This paper proposes high sensitivity temperature sensors based on single port surface acoustic wave (SAW) devices with GHz resonance frequencies, developed on GaN/SiC and GaN/Sapphire, which permit wide range, accurate temperature determinations. In contrast with GaN/Si SAW based temperature sensors, SiC and Sapphire substrates enable the proper functionality of these devices upto 500°C (773 K), as the high resistivity Si substrate becomes conductive at temperatures exceeding 250°C (523 K) due to the relative low bandgap (and high intrinsic carrier concentrations). Low temperature measurements were carried out using a cryostat between -266°C (7 K) and room temperature (RT) while the high temperature measurements are made on a modified RF probe station. A polynomial fit was used below RT and a linear approximation was evidenced between RT and 500°C (773 K). The structures were simulated at different selected temperatures based on a method that couples Finite Element Method (FEM) and Coupling of Modes (COM). The measured temperature coefficient of frequency (TCF) is about 46 ppm/°C for GaN/SiC SAWs and reaches values of 96 ppm/°C for GaN/Sapphire SAW in the temperature range 25 – 500°C (298 K – 773 K).

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 GHz operating 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 analysed. Advanced nano-lithographic techniques have been used to manufacture structures having interdigitated transducers with fingers and finger interdigit spacing width in the 250 – 170 nm range. 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 vs. temperature has been measured in the -267 – +150 °C temperature range, using a cryostat set-up adapted for on wafer microwave measurements up to 50 GHz. The sensitivity and the TCF were determined in the 23 – 150 °C temperature range for all measured structures. High values for the sensitivity as well as for the TCF have been obtained. The performances are compared with previous results obtained for GaN/Si GHz operating sensors. For the first time, a numerical method based on finite element technique and coupling of modes was implemented in order to simulate the variation of the resonance frequency of the envisaged AlN/Si and AlN/glass SAW structures within the 25 – 150 °C temperature range.

We report on the resonant excitation of spin waves in micro-structured magnetic thin films by short-wavelength surface acoustic waves (SAWs). The spin waves as well as the acoustic waves are studied by micro-focused Brillouin light scattering spectroscopy. At low magnetic bias fields, a resonant phonon–magnon conversion is possible, which results in the excitation of short-wavelength spin waves. Using micromagnetic simulations, we verify that during this excitation both energy and linear momentum are conserved and fully transferred from the SAW to the spin wave. This conversion can already be detected after an interaction length of a few micrometers. Thus, our findings pave the way for miniaturized magneto-elastic spin-wave emitters for magnon computing.

A compact analytical model is proposed along with a parameter extraction methodology to accurately capture the steady-state (DC) sequential tunneling current observed in the subthreshold region of the transfer $I_{DS}-V_{GS}$ characteristics of MOSFETs at cryogenic temperatures. The model is shown to match measurements of $p$ -MOSFETs and $n$ -MOSFETs manufactured in a commercial 22nm FDSOI foundry technology, with reasonable accuracy across bias conditions and temperature (2 K - 50 K). Furthermore, the extracted model parameters are used to analyze the impact of the gate and drain voltages and of layout geometry on the device characteristics.

The parametric excitation of spin waves by coherent surface acoustic waves in metallic magnetic thin film structures is demonstrated experimentally using Brillouin light scattering spectroscopy. Complementary micromagnetic simulations and analytical modeling reveal that, depending on the experimental conditions, the spin‐wave instabilities originate from different phonon‐magnon and magnon‐magnon scattering processes. This opens novel ways to create micro‐scaled nonlinear magnonic systems for logic and data processing that profit from the efficient excitation of phonons using piezoelectricity.

ScAlN/Si, a CMOS compatible material, was used to manufacture GHz operating surface acoustic wave devices, targeting manipulation and control of spin waves via SAW devices. A thin ScAlN piezoelectric layer was deposited on high resistivity (111) oriented Silicon and two port SAW devices were processed using advanced nanolithographic techniques. The Surface Acoustic Wave and Spin Wave coupling was performed via a thin magnetostrictive layer (Ni) placed between the SAWs interdigitated transducers. Both Rayleigh (4.67 GHz) and Sezawa (8.05 GHz) propagation modes could be observed. The amplitude of the S ₂₁ parameter around the two resonances was measured for values of the magnetic field $\mu _{0}\text{H}$ from −280 to +280 mT, at different angles ( $\theta $ ) between the SAW propagation direction and the magnetic field direction. A maximum decrease of 2.54 dB occurred in S ₂₁ for the Rayleigh mode at $\mu _{\textbf {0}}\text{H}$ = −90 mT, and of 7.24 dB for the Sezawa mode at $\mu _{0}\text{H}$ = −203 mT, both at $\theta $ = 45°. These values were extracted from time gated processing of the frequency domain raw data. Nonreciprocity associated to the coupling was analyzed for the two propagation modes.