Thin Film Structure of Tetraceno[2,3-b]thiophene Characterized by Grazing Incidence X-ray Scattering and Near-Edge X-ray Absorption Fine Structure Analysis
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- 作者：Quan Yuan ; Stefan C. B. Mannsfeld ; Ming L. Tang ; Michael F. Toney ; Jan Lü ; ning ; Zhenan Bao
- 刊名：Journal of the American Chemical Society
- 出版年：2008
- 出版时间：March 19, 2008
- 年：2008
- 卷：130
- 期：11
- 页码：3502 - 3508
- 全文大小：297K
- 年卷期：v.130,no.11(March 19, 2008)
- ISSN：1520-5126
文摘
Understanding the structure-property relationship for organic semiconductors is crucial in rationalmolecular design and organic thin film process control. Charge carrier transport in organic field-effecttransistors predominantly occurs in a few semiconductor layers close to the interface in contact with thedielectric layer, and the transport properties depend sensitively on the precise molecular packing. Therefore,a better understanding of the impact of molecular packing and thin film morphology in the first few monolayersabove the dielectric layer on charge transport is needed to improve the transistor performance. In thisArticle, we show that the detailed molecular packing in thin organic semiconductor films can be solvedthrough a combination of grazing incidence X-ray diffraction (GIXD), near-edge X-ray absorption spectrafine structure (NEXAFS) spectroscopy, energy minimization packing calculations, and structure refinementof the diffraction data. We solve the thin film structure for 2 and 20 nm thick films of tetraceno[2,3-b]thiophene and detect only a single phase for these thicknesses. The GIXD yields accurate unit celldimensions, while the precise molecular arrangement in the unit cell was found from the energy minimizationand structure refinement; the NEXAFS yields a consistent molecular tilt. For the 20 nm film, the unit cell istriclinic with a = 5.96 Å, b = 7.71 Å, c = 15.16 Å, 
rs/alpha.gif" BORDER=0> = 97.30
, rs/beta2.gif" BORDER=0 ALIGN="middle"> = 95.63, rs/gamma.gif" BORDER=0 > = 90; there are two moleculesper unit cell with herringbone packing (49-59 angle) and tilted about 7 from the substrate normal. Thethin film structure is significantly different from the bulk single-crystal structure, indicating the importanceof characterizing thin film to correlate with thin film device performance. The results are compared to thecorresponding data for the chemically similar and widely used pentacene. Possible effects of the observedthin film structure and morphology on charge carrier mobility are discussed.
rs/alpha.gif" BORDER=0> = 97.30, rs/beta2.gif" BORDER=0 ALIGN="middle"> = 95.63, rs/gamma.gif" BORDER=0 > = 90; there are two moleculesper unit cell with herringbone packing (49-59 angle) and tilted about 7 from the substrate normal. Thethin film structure is significantly different from the bulk single-crystal structure, indicating the importanceof characterizing thin film to correlate with thin film device performance. The results are compared to thecorresponding data for the chemically similar and widely used pentacene. Possible effects of the observedthin film structure and morphology on charge carrier mobility are discussed.