Friction-transferred Poly Tetrafluoroethylene Research Articles

Non-volatile memory characteristics of epitaxially grown PVDF-TrFE thin films and their printed micropattern application

Highly ordered poly(vinylidene fluoride- co-trifluoroethylene) (PVDF-TrFE) ultrathin films epitaxially grown on friction-transferred polytetrafluoroethylene (PTFE) surface were incorporated in the Metal-Ferroelectric-Metal (MFM) and Metal-Ferroelectric-Insulator-Semiconductor (MFIS) memory structure. The non-volatile memory properties in epitaxially ordered ferroelectric films were characterized with polarization and capacitance hysteresis curves at low voltage sweep of ±12 V and ±5 V in each stacking structure of MFM and MFIS, respectively. Furthermore, we present the facile micro- and nano-patterning method of fabricating MFM arrays including highly ordered PVDF-TrFE films by microimprinting. Ultrathin ferroelectric polymer films grown by epitaxy were microimprinted with a silver coated polydimethylesiloxane (PDMS) mold at 170 °C with excellent quality and the simultaneous transfer of silver electrodes on the imprinted PVDF-TrFE enabled us to fabricate the arrays of MFM capacitors in which ferroelectricity in imprinted region was well-maintained after patterning process at high temperature above 170 °C with good thermal stability.

Phase behavior of α, ω-dihexyl- α-quaterthiophene and ordering on a textured substrate

Ordering of α, ω-dihexyl- α-quaterthiophene (DH α4T) thin films on substrates including friction-transferred polytetrafluoroethylene (PTFE) is explored. DH α4T exhibits a high-temperature mesophase from 81 to 181 °C. Textural analysis reveals this phase to be a tilted, highly ordered smectic phase. Upon cooling from the isotropic melt, the smectic phase grows layer by layer on many surfaces. Smectic thin films grown on friction-transferred PTFE exhibit a high degree of alignment with edge dislocations being the primary defect. Upon crystallization from the mesophase, the material retains for the most part the order of the mesophase. Growth of the smectic phase on directional surfaces such as friction-transferred PTFE appears to be a route to control of surface ordering of DH α4T.

Measurements of adhesive forces on a polytetrafluoroethylene (PTFE) film and glass surface by mapping force curve

Force curve maps on a linear region of a friction transferred polytetrafluoroethylene (PTFE) film in both air and water were measured by using an atomic force microscope (AFM) system. The friction-transferred PTFE film, which was made by rubbing a heated glass with a PTFE polymer rod, consisted of many narrow PTFE tracks running parallel to the sliding direction on the glass surface. The measurement of the linear region perpendicular to the PTFE tracks enabled us to measure the force curves of two kinds of surfaces, PTFE and glass, which could be easily distinguished from each other by their different heights. An AFM scanner was driven by an additional computer and a custom high voltage amplifier in order to obtain force curves while scanning a linear region of the sample. The adhesive forces on the PTFE and glass were derived from the force curves. The force curve maps showed that the adhesive force on the PTFE in air was weaker than that on the glass surface. On the other hand, the adhesive force on the PTFE in water was stronger than that on the glass.

Sexithiophene thin films epitaxially oriented on polytetrafluoroethylene substrates: Structure and morphology

The structure and morphology of sexithiophene thin films vacuum-deposited on friction-transferred polytetrafluoroethylene (PTFE) substrates was investigated by optical and electron microscopy and electron diffraction. Highly birefringent 6T films are formed at high or low deposition rates. Electron diffraction indicates the presence of three different crystal populations differing by the orientation of the 6T molecular axis and/or the molecular plane. First, the strongest substrate/deposit interactions are based on epitaxy and lead to a well-defined, symmetric molecular arrangement (Type I) with the 6T molecular and the PTFE chain axes parallel and the 6T molecular planes tilted at ±33° to the substrate. Second, more “defective” orientations result from interactions with the bare glass surface (Type II) and with the PTFE film edges or ridges (Type III), respectively. As shown in a parallel study using spectroscopic techniques, these defective orientations have a definite impact on the overall optical properties of the sexithiophene thin films.

Sexithiophene thin films epitaxially oriented on polytetrafluoroethylene substrates: Structure and morphology

The structure and morphology of sexithiophene thin films vacuum-deposited on friction-transferred polytetrafluoroethylene (PTFE) substrates was investigated by optical and electron microscopy and electron diffraction. Highly birefringent 6T films are formed at high or low deposition rates. Electron diffraction indicates the presence of three different crystal populations differing by the orientation of the 6T molecular axis and/or the molecular plane. First, the strongest substrate/deposit interactions are based on epitaxy and lead to a well-defined, symmetric molecular arrangement (Type I) with the 6T molecular and the PTFE chain axes parallel and the 6T molecular planes tilted at ±33° to the substrate. Second, more “defective” orientations result from interactions with the bare glass surface (Type II) and with the PTFE film edges or ridges (Type III), respectively. As shown in a parallel study using spectroscopic techniques, these defective orientations have a definite impact on the overall optical properties of the sexithiophene thin films.