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Plasmonic piezoelectric nanomechanical resonator for spectrally selective infrared sensing.

Hui Y, Gomez-Diaz JS, Qian Z, Alù A, Rinaldi M - Nat Commun (2016)

Bottom Line: We experimentally demonstrate that it is possible to achieve high thermomechanical coupling between electromagnetic and mechanical resonances in a single ultrathin piezoelectric nanoplate.The combination of nanoplasmonic and piezoelectric resonances allows the proposed device to selectively detect long-wavelength infrared radiation with unprecedented electromechanical performance and thermal capabilities.These attributes lead to the demonstration of a fast, high-resolution, uncooled infrared detector with ∼80% absorption for an optimized spectral bandwidth centered around 8.8 μm.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical &Computer Engineering at Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, USA.

ABSTRACT
Ultrathin plasmonic metasurfaces have proven their ability to control and manipulate light at unprecedented levels, leading to exciting optical functionalities and applications. Although to date metasurfaces have mainly been investigated from an electromagnetic perspective, their ultrathin nature may also provide novel and useful mechanical properties. Here we propose a thin piezoelectric plasmonic metasurface forming the resonant body of a nanomechanical resonator with simultaneously tailored optical and electromechanical properties. We experimentally demonstrate that it is possible to achieve high thermomechanical coupling between electromagnetic and mechanical resonances in a single ultrathin piezoelectric nanoplate. The combination of nanoplasmonic and piezoelectric resonances allows the proposed device to selectively detect long-wavelength infrared radiation with unprecedented electromechanical performance and thermal capabilities. These attributes lead to the demonstration of a fast, high-resolution, uncooled infrared detector with ∼80% absorption for an optimized spectral bandwidth centered around 8.8 μm.

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Overview of the plasmonic piezoelectric nanomechanical resonant infrared detector.(a) Mock-up view: an aluminum nitride nanoplate is sandwiched between a bottom metallic interdigitated electrode and a top nanoplasmonic metasurface. The incident IR radiation is selectively absorbed by the plasmonic metasurface and heats up the resonator, shifting its resonance frequency from f0 to f′ due to the temperature dependence of its resonance frequency. (b) Scanning electron microscopy images of the fabricated resonator, metallic anchors and nanoplasmonic metasurface. The dimensions of the resonator are as follows: L=200 μm; W=75 μm; W0=25 μm (19+6 μm); LA=20 μm; WA=6.5 μm. The dimensions of the unit cell of the plasmonic metasurface are as follows: a=1635, nm; b=310 nm. IR, infrared.
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f1: Overview of the plasmonic piezoelectric nanomechanical resonant infrared detector.(a) Mock-up view: an aluminum nitride nanoplate is sandwiched between a bottom metallic interdigitated electrode and a top nanoplasmonic metasurface. The incident IR radiation is selectively absorbed by the plasmonic metasurface and heats up the resonator, shifting its resonance frequency from f0 to f′ due to the temperature dependence of its resonance frequency. (b) Scanning electron microscopy images of the fabricated resonator, metallic anchors and nanoplasmonic metasurface. The dimensions of the resonator are as follows: L=200 μm; W=75 μm; W0=25 μm (19+6 μm); LA=20 μm; WA=6.5 μm. The dimensions of the unit cell of the plasmonic metasurface are as follows: a=1635, nm; b=310 nm. IR, infrared.

Mentions: The proposed plasmonic piezoelectric NEMS resonator, illustrated in Fig. 1, is composed of an aluminum nitride (AlN) piezoelectric nanoplate (500-nm-thick) sandwiched between the two metal layers (Supplementary Fig. 1). The bottom layer (100-nm-thick platinum (Pt)) is patterned to form an interdigitated transducer (IDT) used to actuate and sense a high-order lateral-extensional mode of vibration in the nanoplate35; the top electrically floating layer (50-nm-thick gold) is patterned with the goal of confining the electric field induced by the bottom IDT across the piezoelectric nanoplate (Supplementary Fig. 2), while simultaneously enabling absorption of infrared radiation in the ultrathin piezoelectric nanoplate thanks to suitably tailored plasmonic resonances (Supplementary Fig. 3). The nanoplate is released from the silicon (Si) substrate to vibrate freely, and it is mechanically supported by two ultrathin Pt tethers (100-nm-thick, 6.5-μm-wide and 20-μm-long), which also provide electrical contact36. Such Pt tethers greatly improve the thermal isolation between the nanoplate and the Si substrate compared with conventional ones composed of an AlN–Pt stack37. The mechanical resonance frequency of the plasmonic piezoelectric resonator is defined by the equivalent Young's modulus Eeq and density ρeq of the resonant material stack, and the pitch of the interdigitated electrode W0 (electrode width plus spacing, see Fig. 1a), given by . When an a.c. signal is applied to the bottom IDT of the device, the top electrically floating electrode acts to confine the electric field across the device thickness, and a high-order contour-extensional vibration mode is excited through the equivalent d31 piezoelectric coefficient of AlN35 when the frequency of the a.c. signal coincides with the natural resonance frequency, f0, of the resonator (Supplementary Note 1). If an infrared beam impinges on the device from the top (Fig. 1a), it is selectively absorbed by the metasurface, leading to a large and fast increase of the device temperature ΔT, due to the excellent thermal isolation and extremely low-thermal mass of the free-standing nanomechanical structure. Such infrared-induced temperature rise results in a shift in the mechanical resonance frequency of the resonator (from f0 to f0−Δf) due to the intrinsically large temperature coefficient of frequency (TCF) of the device38. Therefore, the incident IR power can be readily detected by monitoring the resonance frequency of the device.


Plasmonic piezoelectric nanomechanical resonator for spectrally selective infrared sensing.

