title: Resistive Switching of Individual, Chemically Synthesized TiO2 Nanoparticles.
abstract: Resistively switching devices are considered promising for next-generation nonvolatile random-access memories. Today, such memories are fabricated by means of "top-down approaches" applying thin films sandwiched between nanoscaled electrodes. In contrast, this work presents a "bottom-up approach" disclosing for the first time the resistive switching (RS) of individual TiO2 nanoparticles (NPs). The NPs, which have sizes of 80 and 350 nm, respectively, are obtained by wet chemical synthesis and thermally treated under oxidizing or vacuum conditions for crystallization, respectively. These NPs are deposited on a Pt/Ir bottom electrode and individual NPs are electrically characterized by means of a nanomanipulator system in situ, in a scanning electron microscope. While amorphous NPs and calcined NPs reveal no switching hysteresis, a very interesting behavior is found for the vacuum-annealed, crystalline TiO(2-x) NPs. These NPs reveal forming-free RS behavior, dominantly complementary switching (CS) and, to a small degree, bipolar switching (BS) characteristics. In contrast, similarly vacuum-annealed TiO2 thin films grown by atomic layer deposition show standard BS behavior under the same conditions. The interesting CS behavior of the TiO(2-x) NPs is attributed to the formation of a core-shell-like structure by re-oxidation of the reduced NPs as a unique feature.
authors.affiliation: Institute for Inorganic Chemistry, RWTH Aachen University and JARA-Fundamentals of Future Information Technologies, 52074, Aachen, Germany.
authors.forename: Dirk Oliver
authors.initials: DO
authors.lastname: Schmidt
authors.affiliation: Forschungszentrum Juelich GmbH, Peter-Gruenberg-Institute 7 and JARA-Fundamentals of Future Information Technologies, 52425, Juelich, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Hoffmann-Eifert
authors.affiliation: Forschungszentrum Juelich GmbH, Peter-Gruenberg-Institute 7 and JARA-Fundamentals of Future Information Technologies, 52425, Juelich, Germany.
authors.forename: Hehe
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Institut für Werkstoffe der Elektrotechnik 2, RWTH Aachen University and JARA-Fundamentals of Future Information Technologies, 52074, Aachen, Germany.
authors.forename: Camilla
authors.initials: C
authors.lastname: La Torre
authors.affiliation: Central Institute for Engineering, Electronics and Analytics (ZEA-3), Forschungszentrum Juelich GmbH, 52425, Juelich, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Besmehn
authors.affiliation: Institute for Inorganic Chemistry, RWTH Aachen University and JARA-Fundamentals of Future Information Technologies, 52074, Aachen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Noyong
authors.affiliation: Forschungszentrum Juelich GmbH, Peter-Gruenberg-Institute 7 and JARA-Fundamentals of Future Information Technologies, 52425, Juelich, Germany.|Institut für Werkstoffe der Elektrotechnik 2, RWTH Aachen University and JARA-Fundamentals of Future Information Technologies, 52074, Aachen, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Waser
authors.affiliation: Institute for Inorganic Chemistry, RWTH Aachen University and JARA-Fundamentals of Future Information Technologies, 52074, Aachen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Simon
keywords: electrical properties; nanomanipulation; nanoparticles; resistive switching; titanium dioxide