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The aim of this paper is to establish a fabrication process for non-volatile memory (NVM) transistors using ZnO nanoparticles, polymethylsilsesquioxane (PMSSQ) and soluble pentacene. ZnO nanoparticles mixed into the PMSSQ solution are used to create a nanocomposite layer for charge trapping in the NVM. It has been demonstrated that the nanocomposite layer in a metal–insulator–semiconductor structure can cause a hysteresis of ~ 6 V in a capacitance–voltage (C–V) plot, indicating a significant charge trapping capability. A threshold voltage shift of ~ 2.3 V between a programmed and erased NVM transistor and a carrier mobility of ~ 0.002 cm2/V-s are achieved. At present the fabricated NVMs have a limited life cycle of 4 program/erase cycles.

This paper discusses the application of a DC sputtered ZnO thin film as a dielectric in an optically transparent non-volatile memory. The main motivation for using ZnO as a dielectric is due to its optical transparency and mechanical flexibility. We have established the relationship between the electrical resistivity ( ρ ) and the activation energy ( E a ) of the electron transport in the conduction band of the ZnO film. The ρ of 2 × 10 4 –5 × 10 7 Ω-cm corresponds to E a of 0.36–0.76 eV, respectively. The k -value and optical band-gap for films sputtered with Ar:O 2 ratio of 4:1 are 53 ± 3.6 and 3.23 eV, respectively. In this paper, the basic charge storage element for a non-volatile memory is a triple layer dielectric structure in which a 50 nm thick ZnO film is sandwiched between two layers of methyl silsesquioxane sol–gel dielectric of varying thickness. A pronounced clockwise capacitance–voltage ( C–V ) hysteresis was observed with a memory window of 6 V. The integration with a solution-processable pentacene, 13,6-N-Sulfinylacetamodipentacene resulted in an optically transparent organic field effect transistor non-volatile memory (OFET-NVM). We have demonstrated that this OFET-NVM can be electrically programmed and erased at low voltage (± 10 V) with a threshold voltage shift of 4.0 V.

This paper demonstrates the novel application of d.c. sputtered zinc oxide (ZnO) as a charge trapping dielectric material for the application of an organic thin film transistor (OTFT) based non-volatile memory (NVM). The motivation of using ZnO as a dielectric is due to its chemical stability and optical transparency, enabling future development of transparent electronic devices. Unbalanced magnetron d.c. sputtering with Ar:O"2 ratio of 80:20 was used to obtained a ZnO dielectric of 50nm thick. The ZnO has an optical band gap of 3.23eV, resistivity and k-value of 5x10^7@W-cm and 50, respectively. The ZnO sandwiched between two layers of low-k methyl-silsesquioxane (MSQ) sol-gel dielectric creates a triple layer dielectric structure for charge storage. A solution-processable pentacene, 13,6-N-Sulfinylacetamodipentacene, was used as an active layer of an OTFT-NVM. It has been successfully demonstrated that this OTFT-NVM can be electrically programmed and erased at a low voltage.

Most functionalized thiophenes are difficult to electropolymerize due to nucleophilicity that will attack the radical cation inhibiting polymerization. However, we have successfully electrodeposited a newly synthesized functionalized terthiophene monomer 3-((2′:2″,5″:2‴-terthiophene)-3″-yl) acrylic acid (TAA) as an active layer of a organic field-effect transistor (OFET). The polymer was then oxidized in order to increase its conductivity. Various oxidizing potentials were experimented and their effect on the OFET's charge mobility was examined. A mobility of 0.25 cm2 (V s)−1 is achieved with an oxidizing potential of 0.9 V after vacuum drying.

