Photothermal response in dual-gated bilayer graphene.

The photovoltaic and bolometric photoresponse in gapped bilayer graphene was investigated by optical and transport measurements. A pulse coincidence technique at 1.5 µm was used to measure the response times as a function of temperature. The bolometric and photovoltaic response times were found to be identical implying that the photovoltaic response is also governed by hot electron thermal relaxation. Response times of τ ∼ 100-20 ps were found for temperatures from 3-100 K. Above 10 K, the relaxation time was observed to be τ = 25 ± 5 ps, independent of temperature within noise.