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1. Large electronic wave function extension of the oxygen vacancies on EuO _1−x surface

   https://doi.org/10.1088/2053-1591/ab44ef  

   Wang, Aaron; Rimal, Gaurab; Dahnovsky, Yuri; Tang, Jinke; Chien, TeYu (September 2019, Materials Research Express)
2. Oxygen-bearing functionalities enhancing NO ₂ , NH ₃ , and acetone electronic response and response variation by polythiophenes in organic field-effect transistor sensors

   https://doi.org/10.1039/D1TC04650K  

   Wagner, Justine; Song, Yunjia; Shapiro, Jenna; Katz, Howard E. (February 2022, Journal of Materials Chemistry C)

   We investigated the enhanced vapor responses and altered response ratios of a series of thiophene (co)polymers with oxygenated side chains (CH 2 OH, linear polyethylene glycol, and crown ether), including the novel poly(3-hydroxymethylthiophene) (PTOH) and other newly synthesized polymers. Hydroxymethyl-containing copolymers had higher mobility compared to poly(3-hexylthiophene) (P3HT). The larger crown ether moiety promotes transistor characteristics of P3HT while the smaller one impairs them. Incorporating different oxygen bearing functionalities increased responses of thiophene polymers to NO 2 , NH 3 , and acetone. For example a polyether side chain increases the NO 2 response sensitivity of copolymers of both P3HT and PTOH, but sensitivity towards gas analytes was more prominent for glycol-based functionalities rather than the crown ethers. PTOH is very sensitive to NO 2 and the response likely includes a contribution from conductive protons on the OH group. The lack of correlation among the rank-ordered gas sensitivities imparted by each functional group was found to be useful for designing a selective sensor array. We specifically showed high classification accuracy for all the polymer responses to NO 2 and acetone vapors, both of which gave increased device currents but with response ratios different enough to allow highly classifying discriminant functions to be derived. 

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3. High stability SrTi _1−x Fe _x O _3−δ electrodes for oxygen reduction and oxygen evolution reactions

   https://doi.org/10.1039/c9ta07548h  

   Zhang, Shan-Lin; Cox, Dalton; Yang, Hao; Park, Beom-Kyeong; Li, Cheng-Xin; Li, Chang-Jiu; Barnett, Scott A. (September 2019, Journal of Materials Chemistry A)

   Sr(Ti 1−x Fe x )O 3−δ (STF) has recently been explored as an oxygen electrode for solid oxide electrochemical cells (SOCs). Model thin film electrode studies show oxygen surface exchange rates that generally improve with increasing Fe content when x < 0.5, and are comparable to the best Co-containing perovskite electrode materials. Recent results on porous electrodes with the specific composition Sr(Ti 0.3 Fe 0.7 )O 3−δ show excellent electrode performance and stability, but other compositions have not been tested. Here we report results for porous electrodes with a range of compositions from x = 0.5 to 0.9. The polarization resistance decreases with increasing Fe content up to x = 0.7, but increases for further increases in x . This results from the interaction of two effects – the oxygen solid state diffusion coefficient increases with increasing x , but the electrode surface area and surface oxygen exchange rate decrease due to increased sinterability and Sr surface segregation for the Fe-rich compositions. Symmetric cells showed no degradation during 1000 h life tests at 700 °C even at a current density of 1.5 A cm −2 , showing that all the STF electrode compositions worked stably in both fuel cell mode and electrolysis modes. The excellent stability may be explained by X-ray Photoelectron Spectroscopy (XPS) results showing that the amount of surface segregated Sr did not change during the long-term testing, and by relatively low polarization resistances that help avoid electrode delamination. 

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4. UV-Driven Oxygen Surface Exchange and Stoichiometry Changes in a Thin-Film, Nondilute Mixed Ionic Electronic Conductor, Sr(Ti,Fe)O _3-d

   https://doi.org/10.1021/jacs.4c05764  

   Skiba, Emily J; Buckner, Haley B; Lee, Channyung; McKnight, Grace; Wallick, Rachel F; van_der_Veen, Renske; Ertekin, Elif; Perry, Nicola H (August 2024, Journal of the American Chemical Society)
5. Electronic-grade epitaxial (111) KTaO ₃ heterostructures

   https://doi.org/10.1126/sciadv.adk4288  

   Kim, Jieun; Yu, Muqing; Lee, Jung-Woo; Shang, Shun-Li; Kim, Gi-Yeop; Pal, Pratap; Seo, Jinsol; Campbell, Neil; Eom, Kitae; Ramachandran, Ranjani; et al (May 2024, Science Advances)

   KTaO₃heterostructures have recently attracted attention as model systems to study the interplay of quantum paraelectricity, spin-orbit coupling, and superconductivity. However, the high and low vapor pressures of potassium and tantalum present processing challenges to creating heterostructure interfaces clean enough to reveal the intrinsic quantum properties. Here, we report superconducting heterostructures based on high-quality epitaxial (111) KTaO₃thin films using an adsorption-controlled hybrid PLD to overcome the vapor pressure mismatch. Electrical and structural characterizations reveal that the higher-quality heterostructure interface between amorphous LaAlO₃and KTaO₃thin films supports a two-dimensional electron gas with substantially higher electron mobility, superconducting transition temperature, and critical current density than that in bulk single-crystal KTaO₃-based heterostructures. Our hybrid approach may enable epitaxial growth of other alkali metal–based oxides that lie beyond the capabilities of conventional methods. 

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