Graphite Shell Film Formation Induced by Eduction Phenomenon of Ga Implanted by Focused Ion Beam

Abstract

In this study, we used a transmission electron microscope (TEM) to evaluate the structure of the gallium (Ga) sphere formed on the tip of a diamond-like carbon (DLC) pillar fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD). Until now, details of the phenomenon induced by Ga eduction were remained unclear. We found that a graphite shell was formed on the surface of the Ga sphere after annealing. In addition, we demonstrated that this graphite shell film could be separated from the Ga sphere by performing a second annealing treatment. In-situ observations of the formation of the graphite shell film were carried out using TEM to clarify the process by which it was separated from the Ga sphere. The thermal expansion of Ga led to the separation of the graphite shell film, and Ga was vaporized from within the Ga sphere. These results imply that Ga is able to catalyze for the graphitization of carbon. The development of carbon nanodevices can be expected by using this novel phenomenon induced by Ga. #

Kinetics of Ga droplet decay on thin carbon films

“…In contrast with previous in situ TEM observations, we do not observe graphitic shell formation around the droplets. 19,21,22,24 We do, however, observe small remnants that do not change in size after the bulk of the droplets dissolve. While the images lack sufficient resolution to identify these features, presumably they are graphitic shells as has been reported in the literature.…”

“…While carbon is expected to be insoluble in liquid gallium, previous studies have suggested otherwise and due to the large difference in the surface energies, liquid gallium does not wet amorphous carbon and forms droplets with wetting angles exceeding 120 . 19,[21][22][23] In this letter, we present in situ transmission electron microscopy (TEM) studies of the decay behavior of Ga droplets on amorphous carbon thin films during annealing. From the time-lapsed TEM images, we find that smaller droplets shrink and the volume decay rates depend on the local environment, characteristic of surface-diffusion-limited Ostwald ripening.…”

“…21,[24][25][26][27][28] In this report, we employ a similar approach to prepare Ga droplets on amorphous carbon thin films as described below.…”

“…Energy dispersive spectroscopy (EDS) measurements acquired from the XTEM sample, both before and after annealing, indicate that a significant amount of Ga was present within the carbon film prior to heating and in the droplets observed post-annealing after air-exposure. EDS data also indicated a significant fraction of oxygen but this is likely due to air exposure and not expected in the droplets since gallium oxide does not melt at 773 K. The presence of carbon, if any, 19,[21][22][23] within the droplets could not be determined accurately from EDS due to the large background signal of carbon from the surrounding region. This procedure of forming Ga droplets is highly reproducible and we have obtained similar results, i.e., Ga droplets on carbon films on FIB-prepared XTEM samples of C/Ti/Si, Zr/Al 2 O 3 (0001), and bare Al 2 O 3 (0001) substrates.…”

A Nanomechanical Resonator from HSQ Fabricated by FIB/EB Dual Beam Lithography

“…The increase to the peak value at 200 ºC may be due to Ga-Si structural change by annealing. Ga evaporation during annealing at more than 400 ºC causes decrease of Young's modulus [6]. The slight increase between 600 ºC to 1000 ºC suggests Si-H/Si-O ratio change.…”