We demonstrate the use of high-sensitivity, off-normal transmission IR spectroscopy with s-polarized light to probe the chemical identity and orientation of quaterphenyldithiol (QPDT) molecular assemblies on GaAs as a function of ammonium hydroxide (NH 4OH) concentration. NH 4OH is added to the assembly solution to convert the thioacetyl groups on the QPDT precursor to thiolates. When assembled at high NH 4OH concentrations, the acetyl groups are completely removed, and QPDT is disordered on GaAs. Assembly at low NH 4OH concentrations, however, results in QPDT assemblies that are preferentially upright. The molecular orientation is further quantified with near-edge X-ray absorption fine structure spectroscopy.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Surfaces and Interfaces