[GRAPHICS] Reversible polarity-dependent resistance (PDR) switching in phase-change (PC) films is feasible. Nanometer-scale crystalline marks are produced in amorphous Ge2Sb2+xTe5 films by electrical pulses through an AFM tip. In these marks, PDR switching is demonstrated with three orders of magnitude current contrast using less than 1.5 V. No current contrast between the crystalline marks in the high-resistance state and the amorphous if background is observed.