An ultrahigh vacuum scanning tunneling microscopy (UHV-STM) and a scanning tunneling spectroscopy (STS) are used measure the rectification property of self-assembled viologen single molecules (VC8SH, VC10SH, HSC8VC8SH, and HSC10VC10SH) in the previous study. Using STM we observe viologen single molecules in the self-assembled octanethiol (OT) SAM matrix. In the OT matrix a mixed phase that includes a c(4 x 2) superlattice of high-density standing up-phase is observed. We indicate high peak current-like rectifications at + 1.68 V(VC8SH), + 1.56 V(VC10SH), + 1.14 V(HSC8VC8SH), and + 1.04 V(HSC10VC10SH) based on the experiment implemented in this study. In addition, transition voltages (Vtrans) from direct tunneling to the Fowler-Nordheim tunneling are presented at 1.08 V(VC8SH), 0.97 V(VC10SH), 0.99 V(HSC8VC8SH), and 0.89 V(HSC1VC1SH).