Ion beam sputter-deposited ZnO thin film for broadband shear wave excitation in the GHz range

In-plane and out-of-plane oriented (112̄0) ZnO thin films are attractive for shear wave excitation in the GHz range. It is proposed here that highly oriented and submicron-thick (112̄0) ZnO thin films can be fabricated using ion beam sputter-deposition system with grazing incidence to the substrate surface. This (112̄0) texture formation cannot only be attributed to the well-known ion channeling effect or to the self-shadowing effect since the ion beam incidence direction in the system does not correspond to the ion channeling direction of the ZnO film (the [10̄10] or [112̄0] direction). Full-width-at-half-maximum (FWHM) values of the φ-scan and Ψscan profile curves of the (1122) X-ray diffraction poles were measured to be 5° and 28°, respectively. A shear-wave transducer with a 0.9-μm-thick film exhibited an untuned one-way conversion loss of less than 20 dB at 1 - 2 GHz and a 3dB-fractionaI bandwidth of 100%, without any longitudinal wave excitation.