Graphene microbolometers with superconducting contacts for terahertz photon detection

TL;DR

This study investigates graphene's potential as a terahertz photon detector by measuring noise and thermal conductance, revealing weak electron-phonon coupling suitable for single-photon detection with superconducting contacts.

Contribution

It provides the first detailed Johnson noise thermometry measurements of graphene with superconducting contacts, demonstrating weak electron-phonon coupling conducive to terahertz photon detection.

Findings

Electron-phonon thermal conductance depends quadratically on temperature above 4 K.

Superconducting niobium nitride contacts exhibit low resistance and good ohmic behavior.

Results support graphene's suitability for sensitive terahertz photon detection.

Abstract

We report on noise and thermal conductance measurements taken in order to determine an upper bound on the performance of graphene as a terahertz photon detector. The main mechanism for sensitive terahertz detection in graphene is bolometric heating of the electron system. To study the properties of a device using this mechanism to detect terahertz photons, we perform Johnson noise thermometry measurements on graphene samples. These measurements probe the electron-phonon behavior of graphene on silicon dioxide at low temperatures. Because the electron-phonon coupling is weak in graphene, superconducting contacts with large gap are used to confine the hot electrons and prevent their out-diffusion. We use niobium nitride leads with a $T_\mathrm{c}\approx 10$ K to contact the graphene. We find these leads make good ohmic contact with very low contact resistance. Our measurements find an electron-phonon thermal conductance that depends quadratically on temperature above 4 K and is compatible with single terahertz photon detection.