Self-powered stable high-performance UV-Vis-NIR broadband photodetector based on PVP-Cobalt@Carbon nanofibers/n-GaAs heterojunction.

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 âˆ¼225 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 ∼10-14W.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.

Preparation and characterization study of γ-Fe2O3/carbon composite nanofibers: electrospinning of composite fibers using PVP and iron nitrate as precursors.

A γ-Fe2O3/carbon nanofiber composite was prepared by electrospinning a mixed solution of iron nitrate nonahydrate (Fe(NO3)3·9H2O) and polyvinylpyrrolidone (PVP) with subsequent treatment under an Ar atmosphere. A morphology study of the γ-Fe2O3/carbon nanofiber composite using FE-SEM, TEM, and AFM techniques confirms the formation of randomly oriented carbon fibers that include γ-Fe2O3 nanoparticles, along with an agglomeration in the fibrous environment and surface roughness of the fibers. Structural analysis from the XRD patterns showed that the synthesized sample was ferric oxide having a gamma phase tetragonal crystal structure and amorphous behavior of carbon. FT-IR spectroscopy further demonstrated the presence of functional groups corresponding to γ-Fe2O3 and carbon in the γ-Fe2O3/C structure. DRS spectra of the γ-Fe2O3/C fibers indicate absorption peaks related to γ-Fe2O3 and carbon in the γ-Fe2O3/carbon composite. In view of the magnetic properties, the composite nanofibers showed a high saturation magnetization Ms of 53.55 emu g-1.