Cross-linked Poly 4-vinylphenol Research Articles

Fabrication of Arrayed Si Nanowire-Based Nano-Floating Gate Memory Devices on Flexible Plastics

Arrayed Si nanowire (NW)-based nano-floating gate memory (NFGM) devices with Pt nanoparticles (NPs) embedded in Al2O3 gate layers are successfully constructed on flexible plastics by top-down approaches. Ten arrayed Si NW-based NFGM devices are positioned on the first level. Cross-linked poly-4-vinylphenol (PVP) layers are spin-coated on them as isolation layers between the first and second level, and another ten devices are stacked on the cross-linked PVP isolation layers. The electrical characteristics of the representative Si NW-based NFGM devices on the first and second levels exhibit threshold voltage shifts, indicating the trapping and detrapping of electrons in their NPs nodes. They have an average threshold voltage shift of 2.5 V with good retention times of more than 5 x 10(4) s. Moreover, most of the devices successfully retain their electrical characteristics after about one thousand bending cycles. These well-arrayed and stacked Si NW-based NFGM devices demonstrate the potential of nanowire-based devices for large-scale integration.

Field Effect Transistor with ZnS Active Layer on ITO/Glass Substrate

The organic-inorganic field effect transistors (OIFETs) with ZnS active layer were fabricated on the ITO/glass substrate using cross-linked PVP (poly-4-vinylphenol) as a gate insulator. ZnS semiconductor films were prepared by the atomic layer deposition method. In the case of cross-linked PVP film, the leakage current and capacitance were about 1× 10-8 A and 12 nF/cm2, showing good gate insulation property. The carrier concentration and mobility of ZnS film deposited on SiO2/Si wafer was found to be -9.4×1015 cm-3 and 49.0 cm2/ V·sec, respectively. For the OIFET devices with ITO/PVP/ZnS/Ti:Au structure, the carrier mobility was about 1.9 cm2/V·sec. From the AFM images, lower mobility in the OIFET device compared with ZnS film on SiO2/Si substrate may be attributed to a rough surface morphology of ZnS film.

Formation of PVP- Based Organic Insulating Layers and Fabrication of OTFTs

The formation and processing of organic insulators on the device performance have been studied in the fabrication of organic thin film transistors (OTFTs). The series of polyvinyls, poly-4-vinyl phenol(PVP) and polyvinyltoluene (PVT), were used as solutes and propylene glycol monomethyl ether acetate(PGMEA) as a solvent in the formation of organic insulators. The cross-linking of organic insulators was also attempted by adding the thermosetting material, poly (melamine-co-formaldehyde) as a hardener in the compound. The electrical characteristics measured in the metal-insulator-metal (MIM) structures showed that insulating properties of PVP layers were generally superior to those of PVT layers. Among the layers of PVP series: PVP(10 wt%) copolymer, 5 wt% cross-linked PVP(10 wt%), PVP(20 wt%) copolymer, 5 wt% cross-linked PVP(20 wt%) and 10 wt% cross-linked PVP(20 wt%), the 10 wt% cross-linked PVP(20 wt%) layer showed the lowest leakage current characteristics. Finally, inverted staggered OTFTs using the PVP(20 wt%) copolymer, 5 wt% cross-linked PVP(20 wt%) and 10 wt% cross-linked PVP(20 wt%) as gate insulators were fabricated on the polyether sulphone (PES) substrates. In our experiments, we could obtain the maximum field effect mobility of 0.31 <TEX>$cm^2/Vs$</TEX> in the device from 5 wt% cross-linked PVP(20 wt%) and the highest on/off current ratio of <TEX>$1.92{\times}10^5$</TEX> in the device from 10 wt% cross-linked PVP(20 wt%).