Influence of thiol self-assembled monolayer processing on bottom-contact thin-film transistors based on n-type organic semiconductors

Jangdae Youn, Geetha R. Dholakia, Hui Huang, Jonnathan W. Hennek, Antonio Facchetti, Tobin J Marks

Research output: Contribution to journalArticle

56 Citations (Scopus)

Abstract

The performance of bottom-contact thin-film transistor (TFT) structures lags behind that of top-contact structures owing to the far greater contact resistance. The major sources of the contact resistance in bottom-contact TFTs are believed to reflect a combination of non-optimal semiconductor growth morphology on the metallic contact surface and the limited available charge injection area versus top-contact geometries. As a part of an effort to understand the sources of high charge injection barriers in n-channel TFTs, the influence of thiol metal contact treatment on the molecular-level structures of such interfaces is investigated using hexamethyldisilazane (HMDS)-treated SiO 2 gate dielectrics. The focus is on the self-assembled monolayer (SAM) contact surface treatment methods for bottom-contact TFTs based on two archetypical n-type semiconductors, α,ω- diperfluorohexylquarterthiophene (DFH-4T) and N,N'bis(n-octyl)-dicyanoperylene- 3,4:9,10-bis(dicarboximide) (PDI-8CN 2). TFT performance can be greatly enhanced, to the level of the top contact device performance in terms of mobility, on/off ratio, and contact resistance. To analyze the molecular-level film structural changes arising from the contact surface treatment, surface morphologies are characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The high-resolution STM images show that the growth orientation of the semiconductor molecules at the gold/SAM/semiconductor interface preserves the molecular long axis orientation along the substrate normal. As a result, the film microstructure is well-organized for charge transport in the interfacial region.

Original languageEnglish
Pages (from-to)1856-1869
Number of pages14
JournalAdvanced Functional Materials
Volume22
Issue number9
DOIs
Publication statusPublished - May 9 2012

Fingerprint

n-type semiconductors
Semiconducting organic compounds
organic semiconductors
Self assembled monolayers
Thin film transistors
Contact resistance
contact resistance
Sulfhydryl Compounds
thiols
Charge injection
transistors
Scanning tunneling microscopy
Semiconductor materials
surface treatment
Crystal orientation
Surface treatment
scanning tunneling microscopy
electric contacts
Semiconductor growth
thin films

Keywords

  • bottom-contact organic thin-film transistors
  • n-type organic semiconductors
  • thiol self-assembled monolayers

ASJC Scopus subject areas

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

Cite this

Influence of thiol self-assembled monolayer processing on bottom-contact thin-film transistors based on n-type organic semiconductors. / Youn, Jangdae; Dholakia, Geetha R.; Huang, Hui; Hennek, Jonnathan W.; Facchetti, Antonio; Marks, Tobin J.

In: Advanced Functional Materials, Vol. 22, No. 9, 09.05.2012, p. 1856-1869.

Research output: Contribution to journalArticle

Youn, Jangdae ; Dholakia, Geetha R. ; Huang, Hui ; Hennek, Jonnathan W. ; Facchetti, Antonio ; Marks, Tobin J. / Influence of thiol self-assembled monolayer processing on bottom-contact thin-film transistors based on n-type organic semiconductors. In: Advanced Functional Materials. 2012 ; Vol. 22, No. 9. pp. 1856-1869.
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