# Electrospun Nanofibers for Integrated Sensing, Storage, and Computing Applications
## 3 Electrospun Nanofibers in Transistors: Computation and Multifunctional Electronics
### Advanced Electrospinning Methods for Transistor Production
This could be explained by the transition from a two-dimensional network plane to a three-dimensional spatial structure when the density of NiO nanofiber increases. The irregular channel thickness and morphologies were caused by the overlaying of a large number of individual fibers. Meanwhile, the higher overlapped fibers were unable to directly contact the bottom dielectric, but they were able to raise bulk resistance, resulting in poor carrier modulation under the bias voltage. To address this issue, controllable doping to obtain binary-cation MOS was adopted to parallelly improve metal oxide properties for a variety of applications and fibers with a mixture of metal elements, such as Sn-doped ZnO (ZnSnO), Gd-doped In\({}_{2}\)O\({}_{3}\) (InGdO), Mg-doped In\({}_{2}\)O\({}_{3}\), Sr-doped In\({}_{2}\)O\({}_{3}\), and Al-doped In\({}_{2}\)O\({}_{3}\)[72; 73; 74], have appeared over the past period. Recently, Al doping was used to improve the morphology of ternary-cationInAlZnO (IAZO), nanofiber-based field-effect transistors [75]. As we all know, InZnO nanofibers are representative of the doped metal oxide nanofibers for transistor application, but InZnO nanofibers exhibit a coarse surface and are discrete as disconnected segments. By adding the Al elements to the InZnO fibers, morphology can be greatly improved and the IAXO nanofibers exhibit a smooth surface with invisible broken fibers, as well as an improved on/off current ratio of 10\({}^{7}\) and high electron mobility of \(\sim\)10 cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\). The comparison among the transfer characteristics of the In\({}_{2}\)O\({}_{3}\), InAlZnO, and InZnO FET is shown in Figure 11h. Figure 10: Transfer characteristics of nanofiber-based transistors at different blending ratio of P3 HT/PSA. Reprinted with permission from Reference [69]. Copyright 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Figure 11: **(a)** Transfer characteristics of Zn\({}_{\rm x}\)Sn\({}_{1-x}\)O nanofiber-based FETs with various element composition ratios. **(b)** Output characteristics of Zn\({}_{\rm 0.3}\)Sn\({}_{\rm 0.2}\)O nanofiber-based transistors. **(c)** Mobility and threshold voltage of Zn\({}_{\rm x}\)Sn\({}_{1-x}\)O nanofiber-based FETs as a function of various element composition ratios. Reproduced from Ref. [13] with permission from the Royal Society of Chemistry. **(d)** Schematic representation of aligned electrospinning process with parallel plates as collectors. **(e)** Structure of the transistor based on aligned NiO NW arrays. **(f)** The variation of \(\mu_{\rm FE}\) values for the FETs based on disordered and aligned NiO nanowires with variable channel coverage. Reprinted with permission from Reference [71]. Copyright 2017 American Chemical Society. **(g)** Schematic illustration of the setup for coaxial electrospinning setup and structure for poly(3-hexylthiophene-2,5-diyl) (P3 HT) electrospun nanofiber-based field-effect transistors. Reprinted Reference [70] with permission from MDPI. **(h)** Transfer characteristics of In\({}_{\rm 2}\)O\({}_{\rm 3}\), InZnO, and I/AZO FETs at V\({}_{\rm ds}\) = 30 V, and the inset shows the schematic diagram of the transistors. Reprinted with permission from Reference [75]. Copyright 2017 American Chemical Society. **(i–l)** Transfer characteristics of electrospun In\({}_{\rm 2}\)O\({}_{\rm 3}\) nanofibers FETs with different annealing conditions: **(i)** In\({}_{\rm 2}\)O\({}_{\rm 3}\) fiber-based FET annealed at 280 \({}^{\circ}\)C for 0.5, 5, 10, 15 h; **(j)** In\({}_{\rm 2}\)O\({}_{\rm 3}\) fiber-based FET annealed at 310 \({}^{\circ}\)C for 0.5, 3, 6, 9 h; **(k)** In\({}_{\rm 2}\)O\({}_{\rm 3}\) fiber-based FET annealed at 350 \({}^{\circ}\)C for 0.5, 1, 2, 3 h; **(l)** In\({}_{\rm 2}\)O\({}_{\rm 3}\) fiber-based FET annealed at 380 \({}^{\circ}\)C for 0.5, 1, 1.5 h. Reprinted with permission from Reference [76]. Copyright 2020 IEEE.