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Light exposure dependence of field-effect mobility of pentacene thin films deposited on very thin polyimide photo-alignment layers
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10.1063/1.4729046
/content/aip/journal/jap/111/12/10.1063/1.4729046
http://aip.metastore.ingenta.com/content/aip/journal/jap/111/12/10.1063/1.4729046
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Figures

Image of FIG. 1.
FIG. 1.

(a): Molecular structure of Azo-PAA and Azo-PI, and (b): bottom-gate/top-contact type OFET structure fabricated in this study.

Image of FIG. 2.
FIG. 2.

(a) Polarized IR absorption spectra of the 1.6 nm-thick Azo-PI film aligned with a LP-L exposure of 11 J/cm2. A // and A are the absorbance for the IR light polarized parallel and perpendicular to the polarization direction of the LP-L, respectively. (b) LP-L exposure dependence of the in-plane molecular order parameters: Qφ Azo-PI and Qφ PEN , which are defined by (A  − A// )/(A  + A// ). Qφ Azo-PI and Qφ PEN were calculated from the dichroic ratio of the 1370 cm−1 band of Azo-PI and the 1298 cm−1 band of pentacene, respectively. The broken curves are guides for the eye.

Image of FIG. 3.
FIG. 3.

Polarized IR absorption spectra of the pentacene film deposited on the photo-aligned Azo-PI film (11 J/cm2). These spectra were obtained by subtracting those of the underlying Azo-PI film shown in Fig. 2(a) from those of the whole sample. A // and A are the absorbance for the IR light polarized parallel and perpendicular to the polarization direction of the LP-L, respectively. The inset shows the definition of the molecular axes (XYZ) of pentacene.

Image of FIG. 4.
FIG. 4.

Out-of-plane XRD patterns of the 30 nm-thick pentacene films on the Azo-PI films aligned with different LP-L exposures: 0, 6, 11, and 16 J/cm2. The vertical scale is linear, and the baseline of each pattern is shown by the thin horizontal straight line.

Image of FIG. 5.
FIG. 5.

Molecular orientation models of (a) A-type and (b) B-type domains determined by GIXD measurements.22 Although only the models with the downward c-axis are illustrated, ones with the upward c-axis are equivalent.

Image of FIG. 6.
FIG. 6.

AFM height images of the 30 nm-thick pentacene films on the Azo-PI films aligned with different LP-L exposures: 0, 6, 11, and 16 J/cm2. The double-ended arrows show the polarization direction of the LP-L.

Image of FIG. 7.
FIG. 7.

(a)-(c) Typical current-voltage characteristics of the pentacene-OFETs formed on the non-aligned Azo-PI films (0 J/cm2). The current flow directions of isotropic OFET-1 and OFET-2 are orthogonal to each other. (d)-(f) Typical current-voltage characteristics of the pentacene-OFETs formed on the photo-aligned Azo-PI film (11 J/cm2), whose channel current flow directions are parallel (//) and perpendicular (⊥) to the polarization direction of the LP-L.

Image of FIG. 8.
FIG. 8.

LP-L exposure dependence of the field-effect mobility. μiso , μ , and μ/ / are the field-effect mobilities of the isotropic, perpendicular, and parallel OFETs, respectively. The error bars show not the standard deviation but the maximum and minimum experimental values. The broken curves are guides for the eye.

Image of FIG. 9.
FIG. 9.

Out-of-plane XRD patterns of the 30 nm-thick pentacene films on the Azo-PI films aligned with LP-L exposures of 0 and 300 J/cm2. The vertical scale is logarithmic.

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/content/aip/journal/jap/111/12/10.1063/1.4729046
2012-06-18
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Light exposure dependence of field-effect mobility of pentacene thin films deposited on very thin polyimide photo-alignment layers
http://aip.metastore.ingenta.com/content/aip/journal/jap/111/12/10.1063/1.4729046
10.1063/1.4729046
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