Phase-change thin films growth and functionality

Abstract

Computing and fast data transfers propelled our technological progress in the past few decades with fundamental research on semiconductor materials. However, classical storage and computing technologies face scaling limitations and the Von Neumann architectural bottleneck. Phase-change materials (PCMs), with more than one stable phase and significant electrical and optical contrasts, are the primary contenders for fast, non-volatile, and large storage capacity devices for future optoelectronic applications. GeSbTe alloys, specifically Ge2Sb2Te5 (GST225), are the most studied and at the center of research in the field. However, major reliability issues hinder the full integration of the GeSbTe alloys into functioning devices. This thesis focuses on the growth, characterization, and functionality of various new-generation phase-change alloys. Thin films of phase-change alloys, with unique properties attractive for data storage and optoelectrical applications, have been produced by the pulsed laser deposition (PLD) technique. Growth optimization, characterization, and device designs and testing based on monatomic Sb, binary GaSb and Sb2Se3, and ternary Ge-rich GST thin films are detailed in this thesis. Superior properties, such as thickness-dependent crystallization dynamics, increased crystallization temperatures, and attractive optical contrasts, have been realized through state-of-the-art characterization tools. Moreover, optoelectrical devices utilizing the phase-change alloys and the realized properties have been designed, fabricated, and tested for applications in data storage, reflective-based display, and optical sensors.