Journal article
Formation mechanism and thermoelectric properties of CaMnO3 thin films synthesized by annealing of Ca0.5Mn0.5O films
A two-step synthesis approach was utilized to grow CaMnO3 on M-, R- and C-plane sapphire substrates. Radio-frequency reactive magnetron sputtering was used to grow rock-salt-structured (Ca, Mn)O followed by a 3-h annealing step at 800 °C in oxygen flow to form the distorted perovskite phase CaMnO3. The effect of temperature in the post-annealing step was investigated using x-ray diffraction.
The phase transformation to CaMnO3 started at 450 °C and was completed at 550 °C. Films grown on R- and C-plane sapphire showed similar structure with a mixed orientation, whereas the film grown on M-plane sapphire was epitaxially grown with an out-of-plane orientation in the [202] direction. The thermoelectric characterization showed that the film grown on M-plane sapphire has about 3.5 times lower resistivity compared to the other films with a resistivity of 0.077 Ωcm at 500 °C.
The difference in resistivity is a result from difference in crystal structure, single orientation for M-plane sapphire compared to mixed for R- and C-plane sapphire. The highest absolute Seebeck coefficient value is − 350 µV K−1 for all films and is decreasing with temperature.
Language: | English |
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Publisher: | Springer US |
Year: | 2019 |
Pages: | 8482-8491 |
ISSN: | 15734803 and 00222461 |
Types: | Journal article |
DOI: | 10.1007/s10853-019-03496-7 |
ORCIDs: | Nong, Ngo Van , 0000-0002-3059-7392 , 0000-0003-0858-3792 , 0000-0001-5485-3381 , 0000-0002-0991-6715 , 0000-0003-2982-5914 , 0000-0001-5532-6030 , 0000-0003-1785-0864 and 0000-0002-9970-3616 |