Demonstration of Ferroelectricity in PLD Grown HfO2-ZrO2 Nanolaminates

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dc.contributor.advisorDroopad, Ravi
dc.contributor.advisorAslan, Semih
dc.contributor.authorDas, Sree Sourav
dc.contributor.committeeMemberChen, Maggie
dc.date.accessioned2022-06-01T20:33:02Z
dc.date.available2022-06-01T20:33:02Z
dc.date.issued2021-05
dc.description.abstractFerroelectricity was demonstrated for Pulsed Laser Deposition (PLD) of HfO<sub>2</sub>-ZrO<sub>2</sub> bilayer thin films grown on TiN bottom electrodes on SiO<sub>2</sub>/Si as a function of deposition conditions and individual HfO<sub>2</sub>-ZrO<sub>2</sub> layer thicknesses. Thicknesses of individual layers in HfO<sub>2</sub>-ZrO<sub>2</sub> bilayer system were varied from 5 nm to 15 nm, deposition temperature was varied from room temperature to 750°C and partial oxygen pressure was varied from 10<sup>-6</sup> torr to 0.124 mtorr. The films deposited at higher temperature, higher pressure and have higher thicknesses showed better ferroelectric response with 12 μC/cm<sup>2</sup> remnant polarization and 10<sup>-7</sup> A leakage current (at 8 V) with endurance greater than 10<sup>11</sup> cycles indicative of an orthorhombic crystal phase. On the other hand, films deposited at lower temperatures and pressures did not exhibit ferroelectric behavior. These films were determined to have a monoclinic structure, lower grain size and higher leakage current. The effects of ZrO<sub>2</sub> layer were also demonstrated by changing the sequence in the structure and it was found that ZrO<sub>2</sub> as the top layer provided better mechanical confinement for stabilizing the orthorhombic phase. Finally, the effect of the interfacial layer between HfO<sub>2</sub>-ZrO<sub>2</sub> nanolaminates was investigated by depth profile analysis and a bilayer structure was proposed with proper process conditions and layer thicknesses that could potentially exhibit higher remnant polarization and strong endurance against fatigue for memory applications.
dc.description.departmentEngineering
dc.formatText
dc.format.extent81 pages
dc.format.medium1 file (.pdf)
dc.identifier.citationDas, S. S. (2021). <i>Demonstration of ferroelectricity in PLD grown HfO2-ZrO2 nanolaminates</i> (Unpublished thesis). Texas State University, San Marcos, Texas.
dc.identifier.urihttps://hdl.handle.net/10877/15838
dc.language.isoen
dc.subjectFerroelectricity
dc.subjectOrthorhombic phase
dc.subjectRemnant polarization
dc.subjectHysteresis loop
dc.subjectEndurance
dc.subjectWake-up
dc.subjectLeakage current
dc.titleDemonstration of Ferroelectricity in PLD Grown HfO2-ZrO2 Nanolaminates
dc.typeThesis
thesis.degree.departmentEngineering
thesis.degree.disciplineEngineering
thesis.degree.grantorTexas State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science

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