Spatial sensitivity distribution of surface acoustic wave resonator sensors

The sensitivity distribution of surface acoustic wave (SAW) resonator sensors is investigated by theoretical and experimental means. It is shown that the sensitivity to mass loading varies strongly across the surface due to the confinement of acoustic energy toward the center of the device. A model is developed for this phenomenon based on the extraction of coupling of modes parameters from a rigorous boundary element method analysis based on a periodic Green's function. As SAW sensors for many applications include a layer covering the electrodes, a new technique is introduced to account for the mechanical interactions with buried electrodes. Using this technique, the sensitivity calculations are found to be in good agreement with measurements. It is also shown that while changes in other parameters influence sensitivity, it is velocity change that most strongly determines overall frequency change

Development of nano-structured titanium oxide thin films using a gas carving technique

A method is developed for producing nano-structured titanium oxide thin films using H2 gas interaction with titanium thin film at a high temperature. These nano-structured thin films have been formed on a quartz crystal substrate. Titanium (Ti) thin films were deposited on the quartz crystal using a RF magnetron sputterer. The samples were placed in the oven at 500-800°C for 5 hours. The gas mixture of 1% H2 in N2 was introduced in the oven. The process of Ti annealing in the presence of H2 carves Ti films into nano-structure shapes. The process is a gas-solid interaction. Thin films were characterised using Scanning Electron Microscopes (SEM) and X-Ray Diffraction (XRD) technique. The nano structures formed have dimensions in a range of 25nm - 150nm obtained after gas carving

Polyaniline nanofiber based surface acoustic wave gas sensors - effect of nanofiber diameter on H2 response

A template-free rapidly mixed reaction was employed to synthesize polyaniline nanofibers using chemical oxidative polymerization of aniline. Hydrochloric acid (HCl) and camphor sulfonic acid (CSA) were used in the synthesis to obtain 30- and 50-nm average diameter polyaniline nanofibers. The nanofibers were deposited onto layered ZnO/64 degrees YX LiNbO3 surface-acoustic-wave transducers. The sensors were tested toward hydrogen (H-2) gas while operating at room temperature. The dopant for the polyaniline nanofiber synthesis was found to have a significant effect on the device sensitivity. The sensor response was found to be larger for the 50-nmdiameter CSA-doped nanofiber based sensors, while the response and recovery times were faster for the 30-nm diameter HCl-doped nanofibers

A layered SAW device based on ZnO/LiTaO3 for liquid media sensing applications

Surface Acoustic Wave (SAW) sensors comprising a zinc oxide guiding layer deposited on a 36°-YX lithium tantalate substrate were developed. They were found to have greater mass sensitivity than other LiTaO3 based SAW sensors, such as the -SiO2/LiTaO3 configuration. In this paper, the fabrication of the ZnO/LiTaO3 sensor is described and micro-characterisation of the deposited films is presented. Sensitivity of these devices to surface mass and dielectric perturbations is then presented, followed by an analysis of temperature stability

Optimum sensitive area of surface acoustic wave resonator chemical and bio-sensors

A model is developed to map the variation of sensitivity of a surface acoustic wave (SAW) resonator sensor over its surface, in order to find the region with maximum sensitivity. The model is based on a combined coupling of modes (COM) and periodic Green's function analysis. In order to extend the analysis to layered media, a new efficient technique is introduced to account for the mechanical interactions with buried electrodes. Using this technique the sensitivity calculations are found to be in good agreement with measurements. It is also shown that whilst changes in other parameters influence the sensitivity, it is the velocity change which most strongly determines the overall frequency change

H2 and NO2 gas sensors with ZnO nanobelt layer on 36° LiTaO3 and 64° LiNbO3 SAW transducers

Single crystal nanobelts of ZnO were synthesized and deposited onto 36° YX LiTaO<sub>3</sub> and 64° YX LiNbO<sub>3</sub> surface acoustic wave (SAW) devices for gas sensing applications. Sensor response, defined as the change in resonant frequency, was measured for H<sub>2</sub> and NO<sub>2</sub> between 20 and 200°C. Measured sensor responses were 3.5 kHz towards 10 ppm NO<sub>2</sub> for a 64° LiNbO<sub>3</sub> SAW transducer operating at 160°C and 3 kHz towards 1% H<sub>2</sub> for a 36° LiTaO<sub>3</sub> SAW transducer operating at 185°C temperature

Titanium dioxide based 64° YX LiNbO3 surface acoustic wave hydrogen gas sensors

Amorphous titanium dioxide (TiO2) and gold (Au) doped TiO2-based surface acoustic wave (SAW) sensors have been investigated as hydrogen gas detectors. The nanocrystal-doped TiO2 films were synthesized through a sol-gel route,mixing a Ti-butoxide-based solution with diluted colloidal gold nanoparticles. The films were deposited via spin coating onto 64\ub0 YX LiNbO3 SAWtransducers in a helium atmosphere. The SAW gas sensors were operated at various temperatures between 150 and 310 \ub0C. It was found that gold doping on TiO2 increased the device sensitivity and reduced the optimum operating temperature

Plastic Deformation in Laser-Induced Shock Compression of Monocrystalline Copper

Copper monocrystals were subjected to shock compression at pressures of 10–60 GPa by a short (3 ns initial) duration laser pulse. Transmission electron microscopy revealed features consistent with previous observations of shock-compressed copper, albeit at pulse durations in the µs regime. The results suggest that the defect structure is generated at the shock front. A mechanism for dislocation generation is presented, providing a realistic prediction of dislocation density as a function of pressure. The threshold stress for deformation twinning in shock compression is calculated from the constitutive equations for slip, twinning, and the Swegle-Grady relationship

Deuteron-deuteron collision at 160 MeV

The experiment was carried out using BINA detector at KVI in Groningen. For the first time an extensive data analysis of the data collected in back part of the detector is presented, where a clusterization method is utilized for angular and energy information. We also present differential cross-sections for the (dd$\rightarrow$dpn) breakup reaction within \textit{dp} quasi-free scattering limit and their comparison with first calculations based on Single Scattering Approximation (SSA) approach.Comment: 6 pages, 4 figures, presented at Jagiellonian Symposium 2015 in Krakow, PhD wor