Oxide materials for electronics Inorganic Materials and Ceramics Research Group

Transcription

1 Oxide materials for electronics Inorganic Materials and Ceramics Research Group Sverre M. Selbach, Department of Materials Science and Engineering, NTNU NorTex Nano Summit Oct , 2014.

2 Department of Materials Science and Engineering 25 professors (+11 adjunct professors) ~ 70 Ph.D. students ~ 15 post doc./researchers 4 sections at the DMSE: Physical metallurgy Process metallurgy Electrochemistry Inorganic chemistry 15 PhD and ~60 MSc students graduating annually

3 NTNU Faculty of Natural Sciences and Technology Dept. of Materials Science and Engineering Inorganic and ceramic materials research group Professor Mari-Ann Einarsrud (1988) Professor Kjell Wiik (1991) Professor Tor Grande (1994) Assoc. Professor Hilde Lea Lein (2008) Assoc. Professor Fride Vullum-Bruer (2008) Assoc. Professor Sverre M. Selbach (2012) Currently: 18 PhD students 6 post docs 10 master students

4 Electronic nanomaterials in the Ceramics group Transparent conducting oxides Multiferroics Batteries, SOFC, proton conductors++ Ferroelectric nanorods Manganites Quantum dots

5 Infrastructure and methods Synthesis & processing -NTNU Nanolab -Pilot scale spray pyrolysis: Cerpotech -Chemical synthesis of: Quantum dots Nanoparticles Nanorods Thin films Structural characterization XRD non-ambient, GID total scattering PDF SEM FEG, EDS, EMPA TEM aberration corrected STEM and EELS non-ambient Functional characterization AC/DC non-ambient conductivity Ionic conductivity Di-, ferro- and piezoel. Thermal properties Optical properties Mechanical properties Theory and modelling DFT (VASP) FEM (Comsol)

6 Materials synthesis and processing Aqueous, green chemistry. Sol-gel technology, hydrothermal synthesis Chemical solution deposition dip coating, spin coating Powder synthesis spray pyrolysis Ceramic processing and coating technology Pressing, tape casting, extrusion Spray coating Nano- materials Bulk

7 Labs and infrastructure Materials Characterization Powder X-ray diffraction (REXC) Electron microscopy (SEM, TEM, EMPA) Thermal analysis (TGA,DTA,DSC, dilatometry, thermal conductivity) BET, particle size analysis Mechanical properties (ambient and non-ambient Dielectric/impedance spectroscopy, electrical conductivity Oxygen permeation Polarization, strain versus electrical field (ferroelectricity) NTNU NanoLab NORTEM

8 In situ X-ray diffraction In situ T, atmosphere, up to 20 bar pressure, battery cycling, total scattering. HoMnO 3 upon in situ change of 1623 K. J. Solid State Chem. (2012):

9 Nanoparticles BiFeO 3 Chem. Mater. 19 (2007) BiFeO 3 YMnO 3 Synthesis Structure (XRD, PDF, TEM, spectroscopy) Properties (ferroic, optical, catalytic, thermal) Dalton Trans. 40 (2011) 7583.

10 Ferroic perovskite oxides Aqueous green routes to ferroelectric nanomaterials Methods to induce 1D oxide growth. Rørvik et al., Adv. Mater. (2011). PbTiO 3 nano-urchins Wang et al. Chem. Mater. (2007). Epitaxial PbTiO 3 nanorods on SrTiO 3 by hydrothermal synthesis. Rørvik et al., Cryst. Growth. Des. (2009).

11 Ferroic perovskite oxides Aqueous green routes to ferroelectric nanomaterials Exploiting the anisotropic nature of piezoelectricity: Ba 0.92 Ca 0.08 TiO 3 textured by tape casting with templates. Haugen et al. J. Appl. Phys. 116: (2014).

12 Lead-free ferroelectric perovskites (1-x)Bi 0.5 K 0.5 TiO 3 xbifeo 3 ceramics (0.1 x 0.7). Main focus: interplay between point defects and ferroic properties. Morozov, Einarsrud and Grande ( ).

13 Point defects and chemical expansion/strain Oxygen vacancies usually blamed for everything in oxide electronics Cation vacancies and cation non-stoichiometry much less studied: δ/2o 2 (g) + 2δMn Mn = δo O + 2δMn Mn ''' + δ/3v La ''' + δ/3v Mn La 0.5 Sr 0.5 FeO 3-δ Grande et al. Chem. Mater. (2012) Chen et al. Chem. Mater. (2014)

14 Point defects in thin films, e.g. LSMO Aliovalent substitution La 3+ /Sr 2+ Epitaxial strain Substrate Point defects Growth conditions, po 2 Thermal history O 2- transport kinetics Electronic struct. Crystal structure Domain structure Physical properties MR, MIT, magnetism

15 Defect chemistry of oxide interfaces Aschauer et al. PRB 88 (2013) Kalinin & Spaldin Science 341 (2013) 858.

16 Defect chemistry of oxide interfaces " Ca 2+ Mn 4+ O 3 ó Ca 2+ Mn δ Mn3+ 2δ O 3-δ + δ/2 O 2 (g) " d 3 Mn 4+ (0.54 Å) < d 4 Mn 3+ (0.645 Å)! " Stoich., strain and molar volume affect Gibbs energy, not independent! Aschauer et al. PRB 88 (2013)

17 Oxygen vacancy screened polarization Speculative discussion in 2011: Example here: PbTiO 3 Experimental evidence in 2014: (BiFeO 3 / LSMO epitaxial heterostruct.) Selbach et al. APL 88 (2013) Kim, et al. Nature Mater. 13 (2014) 1019.

18 DFT simulations " " " " MoO3 001 van der Waals layered materials 111 perovskite interfaces Diffusion and transformations Graphene/GaAs vdw interfaces 001 TiO2 terminated 111 TiO2 terminated Alkali diffusion in graphite SrTiO3/LaAlO3: 111

19 NorTex and the Ceramics Research Group " One PhD student (Amy Bergerud) from U. Texas Austin (Delia Milliron) visiting us from February " Funded through NSF GROW. " More visitors are welcome! " Synergies from exchanging people with samples or ideas. Thank you for your attention!