ABSTRACT
(100) ZnO films on silicon will excite Rayleigh SAWs along the z-axis and shear horizontal (SH) SAWs along the y-axis. Rayleigh SAW modes of (100) ZnO films on silicon have smaller film thickness ratios, higher phase velocities, and larger electromechanical coupling coefficient (K(2)) than the those of (002) ZnO films on silicon. This is special for Rayleigh mode 1, where the K(2) curve shows a maximum value of 3.37% at h/lambda = 0.28 and the velocity is 5258 m/s. This is special for SH mode 0, where the K(2) curve shows a maximum value of 3.3% at h/lambda = 0.28 and the velocity is 3242 m/s.
ABSTRACT
(100) AlN films have better surface acoustic wave (SAW) properties than (002) AlN films. In this research, (100) AlN films were combined with diamonds as a new composite SAW substrate. The SAW properties of (100) AlN films on diamonds were analyzed with 4 composite structures: interdigital transducer (IDT)/(100) AlN/diamond, (100) AlN/IDT/diamond, IDT/(100) AlN/metal/diamond, and metal/IDT/(100) AlN/diamond, and they exhibited some excellent SAW properties. Our research results provide a predictable and theoretical basis for further application on high-velocity SAW devices.
Subject(s)
Acoustics/instrumentation , Aluminum Compounds/chemistry , Diamond/chemistry , Transducers , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Reproducibility of Results , Scattering, Radiation , Sensitivity and SpecificityABSTRACT
C-axis-oriented ZnO films were sputtered on Langasite substrate (LGS, La(3)Ga(5)SiO(14)). The crystalline structure of the films was determined by grazing incident angle X-ray diffraction, the surface microstructure of films was investigated by scanning electron microscopy and atomic force microscopy, the atom composition ratio O/Zn of films was determined by energy dispersive X-ray spectroscopy, and the resistivity of films was determined by the four-point probe instrument. The measurement results showed those films prepared were all polycrystalline hexagonal ZnO films. By analyzing the microstructure of the ZnO films, those prepared at the oxygen flow rate (O(2)/O(2)+Ar) of 20%, the RF power of 200 W, and the substrate temperature of 200 degrees C had the best performance: highly c-axis-oriented microstructures, dense surface morphology, and the atom composition ratio 1.02. The measured scattering parameters of the SAW device fabricated on the composite substrate (ZnO/LGS) with film thickness 1.76 microm showed an average shifted velocity around 2741 m/s at 57.1 MHz and a electromagnetic coupling coefficient greater than 1%.
Subject(s)
Acoustics/instrumentation , Membranes, Artificial , Silicates/chemistry , Transducers , Zinc Oxide/chemistry , Equipment Design , Equipment Failure Analysis , Materials Testing , Reproducibility of Results , Scattering, Radiation , Sensitivity and SpecificityABSTRACT
The novel pyroelectric IR detectors have been fabricated using the Polyvinylidene Fluoride (PVDF)/Lead Titanate (PT) pyroelectric bilayer thin films, which were deposited onto Pt(111)/SiO2/Si(100) substrates by a sol-gel process. The ceramic/polymer structure was constructed of the randomly oriented polycrystalline PT film (approximately 1 microm) heated at 700 degrees C for 1 h and the beta-phase PVDF film crystallized at 65 degrees C for 2 h. The effects of PVDF thin film thickness (100 approximately 580 nm) on the pyroelectric response of IR detectors were studied. The results show that the depositions of PVDF thin films onto the PT films will cause the leakage current (J) of the detectors decrease from 6.37 x 10(-7) A/cm2 to 3.86 x 10(-7) A/cm2. The specific detectivity (D*) measured at 100 Hz decreased from 2.72 x 10(7) cm x Hz(1/2)/W for detector without PVDF to 1.71 x 10(7) cm x Hz(1/2)/W for detector with PVDF thickness of 580 nm. By optimizing the ratio of the specific detectivity (D*) to leakage current, D*/J, the detector with PVDF thickness of 295 nm exhibits the best performance.
