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Nanoscale Functional Oxides


New publications:

ACS Appl. Mater. Interfaces (2014)

Site-Selective Ion Beam Synthesis and Optical Properties of Individual CdSe Nanocrystal Quantum Dots in a SiO2 Matrix

H.M. Mangold, H. Karl, H. Krenner



Research:

We synthesize metal oxide and semiconductor nanoscluster by ion beams, laser ablation and sputtering. In our focus stands the control of composition, morphology, size distribution and the resulting physical properties.


Embedded VO2 nano clusters:

Ion beam synthesized of VO2 nanoclusters show a sharp metal-insulator transition (MIT) with an extremely wide and tunable temperature hysteresis loop of up to 50°C with strong superheating and supercooling. By elastic strain, doping and intentional defect generation we manipulate the MIT phase transition and its dynamics. Controlling and engineering these effects, potential applications in extremely fast electro-optical memory and switching technologies can be envisaged: i.e. Bistable thermochromic gratings have been prepared and characterized in close cooperation with Huber Krenner.

Figures:

  • Transmission electron microscopy (TEM) image
  • Temperature hysteresis of the metal-insulator transition

VO2 micro-/nano-crystals:

VO2 micro-/nano-crystals are grown from V2O5 melt by capillary transport and decomposition. We study the growth on different amorphous and crystalline dielectric and metal surfaces. The metal-insulator transition (MIT) and dynamics of phase transition and bimorphs are imaged by polarization microscopy and µ-Raman spectroscopy.

Figures:

  • VO2 nano-crystal/Ir (300nm/30nm) bimorph actuator (temperature sweep up)
  • Growth mechanism
  • Phase boundary evolution during temperature cycle of a fully clamped VO2 micro-crystal

Ca3Co4O9 and Nb:SrTiO3 multilayers by pulsed laser deposition (PLD):

We investigate the structural and electrical properties of the misfit layered cobaltite Ca3Co4O9 and Nb-doped SrTiO3 on silicon. These materials promise high potential for application in thin film energy harvesting systems. These thin films are ideally suited for studying and developing reliable high temperature stable metal contacts to these materials.

Figures:

  • PLD plasma plume
  • Cross-sectional high resolution transmission electron microscopy (HRTEM) image