Diamond probe maps infrared-driven currents below a micrometre
A gold-coated diamond probe concentrated mid-infrared light onto a tiny part of a graphene device, revealing electrical responses near metal contacts. The peer-reviewed experiment achieved about 0.7 micrometre resolution with light around 10 micrometres in wavelength. It offers researchers a closer view of where absorbed light produces an electrical signal in thin materials.
Science··Evening
Light squeezed into a small region
Researchers have made a diamond tip that directs mid-infrared light onto a small patch of graphene, a thin carbon material, and reads the resulting electrical response. In the peer-reviewed laboratory study, the tip distinguished features roughly 0.7 micrometres across while using radiation with a wavelength around 10 micrometres. The setup addresses a practical obstacle in examining small devices: illuminating a broad area blends together responses originating at different positions.[1]
A pyramid guides the beam
The diamond forms a tapering pyramid. Two opposite faces carry gold coatings, while the other pair remains uncovered. This arrangement guides incoming light towards the narrowing tip. Attached to a scanning photovoltage microscope, the probe mapped how the electrical response changed near the junctions between graphene and metal. Rotating the light’s polarisation, the direction of its electric field, changed the pattern. The team tested the system with quantum cascade lasers and free-electron lasers.[1]
Heat and electrical response
The estimated share of incoming optical power delivered to the concentrated tip region was about 1.1 per cent. The device’s response to changing laser power and gate voltage supported an explanation involving heated charge carriers and the conversion of temperature differences into voltage. The demonstrated resolution remains below a micrometre; further gains calculated for smaller tips are prospective. Distance from the sample, absorption and the material under examination also influence the probe’s behaviour.[1]
