Measurement of barrier heights of semiconductor/liquid junctions using a transconductance method: Evidence for inversion at n-Si/CH3OH-1,1′-dimethylferrocene+/0 junctions

Paul E. Laibinis, Colby E. Stanton, Nathan S Lewis

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Transconductance measurements have been used to characterize the space-charge regions of various n-Si/ liquid contacts. To perform these measurements, Si electrodes were photolithographically processed to introduce p+-contact areas into the surface of an n-type Si electrode. The electrical conductance between these p+ regions was then used to probe the minority carrier concentration in the near-surface region of the n-type Si. Unlike conventional differential capacitance or current-voltage measurements, these transconductance measurements can be performed under near-equilibrium conditions and can be performed in the presence of gaseous ambients or when the sample is in contact with ionically conducting electrolyte solutions. In contact with the electrolyte solutions, faradaic and solid-state conduction pathways were distinguished using ac impedance measurements. The impedance spectra provided clear evidence that contact with Me2Fc (1,1′-dimethylferrocene)+/0 and Fc+/0 redox couples in CH3OH(l)-1.0 M LiClO4 formed an inversion layer in the n-Si, but that CH3OH(l)-1.0 M LiClO4-Me10Fc+/0 solutions did not yield an inversion layer. These observations are consistent with prior current-voltage measurements on these junctions. The barrier heights of the n-Si/CH3OH-Me2Fc+/0 and n-Si/CH3OH-Fc+/0 junctions were determined to be 1.01 and 1.02 V, respectively. These measurements provide new insight into the photoelectrochemical behavior of Si/CH3OH contacts and provide an alternate method for characterizing the energetics of semiconductor/liquid contacts.

Original languageEnglish
Pages (from-to)8765-8774
Number of pages10
JournalJournal of Physical Chemistry
Issue number35
Publication statusPublished - 1994


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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