Abstract
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 In 2O 3 (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 In 2O 3. 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 SnO 2, Al-doped ZnO, Sn-doped In 2O 3), making ZITO more versatile for applications.
Original language | English (US) |
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Pages (from-to) | 5633-5639 |
Number of pages | 7 |
Journal | Thin Solid Films |
Volume | 520 |
Issue number | 17 |
DOIs | |
State | Published - Jun 30 2012 |
Keywords
- Indium tin oxide
- Thin film
- Transparent conducting oxide
- Ultraviolet photoelectron spectroscopy
- Work function
- X-ray photoelectron spectroscopy
- Zinc indium tin oxide
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Metals and Alloys
- Materials Chemistry