Jenn-Chang Hwang

Flexible Organic Thin‐Film Transistors with Silk Fibroin as the Gate Dielectric

radio-frequency identifi cation (RFID) tags, [ 4,5 ] and biosensors. [ 6,7 ] OTFTs usually exhibit very low switching speed and are diffi cult to use instead of inorganic thin-fi lm transistors (TFTs), although they possess the merits of fl exibility and low cost. Several challenges for OTFTs of large area are high fi eld-effect mobility ( μ FE ), low operating voltage, and solution processing. The μ FE value and operating voltage of pentacene OTFTs strongly depend on the gate dielectric material. [ 8–10 ]

Ferroelectric properties of (117)- and (001)-oriented Bi3.25La0.75Ti3O12 polycrystalline thin films

Highly (117)- and (001)-oriented Bi3.25La0.75Ti3O12 (BLT) thin films were fabricated on Pt/TiO2/SiO2/Si(100) substrates by chemical solution deposition under the appropriate baking and crystallization conditions. The (117)-oriented BLT films exhibited higher remanent polarization (2Pr=24 μC/cm2), than did (001)-oriented BLT films, which exhibited only a slight amount of polarization (2Pr=6.6 μC/cm2). The results of fatigue and retention tests revealed that neither film was fatigued up to 1×1010 switching cycles, and the retained charge was unchanged for 1×104 s.

Formation and instability of silver nanofilament in Ag-based programmable metallization cells.

In this paper, we report on the formation and rupture of Ag nanofilament on planar Ag/TiO2/Pt cells using visual observation. During the forming process, the filament tends to stay very thin. Specifically, it is so thin that it breaks up into a chain of nanospheres (according to Rayleigh instability) right after the formation has been completed. Similar mechanical breakup may also impact vertically stacked cells, causing reliability concerns.

Argon Plasma Beam Scanning Processes on Polyimide Films for Liquid Crystal Alignment

Argon (Ar) plasma beam scanning treatments were applied to modify the surfaces of polyimide (PI) films deposited on indium tin oxide glasses in favor of liquid crystal (LC) alignment. LC cells were filled with twist nematic LC (ZLI-2293) on the PI films (Chisso 5310) treated with Ar plasma beam scanning. LC alignment occurs for the as-scanned PI films. The modifications of the PI films were characterized by using atomic force microscope and X-ray photoemission spectroscopy. The grooving mechanism is considered not responsible for the LC alignment. The C 1s, N 1s, and O 1s core level spectra support that Ar plasma beam scanning can induce a bond-breaking process of C=O bonds to create available carbon dangling bonds for the re-formation of C–O bonds. A dipole field is generated through the re-formation of C–O bonds, which may favor the LC alignment via the dipole–dipole interaction.

Liquid-crystal alignment on a-C:H films by nitrogen plasma beam scanning

A plasma beam scanning treatment has been developed to modify the surface of the hydrogenated amorphous carbon a-C:H film on the indium tin oxide glass. The plasma beam scanning treatment makes the a-C:H film an excellent layer for liquid-crystal alignment. The qualities of a-C:H films were characterized by using atomic force microscope, micro-Raman spectroscopy, and field-emission scanning electron microscope. The ultrathin a-C:H films were deposited at 50% CH4/H2+CH4 gas ratio, 100 W radio-frequency power, and a gas pressure of 10 mtorr for 15 min by capacitive-coupled plasma chemical-vapor deposition method. The twist nematic cells were filled with liquid crystal ZLI-2293 on the a-C:H film treated with different nitrogen plasma beam scanning time. The grooving mechanism is considered not responsible for the liquid-crystal LC alignment. Raman spectra suggest that a bond-breaking process of aromatic rings occurs in the aC:H film. The O1s ,C 1s, and N1s core-level spectra support that the nitrogen plasma beam scanning treatment induces a bond-breaking process of aromatic rings to create available carbon dangling bonds for the formation of C‐O bonds. The newly formed C‐O bonds are “directional,” which favor the LC alignment on the a-C:H film.

