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21 May 2011 Microstructure of vanadium oxide used in microbolometers
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Reactive pulsed DC sputtering was used to grow a systematic series of films with resistivity ranging from 1 × 10-3 to 6.8 × 104 Ohm cm and TCR varying from 0 to -4% K-1. Throughout the parameter space studied a transition from amorphous to nano-crystalline growth was observed. Films in the resistivity range of interest for microbolometers contained a FCC VOx (0.8 < x < 1.3) phase. Altering the sputtering energetics via substrate biasing resulted in highlycolumnar, nano-twinned grains of FCC VOx, providing a microstructure reminiscent of ion beam sputtered bolometer material. Electron diffraction in the TEM confirmed the presence of a secondary, oxygen-rich amorphous phase. Micro- Raman spectroscopy, which was also found to be sensitive to the secondary amorphous phase, was used to probe the chemical composition and morphology of VOx thin films. Raman spectra from high resistivity amorphous films show a broad feature around ~890 cm-1, while spectra from lower resistivity nano-crystalline films exhibit this same amorphous feature and a second broad feature at ~320 cm-1. The resulting microstructure can be described as a nano-composite material composed of a low-resistivity crystalline phase embedded in a high-resistivity amorphous matrix. Our results suggest that both phases are required to achieve a high TCR, low resistivity material.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
B. D. Gauntt, J. Li, O. M. Cabarcos, H. A. Basantani, C. Venkatasubramanian, S. S. N. Bharadwaja, N. J. Podraza, T. N. Jackson, D. L. Allara, S. Antrazi, M. W. Horn, and E. C. Dickey "Microstructure of vanadium oxide used in microbolometers", Proc. SPIE 8012, Infrared Technology and Applications XXXVII, 80123T (21 May 2011);

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