ABSTRACT
The paper presents an equivalent circuit model of the polymer coated surface acoustic wave (SAW) resonators by combining coupling-of-mode (COM) description of SAW resonators and perturbation calculation of SAW propagation under polymer loading. An expression for the motional load produced by polymer coating is deduced in terms of COM parameters and polymer characteristics. In addition, expressions for the shifts in resonance frequency and attenuation due to polymer loading are obtained. Simulation results are presented for one-port and two-port resonator devices coated with viscoelastic thin polymer film. The influence of polymer film on resonator response is studied with regard to variations in film thickness and shear modulus. The model simplifies understanding of polymer-coated SAW sensors.
Subject(s)
Acoustics/instrumentation , Computer-Aided Design , Electronics/instrumentation , Micro-Electrical-Mechanical Systems/instrumentation , Models, Theoretical , Polymers/chemistry , Transducers , Computer Simulation , Electric Impedance , Equipment Design , Equipment Failure Analysis , Scattering, RadiationABSTRACT
Single phase nanocrystalline lead zirconate titanate (PZT) powder of composition Pb(Zr(0.52)Ti(0.48))O3 has been prepared by sol-gel process by using lead acetate trihydrate, zirconium propoxide and titanium propoxide as lead, zirconium and titanium precursor materials respectively. XRD, FTIR and TGA/DTA techniques are used to characterize structural, vibrational and thermal changes involved during the formation of PZT nanocrystalline powder with tetragonal phase. XRD pattern exhibits the polycrystalline nature of the powder heat treated at 800 degrees C with preferential orientation of (110) plane. Simultaneous TGA/DTA studies of the gel powder show endothermic and exothermic peaks corresponding to weight loss at different temperatures and increase in weight between 750 degrees C and 800 degrees C which confirms the improvement in crystallization. IR transmittance spectra of the powders heat treated at 650 degrees C and 750 degrees C show the coexistence of rhombohedral and teragonal phases and above this temperature only teragonal phase exists.
ABSTRACT
Current-voltage (J-V) characteristics of poly(3-hexylthiophene) (P3HT) are studied at different temperatures upto high voltages approximately 20V in the hole-only device configuration. The characteristics are studied in the temperature range 310-210K. In the intermediate voltage range the J-V characteristics follow J proportional to V(l+1), where l > 1. As the voltage increases to high values J still varies as a power law i.e. as V(m), but contrary to the literature result m becomes < 2. This behavior is explained theoretically in terms of non-zero injection Schottky barriers. The complete analytical expressions for the actual trap filled limit voltage (V'(TFL)) and J-V curves beyond V'(TFL) are presented.
