"HIGH SENSITIVE H 2 GAS SENSOR OF ZnO/PS NANOSTRUCTURE PREPARED VIA PULSED LASER DEPOSITION TECHNIQUE "

Abstract

Porous Silicon (PS) has been prepared by electrochemical etching technique on the (111) Ptype silicon wafer. The surface morphology of PS studied by atomic force microscope (AFM) verifies that the irregular and randomly distributed nanocrystalline silicon pillars and voids over the entire surface of silicon wafer. The average diameter was about 29.96nm and the average roughness about 0.747nm. The FE-SEM image of the PS sample showed a homogeneous pattern and confirms the formation of uniform porous structures on the silicon wafer. From XRD pattern, a broadening in diffraction peak was showed and the fullwidth at half maximum (FWHM) about 0.8951, crystalline size was found about 10.8nm. Photoluminescence spectra (PL) showed blue shift at 775nm (1.610eV). ZnO thin film was prepared by pulsed laser deposition technique deposited on slide glasses. The surface morphology of the film studied by (AFM), it is presented uniform distribution of densely packed of grains. The average diameter of ZnO film is 76.91nm and the roughness 1.88nm. FE-SEM images showed a fine-grained structure and unmodified without any cracks. It is observed that the ZnO particles are homogeneously dispersed in the PS surface. Structural properties of ZnO film investigated by XRD, the peaks appear belongs to hexagonal ZnO in (101) and (100) orientation. The crystalline size of the film is 17.8nm and 9.1nm, respectively. UV-V measurement showed that the energy gap (Eg) is equal to 3.4 eV. D.C. conductivity at the temperature (303-473) K for ZnO film showed that the film has two activation energies Ea1 (in the range from 303 to 383K) and Ea2 (in the range from 383 to 473K). Hall Effect measurements showed that the film has n-type charge carriers with concentration of 25.131x10 14 cm -3 and mobility of 1.03cm 2 /v.sec. ZnO/PS gas sensor showed very high sensitivity for H 2 gas is about 15575.0% in 350 ˚C and a shorter time response about 15.5s