Laser Induced Change in the Electrical and Optical Properties of Amorphous Ge2Sb2Te5 Thin Films

Sheet resistance of laser-irradiated amorphous Ge2Sb2Te5 thin films prepared by magnetron sputtering were measured by the four-point probe method. With the laser power increasing, the sheet resistance undergoes an abrupt change of four orders of magnitude (10(7) - 10(3)Omega/rectangle) at about 580mW. X-ray diffraction studies of the three samples before, at and after the abruption point reveal the phase change process of the Ge2Sb2Te5 thin films from amorphous to crystal states. Optical constants of the three samples measured by ellipsometry have relations as follows, n(amorphous) > n(intermediate) > n(crystalline;) k(crystalline) > k(intermediate) > k(amorphouse;) alpha(crystalline) > alpha(intermediate) >alpha(amorphous). Based on the above results, the relationship between the electrical/optical properties and the structural state of the Ge2Sb2Te5 thin films is discussed.