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Pseudo-SAW frequency vs. wavevector for Ni-based SPCs (inset), with h = 10 nm, f = 0.5, and p as indicated on top x-axis. The reported substrate’s Rayleigh wave linear dispersion (black dashed line) and experimental data (blue empty circles) are taken from Siemens et al., see Ref. 8. The pseudo-SAW frequencies (red circles) are calculated for the same SPC configurations experimentally investigated in Ref. 8. The pseudo-SAW dispersion is calculated beyond a perturbative approach (red line), see Ref. 9. The green circle highlights the pseudo-SAW frequency calculated for p = 50 nm.
(a) SPC mass sensor: schematic drawing of free (top) and loaded (bottom) device. The absolute value of the projection coefficients vs. frequency, calculated for free (empty marks) and loaded (filled marks) device, are reported for both Al-SPC (diamonds) and Ni-SPC (circles). The data sets are fit with a Fano line shape profile. Two mass loading configurations are investigated: (b) 50 ng/cm2 and (c) 10 ng/cm2. Detailed view of the frequency shift of Al-SPC upon mass loading is reported in the inset. The blue bar is the extrinsic frequency resolution GHz.
SPC mass sensors’ performances. Al-SPC is the device proposed in the present work. Ni-SPC is the Ni-based version. Their operating frequency and the line broadening parameter of the calculated projection profiles are reported for different mass loading configurations.
Comparison of mass sensors’ sensitivities. QCM, SAW, and FPW stand for, respectively, quartz crystal microbalance, typical surface acoustic wave-based, and flexural plate wave-based sensors, see Ref. 15.
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