Publication Date

12-2014

Date of Final Oral Examination (Defense)

7-10-2014

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Electrical Engineering

Department

Electrical and Computer Engineering

Supervisory Committee Chair

Maria I. Mitkova, Ph.D.

Supervisory Committee Member

William B. Knowlton, Ph.D.

Supervisory Committee Member

Dmitri Tenne, Ph.D.

Abstract

Continued scaling of memory devices has produced many issues for the current foremost non-volatile memory—the flash memory—leading to the emergence of a wide variety of alternative memory solutions. Redox Conductive Bridge Memory (RCBM) is one such solution that has shown great promise in recent years. However, the performance of these devices under radiation conditions has not been explored in detail. This work investigates the effects of x-rays and electron bombardment on chalcogenide glasses and RCBM devices based on these materials.

RCBM devices are a form of Resistance Change Memory, which rely on two distinct resistive states to represent the binary ‘0’ and ‘1’ memory conditions. The functionality of the RCBM devices is based on the growth and dissolution of a conductive filament through an insulating medium sandwiched between two metal electrodes. The presence of the filament represents the on state, while the absence represents the off state.

In this work, we studied RCBM devices fabricated utilizing amorphous Ge-Se films as the active medium. Various compositions of Ge-Se films were studied in order to fully understand the effect of radiation over their properties and determine the most stable system. Various compositions of Ge-Se films in contact with an Ag source were studied as well to simulate the exact processes occurring in the RCBM devices under radiation. Several different material characterization methods were utilized in order to perceive all of the effects occurring in the systems comprising the RCBM devices. The major characterization methods include Energy Dispersive Spectroscopy to determine the exact compositions, Raman spectroscopy for analyzing the structural properties, and x-ray diffraction to identify the molecular compounds. Both electron beam radiation and x-ray radiation were found to affect the variety of chalcogenide glass compositions and structures containing Ag in different manners, with each radiation type having a specific impact signature. Correspondingly, radiation exposure also affected the performance parameters of the RCBM devices. The performances of these devices under the influence of both forms of radiation were strongly related to the composition of the film within the device.

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