Browsing by Author "Mitchell, A"

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    Lattice guiding for low temperature crystallization of rhombohedral perovskite-structured oxide thin films
    (American Chemical Society, 2010-02) Sriram, S; Bhaskaran, M; Mitchell, DRG; Mitchell, A
    Low temperature crystallization of complex oxide thin films has proved to be a challenge with deposition of such materials often carried out at elevated temperatures in excess of 600°C. This article demonstrates one of the first instances of deposition of preferentially oriented strontium-doped lead zirconate titanate thin films at a relatively low temperature of 300°C. This was achieved by carrying out deposition on gold-coated silicon substrates which exert a guiding influence on thin film growth due to similarity in lattice parameters. The microstructure and preferential orientations were studied using high resolution transmission electron microscopy and X-ray diffraction. These results illustrated the pronounced texture in the deposited thin films due to lattice guiding, with crystal structure simulations also verifying the guiding effect. © 2010, American Chemical Society
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    Microstructural and compositional analysis of strontium-doped lead zirconate titanate thin films on gold-coated silicon substrates
    (Cambridge University Press, 2009-02) Sriram, S; Bhaskaran, M; Mitchell, DRG; Short, KT; Holland, AS; Mitchell, A
    This article discusses the results of transmission electron microscopy (TEM)-based characterization of strontium-doped lead zirconate titanate (PSZT) thin films. The thin films were deposited by radio frequency magnetron sputtering at 300°C on gold-coated silicon substrates, which used a 15 nm titanium adhesion layer between the 150 nm thick gold film and (100) silicon. The TEM analysis was carried out using a combination of high-resolution imaging, energy filtered imaging, energy dispersive X-ray (EDX) analysis, and hollow cone illumination. At the interface between the PSZT films and gold, an amorphous silicon-rich layer (about 4 nm thick) was observed, with the film composition remaining uniform otherwise. The films were found to be polycrystalline with a columnar structure perpendicular to the substrate. Interdiffusion between the bottom metal layers and silicon was observed and was confirmed using secondary ion mass spectrometry. This occurs due to the temperature of deposition (300°C) being close to the eutectic point of gold and silicon (363°C). The diffused regions in silicon were composed primarily of gold (analyzed by EDX) and were bounded by (111) silicon planes, highlighted by the triangular diffused regions observed in the two-dimensional TEM image. © 2009, Cambridge University Press
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    Nanocolumnar preferentially oriented PSZT thin films deposited on thermally grown silicon dioxide
    (Springer, 2009-01) Sriram, S; Bhaskaran, M; Mitchell, A; Mitchell, DRG; Kostovski, G
    We report the first instance of deposition of preferentially oriented, nanocrystalline, and nanocolumnar strontium-doped lead zirconate titanate (PSZT) ferroelectric thin films directly on thermal silicon dioxide. No intermediate seed or activation layers were used between PSZT and silicon dioxide. The deposited thin films have been characterised using a combination of diffraction and microscopy techniques. © 2009, Springer.
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    Synthesis of self-assembled island-structured complex oxide dielectric films
    (American Chemical Society, 2009-09-24) Sriram, S; Bhaskaran, M; Kostovski, G; Mitchell, DRG; Stoddart, PR; Austin, MW; Mitchell, A
    A self-assembly driven process to synthesize island-structured dielectric films is presented. An intermetallic reaction in platinized silicon substrates provides preferential growth sites for the complex oxide dielectric layer. Microscopy and spectroscopy analyses have been used to propose a mechanism for this structuring process. This provides a simple and scalable process to synthesize films with increased surface area for sensors, especially those materials with a complex chemistry. The ability of these island-structured dielectric films to improve sensitivity by a factor of 100 compared to continuous films in applications as substrates for surface-enhanced Raman scattering (SERS) is demonstrated. © 2009, American Chemical Society