An Investigation of PLD-Deposited Barium Strontium Titanate (Ba_xSr_1-xTiO₃) Thin Film Optical Properties

Martin Kocanda, Syed Farhan Mohiudin, Ibrahim Abdel-Motaleb

Department of Electrical Engineering, Northern Illinois University, DeKalb, USA.

DOI: 10.4236/csta.2012.12003                

Abstract

Reflectance and transmittance parameters of pulsed laser deposited barium strontium titanate (BST) were investigated using spectrophotometric methods. Three stoichiometries consisting of Ba_xSr_1-xTiO₃ (x = 0.30, 0.40, 0.50) were deposited on glass substrates using oxygen partial pressures of 1.3 Pa ± 0.13 Pa at 500^oC. Subsequently, the measured optical parameters were employed to determine the refractive index (n), extinction coefficient (k), optical conductivity (σ), absorption coefficient (α) and optical bandgap (E_g) using swept spectra in the ultraviolet, visible and near-infrared range (200 nm - 1100 nm) as these have not been reported in the literature. The calculated parameters for Ba_0.4Sr_0.6TiO₃ are reported in this experimental work. Minimal differences in the transmittance have been observed at the visible band edges when comparing each stoichiometry. Sharp cutoffs were observed at the bands edges and strong absorbance in the 200 nm - 300 nm band as attributed to the crystal structure based upon the oxygen partial pressure during the deposition process.

Keywords

Barium Strontium Titanate; Optical Bandgap; Optical Conductivity; Pulsed Laser Deposition; Stoichiometry

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	M. Kocanda and I. Abdel-Motaleb, “Design of a DNA Probe Using Barium Strontium Titanate,” Proceedings of International Conference on Solid-State and Integrated Circuit Technology, Beijing, 20-23 October 2008, pp. 2573-2576. doi:10.1109/ICSICT.2008.4735098
[2]	M. Kocanda and I. Abdel-Motaleb, “DNA Sensing—An Overview of Present Technology and Future Trends,” Proceedings of International Conference on Solid-State and Integrated Circuit Technology, Beijing, 20-23 October 2008, pp. 2536-2540.
[3]	M. Kocanda and I. Abdel-Motaleb, “Development of a DNA Probe Using Barium Strontium Titanate,” Journal of Applied Physics, Vol. 106, No. 12, 2009, pp. 123916-123916-6. http://dx.doi.org/+10.1063/1.3273314
[4]	M. Kocanda and I. Abdel-Motaleb, “DNA Detection Using a Complimentary Metal-Oxide Semiconductor Ring Oscillator Circuit,” Journal of Applied Physics, Vol. 108, No. 7, 2010, pp. 3483947-3483947-3. http://dx.doi.org/+10.1063/1.3273314
[5]	V. M. Goldschmidt, “Geochemische Verteilungsgesetze der Elemente,” Skrifter der Norske Videnskaps-Akad, Vol. 8, No. 3, 1926, pp. 529-533.
[6]	R. Swanepoel, “Determination of the Thickness and Optical Constants of Amorphous Silicon,” Journal of Physics E: Scientific Instruments, Vol. 16, No. 12, 1983, pp. 1214-1216.
[7]	A. K. Bain, et al., “Optical Properties of Barium Strontium Titanate (BST) Ferroelectric Thin Films,” Ferroelectrics Letters Section, Vol. 34, No. 5-6, 2007, pp. 149- 154.
[8]	J. I. Pankove, “Optical Processes in Semiconductors,” Courier Dover Publications, New York, 1990.
[9]	M. L. Sadowski, M. Potemski and M. Grynberg, “Optical Properties of Semiconductor Nanostructures,” Kluwer Academic Publishers, Boston, 2010.
[10]	J. Tauc and A. Menth, “States in the Gap,” Journal of Non-Crystalline Solids, Vol. 8-10, 1972, pp. 569- 585. doi:10.1016/0022-3093(72)90194-9