Optically transparent Au{111} substrates: flat gold nanoparticle platforms for high-resolution scanning tunneling microscopy.

We demonstrate a new type of Au{111} substrate that is both atomically flat and optically transparent, which consists of solution-grown flat gold nanoparticles (FGNPs) deposited on indium tin oxide (ITO)-coated glass. We show that FGNPs are atomically flat single-crystal plates with large {111} faces that expose only 2-4 atomic layers. These FGNPs are excellent platforms for alkanethiol self-assembled monolayers (SAMs) and for high-resolution scanning tunneling microscopy (STM). Our supported FGNPs are also low-cost Au{111} substrates, employing only basic wet chemical techniques in preparation. This approach should be broadly applicable to other types of substrates for scanning probe microscopies.