Interaction of acoustic waves with spin waves using a GHz operating GaN/Si SAW device with a Ni/NiFeSi layer between its IDTs.

A two port surface acoustic wave (SAW) device was developed to be used for the control and excitation via spin waves (SW). The structure was manufactured using advanced nanolithography techniques, on GaN/Si, enabling fundamental Rayleigh interdigitated transducer (IDT) resonances in GHz frequency range. The ferromagnetic resonance of the magnetostrictive Ni/NiFeSi layer placed between the IDTs of the SAW device can be tuned to the SAW resonance frequency by magnetic fields. Using structures with finger and interdigit spacing of 170 nm and 100 nm, fundamental Rayleigh IDT resonance frequencies of 6.4 and 10.4 GHz have been obtained. Coupling of SAW to SW was demonstrated through transmission measurements at the fundamental Rayleigh frequencies in a magnetic field, µ0H from -280 to +280 mT, at different angles (θ) between the SAW propagation direction and the magnetic field direction. For the 6.4 GHz resonator a maximum decrease of about 1.2 dB occurred in |S21|, at µ0H = 30 mT and at θ = 45. Time-gated processing of the frequency domain raw data was used to remove the direct electromagnetic cross talk and triple transit effects. Nonreciprocity associated to the coupling was analyzed for the two SAW structures. The quantitative influence of the magnetic field strength on the phase of the transmission parameters is also presented.

The Behavior of Gold Metallized AlN/Si- and AlN/Glass-Based SAW Structures as Temperature Sensors.

Thin AlN piezoelectric layers have been deposited on high resistivity Si and glass substrates by reactive RF magnetron sputtering, in order to manufacture one-port gigahertz operating surface acoustic wave (SAW)-type resonators to be used as temperature sensors. The growth morphology surface topography, crystallographic structure, and crystalline quality of the AlN layers have been analyzed. Advanced nanolithographic techniques have been used to manufacture structures having interdigitated transducers with fingers and finger interdigit spacing width in the range of 250-170 nm. High resonance frequency ensures the increase of the sensitivity, but also of its normalized value, the temperature coefficient of frequency (TCF). The resonance frequency shift versus temperature has been measured in the -267°C-+150°C temperature range, using a cryostat setup adapted for on wafer microwave measurements up to 50 GHz. The sensitivity and the TCF were determined in the 25 °C-150 °C temperature range.