The structural and transport properties of evaporated pentacene organic thin film transistors (TFTs) are reported, and they show the influence of the deposition conditions with different inorganic dielectrics. Dielectrics compatible with large area fabrication were explored to facilitate low cost electronics on glass or flexible plastic substrates. X-ray diffraction and atomic force microscopy show a clear correlation between the morphology and the structure of the highly polycrystalline films for all dielectrics investigated. The roughness of the dielectric has a distinct influence on the morphology and the structural properties, whereas the films on smooth thermal oxide are in general highly ordered and independent of the deposition conditions. The ordered films exhibit a “thin film” and a bulk phase, and the bulk phase volume fraction increases with the deposition temperature and the film thickness. Careful control of the deposition conditions gives virtually identical films on thermal oxide and silicon nitride dielectrics. The electronic properties of inverted staggered transistors show that the TFT mobility is correlated with the morphology and structure of the films. The TFTs exhibit very similar mobilities of ∼0.4 cm2/Vs and on/off ratios >108 on thermal oxide and silicon nitride. The impact of the dielectric on the device parameters of mobility, threshold voltage, and subthreshold voltage slope is discussed. Temperature dependent measurements of the mobility were performed to study the influence of traps on electronic transport. Bias stress experiments were carried out to investigate the stability of the TFTs, and to gain understanding of the transport mechanisms of thermally evaporated pentacene TFTs.

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The equilibrium melting temperatures and the induced γ → α crystal transformation in blends of random liquid crystalline copoly(oxybenzoate−ethylene terephthalate) at molar ratio 60/40 (P64) and polyamide 6 (PA6) under different thermal treatments were investigated with differential scanning calorimetry and wide-angle X-ray diffraction, respectively. It was found that the equilibrium melting temperatures of P64/PA6 blends depended strongly on the amount of P64, and the presence of a small amount of P64 in PA6, around 5%, induced additional crystallization of the α-form crystal in the quenched PA6. Moreover, the onset temperature for the γ → α crystal transformation in the 5/95 P64/PA6 blend was reduced by 30 °C as compared to that in the pure PA6 case (160 °C vs 130 °C).

A diffractive optical element (DOE) is used as a beam combiner for an actively phase-locked array of fiber lasers. Use of a DOE eliminates the far-field sidelobes and the accompanying loss of beam quality typically observed in tiled coherent laser arrays. Using this technique, we demonstrated coherent combination of five fiber lasers with 91% efficiency and M2=1.04. Combination efficiency and phase locking is robust even with large amplitude and phase fluctuations on the input laser array elements. Calculations and power handling measurements suggest that this approach can scale to both high channel counts and high powers.

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