Imperial College London
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ProfessorRogerWhatmore

Faculty of Engineering, Department of Materials

Visiting Professor
 
 
 
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r.whatmore

 
 
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Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

343 results found

Molter O, Shaw C, Whatmore RW, 2002, Dopant effects in pyroelectric ceramics in the PMN-PZT system, Ferroelectrics UK 2001 Meeting, Publisher: MANEY PUBLISHING, Pages: 85-92

Conference paper

Hvizdos P, Reece MJ, Bushby AJ, Whatmore RW, Zhang Q, Algueró Met al., 2002, Depolarisation of PZT thin films by nanoindentation, 14th International Symposium on Integrated Ferroelectrics/13th IEEE Int Symposium on the Applications of Ferroelectrics/19th Meeting on Ferroelectric Mat and their Applicat, Publisher: TAYLOR & FRANCIS LTD, Pages: 199-207, ISSN: 1058-4587

Conference paper

Dorey RA, Duval FFC, Haigh RD, Whatmore RWet al., 2002, The effect of repeated sol infiltrations on the microstructure and electrical properties of PZT composite sol-gel films, 10th International Meeting on Ferroelectricity, Publisher: TAYLOR & FRANCIS LTD, Pages: 373-378, ISSN: 0015-0193

Conference paper

Dorey RA, Haigh RD, Stringfellow SB, Whatmore RWet al., 2002, Effect of sol infiltrations on the electrical properties of PZT, Ferroelectrics UK 2001 Meeting, Publisher: MANEY PUBLISHING, Pages: 29-35

Conference paper

Dorey RA, Whatmore RW, 2002, Apparent reduction in the value of the d<sub>33</sub> piezoelectric coefficient in PZT thick films, 14th International Symposium on Integrated Ferroelectrics/13th IEEE Int Symposium on the Applications of Ferroelectrics/19th Meeting on Ferroelectric Mat and their Applicat, Publisher: TAYLOR & FRANCIS LTD, Pages: 111-119, ISSN: 1058-4587

Conference paper

Dunn S, Zhang Q, Whatmore RW, 2002, Growth stages of sol-gel derived PZT(30/70) on Pt/Ti/SiO<sub>2</sub> as shown by SPM (PFM and topography), 14th International Symposium on Integrated Ferroelectrics/13th IEEE Int Symposium on the Applications of Ferroelectrics/19th Meeting on Ferroelectric Mat and their Applicat, Publisher: TAYLOR & FRANCIS LTD, Pages: 87-94, ISSN: 1058-4587

Conference paper

Huang Z, Donohue PP, Zhang Q, Williams D, Anthony CJ, Todd MA, Whatmore RWet al., 2002, Comparative studies of PST thin films as prepared by sol-gel, LDCVD and sputtering techniques, 14th International Symposium on Integrated Ferroelectrics/13th IEEE Int Symposium on the Applications of Ferroelectrics/19th Meeting on Ferroelectric Mat and their Applicat, Publisher: TAYLOR & FRANCIS LTD, Pages: 79-87, ISSN: 1058-4587

Conference paper

Navarro A, Alcock JR, Whatmore RW, 2002, Aqueous tape casting of PZT ceramics, Ferroelectrics UK 2001 Meeting, Publisher: MANEY PUBLISHING, Pages: 93-99

Conference paper

Whatmore RW, Shaw CP, Zhang Q, Roy SS, Gleeson HFet al., 2001, Oxide ferroelectric thin film/nematic liquid crystal devices, Integrated Ferroelectrics, Vol: 41, Pages: 3-16, ISSN: 1058-4587

The visualisation of domains in ferroelectrics by decoration of the surface with nematic liquid crystals (NLC) has been used previously for the study of single crystal ferroelectrics. Until recently there has, however, been no work reported on the coupling between NLC and the polarisation in ferroelectric thin films. Such a coupling would open the possibility of imparting switchable memory to nematic LC displays. This paper reviews work on the fabrication and testing of device structures with the structure: glass/ITO/PZT/LC/ITO/glass (PZT=240nm sol-gel PbZr 0.3Ti 0.7O 3; ITO= sputtered transparent, conductive indium tin oxide). When a voltage pulse is applied to the sandwich via the ITO electrodes, the switched polarisation in the ferroelectric thin film is observed. It has been found that a thin layer of TiO 2, deposited by sol-gel onto the ITO, can be highly beneficial in improving the control of PZT nucleation and grain size/structure, improving the uniformity and quality of the structures. It has also been found possible to measure the poling voltage required to obtain a reorientation in the nematic LC layer and to refer this back to the hysteresis loop obtained from the PZT. The potential of the structure for device applications is discussed. © 2001 Taylor & Francis.

