title: Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials.
abstract: Microspheres with high sphericity exhibit unique functionalities. In particular, their high symmetry makes them excellent omnidirectional optical resonators. As such perfect micrometre-sized spheres are known to be formed by surface tension, melt cooling is a popular method for fabricating microspheres. However, it is extremely difficult to produce crystalline microspheres using this method because their surfaces are normally faceted. Only microspheres of polymers, glass, or ceramics have been available, while single-crystalline microspheres, which should be useful in optical applications, have been awaiting successful production. Here we report the fabrication of single-crystalline semiconductor microspheres that have surfaces with atomic-level smoothness. These microspheres were formed by performing laser ablation in superfluid helium to create and moderately cool a melt of the anisotropic semiconductor material. This novel method provides cooling conditions that are exceptionally suited for the fabrication of single-crystalline microspheres. This finding opens a pathway for studying the hidden mechanism of anisotropy-free crystal growth and its applications.
authors.affiliation: Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Okamoto
authors.affiliation: Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Inaba
authors.affiliation: 1] Nanoscience and Nanotechnology Research Center, Osaka Prefecture University, 1-2, Gakuencho, Nakaku, Sakai, Osaka 599-8570, Japan [2].
authors.forename: Takuya
authors.initials: T
authors.lastname: Iida
authors.affiliation: Department of Physics and Electronics, Osaka Prefecture University, 1-1 Gakuencho, Nakaku, Sakai, Osaka 599-8531, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Ishihara
authors.affiliation: Institute for NanoScience Design, Osaka University, 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ichikawa
authors.affiliation: Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ashida