Photoacoustic Detection of H2 and NH3 Using Plasmonic Signal Enhancement in GaN Microcantilevers

Abstract

Photoacoustic (PA) detection of H2 and NH3 using plasmonic excitation in Pt- and Pd-decorated GaN piezotransistive microcantilevers were investigated using pulsed 520-nm laser illumination. The sensing performances of 1-nm Pt and Pd nanoparticle (NP) deposited cantilever devices were compared, of which the Pd-coated sensor devices exhibited consistently better sensing performance, with lower limit of detection and superior signal-to-noise ratio (SNR) values, compared to the Pt-coated devices. Among the two functionalization layers, Pd-coated devices were found to respond only to H2 exposure and not to NH3, while Pt-coated devices exhibited repeatable response to both H2 and NH3 exposures, highlighting the potential of the former in performing selective detection between these reducing gases. Optimization of the device-biasing conditions were found to enhance the detection sensitivity of the sensors.

Investigation of AlGaN/GaN HFET and VO2 Thin Film Based Deflection Transducers Embedded in GaN Microcantilevers

“…GaN microcantilevers with integrated AlGaN/GaN HFETs and piezoresistive VO 2 thin films were fabricated using epitaxial layers of III-Nitrides, consisting of 20 nm Al x GaN (x = 0.25), 1 μm GaN, and 0.3 μm buffer layers grown on a 0.6 mm Si (111) substrate. The fabrication process of cantilevers with integrated AlGaN/GaN HFET has been discussed in detail elsewhere [ 17 , 18 , 33 , 34 ]. Briefly, the top AlGaN layer was etched using an inductively coupled plasma tool to define the HFET, and the VO 2 mesa regions with dimensions of 35 × 35 μm.…”

“…The dynamic changes in the V DS (∆ V DS ), due to piezoactuator-based oscillations of the microcantilever, were measured using a lock-in amplifier (SR850 Stanford Research Systems, Sunnyvale, CA, USA), which was also used to bias the piezoactuator with a variable frequency sinusoidal AC voltage. Detailed experimental procedures of GaN microcantilever dynamic characterizations have been reported elsewhere [ 18 , 19 , 20 , 33 , 34 ]. To characterize the VO 2 thin film embedded GaN microcantilever, a constant drain source voltage ( V DS ) of 20 V was applied to the drain contact of the VO 2 thin film using the SMU.…”

An AlGaN/GaN Dual Channel Triangular Microcantilever Based UV Detector

“…III-Nitride based microcantilever structures have been demonstrated to be extremely sensitive and versatile. 42,43 They have been used to develop various types of sensors to detect ultralow deflection, photoacoustic waves, 44 trace quantities of chemicals, 45 and volatile organic compounds. 46 In this work, we report a novel UV PD structure utilizing dual AlGaN/GaN heterostructure based 2DEG channels separated by a semi-insulating GaN layer, shaped in the form of a triangular microcantilever.…”