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

Abstract

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.

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

“…However, there are very few reports on the gas-sensing materials using p -type oxide semiconductor, such as NiO373839, CuO40, LaFeO 3 41, Co 3 O 4 ,4243444546474849505152535455 LBCO1623. Compared with n-type oxide semiconductor for gas-sensing, the p-type oxide semiconductors with distinctive surface reactivity and oxygen adsorption can enhance gas selectivity, decrease the dependence of humidity to negligible level and improve the recovery speed, reviewed by Kim and Lee46.…”

“…When LBCO thin film is exposed to the reducing gas, parts of Co +4 changed into Co +3 and the resistance increases. In the contrast, the gas change to oxidizing gas, parts of Co +3 changed into Co +4 and the resistance decreases5152. Ethanol vapor is safer and more active than other gas, such as H 2 , ammonia, hydrogen sulfide, which is used as the representative of reducing gases.…”

Определение зарядовых состояний ионов кобальта в наноструктурированных кобальтитах GdBaCo-=SUB=-2-=/SUB=-O-=SUB=-5.5-=/SUB=- с помощью рентгеновской абсорбционной спектроскопии

“…На дефектность приповерхностных слоев нанострук-турированного GdBaCo 2 GdBaCo 2 O 5.55 и GdBaCo 2 O 5.1 -крупнозернистые об-разцы, полученные по стандартной керамической тех-нологии при различных давлениях кислорода. Спек-тральная область от 528 до 532 eV (особенности a и b) образована смешиванием незанятых Co 3d(t 2g )-и Co 3d(e g )-состояний с O 2p-состояниями.…”

“…Изучение природы наносостояния в двойных слоистых оксидах кобальта в основном сосредо-точено на проведении исследований пленок соответству-ющего состава [1,2]. В меньшей степени представлены исследования разупорядочения в системах LnBaCo 2 O 5+δ методами нагружения образцов высоким давлением [3].…”

Anisotropic Strain Induced Directional Metallicity in Highly Epitaxial LaBaCo2O5.5+δ Thin Films on (110) NdGaO3

“…In particular, LaBaCo 2 O 5.5+δ (LBCO) exhibits exotic electronic and magnetic properties from the intricate coupling of charge, spin, orbital, and lattice degrees of freedoms8910. It has been reported that different the oxygen content in LBCO can lead to CoO 5 pyramidal, CoO 6 octahedral or mixed structure, and it can significantly influence its electric transport properties1112. If there are the mixture of Co 3+ /Co 4+ in the film, the film will shows the semiconductor or metallic behavior dependent on the test temperature range due to double exchange mechanism.…”