Journal article

Kirby P, Su QX, Komuro E, Imura M, Zhang Q, Whatmore Ret al., 2001, High frequency thin film acoustic ferroelectric resonators, Materials Research Society Symposium - Proceedings, Vol: 655, ISSN: 0272-9172

Both ZnO and PZT Thin Film Bulk Acoustic Resonator filters were fabricated, tested and modeled in this study. The development of an accurate Mason model allows the effect of particular parasitic components on the microwave s-parameters in the region of the series and parallel resonances to be identified. The parasitic components that limit the performance of our ZnO and PbZr0.3T0.7O3 Thin Film Bulk Acoustic Resonator filters are analysed. From an analysis of PbZr0.3Ti0.7O3 Thin Film Bulk Acoustic Resonator measurements values for the longitudinal acoustic velocity and electromechanical coupling coefficient can be derived. Measured PbZ0.3T0.7O3 Thin Film Bulk Acoustic Resonator filter responses confirm that the larger electromechanical coupling coefficients in this material compared to ZnO give wider filter band-widths. © 2001 Materials Research Society.

Journal article

Zhang Q, Whatmore RW, 2001, Sol-gel PZT and MN-doped PZT thin films for pyroelectric applications, Integrated Ferroelectrics, Vol: 41, Pages: 43-50, ISSN: 1058-4587

Thin films of ferroelectric lead zirconate titanate (PbZr 0.3Ti 0.7O 3 PZT30/70) and manganese doped lead zirconate titanate ((Pb(Zr 0.3Ti 0.7) 1-xMn x)O 3-x = 0.01, PM01ZT30/70 and x = 0.03, PM03ZT30/70) have been prepared using sol-gel processing techniques. These materials can be used as the pyroelectric thin films in uncooled infrared (IR) detectors. Films deposited on Pt/Ti/SiCVSi substrates and annealed on a hot plate at 530°C for 5 min were seen to fully crystallize into the required perovskite phase and showed excellent ferroelectric behavior, demonstrated by reproducible hysteresis loops (P r = 33 to 37 μC/cm 2, Ec(+) = 70 to 100 kV/cm, E c(-) = -170 to -140 kV/cm). The pyroelectric coefficients (p) were measured using the Byer-Roundy method. At 20°C, p was 2.11 × 10 -4 Cm -2K -1 for PZT30/70, 3.00×10 -4 Cm -2K -1 for PM01ZT30/70 and 2.40×10 -4 Cm -2K -1 for PM03ZT30/70 thin films. The detectivity figures-of-merit (F D) were 1.07×10 -5 Pa -0.5 for PZT30/70, 3.07×10 -5 Pa -0.5 for PM01ZT30/70 and 1.07×10 -0.5 Pa -0.5 for PM03ZT30/70. These figures compare well with values reported previously. © 2001 Taylor & Francis.

Journal article

Algueró M, Bushby AJ, Hvizdos P, Reece MJ, Whatmore RW, Zhang Qet al., 2001, Mechanical and electromechanical properties of PZT sol-gel thin films measured by nanoindentation, Integrated Ferroelectrics, Vol: 41, Pages: 53-62, ISSN: 1058-4587

Microelectromechanical systems (MEMS) with ferroelectric thin films as the actuating element are currently under development. Micromotors, microcantilevers for atomic force microscopy, and microwave switches are three examples of MEMS that have been demonstrated. The potential commercialisation of MEMS rests on addressing design and reliability issues. Their design requires knowledge of the elastic coefficients of the ferroelectric film, as well as the other materials in the system. Understanding their reliability requires the determination of stress thresholds for depolarisation. Lead zirconate titanate (PZT) compositions are preferred for actuation applications. We present here the mechanical properties of PZT films with Zr/Ti ratios of 30/70 and 50/50, prepared by sol-gel processing. Nanoindentation with spherical tipped indenters was used to obtain the elastic stiffness coefficient of the films. Electromechanical measurements were also performed with the nanoindentation system. Films were poled by using the spherical tipped indenter as the top electrode. Current intensity transients were recorded during subsequent indentation of poled areas. © 2001 Taylor & Francis.

