Conducting atomic force microscopy studies of nanoscale cobalt silicide Schottky barriers on Si(111) and Si(100)

Abstract

Cobalt silicide (CoSi 2 ) islands have been formed by the deposition of thin films (~0.1 to 0.3 nm) of cobalt on clean Si(111) and Si(100) substrates in ultrahigh vacuum (UHV) followed by annealing to ~880ºC. Conducting atomic force microscopy has been performed on these islands to characterize and measure their current-voltage (I-V) characteristics.Current-voltage curves were analyzed using standard thermionic emission theory to obtain the Schottky barrier heights and ideality factors between the silicide islands and the silicon substrates. Current-voltage measurements were performed ex situ for one set of samples (termed "passivated surfaces") where the silicon surface surrounding the islands was passivated with a native oxide. Other samples (termed "clean surfaces") remained in UHV while I-V curves were recorded. By comparing the barrier heights and ideality factors for islands on passivated surfaces and clean surfaces, the effects of the non-passivated surfaces on conduction have been studied. The barrier heights measured from CoSi 2 islands on clean surfaces are found to be ~0.2 to 0.3 eV below barrier heights measured from similar islands on passivated surfaces. The main cause of the reduced Schottky barrier in the clean surface samples is attributed to Fermi level pinning by non-passivated surface states of the clean silicon surface. However, the measured barrier heights of the islands are equivalent on both clean Si(111) and Si(100) surfaces, suggesting that the non-passivated surface is influenced

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Kelvin probe force microscopy of the nanoscale electrical surface potential barrier of metal/semiconductor interfaces in ambient atmosphere

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