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SUMMARY:Chemical Control of Correlated Metals as Transparent Conductors - 
 Dr. Jonathan Alaria\, University of Liverpool
DTSTART:20190306T111500Z
DTEND:20190306T123000Z
UID:TALK120346@talks.cam.ac.uk
CONTACT:Romy Hall
DESCRIPTION:Transparent conducting materials have a wide variety of applic
 ations. They are a key component of photovoltaic and display technologies\
 , and increasing demands are being made of such materials to continue the 
 rapid growth of these industries. Suitable TCMs are identified primarily v
 ia a high electrical conductivity and a small optical absorption in the vi
 sible part of the spectrum (1.75 – 3.2 eV). Transparent Conducting Oxide
 s (TCOs) are the current front-running commercial materials with Tin-doped
  Indium Oxide (ITO) and Fluorine-doped Tin Oxide (FTO) being the most wide
 ly used. Practical limitations of doped semiconductor TCOs include low sol
 ubility limit of the dopant\, toxicity of common dopants such as fluorine 
 in FTO (with the use of HF in the production process) and the scarcity of 
 In increasing the cost of ITO. The current alternative to TCO materials ar
 e very thin layer of conventional metals such as Ag. In this case the over
 all performance of the material as a TCM is limited by the large electron 
 mean free path of conventional metals ( 50 nm) increasing the interfaci
 al scattering and therefore reducing the coating conductivity.\n\nCorrelat
 ed metallic transition metal oxides offer a route to thin film transparent
  conductors that is distinct from the degenerate doping of broad band wide
  gap semiconductors. In a correlated metal transparent conductor\, inter-e
 lectron repulsion shifts the plasma frequency out of the visible region to
  enhance optical transmission\, while the high carrier density of a metal 
 retains sufficient conductivity. By exploiting control of the filling\, po
 sition and width of the bands derived from the B site transition metal in 
 ABO3 perovskite oxide films\, we show (Adv. Funct. Mater. 2019\, 1808609) 
 that pulsed laser deposition-grown films of cubic SrMoO3 and orthorhombic 
 CaMoO3 based on the second transition series cation 4d2 Mo4+ have superior
  transparent conductor properties to the first transition series 3d1 V4+-b
 ased SrVO3. The increased carrier concentration offered by the greater ban
 dfilling in the molybdates gives higher conductivity while retaining suffi
 cient correlation to keep the plasma edge below the visible region. The re
 duced binding energy of the n = 4 frontier orbitals in the second transiti
 on series materials shifts the energies of oxide 2p to metal nd transition
 s into the near-ultra violet to enhance visible transparency. The A site s
 ize-driven rotation of MoO6 octahedra in CaMoO3 optimizes the balance betw
 een plasma frequency and conductivity for transparent conductor performanc
 e. We have demonstrated that by using the three chemically controllable pa
 rameters of carrier density\, orbital energy and bandwidth we can tune the
  charge transfer band position\, plasma frequency and conductivity to opti
 mize the transparent conductor performance of non-toxic\, earth abundant M
 o-based correlated metal perovskite oxides to match the best-in-class wide
  band gap semiconductors. These strategies open new paths to chemically co
 ntrol the performance of correlated transparent conductors.
LOCATION:Mott Seminar Room (531)\, Cavendish Laboratory\, Department of Ph
 ysics
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