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MATERIALS ENGINEERING

SEMINAR

“Structural, Thermodynamic, and Electronic Properties of Mixed Ionic-Electronic Conductor Materials”

By

David M. Guzman

Purdue MSE PhD Final Exam

Advisor:

Professor Alejandro Strachan

ABSTRACT

Resistive switching electronic devices based on electrochemical metallization (ECM) cells are promising candidates from many beyond-CMOS applications. With the aim of unraveling the physics behind filamentary and threshold switching in ECM cells consisting of solid mixed ionic-electronic conductor electrolytes, this work focused on using first-principles calculations to characterize the structural, thermodynamic, and electronic properties of copper-doped amorphous silicon dioxide and copper-doped germanium-based glassy chalcogenides. The morphology and diffusion of small copper clusters embedded in amorphous silicon dioxide were characterized by density functional theory calculations. The average formation energy of a single copper ion in the amorphous matrix is found to be 2.4 eV. The theoretical predictions show that copper clusters with an equiaxed morphology are always energetically favorable relative to the dissolved copper ions in a-SiO₂. Threshold conduction is predicted to be the transport mechanism for glassy sulfides and selenides due to the ability of copper to remain dissolved in the amorphous matrix even at high metal concentration. Furthermore, the charge carrier transport in sulfur and selenium glasses was found to be assisted by defective states derived from chalcogen atoms whose bonds exhibit a polar character.

Date:         Wednesday, April 18, 2018

Time:     1:00 P.M.

Place:        ARMS 1109