In this paper, we prepared reduced graphene oxide (rGO) films by first drop-casting graphene oxide (GO)/ethanol dispersion on top of silicon nanowires array, followed by thermal reduction in 95% Ar-5% H₂ (volume ratio) atmosphere. A series of rGO thin films were prepared by thermal reduction at different annealing temperatures ranging from 100℃ to 1200℃, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, four-probe square resistance tester and scanning electron microscopy (SEM). The experimental results indicate that reduction of oxygen-containing groups, dehydrogenation of C-H groups and reconstruction of C=C skeleton occurred significantly on the GO plane. Compared with the insulating GO film, the resistance of rGO thin films decreases greatly, and the sheet resistance of rGO films shows a decreasing trend with increase of reduction temperature. Then, flexible polydimethylsiloxane (PDMS) encapsulated graphene-based devices (P-rGO-P) were fabricated by spin-coating PDMS on the surface of obtained rGO films with evaporated Au interdigital electrodes. The flexible devices maintained the integrity of the rGO films while providing self-supporting characteristics. The rGO film in the device had a clear layered structure, and a certain movable space between the upper and lower PDMS layers. This sandwich structure ensures that when the P-rGO-P flexible detector is bent and squeezed, the rGO film has sufficient buffer space, and would not be subjected to excessive stress arising from adhesion to PDMS. In short, the sandwich structure endows the originally fragile device with excellent flexibility. The P-rGO-P detector was successfully applied to detecting infrared laser irradiation, human body infrared radiation, bending motions and pressure changes. The experimental results showed that the flexible encapsulated P-rGO-P infrared detectors derived from the rGO thin films reduced at varied temperatures all had response to near-infrared (1064 nm) laser irradiation, and the maximum response reached up to 2.78 mA/W. In addition, the P-rGO-P flexible detector also demonstrated fast and sensitive response to human body infrared radiation and bending changes, and could maintain its integrity and responsiveness after repeated bending.

Key words: reduced graphene oxide, flexibility, photoelectric conversion, infrared detector, strain detector