Atomic Layer Deposition of Indium Tin Oxide Thin Films Using Nonhalogenated Precursors

J. Phys. Chem. C, 112 (6), 1938 -1945, 2008. 10.1021/jp7097312 S1932-7447(70)09731-5
Web Release Date: January 23, 2008

Atomic Layer Deposition of Indium Tin Oxide Thin Films Using Nonhalogenated Precursors

Jeffrey W. Elam,* David A. Baker, Alex B. F. Martinson, Michael J. Pellin, and Joseph T. Hupp

Energy Systems Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, and Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208

Received: October 4, 2007

In Final Form: November 8, 2007

Abstract:

This article describes a new atomic layer deposition (ALD) method for preparing indium tin oxide (ITO) thin films using nonhalogenated precursors. The indium oxide (In₂O₃) was deposited using alternating exposures to cyclopentadienyl indium (InCp) and ozone, and the tin oxide (SnO₂) used alternating exposures to tetrakis(dimethylamino) tin (TDMASn) and hydrogen peroxide. By adjusting the relative number of In₂O₃ and SnO₂ ALD cycles, we deposited ITO films with well-controlled SnO₂ content. The ITO films were examined using four-point probe and Hall probe measurements, spectrophotometry, ellipsometry, scanning electron microscopy, atomic force microscopy, X-ray fluorescence, and X-ray diffraction. The lowest resistivity (3 × 10^-4 cm) and highest optical transparency (92%) were obtained for films containing 5% SnO₂. The ITO films were slightly thinner and contained more SnO₂ than expected on the basis of rule-of-mixtures predictions. In situ measurements revealed that these discrepancies result from an inhibition of the In₂O₃ growth following the SnO₂ doping layers. This new ALD method is suitable for applying ITO layers on very high aspect ratio nanoporous membranes to be used in photovoltaic or spectroelectrochemical applications.

Download the full text: PDF | HTML