SAW UV sensors using ZnO nanorods grown on AlN/Si structures

Abstract

In this study, we demonstrate the ZnO nanorods grown on aluminum nitride (AlN)/silicon (Si) layered structure to obtain surface acoustic wave (SAW) UV sensor. The ZnO nanorods act as high UV sensing material due to large surfaceto-volume ratio. The X-ray Diffraction (XRD) and photoluminescence (PL) spectra showed that the ZnO nanorods grown on AlN/Si had highly (002)-oriented and good optical properties. The piece of ZnO nannorods grown at center of twoport SAW delay line, which based on inter-digital transducer (IDT)/AlN/Si structure was fabricated and exposed under UV light. Resulting in the SAW UV sensor shifted a maximum of 26 kHz under the UV intensity of 0.6 mW/cm 2 .I.

Shadow mask assisted direct growth of ZnO nanowires as a sensing medium for surface acoustic wave devices using a thermal evaporation method

“…There have been several reports in the past where ZnO film [33][34][35][36][37][38][39][40] and nanostructures [5][6][7]41] have been used as sensing medium for SAW UV detection purposes. The sensing mechanism employed is the SAW acoustoelectric effect, where an induced change in electrical conductivity of the ZnO layer upon detecting light at UV wavelengths leads to attenuation of the SAW and a shift in its velocity of propagation.…”

“…This is because this method has a lower temperature of synthesis compared to the thermal evaporation method and, hence, does not require the SAW device to be exposed to elevated temperatures during the ZnO nanowire growth process. By contrast, in previous reports where the solution grown method was used for growth of ZnO nanowires as a sensing medium on SAW devices, a pre-deposited ZnO seed layer was required to assist the nucleation of ZnO nanowires [5,7]. The use of this seed layer results in the growth of ZnO nanowires with fusion among their roots, thereby reducing the exposed surface area of the nanowires used for sensing purposes [10].…”

“…Recently, considerable research has been conducted into the use of one-dimensional (1D) Zinc oxide (ZnO) nanostructures as sensing medium in surface acoustic wave (SAW) based gas sensors [1][2][3][4] and ultraviolet (UV) light detectors [5][6][7]. ZnO nanowires have an enhanced ability to selectively adsorb certain gas molecules and light at UV wavelength to induce a change in their electrical conductivity.…”

“…SAW devices are typically fabricated by patterning electrically conductive metal electrodes on the surface of a piezoelectric substrate such as quartz, lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), langasite (La 3 Ga 5 SiO 14 ) or gallium orthophosphate (GaPO 4 ). Previous reports suggest that growth of 1D ZnO nanostructures on piezoelectric substrates is possible through the solution grown method [1][2][3][4][5]7] and thermal evaporation method [8,9]. In our previous study [9], we synthesized high aspect ratio catalyst-free ZnO nanowires on blank LiNbO 3 substrates through a self-seeding thermal evaporation method for the first time and examined the alignment nature of the as-grown ZnO nanowires on the LiNbO 3 surface.…”