Conductometric assisted ZnO and polypyrole composite based NH3 gas sensor

Metal oxides are excellent choices as base materials in emerging technologies in the field of Gas Sensors. In this work, an effort is made to prepare the ZnO and polypyrrole composite thin film using sol-gel technique. Nanocomposite thins film was prepared using spin coating on glass substrates for ammonia gas sensing. ZnO and polypyrrole sols were prepared using sol-gel technique and thin films were prepared by using spin coater. The nanocomposite thin films were prepared by varying the percentage composition of ZnO and Polypyrrole. Structural, optical and morphological properties of the prepared films were done using XRD, UV-Visible and SEM studies. The films were separately prepared on Inter-Digital Transducers for gas sensing applications. Gas sensing response characteristics of the prepared sensor were performed using laboratory. The sensing response of the prepared films is observed and found to be maximum (~33) for the 70%PPy+30%ZnO film at a relatively low operating temperature of about 150°C.

Periodic Analysis of Surface Acoustic Wave Resonator with Dimensionally Reduced PDE Model Using COMSOL Code

Radio-frequency (RF) surface acoustic wave (SAW) resonators used as filters and duplexers are mass-produced and widely used in current mobile phones. With the numerous emergences of the diverse device structure, a universal method used for the accurate and fast simulation of the SAW resonator calls for urgent demand. However, there are too many instances where the behavior of the entire acoustic resonator cannot be characterized rapidly and efficiently due to limitations in the current computer memory and speed. This is especially true for SAW resonators configured with long arrays of inter-digital transducers (IDTs), and we have to resort to a periodic analysis. In this paper, the previously reported generalized partial differential equations (PDE) based on the two-dimensional finite element method (2D-FEM) model is extended to analysis for the periodic structure of the SAW resonator. We present model order reduction (MOR) techniques based on FEM and periodic boundary conditions to achieve a dimensionally reduced PDE model without decreasing the accuracy of computations. Examples of different SAW devices, including the regular SAW, IHP-SAW and TC-SAW resonators, are provided which shows the results of the periodic analysis compared with the experimental results of the actual resonators. The investigation results demonstrate the properties of the proposed methodology and prove its effectiveness and accuracy.

Electrical Performances of a Surface Acoustic Wave Device With Inter-Digital Transducers Electrodes in Local Resonances

In this paper, we investigate numerically the coupling of the Rayleigh mode with the micro-wall resonance modes in inter-digital transducers (IDTs) electrodes of surface acoustic wave (SAW) devices. We perform a finite element analysis (FEA) of the SAW features using an implemented model using comsol Multiphysics® software. The SAW structure comprises identical transmitter and receiver IDTs electrodes, with different electrode heights (he). The proposed FEA study is based on the extraction of reflection (S11) and transmission (S21) coefficients of the SAW device. The IDTs are considered to be a micro-wall phononic crystal acting as local resonators at frequencies inside the SAW passband. The locally resonance gap is strongly dependent on the he value, and S11 and S21 parameters are affected by the SAW energy absorption in the IDTs system. We have chosen two he values (0.5 and 3 µm) to study low and high aspect ratios of micro-walls, corresponding respectively to Bragg-type and resonance-type bandgaps appearing near the SAW central frequency. At the SAW resonance frequency, the return (S11) and the insertion (S21) losses are reduced. S21 is reduced by 12.73 and 18.49 dB for he = 0.5 and 3 µm, respectively, accompanied by an increase in the quality factor, and S11 parameter is reduced by 1.357 and 4.98 dB for he = 0.5 and 3 µm, respectively.