Hui Y, Gomez-Diaz JS, Qian Z, Alù A, Rinaldi M - Nat Commun (2016)

Overview of the plasmonic piezoelectric nanomechanical resonant infrared detector.(a) Mock-up view: an aluminum nitride nanoplate is sandwiched between a bottom metallic interdigitated electrode and a top nanoplasmonic metasurface. The incident IR radiation is selectively absorbed by the plasmonic metasurface and heats up the resonator, shifting its resonance frequency from f0 to f′ due to the temperature dependence of its resonance frequency. (b) Scanning electron microscopy images of the fabricated resonator, metallic anchors and nanoplasmonic metasurface. The dimensions of the resonator are as follows: L=200 μm; W=75 μm; W0=25 μm (19+6 μm); LA=20 μm; WA=6.5 μm. The dimensions of the unit cell of the plasmonic metasurface are as follows: a=1635, nm; b=310 nm. IR, infrared.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835539&req=5

f1: Overview of the plasmonic piezoelectric nanomechanical resonant infrared detector.(a) Mock-up view: an aluminum nitride nanoplate is sandwiched between a bottom metallic interdigitated electrode and a top nanoplasmonic metasurface. The incident IR radiation is selectively absorbed by the plasmonic metasurface and heats up the resonator, shifting its resonance frequency from f0 to f′ due to the temperature dependence of its resonance frequency. (b) Scanning electron microscopy images of the fabricated resonator, metallic anchors and nanoplasmonic metasurface. The dimensions of the resonator are as follows: L=200 μm; W=75 μm; W0=25 μm (19+6 μm); LA=20 μm; WA=6.5 μm. The dimensions of the unit cell of the plasmonic metasurface are as follows: a=1635, nm; b=310 nm. IR, infrared.
Mentions: The proposed plasmonic piezoelectric NEMS resonator, illustrated in Fig. 1, is composed of an aluminum nitride (AlN) piezoelectric nanoplate (500-nm-thick) sandwiched between the two metal layers (Supplementary Fig. 1). The bottom layer (100-nm-thick platinum (Pt)) is patterned to form an interdigitated transducer (IDT) used to actuate and sense a high-order lateral-extensional mode of vibration in the nanoplate35; the top electrically floating layer (50-nm-thick gold) is patterned with the goal of confining the electric field induced by the bottom IDT across the piezoelectric nanoplate (Supplementary Fig. 2), while simultaneously enabling absorption of infrared radiation in the ultrathin piezoelectric nanoplate thanks to suitably tailored plasmonic resonances (Supplementary Fig. 3). The nanoplate is released from the silicon (Si) substrate to vibrate freely, and it is mechanically supported by two ultrathin Pt tethers (100-nm-thick, 6.5-μm-wide and 20-μm-long), which also provide electrical contact36. Such Pt tethers greatly improve the thermal isolation between the nanoplate and the Si substrate compared with conventional ones composed of an AlN–Pt stack37. The mechanical resonance frequency of the plasmonic piezoelectric resonator is defined by the equivalent Young's modulus Eeq and density ρeq of the resonant material stack, and the pitch of the interdigitated electrode W0 (electrode width plus spacing, see Fig. 1a), given by . When an a.c. signal is applied to the bottom IDT of the device, the top electrically floating electrode acts to confine the electric field across the device thickness, and a high-order contour-extensional vibration mode is excited through the equivalent d31 piezoelectric coefficient of AlN35 when the frequency of the a.c. signal coincides with the natural resonance frequency, f0, of the resonator (Supplementary Note 1). If an infrared beam impinges on the device from the top (Fig. 1a), it is selectively absorbed by the metasurface, leading to a large and fast increase of the device temperature ΔT, due to the excellent thermal isolation and extremely low-thermal mass of the free-standing nanomechanical structure. Such infrared-induced temperature rise results in a shift in the mechanical resonance frequency of the resonator (from f0 to f0−Δf) due to the intrinsically large temperature coefficient of frequency (TCF) of the device38. Therefore, the incident IR power can be readily detected by monitoring the resonance frequency of the device.

Bottom Line: We experimentally demonstrate that it is possible to achieve high thermomechanical coupling between electromagnetic and mechanical resonances in a single ultrathin piezoelectric nanoplate.The combination of nanoplasmonic and piezoelectric resonances allows the proposed device to selectively detect long-wavelength infrared radiation with unprecedented electromechanical performance and thermal capabilities.These attributes lead to the demonstration of a fast, high-resolution, uncooled infrared detector with ∼80% absorption for an optimized spectral bandwidth centered around 8.8 μm.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical &Computer Engineering at Northeastern University, 360 Huntington Avenue, Boston, Massachusetts 02115, USA.

ABSTRACT
Ultrathin plasmonic metasurfaces have proven their ability to control and manipulate light at unprecedented levels, leading to exciting optical functionalities and applications. Although to date metasurfaces have mainly been investigated from an electromagnetic perspective, their ultrathin nature may also provide novel and useful mechanical properties. Here we propose a thin piezoelectric plasmonic metasurface forming the resonant body of a nanomechanical resonator with simultaneously tailored optical and electromechanical properties. We experimentally demonstrate that it is possible to achieve high thermomechanical coupling between electromagnetic and mechanical resonances in a single ultrathin piezoelectric nanoplate. The combination of nanoplasmonic and piezoelectric resonances allows the proposed device to selectively detect long-wavelength infrared radiation with unprecedented electromechanical performance and thermal capabilities. These attributes lead to the demonstration of a fast, high-resolution, uncooled infrared detector with ∼80% absorption for an optimized spectral bandwidth centered around 8.8 μm.

No MeSH data available.


Related in: MedlinePlus