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Issue Eur. Phys. J. AP
Volume 18, Number 1, April 2002
Page(s) 9 - 15
Section Surfaces, Thin Foils and Nanomaterials
DOI 10.1051/epjap:2002021



Eur. Phys. J. AP 18, 9-15 (2002)
DOI: 10.1051/epjap:2002021

Unusual high sensitivity in highly oriented laser ablated thin films of $\mathsf{SnO_2}$ on (1102) sapphire and (100) $\mathsf{LaAlO_3}$

K.I. Gnanasekar1, B. Rambabu1 and K.C. Langry2

1  Surface Science, Spectroscopy and Solid State Ionics Laboratory, Department of Physics, Southern University and A&M College, Baton Rouge, Louisiana 70813, USA
2  Chemical and Biological Detection Group, Lawrence Livermore National Laboratory, Livermore, California 94550, USA

Rambabu@grant.phys.subr.edu

(Received: 28 April 2001 / Received in final form: 15 November 2001 / Accepted: 17 December 2001)

Abstract
A systematic investigation on growth and sensor characteristics of SnO 2 thin films of different orientations is reported for the first time. Thin films were grown by pulsed laser (KrF; $\lambda=248$ nm) ablation technique under in-situ conditions. Films deposited at 525 °C on (1102) sapphire were predominantly (101) orientated whereas those deposited on (100) LaAlO 3 were highly a-axis orientated. Sensors made of predominantly (101) oriented films exhibited more than two orders magnitude change in resistance even for 100 ppm of H 2 in air at 310 °C. The response and retracing times of the sensor were remarkably short respectively 30 and 200 s. Sensors made of a-axis oriented films also exhibited similar sensitivity and response time for the same quantity of both H 2 and LPG. However, the retrace time was very long typically about 20 min. Atomic force microscopic (AFM) investigation reveals that the films are highly granular with an average size of about 100-150 nm which is ten times larger than the critical size of 6 nm, a criterion required for high sensitivity. (The Debye length of ${\rm SnO}_2 \cong 3.07$  nm at 293 K and the critical grain size is therefore $2~\times$ Debye length, which is 6 nm.)

PACS
07.07.Df - Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing.
81.15.Fg - Laser deposition.
73.61.Jc - Amorphous semiconductors; glasses.


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