Date of Award

2017-01-01

Degree Name

Doctor of Philosophy

Department

Engineering

Advisor(s)

David Zubia

Abstract

Resistive switching in metal oxide is a phenomenon in which the metal oxide changes its resistance upon application of electric field and thus giving two states; high resistance state (HRS) and low resistance state (LRS). Many metal oxides have been investigated however very little is known about unipolar resistive switching in SnO2 though it has shown excellent resistive switching characteristics. Defects in the material play a vital role in resistive switching of the metal oxides. In this work, the role of defects in resistive switching of SnO2 are investigated in Ti/SnO2/Au structures. Two methods were used to control the concentration of defects in the SnO2 layer. One method was by changing the concentration of O2 during reactive sputtering deposition of SnO2, and the other was through post-deposition heat treatment in an oxygen atmosphere.

The structural study of each of the devices was conducted using X-ray diffraction spectroscopy (XRD) and photoluminescence spectroscopy (PL). XRD analysis revealed that devices fabricated with low oxygen concentration have Sn particles in the deposited films while high oxygen concentration did not have Sn crystals. The PL analysis further confirmed that the devices fabricated with low oxygen concentration have energy states within the band gap attributed to Sn interstitial defects.

Electrical characterization showed that resistive switching occurred only in the devices with the Sn defects which were fabricated with low oxygen concentration. Furthermore, the switching type is unipolar. The switching mechanism is of the filament formation type. The current conduction mechanism in the HRS state is Ohmic at low applied electric field but transitions to Schottky emission at higher electric field strength. In contrast, the current conduction in the LRS state is Ohmic throughout the applied voltage range.

The contribution of this work is the development of a method to study the switching mechanism in SnOX using reactive sputtering of Sn. Through application of this technique, it was revealed that Sn defects play a dominant role in resistive switching in SnOX via the formation of conductive filaments.

Language

en

Provenance

Received from ProQuest

File Size

69 pages

File Format

application/pdf

Rights Holder

Arka Talukdar

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