title: Understanding the crystallization behavior of as-deposited Ti-Sb-Te alloys through real-time radial distribution functions.
abstract: Phase change materials, successfully used in optical data-storage and non-volatile electronic memory, are well-known for their ultrafast crystallization speed. However, the fundamental understanding of their crystallization behavior, especially the nucleation process, is limited by present experimental techniques. Here, real-time radial distribution functions (RDFs), derived from the selected area electron diffractions, are employed as structural probes to comprehensively study both nucleation and subsequent growth stages of Ti-doped Sb2Te3 (TST) materials in the electron-irradiation crystallization process. It can be found that the incorporation of Ti atoms in Sb2Te3 forms wrong bonds such as Ti-Te, Ti-Sb, breaks the originally ordered atomic arrangement and diminishes the initial nucleus size of the as-deposited films, which results in better thermal stability. But these nuclei hardly grow until their sizes exceed a critical value, and then a rapid growth period starts. This means that an extended nucleation time is required to form the supercritical nuclei of TST alloys with higher concentration. Also, the increasing formation of four-membered rings, which served as nucleation sites, after doping excessive Ti is responsible for the change of the crystallization behavior from growth-dominated to nucleation-dominated.
authors.affiliation: State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China. minzhu@mail.sim.ac.cn ztsong@mail.sim.ac.cn.
authors.forename: Min
authors.initials: M
authors.lastname: Zhu
authors.forename: Mengjiao
authors.initials: M
authors.lastname: Xia
authors.forename: Zhitang
authors.initials: Z
authors.lastname: Song
authors.forename: Yan
authors.initials: Y
authors.lastname: Cheng
authors.forename: Liangcai
authors.initials: L
authors.lastname: Wu
authors.forename: Feng
authors.initials: F
authors.lastname: Rao
authors.forename: Sannian
authors.initials: S
authors.lastname: Song
authors.forename: Miao
authors.initials: M
authors.lastname: Wang
authors.forename: Yegang
authors.initials: Y
authors.lastname: Lu
authors.forename: Songlin
authors.initials: S
authors.lastname: Feng