TY - JOUR

T1 - In situ microscopy of composite Germanium/Germanium oxide microneedle growth

AU - Rybakov, Alexey S.T.

AU - Meyer, Lea L.

AU - Kuper, Henning

AU - Chalupa, Mark

AU - Becker, Verena

AU - Becker, Jörg August

N1 - Funding Information: We thank Prof. Dr. rer. nat. habil. Armin Feldhoff from the Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover (LUH) for providing us access to the FE-SEM JEOL JSM-6700F with the EDX spectrometer Oxford Instruments INCA 300, the FE-TEM JEOL JEM-2100F-UHR with the EDX spectrometer Oxford Instruments INCA 200 and the preparation laboratories, and the support of our electron microscopy research. We are grateful to Frank Steinbach from the Institute of Physical Chemistry and Electrochemistry, LUH for his generous technical advices and for carrying out the STEM analysis. We thank the Institute of Materials Science, LUH and especially Dr.-Ing. Torsten Heidenblut for the preparation of the needle TEM lamella and longitudinal sections with the FE-SEM-FIB Zeiss AURIGA, and high-quality EDX analysis with the Oxford X-Max detector. Also, we extend our thanks to Prof. Dr. rer. nat. Claus Rüscher from the Institute of Mineralogy, LUH for allowing us access to the Olympus BX microscope with the Raman spectrometer Bruker Senterra and for helping in analysing the needles.

PY - 2023/4/15

Y1 - 2023/4/15

N2 - 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.

AB - 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.

KW - A1. Chemical transport reactions

KW - A1. Composite structure

KW - A1. Needle growth

KW - A1. Optical microscopy

KW - B1. Germanium

KW - B1. Germanium oxide

UR - http://www.scopus.com/inward/record.url?scp=85149399013&partnerID=8YFLogxK

U2 - 10.1016/j.jcrysgro.2023.127133

DO - 10.1016/j.jcrysgro.2023.127133

M3 - Article

AN - SCOPUS:85149399013

VL - 608

JO - Journal of crystal growth

JF - Journal of crystal growth

SN - 0022-0248

M1 - 127133

ER -