Influence of electric field on microstructures of pentacene thin films in field-effect transistors

Horng Long Cheng, Wei Yang Chou, Chia Wei Kuo, Yu Wu Wang, Yu Shen Mai, Fu Ching Tang, Shu Wei Chu

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

We report on electric-field-induced irreversible structural modifications in pentacene thin films after long-term operation of organic field-effect transistor (OFET) devices. Micro-Raman spectroscopy allows for the analysis of the microstructural modifications of pentacene in the small active channel of OFET during device operation. The results suggest that the herringbone packing of pentacene molecules in a solid film is affected by an external electric field, particularly the source-to-drain field that parallels the a-b lattice plane. The analysis of vibrational frequency and Davydov splitting in the Raman spectra reveals a singular behavior suggesting a reduced separation distance between pentacene molecules after long-term operations and, thus, large intermolecular interactions. These results provide evidence for improved OFET performance after long-term operation, related to the microstructures of organic semiconductors. It is known that the application of large electric fields alters the semiconductor properties of the material owing to the generation of defects and the trapping of charges. However, we first suggest that large electric fields may alter the molecular geometry and further induce structural phase transitions in the pentacene films. These results provide a basis for understanding the improved electronic properties in test devices after long-term operations, including enhanced field-effect mobility, improved on/off current ratio, sharp sub-threshold swing, and a slower decay rate in the output drain current. In addition, the effects of source-to-drain electric field, gate electric field, current and charge carriers, and thermal annealing on the pentacene films during OFET operations are discussed.

Original languageEnglish
Pages (from-to)285-293
Number of pages9
JournalAdvanced Functional Materials
Volume18
Issue number2
DOIs
Publication statusPublished - 2008 Jan 24

Fingerprint

Field effect transistors
Organic field effect transistors
field effect transistors
Electric fields
Thin films
microstructure
Microstructure
electric fields
thin films
Molecules
Semiconducting organic compounds
Drain current
organic semiconductors
Vibrational spectra
Charge carriers
Electronic properties
decay rates
Raman spectroscopy
pentacene
Raman scattering

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Condensed Matter Physics
  • Electrochemistry

Cite this

Cheng, Horng Long ; Chou, Wei Yang ; Kuo, Chia Wei ; Wang, Yu Wu ; Mai, Yu Shen ; Tang, Fu Ching ; Chu, Shu Wei. / Influence of electric field on microstructures of pentacene thin films in field-effect transistors. In: Advanced Functional Materials. 2008 ; Vol. 18, No. 2. pp. 285-293.
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Influence of electric field on microstructures of pentacene thin films in field-effect transistors. / Cheng, Horng Long; Chou, Wei Yang; Kuo, Chia Wei; Wang, Yu Wu; Mai, Yu Shen; Tang, Fu Ching; Chu, Shu Wei.

In: Advanced Functional Materials, Vol. 18, No. 2, 24.01.2008, p. 285-293.

Research output: Contribution to journalArticle

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