Electrical, Optical, and Structural Characteristics of
Indium-Tin-Oxide Thin Films Deposited on Glass and
Polymer Substrates
Ahnand K. Kulkarni and T.-S. Lim
Department of Electrical Engineering
Michigan Technological University
Houghton, Michigan 49931
Electronic Mail: akkulkar@mtu.edu
Kirk H. Schulz and Mohammed Khan
Department of Chemical Engineering
Michigan Technological University
Houghton, Michigan 49931
Thin Solid Films, 308, 1 (1997)
The sheet resistance, optical transmittance and microstructure of tin-doped indium oxide
(ITO) thin films (50-100-nm thick) rf sputter deposition on polymer substrates are
investigated using a four-point probe, spectrophotometer, X-ray diffractometer and a
transmission electron microscope (TEM). Sheet resistances vary from 250 ohms/sq. to
170 kohms/sq. Sheet resistances for the ITO films on polycarbonate substrates are at
least an order of magnitude higher than those ITO films deposited on glass substrates at
the same time. Annealing ITO films on polycarbonate substrates at 100°C in air for 1 h
decreased the sheet resistances significantly (almost 50%). The X-ray diffraction data
indicate polycrystalline films with grain orientations predominantly along (222) and
(400) directions. TEM photographs show two distinct regions of growth: a dense growth
close to the substrate and a sparse growth away from the substrate. The vertical growth is
columnar and rod shaped. Changes in the ITO film sheet resistance either due to the
types of substrate used or due to annealing can be correlated to the grain size and grain
orientation.