Browsing by Author "Campbell, JA"

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    Characterisation and properties of low temperature ALD TiO2 films
    (Pielaszek Research, 2007-09-18) Triani, G; Evans, PJ; Campbell, JA; Latella, BA; Atanacio, AJ; Attard, DJ; Burford, RP
    The atomic layer deposition of films under conditions outside the ALD window involves additional processes that have to be accounted for in order to achieve good quality films. [1] In the present study, the growth of ALD TiO2 films on silicon and polycarbonate in the temperature range 80 - 120°C has been investigated in detail for two combinations of pulsing times. Furthermore, both substrate materials were exposed to a low-pressure water plasma to investigate the effect of pre-treatment on the deposited films. A suite of characterisation techniques including XRD, SIMS, RBS, AFM, XTEM and spectroscopic ellipsometry was used to probe the physical and chemical properties of the films. In addition, microtensile testing of the films enable the interface energy and toughness to be determined. These measurements showed water plasma treatment prior to deposition increased the interface energy and interface toughness from 11 to 26 Jm-2 and 1.24 to 1.96 MPa.m1/2 respectively. The contact angle of the TiO2 films was measured to assess their wettability. These tests involved subjecting the films to single and cumulative exposures of UV radiation followed by measurement of the contact angle. For an 85 nm film on polycarbonate, the contact angle decreased from 60° for the as-deposited surface to 10° following a 15 minute exposure. A 25 nm film yielded a similar decrease though this was only achieved after a 50 minute exposure. 1.M. Ritala and M. Leskelä, in Handbook of Thin Film Materials, Volume 1: Deposition and Processing of Thin Films, H.S. Halwa (ed.), Chap. 2, Academic, NY, 2002. © 2007 Pielaszek Research
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    Low temperature atomic layer deposition of titania thin films
    (Elsevier, 2010-04-02) Triani, G; Campbell, JA; Evans, PJ; Davis, J; Latella, BA; Burford, RP
    This paper presents a comprehensive study of atomic layer deposition of TiO2 films on silicon and polycarbonate substrates using TiCl4 and H2O as precursors at temperatures in the range 80–120°C. An in-situ quartz crystal microbalance was used to monitor different processing conditions and the resultant films were characterised ex-situ using a suite of surface analytical tools. In addition, the contact angle and wettability of as-deposited and UV irradiated films were assessed. The latter was found to reduce the contact angle from ≥ 80° to < 10°. Finally, the effect of surface pre-treatment on film toughness and adhesion was investigated and the results show a significant improvement for the pre-treated films. © 2010, Elsevier Ltd.
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    Pyrolysis behaviour of titanium dioxide-poly(vinyl pyrrolidone) composite materials
    (Elsevier, 2009-10) Holmes, R; Campbell, JA; Burford, RP; Karatchevtseva, I
    Inorganic–organic hybrid materials are studied due to the unique properties they exhibit. As these materials become more widely applied, particularly as precursor materials for forming inorganic materials, it is essential that the pyrolysis behaviour is understood. Transparent yellow hybrid materials consisting of titanium dioxide and poly(vinyl pyrrolidone) were prepared using sol–gel processing techniques. The hybrids maintained their transparency up to the highest achieved inorganic loading of 57 wt.%. These materials were characterised using thermogravimetric analysis in which the organic component was pyrolysed. The resultant chars were then investigated using optical microscopy, x-ray diffraction, scanning electron microscopy, and atomic force microscopy. The inorganic loading had an effect on char formation, with higher loadings leading to the formation of pyrolysis intermediates which were less apparent in samples of lower inorganic content. The pyrolysis intermediates were found to be carbon-rich. © 2009, Elsevier Ltd.