Hg/Molecular Monolayer-Si Junctions: Electrical Interplay between Monolayer Properties and Semiconductor Doping Density

O. Yaffe, L.M.W. Scheres, O. Segev, A. Biller, I. Ron, E. Salomon, M. Giesbers, A. Kahn, L. Kronik, H. Zuilhof, A. Vilan, D. Cahen

Research output: Contribution to journalArticleAcademicpeer-review

54 Citations (Scopus)

Abstract

Metal-organic molecule-semiconductor junctions are controlled not only by the molecular properties, as in metal-organic molecule-metal junctions, but also by effects of the molecular dipole, the dipolar molecule-semiconductor link, and molecule-semiconductor charge transfer, and by the effects of all these on the semiconductor depletion layer (i.e., on the internal semiconductor barrier to charge transport). Here, we report on and compare the electrical properties (current-voltage, capacitance-voltage, and work function) of large area Hg/organic monolayer-Si junctions with alkyl and alkenyl monolayers on moderately and highly doped n-Si, and combine the experimental data with simulations of charge transport and electronic structure calculations. We show that, for moderately doped Si, the internal semiconductor barrier completely controls transport and the attached molecules influence the transport of such junctions only in that they drive the Si into inversion. The resulting minority carrier-controlled junction is not sensitive to molecular changes in the organic monolayer at reverse and low forward bias and is controlled by series resistance at higher forward bias. However, in the case of highly doped Si, the internal barrier is smaller, and as a result, the charge transport properties of the junction are affected by changing from an alkyl to an alkenyl monolayer. We propose that the double bond near the surface primarily increases the coupling between the organic monolayer and the Si, which increases the current density at a given bias by increasing the contact conductance.
Original languageEnglish
Pages (from-to)10270-10279
JournalThe Journal of Physical Chemistry Part C: Nanomaterials and Interfaces
Volume114
Issue number22
DOIs
Publication statusPublished - 2010

Keywords

  • crystalline silicon surfaces
  • voltaic energy-conversion
  • linked organic monolayers
  • self-assembled monolayers
  • flat h-si(111) surfaces
  • alkyl chain monolayers
  • metal work function
  • mis tunnel-diodes
  • current transport
  • si(111) surfaces

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