AlN-based BAW resonators with CNT electrodes for gravimetric biosensing

Abstract

ARTICLE INFO ABSTRACTSolidly mounted resonators (SMRs) with a top carbón nanotubes (CNTs) surface coating that doubles as an electrode and as a sensing layer have been fabricated. The influence of the CNTs on the frequency response of the resonators was studied by direct comparison to identical devices with a top metallic electrode. It was found that the CNTs introduced significantly less mass load on the resonators and these devices exhibited a greater quality factor, Q.(>2000, compared to ~1000 for devices with metal electrodes), which increases the gravimetric sensitivity of the devices by allowing the tracking of smaller ~ " frequency shifts. Protein solutions with different concentrations were loaded on the top of the resonators Keywords' Biosensor anc ' me ' r res P onses to mass-load from physically adsorbed coatings were investigated. Results show Carbón nanotube (CNT) tnat resonators using CNTs as the top electrode exhibited a higher frequency change for a given load Aluminum nitride (A1N) (~0.25 MHz cm 2 ng _1 ) compared to that of a metal thin film electrode (~0.14 MHz cm 2 ng _1 ), due to the Bulk acoustic wave resonator (BAW) lower mass of the CNT electrodes and their higher active surface área compared to that of a thin film Gravimetric biosensor metal electrode. It is therefore concluded that the use of CNT electrodes on resonators for their use as gravimetric biosensors is a significant improvement over metallic electrodes that are normally employed.

A Novel Bulk Acoustic Wave Resonator for Filters and Sensors Applications

“…AlN based BAW resonators have two basic architectures: Thin Film Bulk Acoustic Wave Resonator (FBAR), which is suspended above an air cavity, and Solidly Mounted Resonator (SMR), which utilizes a series of high and low impedance reflectors to isolate the resonator from the substrate. Thanks to their miniature sizes, high quality factors (Q) in air, and compatibilities with integrated circuit processing, BAW resonators have been used in a widespread applications, such as filters and duplexers in communication electronics [1,2], oscillators for frequency control, gravimetric sensors for physical [3], chemical [4] and biological [5,6] sensing, and general physics applications [7].…”

Novel flexible FBAR on PET substrate

“…Fig. 2(b) is the simulated reflection spectrum using the COMSOL Multiphysics for FBAR on PET substrate with the actual device parameters and material properties [2][3][4]. Although the actual device has poor reflection than the simulated one, both have the same resonant frequencies, indicating the peak is indeed the resonant wave in the FBARs on PET.…”

“…FBARs have also been utilized as sensors with high-sensitivity for various applications such as humidity, UV and biosensors [1][2][3]. There are three types of FBAR device structures, namely the back-trench, air-bag and Bragg reflector.…”

Acoustic Wave Based Microfluidics and Lab-on-a-Chip

“…An improvement of Q-value by 5 times was demonstrated simply by using a CNT layer on top of existing metal electrodes [120]. Garcia-Gancedo et al recently fabricated FBARs with CNT layer as the top electrode and demonstrated FBARs with a quality factor over 2000 [121,122], one of the best values reported. Also the spurious ripples round a resonant peak found in Au electrode FBARs disappeared when CNTs were used as shown in Fig.…”