In situ microscopy of composite Germanium/Germanium oxide microneedle growth
•In situ video microscopy allows studying of microneedle growth in a miniature cell.•Different longitudinal and lateral growth mechanisms can occur simultaneously.•Microneedles have a carcass/filler structure; carcass consists of core and branches.•Needle surface structure is either highly regular o...
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| Published in: | Journal of crystal growth Vol. 608; p. 127133 |
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| Main Authors: | , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Elsevier B.V
15-04-2023
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | •In situ video microscopy allows studying of microneedle growth in a miniature cell.•Different longitudinal and lateral growth mechanisms can occur simultaneously.•Microneedles have a carcass/filler structure; carcass consists of core and branches.•Needle surface structure is either highly regular or irregular; tips are also varied.
Composite germanium/germanium oxide needles with a carcass/filler structure, thicknesses of 0.25–10 µm and lengths up to 450 µm were grown by chemical transport involving gaseous GeO. The synthesis was carried out at temperatures of 897–1100 K in a newly developed miniature cell. Through a top window one can observe the growth process in situ via video microscopy. The cell can be evacuated and sealed, enclosing all products generated in reactions, but can easily be opened afterwards for an ex situ analysis of the needles. The in situ observations show that the needles grow with longitudinal velocities of up to 30 µm/s, depending on temperature and needle thickness, and with lateral velocities of up to 0.11 µm/s. The surface structure and the cross-sections of the needles were studied ex situ by SEM as well as EDX spectroscopy combined with element mapping. The surface structure of needles exhibits highly regular arrays of germanium/germanium oxide microunits but also shows irregularities and defects. The study of the longitudinal section and the lamella showed that this regularity is remarkable also inside the needle all way down to the core. Furthermore, according to the SAED and Raman spectroscopy, the needle carcass (core with branches) is mainly composed of a cubic Ge and an amorphous filling mass of Ge and O, which presumably corresponds to GeO2. |
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| ISSN: | 0022-0248 1873-5002 |
| DOI: | 10.1016/j.jcrysgro.2023.127133 |