Two soluble 1,4,5,8-naphthalenetetracarboxylic diimide (NTCDI) derivatives with phenylmethyl and (trifluoromethyl)benzyl groups (NTCDI-P and NTCDI-F, respectively) were synthesized and used as semiconductor layers in organic thin-film transistors (OTFTs) by a spin-coating process in air. These two synthesized materials were characterized by 1 H NMR and UV-vis spectra as well as mass analysis. The morphology and crystallinity of spin-coated NTCDI-P and NTCDI-F films have been inspected using atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. The channel mobilities of these two NTCDI derivatives were calculated to be about 1.2 × 10 -3 cm 2 V -1 s -1 in air, which degraded slightly while stabilized for NTCDI-F OTFTs after exposure in air for 1 month.
A variety of microelectrode arrays (MEAs) has been developed for monitoring intra-cortical neural activity at a high spatio-temporal resolution, opening a promising future for brain research and neural prostheses. However, most MEAs are based on metal electrodes on rigid substrates, and the intra-cortical implantation normally causes neural damage and immune responses that impede long-term recordings. This communication presents a flexible, carbon-nanotube MEA (CMEA) with integrated circuitry. The flexibility allows the electrodes to fit on the irregular surface of the brain to record electrocorticograms in a less invasive way. Carbon nanotubes (CNTs) further improve both the electrode impedance and the charge-transfer capacity by more than six times. Moreover, the CNTs are grown on the polyimide substrate directly to improve the adhesion to the substrate. With the integrated recording circuitry, the flexible CMEA is proved capable of recording the neural activity of crayfish in vitro, as well as the electrocorticogram of a rat cortex in vivo, with an improved signal-to-noise ratio. Therefore, the proposed CMEA can be employed as a less-invasive, biocompatible and reliable neuro-electronic interface for long-term usage.
Abstract:In situ Yb-doped amorphous carbon thin films were grown on Si substrates at low temperatures (<200 °C) by a simple one-step RF-PEMOCVD system as a potential photonic material for direct integration with Si CMOS back end-of-line processing. Room temperature photoluminescence around 1 µm was observed via direct incorporation of optically active Yb 3+ ions from the selected Yb(fod) 3 metal-organic compound. The partially fluorinated Yb(fod) 3 compound assists the suppression of photoluminescence quenching by substitution of C-H with C-F bonds. A four-fold enhancement of Yb photoluminescence was demonstrated via deuteration of the a-C host. The substrate temperature greatly influences the relative deposition rate of the plasma dissociated metal-organic species, and hence the concentration of the various elements. Yb and F incorporation are promoted at lower substrate temperatures, and suppressed at higher substrate temperatures. O concentration is slightly elevated at higher substrate temperatures.
OPEN ACCESSMaterials 2014, 7
5644Photoluminescence was limited by the concentration of Yb within the film, the concentration of Yb ions in the +3 state, and the relative amount of quenching due to the various de-excitation pathways associated with the vibrational modes of the host a-C network. The observed wide full-width-at-half-maximum photoluminescence signal is a result of the variety of local bonding environments due to the a-C matrix, and the bonding of the Yb 3+ ions to O and/or F ions as observed in the X-ray photoelectron spectroscopy analyses.
A soluble organic material, polyacrylonitrile (PAN), was investigated for its feasibility of gate dielectric applications. The solution-processed PAN was spin coated in air. Results show that leakage current density as low as 0.3nA∕cm2 for 50nm PAN dielectrics could be achieved via process optimization. Functional transistor characteristics were achieved in air for the implementation of PAN in organic thin-film transistors using pentacene or poly(3-hexylthiophene) as a semiconductor material.
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