The effect of nonadiabatic annealing on poly(3,4-ethylendioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) thin films prepared on silicon substrate has been investigated by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The analysis indicates the formation of an annealing-induced doping in PEDOT structure, suggesting a modification of the polymer electronic structure and the formation of a PEDOT-rich film surface.