Fig. 1. (a) Schematic of carrier migration in graphene crystals driven by external bias voltage. (b) Graphene energy band diagrams of electron transitions and infrared radiation. (c) Basic device structure diagram of graphene/PZT heterostructure for the study of infrared emission.

Fig. 2. (a) SEM images of top and cross views of graphene/PZT composite sample. (b) I-V curve measurements of graphene on mica substrate and PZT/mica substrate. (c) Carrier mobility testing of graphene based on Hall device. (d) Raman spectra of graphene/PZT excited by different external bias voltage values.

Fig. 3. (a) Near-infrared emitting efficiency of graphene/PZT and graphene/mica reference sample. (b) Emission efficiency of graphene/PZT sample at different control voltage values in mid-infrared frequency band. (c) Current and optical power density characterization of graphene/PZT heterostructure at different bias voltages. (d) Electrical power and optical power as a function of bias voltage applied on both sides of graphene/PZT heterostructure.

Fig. 4. (a), (c) Fourier infrared image of graphene/mica sample and graphene/PZT sample at different bias voltage. (b), (d) Statistical data of applied voltage and thermal temperature were recorded from FLIR tools software.

Fig. 5. (a), (b) Current and temperature impulse response with 5 s intervals. (c), (d) Step tests of current and corresponding temperature were tested by the same sample. (e) 2000 cycles were carried out to verify the reliability of the graphene/PZT sample.

Fig. 6. (a) Optical image of infrared emitter and Fourier infrared camera in night environment. (b), (c) Current and temperature output signals with specific length of time arrangement. (d)–(g) Infrared emission bright spot was observed by an infrared camera at 1 m, 5 m, 10 m, and 20 m, respectively.

Fig. 7. (a) Series infrared emitting unit and corresponding simple control system. (b)–(d) Five infrared emission sources arranged in a straight line with different infrared emission intensity. (e) The letters N, U, and C are transmitted in the form of infrared Morse code.