Homoepitaxy of Crystalline Rubrene Thin Films

Michael A. Fusella, Frank Schreiber, Kevin Abbasi, Jae Joon Kim, Alejandro L. Briseno, Barry P. Rand

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

The smooth surface of crystalline rubrene films formed through an abrupt heating process provides a valuable platform to study organic homoepitaxy. By varying growth rate and substrate temperature, we are able to manipulate the onset of a transition from layer-by-layer to island growth modes, while the crystalline thin films maintain a remarkably smooth surface (less than 2.3 nm root-mean-square roughness) even with thick (80 nm) adlayers. We also uncover evidence of point and line defect formation in these films, indicating that homoepitaxy under our conditions is not at equilibrium or strain-free. Point defects that are resolved as screw dislocations can be eliminated under closer-to-equilibrium conditions, whereas we are not able to eliminate the formation of line defects within our experimental constraints at adlayer thicknesses above ∼25 nm. We are, however, able to eliminate these line defects by growing on a bulk single crystal of rubrene, indicating that the line defects are a result of strain built into the thin film template. We utilize electron backscatter diffraction, which is a first for organics, to investigate the origin of these line defects and find that they preferentially occur parallel to the (002) plane, which is in agreement with expectations based on calculated surface energies of various rubrene crystal facets. By combining the benefits of crystallinity, low surface roughness, and thickness-tunability, this system provides an important study of attributes valuable to high-performance organic electronic devices.

Original languageEnglish (US)
Pages (from-to)3040-3046
Number of pages7
JournalNano Letters
Volume17
Issue number5
DOIs
StatePublished - May 10 2017

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

Keywords

  • Homoepitaxy
  • crystals
  • electron backscatter diffraction
  • line defect
  • roughness
  • rubrene
  • screw dislocation
  • thin films

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  • Cite this

    Fusella, M. A., Schreiber, F., Abbasi, K., Kim, J. J., Briseno, A. L., & Rand, B. P. (2017). Homoepitaxy of Crystalline Rubrene Thin Films. Nano Letters, 17(5), 3040-3046. https://doi.org/10.1021/acs.nanolett.7b00380