UHV STM I(V) and XPS studies of aryl diazonium molecules assembled on Si(111)
Abstract
Molecular layers formed from 4-trifluoromethylbenzenediazonium tetrafluoroborate and 4-Methylbenzenediazonium tetrafluoroborate have been assembled on H-passivated Si(111) and studied by UHV STM and XPS. STM imaging shows well-developed Si(111) step edges and terraces both on Si(111):H and Si(111) substrates covered with a molecular layer. STM I(V) data acquired at different tip-substrate separations reveals a factor of similar to 10 enhancement in current for positive bias voltage when current flows through the 4-trifluoromethyl molecule when compared to the 4-methyl variant. The observed current enhancement in I(V) can be understood by comparing the projected density of states of the two molecule-Si systems calculated using a density functional theory local density approximation after geometry optimization was performed via the conjugate gradient method. XPS data independently confirm that H-passivated Si(111) remains oxygen free for short exposures to ambient conditions and provide evidence that the molecules chemically react with the silicon surface.
Published in:
Langmuir 23,9 (2007) 4700-4708;
Link to original published article:
http://dx.doi.org/10.1021/la063235i
Keywords
Chemistry, Physical
Date of Version
1-1-2007
Recommended Citation
Pandey, D.; Zemlyanov, D. Y.; Bevan, K.; Reifenberger, R. G.; Dirk, S. M.; Howell, S. W.; and Wheeler, D. R., "UHV STM I(V) and XPS studies of aryl diazonium molecules assembled on Si(111)" (2007). Department of Physics and Astronomy Faculty Publications. Paper 702.
https://docs.lib.purdue.edu/physics_articles/702