The first accepted experimental observation came many years later in the work by Crommie et al. . Later that year, Avouris and Hasegawa 27 also presented similar observations. These contributions are the first widely recognized experimental evidence of FOs . Crommie and co-workers used scanning tunneling microscopy (STM) to probe the so-called local density of states, or electron surface states, around defects on Cu(111) surface. They have observed the formation of concentric rings around point defects as well as step edges at a temperature range of 4 -77 K (see Fig. ). Scanning tunneling microscopy (STM) is a powerful technique used to visualize surfaces at the atomic level by measuring the tunneling current between a sharp tip and a conductive surface, which often involves an electron gas. The interaction of the tip with the surface can reveal information about the electron density and electronic states of the surface, providing insights into phenomena such as Friedel oscillations in the electron gas .