Young modulus and Poisson ratio measurements of TiO2 thin films deposited with Atomic Layer Deposition

Atomic Layer Deposition (ALD) allows the deposition of thin films onto flat as well as complex geometry surfaces with excellent conformality. Thicknesses of few atomic layers can be achieved. Moreover, low-temperature deposition is possible and this enables the change of surface properties of many kinds of materials. Good adhesion characteristics and also good mechanical performance of ALD deposited thin films make the technique extremely interesting for several applications, as for example micro-electronics. TiO2 is a well studied semiconductor material because of its multifunctional properties that open a wide range of applications for example in photocatalysis, optics and solar cells. ALD is extremely completive to other technique, to deposit titania thin films, employed even to improve the biocompatibility of many kind of materials. TiO2 thin films are deposited with ALD technique at low temperature (90 degrees C) onto Kapton substrate and then crystallized ex-situ after annealing at 300 degrees C. X-ray diffraction (XRD) techniques are very suitable for the analysis of structure and microstructure of films and surface layers. In this work, XRD in combination with in situ tensile testing has been applied for the first time to measure elastic properties (elastic modulus and Poisson ratio) of TiO2 anatase thin films obtained by ALD. For the experimental conditions, the tensile stage was installed in a Synchrotron laboratory of Soleil. The information extracted from diffraction patterns is presented. (C) 2011 Elsevier B.V. All rights reserved.