Surface Sensitivity of PiFM

Since photo-induced force (PiF) is generated from the tipenhanced field, which extends only about 20 nm from the apex of the AFM tip, PiFM enjoys excellent surface sensitivity along with ~ 5 nm spatial resolution. PS(polystyrene)-b-PTMSS[poly(4-trimethylsilylstyrene)] block copolymer (PS-PTMSS BCP) with horizontal lamellae is used to demonstrate the surface sensitivity. BCP is an excellent sample to demonstrate both spatial and depth resolution since the thickness of each block componentcan be controlled precisely by adjusting the molecular weights of the components. In this case, the full pitch L0 of the BCP is ~22 nm as shown in figure 1. One sample with island features with PTMSS at the top (shown in the top row of figure 1) and another sample with holes with PS at the bottom (shown in the bottom row of figure 1) were prepared on silicon substrate.