Optical Reflectance of Pure and Doped Tin Oxide: From Thin Films to Poly-Crystalline Silicon/Thin Film Device

Films of pure tin oxide SnO2 and in presence of antimony atoms (SnO2-Sb) deposited onto glass substrates have shown a sufficiently high energy gap to be transparent in the visible region, a high electrical mobility and a carrier concentration which displays a good electrical conductivity [1]. In this work, the effects of polycrystalline silicon substrate on the optical properties of pure and Sb doped tin oxide is investigated. We used the APCVD (atmospheric pressure chemical vapour deposition) technique, which is a low-cost and simple technique, under nitrogen ambient, for growing this material. A series of SnO2 and SnO2-Sb have been deposited onto polycrystalline silicon substrates with different contents of antimony atoms at the same conditions of deposition (substrate temperature, flow oxygen, duration and nitrogen atmosphere of the reactor). The effect of the substrate in terms of morphology and nonlinear optical properties, mainly the reflectance, was studied. The reflectance intensity of the device, compared to the reflectance of tin oxide films deposited directly on glass substrate, is clearly reduced on the overall wavelength range. It is obvious that the roughness of the poly-c silicon plays an important role by improving the reflectance and hence the optical parameters. A clear shift in the minimum of the reflectance upon doping level is observed. This minimum corresponds to strong free carrier absorption, resulting in different plasma frequency. This effect is followed by an increase in the reflectance depending of the antimony doping. Applying the extended Drude theory to the combining optical and electrical obtained results these effects are discussed.

Authors:

• Smaali Assia
• Outemzabet Ratiba
• Media El Mahdi
• Kadi Mohamed

Keywords:

• Doping
• oxide
• reflectance.

References:

[1] T. Brouse, R. Retoux, U. Herterich, D.M. Schleich, J. Electrochemical.
Soc. 145 (1998) 1.
[2] Hironori Kobayashi, Yasushi Uebou, Tadashi Ishida, Shigeharu Tamura,
Shoichi Mochizuki, Toshiyuki Mihara, Mitsuhara tabuchi, Hiroyuki
Kageyama, Yoshifumi Yamamoto, Electrochemical property of tin oxide
thin film by photo-CVD process, Journal of Power Sources 97-98 (2001)
229-231.
[3] D. Davazoglou, Thin Solid Films 302 (1997) 204-213.
[4] R.Outemzabet, N. Bouras, N. Kesri, Microstructure and physical
properties of nanofacetted antimony doped tin oxide thin films deposited
by CVD on different substrates, Thin Solid Films, 515, 6518-6520
(2007).
[5] E. Elangovan, K. Ramamurthi, Studies on optical properties of
polycrystalline SnO2:Sb thin films prepared using SnCl2 precursor,
Cryst. Res. Technol. 38, No. 9 (2003) 779-784.
[6] M. Kojima, H. Kato, M. Gatto, Phil. Mag. B 68, 215 (1993).
[7] Keun-Soo Kim, Seog-Young Yoon, Won-Jae Lee, Kwang Ho Kim,
Surface morphologies and electrical properties of antimony-doped tin
oxide films deposited by plasma-enhanced chemical vapor deposition,
Surface and Coatings Technology 138, 229-236, (2001).
[8] B. Thangaraju, Structural and electrical studies on highly conducting
spray deposited fluorine and antimony doped SnO2 thin films from
SnCl2 precursor, Thin Solid Films, 402, 71 (2002).
[9] R. P. Howson, M. Ridge and A. Bishop, Production of transparent
electrically conducting films ion plating, Thin Solid Films 80 (1981)
137-142.
[10] H. Gueddaoui, S. Maabed, G. Schmerber, M. Guemmaz and J. C.
Parlebas, Structural and optical properties of vanadium and hafnium
nitride nanoscale films: effect of stoichiometry, Eur. Phys. J. B 60, 305-
312 (2007).