample, a solid-to-liquid phase transition was observed as an immediate change of reflectivity from 10.0 to 10.5 %. CL spectra were measured immediately before and after the phase transition. The spectra show that gallium nanoparticles luminesce in the range of 400-650 nm, in which there at 520 nm is a 10 % difference of emission before and after the phase transition, due to a difference in optical properties. In future continuation of this first demonstration of electron beam read-out of the phase of nanoparticles, it is likely that the electron beam itself can change the phase of individual nanoparticles in the film, and that this phase furthermore can be read out at lower power by its cathode luminescence response with the same electron beam

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Towards femtojoule nanoparticle phase-change memory

In this article we review the concept of electron-beam-addressed high density phase-change nanoparticle memory, where information is written in the phase state of gallium nanoparticles by electron beam excitation, and read-out via measurements of cathodoluminescent emission. The high spatial resolution provided by a focused electron beam, far below the optical diffraction limit, offers the possibility of addressing individual nanoparticles within a close-packed array, thereby enabling a new conceptual basis for high density phase-change memory

Optical nanoantennas

The field of optical nanoantennas, a rapidly developing area of optics, is reviewed. The basic concept of an optical antenna is formulated and major characteristics relevant to this structure are identified. A classification of nanoantennas into metalli

Emission hotspots in complex metal nanostructures

We have observed that in complex nanostructures, such as pairs of nanorods, hotspots of optical emission induced by electron-beam excitation exist at their point of closest proximity, where strong local field enhancements are expected

Observation of optical domino-modes in arrays of non-resonant plasmonic nanoantenas

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