A new method is described to prepare strongly bonded, compact monolayer films of alkyl- or arylphosphonates on the native oxide surface of Si (SiO 2/Si). This method is illustrated for octadecyl- and α-quarterthiophene-2-phosphonates. For both cases, AFM shows comprehensive coverage of the SiO2/Si surface. The thickness of the continuous film of 4TP/SiO2/Si was measured both by AFM and by X-ray reflectivity to be ca. 18 Å. Direct gravimetric analysis shows surface coverage by α-quarterthiophene-2-phosphonate to be about 0.66 nmol/cm 2, which corresponds to molecular packing in the film close to that of crystalline α-quarterthiophene. Coverage by octadecylphosphonate was ca. 0.90 nmol/cm2, corresponding to a cross-sectional area of about 18.5 Å2/molecule, consistent with close-packed alkyl chains.
All Science Journal Classification (ASJC) codes
- General Chemistry
- Colloid and Surface Chemistry