Abstract
In this work, the nanoscale footprints of self-driven liquid gallium droplet movement on a GaAs (001) surface will be presented and analyzed. The nanoscale footprints of a primary droplet trail and ordered secondary droplets along primary droplet trails are observed on the GaAs surface. A well ordered nanoterrace from the trail is left behind by a running droplet. In addition, collision events between two running droplets are investigated. The exposed fresh surface after a collision demonstrates a superior evaporation property. Based on the observation of droplet evolution at different stages as well as nanoscale footprints, a schematic diagram of droplet evolution is outlined in an attempt to understand the phenomenon of stick-slip droplet motion on the GaAs surface. The present study adds another piece of work to obtain the physical picture of a stick-slip self-driven mechanism in nanoscale, bridging nano and micro systems.
Highlights
Using scanning electron microscopy (SEM) and atomic force microscopy (AFM), footprints from the primary running droplet are reviewed in greater detail, showing nanoscale terraces as a result of stick-slip motionand findings on the nanoscale footprints of Ga droplets on a GaAs surface are presented in this study
The sample is prepared in a molecular beam epitaxy (MBE) chamber
Upon removal from the growth chamber, a large milky area can be seen on the surface of the sample with unassisted naked eyes
Summary
Droplets have received increasing attention for potential applications in lab-on-a-chip, droplet epitaxy, and micro/nanofluids.[1,2,3,4,5,6] Gallium (Ga) droplets are currently of great interest for their potential applications in advanced quantum devices; these droplets can be transformed under irradiation of group-V molecular beams into various semiconducting nanostructures such as quantum dots and rings.[7,8,9,10,11,12,13,14,15,16,17] Recently, Tersoff et al and Hilner et al found a new type of self-driven motion of Ga droplets on the III-V crystalline semiconductor surfaces through the thermal decomposition of semiconductors.[1,2] The movement of the droplets was investigated by using mirror electron microscopy (MEM) in real time.
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