This paper discusses the effect of forming gas (93%N2 + 7%H2) plasma treatment for sol-gel methyl-silsesquioxane (MSQ) as a dielectric film towards the grain morphology of a solution processable pentacene. Atomic force microscopy and X-ray diffractometer results confirm that a brief (10 s) plasma treatment for MSQ increases the grain size of pentacene and encourages its growth in thin-film phase. This paper also demonstrates that the presence of large Si(CH3)3 bonds on the MSQ surface are very important to encourage the growth of pentacene’s molecules in thin-film phase. In addition, this paper also suggests that there is no strong relationship between the grain size and ordering of pentacene molecules.

Polyaniline (PANI) nanotubes configured as a field effect transistor (FET) exhibits a p–n junction diode behavior. The forward-bias current can be modulated by a gate voltage; turning on at negative gate voltage and turning off at positive gate voltage. An energy band diagram model has been proposed to explain the rectifying effect of the PANI nanotubes FET (PNT-FET). All the four different forward bias conduction mechanisms of a typical p–n junction diode can be identified for this PNT-FET using a semi-log graph to confirm this resemblance.

Cold-spraying has been developed as a high-quality metallic coating process. Recently, it became possible to fabricate a brittle ceramic coating using a particular nano-structured powder. In order to improve and control the process, the bonding mechanism should be understood. In this study, the bonding mechanism between cold-sprayed TiO2 particle and stainless steel substrate was investigated by cross-section observation and quantitative adhesion strength measurement for the individual particles. The adhesion strength was measured by the combination using of scanning probe microscope (SPM) imaging and nano scratch test. The result clearly revealed a correlation in adhesion strength with splat diameter. The smaller splat diameter exhibited higher adhesion strength, though it is generally difficult to penetrate the cold-sprayed small particles through a shock wave formed in front of the substrate. The cross-section microstructure of the splats prepared by focused ion beam (FIB) showed the particular deposition behavior of the TiO2 particle. The collided particle didn’t deform the substrate surface and deformed the particle itself. The bottom center of the splat is densified by the deformation and the other parts maintain the porous structure or broke up. Hence the higher adhesion strength of smaller splat was caused by this typical TiO2 deposition behavior.

We have shown the fabrication of ceramics titanium dioxide (TiO2) coating via cold spray process. Cold spraying of any hard ceramics coating is considered to be difficult, including TiO2. However, we could obtain a coating with thickness greater than 100 µm. The adhesion mechanism of this cold sprayed TiO2 coating needs to be clarified. The effects of process gas parameters and substrate materials on coating's adhesion strength were studied. It was found that adhesion strength did not vary significantly with the change of process gas parameters, indicating that mechanical embedment is not the sole factor of coating¡¦s adhesion. The study of changing substrate materials reveals the degradation of adhesion strength due to surface oxide layer and that TiO2 shows better adhesion on bare metal surface. Hence, by altering the surface chemistry, the adhesion of TiO2 is varied, indicating the possibility of physical or chemical bonding between cold sprayed TiO2 and substrate.

Titanium dioxide (TiO2) has attracted numerous attentions due to its high photocatalytic property. TiO2 as photocatalyst is best to be coated over large area substrate (walls, windows, etc.). In this case, cold spray process is the most suitable technique, not only because its simplicity and efficiency for large area deposition, but also because it is a low temperature process that would retain the high photocatalytic anatase phase of TiO2 in the coating. However, cold spraying of hard ceramic materials, such as TiO2, is widely known to be difficult. In this study, we are reporting a novel synthesis method of TiO2 powder for cold spray via the hydrolysis of titanyl sulphate (TiOSO4) with addition of ammonium sulphate ((NH4)2SO4). It is a relatively simple synthesis method that can obtain pure anatase structure even without high temperature treatment, although post treatments, such as hydrothermal and calcination further increase the crystallinity and change the morphology of synthesised TiO2. It is believed that the synergetic effect of post treatments and adsorption of NH4+ and SO42− ions on the surface of TiO2 causes the alteration in morphology of TiO2 powder. Finally, the cold spray spot test shows that the TiO2 powders can be cold sprayed. This is a remarkable finding as the difficulty of cold spraying TiO2 is widely known.