Thermal stability study of TiN/TiSi2 diffusion barrier between Cu and n+Si

The failure mechanism of the TiN/TiSi2 bilayers as diffusion barriers between Cu and n+Si was investigated. The TiN/TiSi2 bilayers were formed by either annealing Ti (50 nm)/n+Si via various rapid thermal processes or reactively sputtering TiN (50 nm) on TiSi2. The degradation study of the Cu/TiN/TiSi2/n+Si contact system was undertaken by scanning electron microscopy, cross‐section transmission electron microscopy (XTEM), secondary‐ion‐mass spectrometry (SIMS), and diode leakage current and contact resistance measurements. Leakage current measurements indicated no deterioration of n+‐p diode junctions up to 475 °C for 30 min in a N2 ambient. For the sintering temperature at 500 °C, the leakage current increased abruptly and SIMS profiles revealed a large amount of Cu atoms diffusing into the junctions of n+‐p diodes. XTEM showed that the small pyramidal‐shaped Cu3Si crystallite (with a size 0.25 μm) precipitated in the n+Si substrate. The formation of Cu3Si increased the occupied volume, then generated t...

Orientation-Dependent Grain Growth in La-Doped Bismuth Titanate Thin Films Prepared by Chemical Solution Deposition

La-doped bismuth titanate (BLT) thin films were grown on Pt/TiO2/SiO2/Si(100) substrates by chemical solution deposition. The BLT films were found to crystallize preferably either with (001)-oriented or (117)-oriented grains depending on baking conditions used in the film-coating process. The grain growth rate of (001)-oriented grains is considerably higher than that of (117)-oriented grains; consequently, the crystallized BLT films appeared to be packed with grains of two different sizes. Ferroelectric properties of the crystallized BLT films were also closely related to the volume fraction of (001)-oriented grains with respect to that of (117)-oriented grains.

Epitaxial iridium silicide formation during deposition of Ir on Si(100) at high temperature under ultrahigh vacuum

The iridium silicide formation has been examined by depositing Ir on Si(100) at different substrate temperatures under ultrahigh vacuum. An epitaxial Ir3Si4 film was formed when an Ir film of 100 A was directly deposited on Si(100) at 475 °C and annealed at the same temperature for 1.5 h. The Ir3Si4 was not observed in the conventional annealing process at 475 °C. In contrast, a polycrystalline IrSi film was formed after deposition of an Ir film of 100 A on Si(100) at room temperature and followed by annealing at 475 °C for 1.5 h under ultrahigh vacuum. Formation of the epitaxial Ir3Si4 on Si(100) is attributed to the interfacial energy of the Ir3Si4/Si(100) interface.

Microstructural and electrical properties of epitaxial PtSi/p-Si(100) co-deposited under ultrahigh vacuum

Epitaxial PtSi/p‐Si(100) contacts were fabricated by co‐depositing Pt and Si on p‐Si(100) at 450 °C in a dual electron gun chamber at a base pressure of 10−10 Torr. The PtSi/p‐Si(100) film possessed six types of epitaxial modes, as indicated in the electron diffraction patterns. The average grain size of the PtSi grains was measured to be 100–300 A through the Moire fringe image. The Schottky barrier height of the epitaxial PtSi/p‐Si(100) diode was determined to be 0.249 eV at 100 K, with an ideality factor of 1.04. In contrast to this, the Schottky barrier height of the polycrystalline PtSi/p‐Si(100) diode was 0.229 eV at 100 K, with an ideality factor of 1.05. The difference in Schottky barrier height was attributed to the difference in the atomic arrangement at interface.

Solution-based silk fibroin dielectric in n-type C60 organic field-effect transistors: Mobility enhancement by the pentacene interlayer

A pentacene interlayer of 2 nm thick is inserted between fullerene (C60) and the solution-based silk fibroin dielectric in C60 organic field-effect transistors (OFETs). The pentacene interlayer assists to improve crystal quality of the C60 layer, leading to the increase of field-effect mobility (μFE) from 0.014 to 1 cm2 V−1 s−1 in vacuum. The μFE value of the C60 OFET is further enhanced to 10 cm2 V−1 s−1 when the OFET is exposed to air in a relative humidity of 55%. Generation of mobile and immobile charged ions in solution-based silk fibroin in air ambient is proposed.