Detection of various self-assembled monolayers by AlN-based film bulk acoustic resonator

Various self-assembled monolayers such as carcinoembryonic antigen (CEA), beta actin, and bovine serum albumin (BSA) were detected using an AlN-based film bulk acoustic resonator (FBAR). AlN thin film was deposited by reactive RF magnetron sputtering, on a substrate of Mo (100 nm)/Ti (34 nm)/SiO₂ (480 nm)/Si (300 μm)/Si₃N₄ (300 nm). The film showed a strongly c-axis preferred orientation with a main (0 0 2) peak, as well as a good full width at half maximum (FWHM) of 2.50° in XRD and rocking curve results. The AlN-based FBAR was confirmed to have a resonant frequency of 2.477 GHz and a sensitivity of 3514 Hz cm²/ng. In beta actin, BSA, and CEA, the frequency properties showed variation values of 472.142, 932.573, and 685.421 kHz and mass sensitivities of 3530, 3506, and 3514 Hz-cm²/ng, respectively. The FBAR sensor was confirmed to be very useful for detecting target antigens through the binding of an antigen and an anti-body.