Material's Properties Control by Nano-Scale Surface Functionalization

Theme

We aim at developing an original synthesis approach to design and control new materials properties; we choose to focus on superconducting thin film and heterostructures, doping of matrices for light harvesting materials (up and down conversion), and multilayers structures for synchrotron elemental analysis. In order to create a positive feedback loop to correlate materials’ properties and structures/composition/chemistry, we have access to state of the art surface and bulk characterization techniques; tunneling spectroscopy (transport, point contact), SQUID, XPS, UPS, ellispometry, AFM, SEM, TEM, RBS, collaboration with APS and CNM for an in-depth investigation of our materials. This is a cross-disciplinary research effort that encompasses several division within Argonne (MSD, HEP, PHYS, ES, APS, CNM) as well as collaboration with domestic and international universities/institutes.

Staff

Principal Investigators

  • Thomas Proslier
  • Michael J. Pellin

Postdoctoral Appointees

  • Jeffrey Klug
  • Kan-Sheng Chen
  • Nickolas Groll
  • Lin Fareh
  • Matej Hala

Visiting Scientist

  • Serdar Altin

Graduate Students

  • Nicholas J. Becker
  • Cao Chaoyue
  • Matthew Weimer

Secretary

  • Barbara Hall

Equipment

  • 1 custom ALD system
  • 1 SavannahS100 ALD system
  • 1 plasma ALD system
  • 1 large object UHV-Oven ALD system

Highlights

  • Atomic layer deposition of superconductors and hetero-structures. A growing interest in superconductor-based application for energy storage, bolometers, high energy particle accelerators and fusion reactors stems from their unique ability to carry current with zero resistance and hence a quasi-null dissipation. These properties in conjunction with nano-heterostructures (multilayers) design and control enable the improvement of superconductors’ performance in magnetic fields environment. However such applications demand non-line of sight, homogeneities down to the nanometer scale on large surfaces coatings and only ALD can meet such drastic requirements. We are studying and characterizing the growth of various superconducting alloys such as Nitrides (MoN, MoNbN, NbN, NbTiN, TiN), Selenides-Tellurides (FeSeTe, KFeSe2), Borides (MgB2) and Silicides (NbSi, NbSiN…).
  • Doped matrices for light harvesting materials grown by Atomic layer deposition: lanthanides doped phosphors as a proof of principle. The local structure and coordination of the rare earth dopants has critical implications for the emission properties – insufficient distance between adjacent emitters can lead to non-radiative losses/quenching, and in the case of multiple co-dopants, the distance between absorbing and emitting ions can strongly influence the energy transfer between them. However, conventional methods of deposition (ion implantation, sintering…) lack local control, and instead rely on the overall statistical concentration and distribution of dopants into the matrix or host material. In contrast, we have successfully shown that using ALD we can not only control at the atomic level the dopant concentration, but also the distance between dopants and their chemical environment; bulk-like Er lifetime emission (~ 7ms) have been obtained in 100 nm thick Yttria films grown by ALD. With atomic-scale local doping control, ALD can enable more efficient use of lanthanide ions – achieving superior performance with the same amount of rare earth materials, or maintaining equivalent performance while using less Rare-Earths.
  • X-ray fluorescent standards made by Atomic layer deposition. Synchrotron x-ray microprobes (XRM) have become valuable instruments for spatially-resolved trace element concentration quantification in materials ranging from biological cells to extraterrestrial rocks. XRM studies are having high impact in a wide range of scientific endeavors and there is extensive literature. Recent research that has relied on the availability of XRF standards includes the following: Cosmo-chemistry and planetary science, Geochemistry and bio-accessibility of contaminants, Human health and drug development, Environmental toxicology and genomics, Agronomy and phyto-remediation, Paleo-thermometry. Unfortunately, standards have some heterogeneity issues and are also no longer being produced. New and improved standards are desperately needed by this community. We use the Atomic Layer Deposition technique (ALD) to synthesize multilayer SXRF standards that improve significantly the homogeneity issue encounter so far and open the route to new possibilities for specialized standards beyond what is currently available and achievable.
  • Fundamental studies of superconductors
    • We are studying the proximity effect by transport and tunneling spectroscopy of classical s-wave (MoGe) on top of pnictides s+- superconductors (FeSeTe and BaKFeAs) as a mean to probe the pairing symmetry. Under particular coupling conditions between the 2 superconductors, a negative proximity effect is expected.
    • We are also investigating the quasi-2D properties of superconducting films made by ALD. We have shown that ultra-thin NbSi films grown by ALD also reveal a super-insulating transition at ultralow temperature. The only previous example is TiN (also grown by ALD) ultra-thin films. Insulator/Ultrathin films structure have also been synthesized for gate geometry in order to tune coulomb interactions. We plan on expanding this study to other alloy in the ultra-thin film limit and hope to demonstrate a universal behavior of 2D superconductors.
    • We are studying the fundamental surface dissipation mechanism of classical superconductors; a model has been developed to explain the residual losses in Nb-based superconductors that originate from the presence of magnetic impurities near the interface with the native oxides. Our on-going work focuses on the microscopic origin of these magnetic impurities, suspected to be Nb-H-Vacancies complexes pinned at the surface of the niobium.