Fabrication and characterization of the electrical properties of phase change materials

• Main Author: Lam, Rachel Wei Qin
• Other Authors: Gan Chee Lip
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Materials::Material testing and characterization; DRNTU::Engineering::Materials::Microelectronics and semiconductor materials
• Online Access: http://hdl.handle.net/10356/46483
• Institution: Nanyang Technological University

Phase change materials have been extensively studied due to their promising applications in phase change memory. Chalcogenide materials used in these memories can be switched repeatedly between the amorphous and crystalline phase and the corresponding different electrical properties can be used for data storage. Ge2Sb2Te5 (GST) has been one of the most attractive candidates because of its outstanding properties and distinct changes in electrical conductivity between the two phases which can be utilised in phase-change random excess memory (PCRAM). In this study, the electrical resistivity values for both the amorphous and crystalline phases of GST films were obtained and compared. Amorphous thin films were annealed to enable crystallization. SEM-EDX characterization was performed to analyse the morphological and compositional variation from the phase change. The films displayed a general ohmic behaviour and gave consistent resistance values which were proportional to corresponding film dimensions. The phase change appeared to be driven by thermal nucleation mechanism. Scaling properties of GST were also studied. The films were milled into nanowires by Focused Ion Beam and the resulting crystalline resistivity was comparable to that of the films, indicating reasonable physical scalability.