Journal article

Kirby P, Komuro E, Imura M, Zhang Q, Su QX, Whatmore Ret al., 2001, High frequency thin film ferroelectric acoustic resonators and filters, Integrated Ferroelectrics, Vol: 41, Pages: 91-100, ISSN: 1058-4587

There is a need for more compact filters that are able to meet the needs of the next generation of mobile phone operating in the l-2GHz frequency band. These filters are required to have low insertion loss, high Q, low sensitivity to temperature and in some cases wider bandwidths than those currently available. In this paper we review some of our recent work on the application of PZT (sol-gel PbZr 0.3Ti 0.7O 3) as the piezoelectric layer in FBARs (thin Film Bulk Acoustic Resonators) and FBAR filters. The high electromechanical coupling coefficients in PZT offer the possibility of realising wide band-width filters. It is shown possible to incorporate PZT into a FBAR structure previously designed for piezoelectric ZnO by the simple addition of a TiO 2 layer that avoids the crazing that occurs when PZT is deposited directly on SiN x. PZT FBAR filters of extremely small area (<300 μ 2) can be produced. Preliminary measurements suggest that the resonance frequencies in PZT FBARs are only weakly temperature dependent. The advantages and disadvantages of using PZT in FBAR structures is discussed. © 2001 Taylor & Francis.

Journal article

Huang Z, Donohue PP, Todd MA, Jones JC, Whatmore RWet al., 2001, Sputtered lead scandium tantalate thin films: crystallization behaviour during post-deposition annealing, JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 34, Pages: 3121-3129, ISSN: 0022-3727

Journal article

Zhang Q, Whatmore RW, 2001, Sol-gel PZT and Mn-doped PZT thin films for pyroelectric applications, JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 34, Pages: 2296-2301, ISSN: 0022-3727

Journal article

Southin JEA, Wilson SA, Schmitt D, Whatmore RWet al., 2001, e<sub>31</sub>,<i><sub>f</sub></i> determination for PZT films using a conventional '<i>d</i><sub>33</sub>' meter, JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 34, Pages: 1456-1460, ISSN: 0022-3727

Journal article

Rayner PJ, Whatmore RW, 2001, Travelling wave ultrasonic motor using the B<sub>08</sub> flexural mode of a circular membrane, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, Vol: 48, Pages: 683-690, ISSN: 0885-3010

Journal article

Su QX, Kirby P, Komuro E, Imura M, Zhang Q, Whatmore Ret al., 2001, Thin-film bulk acoustic resonators and filters using ZnO and lead-zirconium-titanate thin films, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, Vol: 49, Pages: 769-778, ISSN: 0018-9480

Journal article

Komuro E, Su Q, Huang Z, Kirby PB, Whatmore RWet al., 2001, Effect of electrodes on GHZ ZnO thin film bulk-acoustic-wave resonator, Pages: 227-236, ISSN: 1058-4587

Thin film bulk acoustic resonators (FBARs) were prepared with ZnO films using Al and Cr/Au electrodes. ZnO films were deposited by RF sputtering. Al and Cr/Au electrodes were prepared by DC sputtering and thermal evaporation respectively. S parameters were measured with a network analyzer. From TEM images, it is apparent that there are some defects on ZnO with Al electrode while no defects are detected on ZnO with Cr/Au. Also, an intermediate layer is observed between ZnO and Al but nothing between ZnO and Au. As a result of those differences, the resonant frequency, the width between series and parallel frequency and the value of S11 between peak and valley, are different between the FBAR samples with Al or Cr/Au even though both FBAR samples have the same thickness of ZnO.

Conference paper

De Kroon AP, Dunn SC, Whatmore RW, 2001, Piezo- and pyroelectric properties of lead scandium tantalate thin films, Pages: 209-218, ISSN: 1058-4587

This paper discusses the piezo- and pyroelectric properties of lead scandium tantalate thin films prepared by modified sol-gel technology. Films were deposited on Pt/Ti/SiO2/Si-substrates at 530-630°C. The quality of the thin films was optimized by design of both the deposition conditions and the solution chemistry. These approaches include spin coating speed, drying plus crystallization temperature and time, drying atmosphere, the use of rapid thermal annealing, PST sol composition, Pb-excess concentration and mixing method. The finished thin films were characterized by optical microscopy, X-ray diffraction, atomic force microscopy, and pyroelectric measurements at 30°C under a DC-bias. Piezo-response AFM was conducted on PST to monitor various piezoelectric responses, which depend on the microstructure of the film. The maximum pyroelectric figure-of-merit FD was 3.85×10-5 Pa-1/2 at 30°C and 1 kHz under a 35 V DC-bias.

