Sponsor: Micron Foundation Supervisor: Prof AL Greer (email@example.com) Starting date: October 2018 Eligibility: UK/EU students only. Students liable for fees at the 'overseas' rate are not eligible.
Fixed-term: The funds for this post are available for 3 years in the first instance.
Applications are invited for a PhD studentship (funded for 3 years in the first instance) within the Microstructural Kinetics Group in the Department of Materials Science & Metallurgy. The project focuses on chalcogenide materials (e.g. Ge2Sb2Te5) of interest for phase-change memory (PCM). In this technology a sub-micrometre memory cell is switched reversibly between glassy and crystalline states by applying short (~10 ns) electrical pulses. The glassy state has a higher resistivity than the crystalline; the state of the cell is thus easily detected. PCM has several advantages for memory, in particular its scalability ¿ the prospect to achieve higher data-storage densities .
The project focuses on the kinetics of the crystallization of the chalcogenides, as this is the rate-limiting step for memory performance. We have shown that the kinetics can be studied in detail using ultra-fast differential scanning calorimetry , a now widely applied technique. The crystallization kinetics can deviate markedly from Arrhenius temperature dependence [3,4], and the project will examine how the extent and nature of this deviation depends on the chalcogenide system and on its processing. The project will also consider how the deviation must influence PCM switching and device performance , and will look toward future systems, possibly metallic .
 S Raoux, W We¿nic & D Ielmini, Phase change materials and their application to nonvolatile memories, Chemical Reviews 110 (2010), 240¿267.  J Orava, AL Greer, B Gholipour, DW Hewak & CE Smith, Characterization of supercooled liquid Ge2Sb2Te5 and its crystallization by ultra-fast-heating calorimetry, Nature Materials 11 (2012) 279¿283.  J Orava, DW Hewak & AL Greer, Fragile-to-strong crossover in supercooled liquid Ag-In-Sb-Te studied by ultrafast calorimetry, Advanced Functional Materials 25 (2015) 4851¿4858.  J Orava, H Weber, I Kaban & AL Greer, Viscosity of liquid Ag-In-Sb-Te: Evidence of a fragile-to-strong crossover, Journal of Chemical Physics 144 (2016) 194503.  J Orava & AL Greer, Classical-nucleation-theory analysis of priming in chalcogenide phase-change memory, Acta Materialia 139 (2017) 226¿235.  AL Greer, New horizons for glass formation and stability, Nature Materials 14 (2015) 542¿546.
Applicants should have (or expect to be awarded) an upper second or first-class UK honours degree at the level of MSci, MEng (or overseas equivalents) in a relevant subject (Materials Science, Physics, Chemistry,) and should be liable for 'home rate' fees. The studentship is fully funded, covering fees and a tax-free stipend (currently set at £14,777 per annum).
Applications can be made on-line via http://www.graduate.study.cam.ac.uk/courses/directory/pcmmpdmsm.
Please quote reference LJ14915 on your application and in any correspondence about this vacancy.
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