Fig. 1: On-chip phononic SEIRA detection of molecular vibrations.
From: On-chip phonon-enhanced IR near-field detection of molecular vibrations
a Far-field SEIRA spectroscopy. Local field enhancement is illustrated by red lines. b Sketch of an on-chip SEIRA spectroscopy experiment, where a detector is placed in the near field of a SEIRA structure. c Illustration of a graphene split-gate detector with intrinsic mid-IR field enhancement, covered by a thin layer of CBP molecules. The detector consists of a heterostructure comprising an exfoliated monolayer of graphene encapsulated between two thin h-BN layers of 5 and 3 nm thickness. It is placed on top of a metal split gate used for creating a p–n junction in graphene via electric gating. For measuring the photocurrent induced in the p–n junction under illumination, the graphene is contacted by metal electrodes (source and drain). The detector surface is covered by a thin organic layer exhibiting mid-IR molecular vibrations. The size of the detector and thus the maximum size of the probed area of molecules is about 7 × 4 μm2 < λIR2 (Supplementary Fig. 1), where λIR is about 6.5–7 μm. d Red line illustrates an infrared wave with wavelength (indicated by the black double arrow), λIR, on the scale of the detector device.
