Browsing by Author "Wright, Robert V."
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Item Open Access Growth and high frequency characterization of Mn doped sol-gel Pb xSr1-xTiO3 for frequency agile applications(American Institute of Physics, 2009-06) Fragkiadakis, Charalampos; Luker, Arne; Wright, Robert V.; Floyd, L.; Kirby, Paul B.In pursuit of thin film ferroelectric materials for frequency agile applications that are both easily adapted to large area deposition and also high performance, an investigation has been carried out into sol-gel deposition of 3% Mn doped (Pb0.4Sr0.6)TiO3. Large area capability has been demonstrated by growth of films with good crystallinity and grain structure on 4 in. Si wafers. Metal-insulator-metal capacitors have also been fabricated and development of an improved de-embedding technique that takes parasitic impedances fully into account has enabled accurate extraction of the high frequency dielectric properties of the PbxSr1−xTiO3 films. Practically useful values of ε ∼ 1000, tan δ ∼ 0.03, and tunability ∼ 50% have been obtained in the low gigahertz range (1–5 GHz). Peaks in the dielectric loss due to acoustic resonance have been modeled and tentatively identified as due to an electrostrictive effect with an electromechanical coupling coefficient of ∼ 0.04 at an electric field of 240 kV/cm which is potentially useful for tunable thin film bulk acoustic wave devices.Item Open Access Integration of thin film bulk acoustic resonators onto flexible liquid crystal polymer substrates(Elsevier Science B.V., Amsterdam., 2011-06-30T00:00:00Z) Wright, Robert V.; Hakemi, Ghazal; Kirby, Paul B.Thin film bulk acoustic resonators (FBARs) have been directly integrated on liquid crystal polymer (LCP) substrates for application to the field of flexible electronics. Particular developments required were chemo-mechanical polishing for LCP roughness reduction to enable growth of high quality ZnO films and a through substrate deep reactive ion etch process. Q values of up to 126 and 78 for series and parallel resonances combined with an electromechanical coefficient ∼ 6.7% were achieved. Further device development is needed but this performance is already sufficient for some chemical/biological sensing applications.Item Open Access Laser transfer of sol-gel ferroelectric thin films using an ITO release layer(Elsevier Science B.V., Amsterdam., 2011-02-01T00:00:00Z) Bansal, A.; Hergert, R.; Dou, G.; Wright, Robert V.; Bhattacharyya, Debabrata; Kirby, Paul B.; Yeatman, E. M.; Holmes, A. S.A new laser transfer process is reported which allows damage-free transfer of ferroelectric thin films from a growth substrate directly to a target substrate. The thin film ferroelectric material is deposited on a fused silica growth substrate with a sacrificial release layer of ITO (indium tin oxide). Regions of the film that are to be transferred are then selectively metallised, and bonded to the target substrate. Separation from the growth substrate is achieved by laser ablation of the ITO release layer by a single pulse from a KrF excimer laser, with the laser light being incident through the growth substrate. The residual ITO on the transferred ferroelectric layer is electrically conducting, and may be suitable for incorporation into the final device, depending on the application. The new process has been demonstrated for 500 nm-thick layers of sol-gel PZT which were thermosonically bonded to a silicon target substrate prior to laser release. The transferred films show ferroelectric behaviour and have a slightly reduced permittivity compared to the as-depositItem Open Access Synthesis of silver nano particles and fabrication of aqueous Ag inks for inkjet printing(Elsevier Science B.V., Amsterdam., 2011-10-03T00:00:00Z) Kosmala, A.; Wright, Robert V.; Zhang, Qi; Kirby, Paul B.The main problem in preparing stable and printable inks containing nanoparticles for inkjetprinting is to overcome the strong agglomeration of the particles in dispersion medium. In thisstudy, the silver particles with diameter around 50 nm were produced by a simple wet chemistrymethod. Stable aqueous printable inks were formulated by using the combination of a triblockcopolymer and high intensity focused ultrasound (HIFU). Various factors that affect the inkstability, such as, copolymer content and time of HIFU treatment, were investigated. The inkcontaining 5 wt% silver has a viscosity of about 2 mPas and surface tension 30 mN/m at 25◦C,which meet inkjet printer requirements. Such inks have been successfully printed on Al2O3ceramics and low-temperature co- fired ceramics (LTCC) and the printed films show lowresistivit