37 research outputs found
Electrical property measurements of Cr-N codoped TiO2 epitaxial thin films grown by pulsed laser deposition
The temperature dependent resistivity and thermo-electric power of Cr-N codoped TiO2 were compared with that of single element N and Cr doped and undoped TiO2 using epitaxial anatase thin films grown by pulsed laser deposition on (100) LaAlO3 substrates. The resistivity plots and especially the thermoelectric power data confirm that codoping is not a simple sum of single element doping. However, the negative sign of the Seebeck coefficient indicates electron dominated transport independent of doping. The narrowing distinction among the effects of different doping methods combined with increasing resistivity of the films with improving crystalline quality of TiO2 suggest that structural defects play a critical role in the doping process
Unusual Electrical Conductivity Driven by Localized Stoichiometry Modification at Vertical Epitaxial Interfaces
Precise control of lattice mismatch accommodation and cation interdiffusion
across the interface is critical to modulate correlated functionalities in
epitaxial heterostructures, particularly when the interface composition is
positioned near a compositional phase transition boundary. Here we select
La1-xSrxMnO3 (LSMO) as a prototypical phase transition material and establish
vertical epitaxial interfaces with NiO to explore the strong interplay between
strain accommodation, stoichiometry modification, and localized electron
transport across the interface. It is found that localized stoichiometry
modification overcomes the plaguing dead layer problem in LSMO and leads to
strongly directional conductivity, as manifested by more than three orders of
magnitude difference between out-of-plane to in-plane conductivity.
Comprehensive structural characterization and transport measurements reveal
that this emerging behavior is related to a compositional change produced by
directional cation diffusion that pushes the LSMO phase transition from
insulating into metallic within an ultrathin interface region. This study
explores the nature of unusual electric conductivity at vertical epitaxial
interfaces and establishes an effective route for engineering nanoscale
electron transport for oxide electronics
Correlated oxide Dirac semimetal in the extreme quantum limit
Quantum materials (QMs) with strong correlation and nontrivial topology are indispensable to next-generation information and computing technologies. Exploitation of topological band structure is an ideal starting point to realize correlated topological QMs. Here, we report that strain-induced symmetry modification in correlated oxide SrNbO3 thin films creates an emerging topological band structure. Dirac electrons in strained SrNbO3 films reveal ultrahigh mobility (mu(max) approximate to 100,000 cm(2)/Vs), exceptionally small effective mass (m* similar to 0.04m(e)), and nonzero Berry phase. Strained SrNbO3 films reach the extreme quantum limit, exhibiting a sign of fractional occupation of Landau levels and giant mass enhancement. Our results suggest that symmetry-modified SrNbO3 is a rare example of correlated oxide Dirac semimetals, in which strong correlation of Dirac electrons leads to the realization of a novel correlated topological QM