Study on electrical switching behaviour of Ge-Se-S and Ge-Se_0.5-S_1.5 thin films

Ternary glassy chalcogenides of Ge-Se-S and Ge-Se_0.5-S_1.5 systems were prepared by vacuum evaporation technique. Their electrical switching characteristics were examined in detail, where the resistance of the prepared thin films changed from mega to several tens of ohms. The amorphous-crystalline transition temperature (T_C) for GeSeS and GeSe_0.5S_1.5 thin films are around 380 K and 360 K, respectively. Due to the electrothermal mechanism a rapid transition from resistive to conductive nature was observed and the results obtained were discussed by Joule heating effect. In the prepared compositions of Ge-Se-S and GeSe_0.5S_1.5, sulphur atoms get their preferred bonding when connected to the two-fold coordinated selenium atoms, and the Se-S chains are cross linked by the four-fold germanium atoms. Incorporating more sulphur to Ge-Se-S system, gives the sulphur more space to adapt in the network due the smaller size of the sulphur atoms when compared to selenium. Furthermore, this method of preparation and results open-up a new approach towards the phase change memory devices that rely on easy structural transformation.