Microstructure of vanadium oxide used in microbolometers

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; E. C. Dickey

doi:10.1117/12.884161

21 May 2011 Microstructure of vanadium oxide used in microbolometers

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, E. C. Dickey

Author Affiliations +

Proceedings Volume 8012, Infrared Technology and Applications XXXVII; 80123T (2011) https://doi.org/10.1117/12.884161
Event: SPIE Defense, Security, and Sensing, 2011, Orlando, Florida, United States

Abstract

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 VO_x, 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 VO_x 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.

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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); https://doi.org/10.1117/12.884161

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