ABSTRACT
The self-powered PVP-Co@C nanofibers/n-GaAs heterojunction photodetector (HJPD) was fabricated by electrospinning of the nanofibers onto GaAs. An excellent rectification ratio of 6.60 × 106was obtained fromI-Vmeasurements of the device in the dark. TheI-Vmeasurements of the fabricated device under 365 nm, 395 nm and 850 nm lights, as well asI-Vmeasurements in visible light depending on the light intensity, were performed. The HJPD demonstrated excellent photodetection performance in terms of a good responsivity of â¼225 mA W-1(at -1.72 V) and at zero bias, an impressive detectivity of 6.28 × 1012Jones, and a high on/off ratio of 8.38 × 105, all at 365 nm wavelength. In addition, the maximum external quantum efficiency and NPDR values were 3495% (V = -1.72 V) and 2.60 × 1010W-1(V= 0.0 V), respectively, while the minimum NEP value was â¼10-14W.Hz-1/2for 365 nm atV= 0.V volts. The HJPD also exhibited good long-term stability in air after 30 d without any encapsulation.
ABSTRACT
Carbon fibers were successfully fabricated via the electrospinning technique, followed by stabilizing and carbonizing electrospun PAN fibers. A wide range of analytical techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), vibrating sample magnetometer (VSM) techniques, and Hall effect were performed to study of the effect of carbonization temperature on the physical and chemical characterization of carbon fibers. The SEM images of the PAN precursor exhibit a smooth outer surface, after the stabilization and carbonization process, along with a broken fiber at higher carbonization temperature about 1400 °C. Morphological characterization based on the recorded TEM images of carbonized fibers at 1000 °C and 1400 °C, showed that the obtained morphology can be classified as fiber structures, where their diameters ranged from 196 to 331 nm. The XRD patterns of PAN-based carbon fibers confirm the structural changes from linear structure into a graphite-like structure. The DRS study indicates the possible π-π*/σ-π* and n-π* transitions. The presence of the surface functional groups and different trapped radiative recombination on the emission bands is confirmed by the PL. VSM results shows the weak ferromagnetic nature of the carbon fibers.
