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Ferroelectricity in hafnium oxide thin films

: Böscke, T.S.; Müller, J.; Bräuhaus, D.; Schröder, U.; Böttger, U.


Applied Physics Letters 99 (2011), No.10, Art. 102903
ISSN: 0003-6951 (Print)
ISSN: 1077-3118
ISSN: 1931-9401 (online)
Journal Article
Fraunhofer CNT ()

We report that crystalline phases with ferroelectric behavior can be formed in thin films of SiO2 doped hafnium oxide. Films with a thickness of 10 nm and with less than 4 mol%. of SiO2 crystallize in a monoclinic/tetragonal phase mixture. We observed that the formation of the monoclinic phase is inhibited if crystallization occurs under mechanical encapsulation and an orthorhombic phase is obtained. This phase shows a distinct piezoelectric response, while polarization measurements exhibit a remanent polarization above 10 C/cm2 at a coercive field of 1 MV/cm, suggesting that this phase is ferroelectric. Ferroelectric hafnium oxide is ideally suited for ferroelectric field effect transistors and capacitors due to its excellent compatibility to silicon technology.