Epitaxial behavior and transport properties of PrBaCo2O5 thin films on (001) SrTiO3

Giant optical transmittance changes of over 300% in wide wavelength range from 500 nm to 2500 nm were observed in LaBaCo2O5.5+δ thin films annealed in air and ethanol ambient, respectively. The reduction process induces high density of ordered oxygen vacancies and the formation of LaBaCo2O5.5 (δ = 0) structure evidenced by aberration-corrected transmission electron microscopy. Moreover, the first-principles calculations reveal the origin and mechanism of optical transmittance enhancement in LaBaCo2O5.5 (δ = 0), which exhibits quite different energy band structure compared to that of LaBaCo2O6 (δ = 0.5). The discrepancy of energy band structure was thought to be the direct reason for the enhancement of optical transmission in reducing ambient. Hence, LaBaCo2O5.5+δ thin films show great prospect for applications on optical gas sensors in reducing/oxidizing atmosphere.

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confidence: 99%

Manipulation of Optical Transmittance by Ordered-Oxygen-Vacancy in Epitaxial LaBaCo2O5.5+δ Thin Films

Cheng

Han

et al. 2016

“…Cobalt-based oxides have attracted scientists and engineers much attention due to their unique magnetic, electrical transport and optical properties, which have been used to design various new concept devices, such as solid state fuel cell, energy harvest, gas sensors, etc12345678910. Among them, the oxygen-deficient double perovskite cobaltates, LaBaCo 2 O 5.5+δ (LBCO), show particularly interesting phenomena with the A-site order, nanoscale order, and disorder structures, such as, different spin state configurations, giant MR effect, etc111213141516.…”

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confidence: 99%

Gas Sensing Properties of Epitaxial LaBaCo2O5.5+δ Thin Films

Liu

Ren

Zhang

et al. 2015

Self Cite

Chemical reactivity and stability of highly epitaxial mixed-conductive LaBaCo2O5.5+δ (LBCO) thin films on (001) LaAlO3 (LAO) single-crystalline substrates, fabricated by using pulsed laser deposition system, were systematically investigated. Microstructure studies from x-ray diffraction indicate that the films are c-axis oriented with the interface relationship of [100]LBCO//[100]LAO and (001)LBCO//(001)LAO. LBCO thin films can detect the ethanol vapor concentration as low as 10ppm and the response of LBCO thin film to various ethanol vapor concentrations is very reliable and reproducible with the switch between air and ethanol vapor. Moreover, the fast response of the LBCO thin film, as the p-type gas sensor, is better than some n-type oxide semiconductor thin films and comparable with some nanorods and nanowires. These findings indicate that the LBCO thin films have great potential for the development of gas sensors in reducing/oxidizing environments.

“…1 (b) can be formed in the forms of order and disorder structures. Recently, highly epitaxial thin films of single-crystalline LnBCO (Ln = La, Er, Pr) were grown on (001) LaAlO 3 by using pulsed laser deposition with a KrF excimer pulsed laser1213141516. The oxidation and redox reactions of these films were monitored by measuring their resistance R under a switching flow of O 2 and H 2 as a function of the gas flow time t. The ac conductivity measurements indicate that both oxidation under O 2 and reduction under H 2 can occur at the temperature as low as ~200°C.…”

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confidence: 99%

Ultrafast Atomic Layer-by-Layer Oxygen Vacancy-Exchange Diffusion in Double-Perovskite LnBaCo2O5.5+δ Thin Films

Bao

Chen

et al. 2014

Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; −0.5 < δ < 0.5) by carefully monitoring the resistance changes under a switching flow of oxidizing gas (O2) and reducing gas (H2) in the temperature range of 250 ~ 800°C. A giant resistance change ΔR by three to four orders of magnitude in less than 0.1 s was found with a fast oscillation behavior in the resistance change rates in the ΔR vs. t plots, suggesting that the oxygen vacancy exchange diffusion with oxygen/hydrogen atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.