Thin Film Morphology and GrowthMechanism of Pentacene Thin Film Using Low-Pressure Organic Vapor Deposition

  • PDF / 706,534 Bytes
  • 6 Pages / 612 x 792 pts (letter) Page_size
  • 84 Downloads / 237 Views

DOWNLOAD

REPORT


H6.19.1

Thin Film Morphology and Growth Mechanism of Pentacene Thin Film Using LowPressure Organic Vapor Deposition Seong Deok Ahn, Seung Youl Kang, Yong Eui Lee, Meyoung Ju Joung, Chul Am Kim, and Kyung Soo Suh Applied Devices Department, Basic Research Laboratory, ETRI, 161 Gajeong-dong, Yuseong-gu, Daejeon, 305-350, Korea ABSTRACT We have investigated the growth mechanism and thin film morphology of pentacene thin films by the process of low-pressure gas assisted organic vapor deposition (LP-GAOVD). As the source temperature, flow rate of the carrier gas, substrate temperature and chamber pressure were varied, the growth rate, morphology and grain size of the films were differently obtained. The electrical properties of pentacene thin films for applications in organic thin film transistor and electrophoretic displays were discussed INTRODUCTION In recent years, thin film transistor (TFTs) based on organic materials as active layer have received considerable interest. Organic TFTs have emerged as promising technology for lowcost electronics such as smart cards or identification tags[1-4]. Pentacene, a polyacene, consists of five linear benzene rings and has demonstrated the highest electron and hole mobility of organic small molecules. The material exhibits a strong tendency to form highly ordered films which depend on the growth conditions and the substrate. Pentacene thin film have been fabricated by solution precipitation,[5] organic molecular beam deposition,[6] vacuum thermal evaporation,[7] organic vapor phase deposition,[8] all having compared performance. In this work, we have grown the pentacene thin film with new deposition technique, lowpressure gas assisted organic vapor deposition (LP-GAOVD). LP-GAOVD proceeds by evaporation of the molecular source material into a stream of cold inert carrier gas that transports the vapors toward a substrate where condensation of the organic occurs. We characterized the pentacene thin films by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) images as a function of the working pressure during the evaporation process.

Downloaded from https://www.cambridge.org/core. Columbia University - Law Library, on 17 Aug 2019 at 01:24:58, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-769-H6.19

H6.19.2

EXPERIMENTAL DETAILS As received pentacene, obtained from Aldrich Chemical Co., is used without additional purification. Si-wafers, thermally oxidized in a dry atmosphere (SiO2 thickness about 500 nm) are used as a substrate. The background pressure was at 10-3 Torr. Nitrogen carrier gas at flow rates ranged from 25 to 130 sccm, while the source material was maintained at 295 oC during pentacene thin film deposition. The pressure in the deposition chamber was varied from 0.1 to 10 Torr, and substrate temperature was maintained at 100 oC. The deposition time was 2 hours. The temperature is measured by chromel-alumel thermocouples. All transistor was fabricated on Si-wafers using t