Surface studies of crystalline and amorphous Zn-In-Sn-O transparent conducting oxides

Journal Article · Wed Nov 28 23:00:00 EST 2012 · Thin Solid Films

DOI:https://doi.org/10.1016/j.tsf.2012.04.075· OSTI ID:1056683

Proffit, Diana E; Harvey, Steven P; Klein, Andreas; Schafranek, Robert; Emery, Jonathan D; Buchholz, D Bruce; Chang, Robert P.H.; Bedzyk, Michael J; Mason, Thomas O ^[1]

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1. NWU

X-ray and ultraviolet photoelectron spectroscopy (UPS) studies were made of in situ RF magnetron-sputtered crystalline (c) and amorphous (a) Zn–In–Sn–O (ZITO) thin films, ex situ pulsed laser deposited c- and a-ZITO thin films, and bulk ZITO ceramics. Cosubstitution of Zn and Sn for In results in an increase of the In core level binding energy at a given Fermi level compared to that measured in undoped and Sn-doped In₂O₃ (ITO). In plots of work function vs. Fermi level, in situ c-ZITO and a-ZITO films have low ionization potentials (7.0–7.7 eV) that are similar to undoped In₂O₃. In contrast, dry-air-annealed in situ films, ex situ films, and bulk ceramics have higher ionization potentials (7.7–8.1 eV) that are more similar to ITO and match well with previous work on air-exposed surfaces. Kelvin Probe measurements were made of select a-ZITO films exposed to air and ultraviolet/ozone-treated so as to measure work functions under conditions commonly employed for device fabrication. Results (4.8–5.3 eV) were in good agreement with the UPS work functions of oxygen-exposed materials and with literature values. Lastly, a parallelogram plot of work function vs. Fermi level shows that a wider range of work functions is achievable in ZITO materials as compared to other transparent conducting oxides (Sb-doped SnO₂, Al-doped ZnO, Sn-doped In₂O₃), making ZITO more versatile for applications.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: FOREIGNNSFDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1056683
• Journal Information: Thin Solid Films, Journal Name: Thin Solid Films Journal Issue: (17) ; 06, 2012 Vol. 520; ISSN 0040-6090
• Publisher: Elsevier
• Country of Publication: United States
• Language: ENGLISH