Browsing by Author "Jalan, Bharat"
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Item Dopant segregation inside and outside dislocation cores in perovskite BaSnO 3 and reconstruction of the local atomic and electronic structures(2021-04-26) Yun, Hwanhui; Prakash, Abhinav; Birol, Turan; Jalan, Bharat; Mkhoyan, K. Andre; yunxx133@umn.edu; Yun, HwanhuiDistinct dopant behaviors inside and outside dislocation cores are identified by atomic-resolution electron microscopy in perovskite BaSnO3 with considerable consequences on local atomic and electronic structures. Driven by elastic strain, when A-site designated La dopants segregate near a dislocation core, the dopant atoms accumulate at the Ba sites in compressively strained regions. This triggers formation of Ba-vacancies adjacent to the core atomic sites resulting in reconstruction of the core. Notwithstanding the presence of extremely large tensile strain fields, when La atoms segregate inside the dislocation core, they become B-site dopants, replacing Sn atoms and compensating the positive charge of the core oxygen vacancies. Electron energy-loss spectroscopy shows that the local electronic structure of these dislocations changes dramatically due to segregation of the dopants inside and around the core ranging from formation of strong La-O hybridized electronic states near the conduction band minimum to insulator-to-metal transition.Item Renewable Energy for Minnesota's Future(2020) Hanson, Aaron; Leighton, Chris; James, Richard D; Jalan, Bharat; Shen, Lian; Mohan, NedItem Structural and chemical characterization data for Ir and Ru metal/metal-oxide thin films showing strain dependence of metal oxidation(2023-04-05) Nair, Sreejith T; Yang, Zhifei; Lee, Dooyong; Guo, Silu; Sadowski, Jerzy T; Johnson, Spencer; Saboor, Abdul; Li, Yan; Zhou, Hua; Comes, Ryan B; Jin, Wencan; Mkhoyan, Andre K; Janotti, Anderson; Jalan, Bharat; nair0074@umn.edu; Nair, Sreejith T; University of Minnesota Jalan MBE LabIn this work, the authors uncover a previously unexplored effect of substrate imposed epitaxial strain on the formation energy of a crystalline epitaxial metal oxide thin film, thereby revealing an additional tuning knob to engineer synthesis of oxide thin films of hard-to-oxidize metals.Item Supporting data for "Semi-metallic SrIrO3 films using solid-source metal-organic molecular beam epitaxy"(2022-12-20) Choudhary, Rashmi; Nair, Sreejith; Yang, Zhifei; Lee, Dooyong; Jalan, Bharat; choud140@umn.edu; Choudhary, Rashmi; Jalan MBE LabThe data contains X-ray and electrical characterization of SrIrO3 films grown by solid-source metal-organic molecular beam epitaxy (SSMOMBE). It reveals that SSMOMBE can produce high-quality crystals and has numerous other advantages compared to conventional molecular beam epitaxy.Item Supporting data for Mending Cracks Atom-by-atom in Rutile TiO2 with Electron Beam Radiolysis(2023-08-28) Guo, Silu; Yun, Hwanhui; Nair, Sreejith; Jalan, Bharat; Mkhoyan, K. Andre; mkhoyan@umn.edu; Mkhoyan, K. Andre; Materials Research Science & Engineering CenterExperimental data for a manuscript "Mending Cracks Atom-by-atom in Rutile TiO2 with Electron Beam Radiolysis". Essential data includes scanning transmission electron microscopy (STEM) raw images and electron energy-loss spectroscopy (EELS) spectrum data. Important atomic line scans data and radiolysis cross section data file are included to support our “two-step rolling” model of mobile octahedral building blocks enabling radiolysis-driven atomic migration.Item Supporting data for Metallic line defect in wide-bandgap transparent perovskite BaSnO₃(2021-01-22) Yun, Hwanhui; Topsakal, Mehmet; Prakash, Abhinav; Jalan, Bharat; Jong Seok, Jeong; Birol, Turan; Mkhoyan, K Andre; yunxx133@umn.edu; Yun, HwanhuiA line defect with metallic characteristics has been found in optically transparent BaSnO₃ perovskite thin films. The distinct atomic structure of the defect core, composed of Sn and O atoms, was visualized by atomic-resolution scanning transmission electron microscopy (STEM). When doped with La, dopants that replace Ba atoms preferentially segregate to specific crystallographic sites adjacent to the line defect. The electronic structure of the line defect probed in STEM with electron energy-loss spectroscopy was supported by ab initio theory, which indicates the presence of Fermi level–crossing electronic bands that originate from defect core atoms. These metallic line defects also act as electron sinks attracting additional negative charges in these wide-bandgap BaSnO₃ films.Item Supporting data for Temperature-dependent thermal conductivity of MBE-grown epitaxial SrSnO₃ films(2023-11-06) Zhang, Chi; Liu, Fengdeng; Guo, Silu; Zhang, Yingying; Xu, Xiaotian; Mkhoyan, Andre; Jalan, Bharat; Wang, Xiaojia; wang4940@umn.edu; Wang, Xiaojia; Materials Research Science & Engineering CenterThis work studies the temperature-dependent thermal properties of a single crystalline SSO thin film prepared with hybrid molecular beam epitaxy. By combining time-domain thermoreflectance and Debye–Callaway modeling, physical insight into thermal transport mechanisms is provided. At room temperature, the 350-nm SSO film has a thermal conductivity of 4.4 W m¯¹ K¯¹ , ∼60% lower than those of other perovskite oxides (SrTiO₃, BaSnO₃) with the same ABO₃ structural formula. This difference is attributed to the low zone-boundary frequency of SSO, resulting from its distorted orthorhombic structure with tilted octahedra. At high temperatures, the thermal conductivity of SSO decreases with temperature following a ∼T ¯⁰∙⁵⁴ dependence, weaker than the typical T¯¹ trend dominated by the Umklapp scattering. Corresponding author for STEM data is K. Andre Mkhoyan. Corresponding author for film growth and XRD data is Bharat Jalan. Corresponding author for TDTR data is Xiaojia Wang.Item X-ray Diffraction and Atomic Force Microscopy of RuO2 thin films(2022-08-18) Nunn, William; Manjeshwar, Anusha K; Nair, Sreejith; Jalan, Bharat; bjalan@umn.edu; Jalan, Bharat; University of Minnesota Jalan MBE LabX-ray Diffraction data of the RuO2 samples were obtained to assess the crystallinity and epitaxial nature of the thin films grown on different substrates. Atomic Force Microscopy was used to determine the surface morphology changes as a function of thickness and epitaxial strain and correlate it with the observed oxygen evolution activity.