Laser Induced Change in the Electrical and Optical Properties of Amorphous Ge_2Sb_2Te_5 Thin Films

Sheet resistance of laser-irradiated amorphous Ge_2Sb_2Te_5 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(10~7-10~3Ω/□)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 Ge_2Sb_2Te_5 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_(amorphous),α_(crystalline)α_(intermediate)α_(amorphous).Based on the above results,the relationship between the electrical/optical properties and the structural state of the Ge_2Sb_2Te_5 thin films is discussed.