Dresden 2014 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 32: Focus session: Resistive Switching by Redox and Phase Change Phenomena III (Defect and material engineering in oxides)

DS 32.2: Vortrag

Mittwoch, 2. April 2014, 15:15–15:30, CHE 89

Towards forming free switching in HfO_2−x/TiN thin films grown by molecular beam epitaxy — •S Ulhas Sharath¹, Thomas Bertaud², Jose Kurian¹, Erwin Hildebrandt¹, Christian Walczyk², Pauline Calka², Peter Zaumseil², Malgorzata Sowinska², Damian Walczyk², Andrei Gloskovskii³, Thomas Schroeder², and Lambert Alff¹ — ¹Materialwissenschaft, Technische Univerität, Darmstadt — ²IHP, Frankfurt/Oder, Germany — ³Deutsches Elektronen-Synchroton DESY, Hamburg, Germany

Oxygen deficient thin films of hafnium dioxide (HfO₂) were grown using reactive molecular beam epitaxy on epitaxial and polycrystalline titanium nitride films with varying thicknesses and deposition temperatures. The oxygen content was engineered by controlled oxidation using RF-activated oxygen during growth [1]. The crystallinity of the films was studied using X-ray diffraction. Under oxygen deficient conditions, a mixture of monoclinic and tetragonal or cubic phases of HfO₂ was stabilized whereas close to stoichiometric films were purely monoclinic. The films were further probed using hard X-ray photoelectron spectroscopy (HAXPES) confirming the presence of sub-stoichiometric hafnium oxide and defect states near the Fermi level. Resistive switching in Pt/HfO_2−x/TiN stack devices was then studied for different electrode size, thickness and crystallinity of the HfO₂ thin films. Oxygen deficient hafnium oxide thin films show bipolar switching with an electroforming step occurring at voltages less than 2V and slightly higher than the set voltage. [1] E. Hildebrandt et al., Appl. Phys. Lett. 99, 112902 (2011).