Conference paper

Roy SS, Gleeson HF, Whatmore RW, Shaw CP, Zhang Qet al., 2001, Effects of pulsed electric fields on a nematic device with a ferroelectric ceramic substrate, Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals, Vol: 368, Pages: 9-15, ISSN: 1058-725X

We report details of the interaction between a thin film of ferroelectric ceramic (lead zirconate-lead titanate) and an overlying layer of nematic liquid crystal. Pulsed electric fields of 1ms duration and of varying amplitudes and polarity have been used to achieve different degrees of poling within devices in which one substrate includes the ferroelectric ceramic layer. The degree of orientation of the nematic liquid crystal is found to depend on both the amplitude and polarity of the poling voltage employed. The magnitude of the poling voltage necessary to induce reorientation in the liquid crystal compares reasonably with the calculated value. The reorientation of the nematic liquid crystal due to the interaction with poled grains of PZT is stable for at least several months. © 2001 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint, a member of the Taylor & Francis Group,.

Journal article

Dunn S, De Kroon AP, Whatmore RW, 2001, An examination of thin film lead scandium tantalum oxide (PST) using piezoAFM, JOURNAL OF MATERIALS SCIENCE LETTERS, Vol: 20, Pages: 179-181, ISSN: 0261-8028

Journal article

Waser R, Wouters D, Whatmore R, 2001, Proceedings of the Twelfth International Symposium on Integrated Ferroelectrics - Aachen, Germany - March 12-15, 2000 Part III of VI parts - Guest editorial, INTEGRATED FERROELECTRICS, Vol: 32, Pages: IX-X, ISSN: 1058-4587

Journal article

Waser R, Wouters D, Whatmore R, 2001, Proceedings of - The Twelfth International Symposium on Integrated Ferroelectrics - Aachen, Germany - March 12-15, 2000 part VI of VI parts - Guest editorial, INTEGRATED FERROELECTRICS, Vol: 35, Pages: XXXIII-XXXIV, ISSN: 1058-4587

Journal article

Waser R, Wouters D, Whatmore R, 2001, Proceedings of the Twelfth International Symposium on Integrated Ferroelectrics - Aachen, Germany - March 12-15, 2000 Part V of VI parts - Guest editorial, INTEGRATED FERROELECTRICS, Vol: 34, Pages: IX-X, ISSN: 1058-4587

Journal article

Waser R, Wouters D, Whatmore R, 2001, Proceedings of - The Twelfth International Symposium on Integrated Ferroelectrics - Aachen, Germany - March 12-15, 2000 part IV of VI parts - Guest editorial, INTEGRATED FERROELECTRICS, Vol: 33, Pages: IX-X, ISSN: 1058-4587

Journal article

Kirby P, Komuro E, Imura M, Zhang Q, Su QX, Whatmore Ret al., 2001, High frequency thin film ferroelectric acoustic resonators and filters, 13th International Symposium on Integrated Ferroelectrics, Publisher: TAYLOR & FRANCIS LTD, Pages: 1743-1752, ISSN: 1058-4587

Conference paper

Shaw CP, Roy SS, Whatmore RW, Gleeson H, Huang Z, Zhang Q, Dunn Set al., 2001, Growth and characterisation of lead zirconate titanate (30/70) thin films using TiO<sub>2</sub> seeding for oxide ferroelectric-liquid crystal display application, FERROELECTRICS, Vol: 256, Pages: 159-+, ISSN: 0015-0193

Journal article

Dunn S, Whatmore RW, 2001, Transformation dependence of lead zirconate titanate (PZT) as shown by PiezoAFM surface mapping of Sol-gel produced PZT on various substrates., 13th International Symposium on Integrated Ferroelectrics, Publisher: TAYLOR & FRANCIS LTD, Pages: 683-691, ISSN: 1058-4587

Conference paper

Komuro E, Su QX, Huang ZR, Kirby PB, Whatmore RWet al., 2001, Effect of electrodes on GHZ ZnO thin film bulk-acoustic-wave resonator, 12th International Symposium on Integrated Ferroelectrics, Publisher: TAYLOR & FRANCIS LTD, Pages: 1667-1676, ISSN: 1058-4587

Conference paper

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