Impact of annealing on the chemical structure and morphology of the thin-film CdTe/ZnO interface

Journal Article · Mon Jul 14 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4890235· OSTI ID:22308736

Hanks, D. A.; Weir, M. G. ^[1]; Beal, R. J. ^[2]; Wilks, R. G. ^[3]; Blum, M. ^[1]; Häming, M. ^[1]; Hofmann, T. ^[1]; Weinhardt, L. ^[1]; others, and

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1. Department of Chemistry, University of Nevada, Las Vegas (UNLV), Las Vegas, Nevada 89154 (United States)
2. Materials Science and Engineering Department, University of Arizona, Tucson, Arizona 85721 (United States)
3. Solar Energy Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), 14109 Berlin (Germany)

To enable an understanding and optimization of the optoelectronic behavior of CdTe-ZnO nanocomposites, the morphological and chemical properties of annealed CdTe/ZnO interface structures were studied. For that purpose, CdTe layers of varying thickness (4–24 nm) were sputter-deposited on 100 nm-thick ZnO films on surface-oxidized Si(100) substrates. The morphological and chemical effects of annealing at 525 °C were investigated using X-ray Photoelectron Spectroscopy (XPS), X-ray-excited Auger electron spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, and atomic force microscopy. We find a decrease of the Cd and Te surface concentration after annealing, parallel to an increase in Zn and O signals. While the as-deposited film surfaces show small grains (100 nm diameter) of CdTe on the ZnO surface, annealing induces a significant growth of these grains and separation into islands (with diameters as large as 1 μm). The compositional change at the surface is more pronounced for Cd than for Te, as evidenced using component peak fitting of the Cd and Te 3d XPS peaks. The modified Auger parameters of Cd and Te are also calculated to further elucidate the local chemical environment before and after annealing. Together, these results suggest the formation of tellurium and cadmium oxide species at the CdTe/ZnO interface upon annealing, which can create a barrier for charge carrier transport, and might allow for a deliberate modification of interface properties with suitably chosen thermal treatment parameters.

• OSTI ID: 22308736
• Journal Information: Journal of Applied Physics, Vol. 116, Issue 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
ANNEALING
ATOMIC FORCE MICROSCOPY
AUGER ELECTRON SPECTROSCOPY
CADMIUM OXIDES
CADMIUM TELLURIDES
CHARGE CARRIERS
COMPOSITE MATERIALS
ELECTRO-OPTICAL EFFECTS
INTERFACES
LAYERS
NANOCOMPOSITES
NANOSTRUCTURES
SCANNING ELECTRON MICROSCOPY
SUBSTRATES
SURFACES
TEMPERATURE RANGE 0400-1000 K
THIN FILMS
X-RAY PHOTOELECTRON SPECTROSCOPY
X-RAY SPECTROSCOPY
ZINC OXIDES