How do electronic carriers cross Si-bound alkyl monolayers?

TL;DR

This paper investigates electron transport mechanisms through Si-bound alkyl monolayers, revealing thermionic emission at low voltages and tunneling at higher voltages, with detailed barrier estimations.

Contribution

It provides a detailed analysis of the distinct electron transport regimes and quantifies the tunneling barrier and effective mass in Si-alkyl monolayers.

Findings

Transport is thermionic at low voltage, tunneling at high voltage.

Barrier height estimated at ~1.5 eV with a 0.25 m_e effective mass.

Current depends on temperature at low voltage, not on molecular length.

Abstract

Electron transport through Si-C bound alkyl chains, sandwiched between n-Si and Hg, is characterized by two distinct types of barriers, each dominating in a different voltage range. At low voltage, current depends strongly on temperature but not on molecular length, suggesting transport by thermionic emission over a barrier in the Si. At higher voltage, the current decreases exponentially with molecular length, suggesting tunneling through the molecules. The tunnel barrier is estimated, from transport and photoemission data, to be ~1.5 eV with a 0.25me effective mass.