Substrate-sensitive mid-infrared photoresponse in graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Graphene exhibits unique electronic and optical properties, making it a promising material for infrared photodetectors.
• Substrate interactions significantly influence the performance of graphene-based devices, particularly in the mid-infrared spectrum.
• Understanding these interactions is crucial for optimizing graphene photodetector sensitivity and tunability.

Purpose of the Study:

• To investigate the mid-infrared photocurrent spectra of graphene nanoribbon arrays on SiO2 dielectrics.
• To elucidate the dual signatures of substrate interaction on graphene's photocurrent response.
• To explore the potential for tailoring graphene photodetector responsivity through substrate selection.

Main Methods:

• Fabrication of graphene nanoribbon arrays on SiO2 substrates.
• Measurement of mid-infrared photocurrent spectra under varying gate voltages, nanoribbon widths, and light polarizations.
• Theoretical modeling of hybrid polaritonic modes and phonon polariton excitation.
• Analysis of substrate-dependent responsivity for different dielectric materials.

Main Results:

• Observed dual photocurrent signatures attributed to hybrid graphene plasmon-phonon polariton modes and substrate-mediated phonon polaritons.
• Demonstrated tunability of spectral features by gate voltage, nanoribbon width, and light polarization.
• Identified fixed spectral features arising from indirect substrate heating.
• Modeled substrate effects, showing potential for tailoring responsivity to specific mid-IR bands.

Conclusions:

• Substrate interactions play a critical role in the mid-infrared photocurrent generation in graphene nanoribbons.
• The choice of dielectric substrate offers a powerful method for engineering the spectral response of graphene infrared photodetectors.
• This work provides a pathway for designing highly specific and efficient mid-infrared optoelectronic devices based on graphene.