Characterization of self-assembled monolayers by using a near-field microwave scanning microprobe

A near-field microwave scanning microprobe (NSMM) technique has been used to investigate the material properties of n-alkanethiol self-assembled monolayers (SAMs) on a gold (Au) surface. We demonstrate that near-field microwave probing technique can achieve the noncontact detection of the thickness of SAMs by measuring the microwave reflection coefficient S11 at an operating frequency near 5.3 GHz. We also directly image the patterned SAMs by NSMM. The thickness (chain length) of SAMs is determined from the visualized microwave reflection coefficient changes on the Au surface with high sensitivity. This nano-scale measurement of SAMs has a great potential for investigating the surface profile with high sensitivity.