Fabrication And Characteristics Of Ferroelectric Field Effect Transistors With ZnO Nanofiber Channels

Ferroelectric-gate feld effect transistors (FETs), the promising nonvolatile memorycomponents, have attracted much of attention. In this paper, bottom-gate nano-channelferroelectric-gate field effect transistors based on Bi3.15Nd0.85Ti3O12(BNT) thin film and ZnOnanofibers were fabricated. BNT thin film working as gate insulator was deposited on thehighly doped n-type Si (N++Si) substrate via chemical solution deposition, and ZnOnanofibers which work as the semiconductor channel were prepared by electrospinning on theBNT thin film. The main research work and results are as follows:1. We fabricated the BNT thin film via chemical solution deposition and investigated thethickness, hysteresis loop (P-V), leakage current, C-V, D-F and XRD, SEM characterization.The experimental results showed that thin film prepared by sol-gel method was quite evenly,and the ferroelectric properties of the BNT thin films got better with the increased of thethickness. While the leakage current decreased with the increased of the thickness. Inparticular, the ferroelectric properties of BNT on Pt were better than than on N++Si, and therelatively dielectric constant of the BNT was calculated as352by the D-F test.2. We prepared the ZnO nanofibers by electrospinning and then investigated themicrostructures, scanning electron microscopy (SEM), X-ray Diffraction (XRD) and thermalweight loss characteristics of the ZnO nanofibers. Experiments showed that when theconcentration of PVP ranged from0.26g/4mL to0.36g/4mL or even higher could obtaingood fibers and the best concentration of PVP was0.36g/4mL. And when the spinningvoltage was18.5kV and19kV, the fibers were very good with few drops and particles. Inaddition, the TGA test showed above4500C, the weight of ZnO nanofibers were unchanged,which could be used to calcine fibers. After calcination, the diameter of fibers decreased firstand then increased a little with the temperature increased, and the fibers broken easily at hightemperature. The XRD showed that the fibers were almost no impurities.3. We fabricated ZnO nanofiber/BNT ferroelectric-gate FET with BNT thin filmprepared on N++Si with ZnO nanofibers directly received on BNT thin film. After calcinationand plating electrode, we investigated the electrical characteristics of the transistors. Theelectrical characteristics of ZnO nanofber/BNT FETs showed a typical p-channel transistorproperty with a low threshold voltage of-0.5V, a low subthreshold swing of0.5V/decade, ahigh feld effect mobility of132.4cm2/Vs, and a large on/off current ratio of104, respectively.All these excellent performances were attributed to the ZnO nanofibers with large surface tovolume ratio and high mobility electronic transport properties, and BNT thin flim with large relatively dielectric constant and spontaneous polarization. While single and muti-channel ofthe ZnO nanofibers/SiO2transistors all showed a N-channel characteristics, and thecharacteristics were not evident. Moreover, the characteristics of ZnO nanofibers/BNT FETwere better than that of ZnO nanofibers/SiO2FET, which were attributed to BNTferroelectric-gate insulators to induce large charge density due to the spontaneouspolarization.