Electrical, optical, and structural characteristics of ITO thin films by krypton and oxygen dual ion-beam assisted evaporation at room temperature

Transparent conducting tin-doped indium oxide (ITO) thin films on polycarbonate and glass substrates were deposited without substrate heating and post-deposition annealing using a dual ion-beam assisted evaporation technique, where the bombardment of the growing film surfaces during electron beam evaporation was done using krypton (varied ion flux, J(Kr+), and grid acceleration voltage, V-a, of the krypton ion source) and oxygen (fixed ion flux and grid acceleration voltage of the oxygen ion source) ion beams. The electrical, optical, and structural effects of krypton ion-beam bombardment of the growing ITO thin films were investigated using Hall-effect measurements, X-ray photoelectron spectroscopy (XPS), W-visible spectrometry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The total him thickness and the deposition rate were 100 nm and 0.06 nm/s, respectively. All ITO films grown with J(Kr+) = 1.92-3.76 x 10(14) cm(-2) s(-1) and V-a = 100-500 V showed an amorphous structure and no other crystalline phases. As J(Kr+) increased, the electrical conductivity and the optical transmittance of the grown films were improved compared with those of the ITO films deposited using the oxygen ion-beam only. Also, an increase of the bombardment energy by increasing V-a of the krypton ion source caused the deterioration of ITO film properties. The conductivity and the optical transmittance of ITO films deposited on polycarbonate substrates were a little lower than those of films on glass substrates. At room-temperature, using optimal growth conditions, the electrical resistivity was as low as 6.4 x 10(-4) Omega cm with an electron carrier concentration n(e) = 4.3 x 10(20) cm(-3) and a Hall mobility mu (H) = 26.7 cm(2) V-1 s(-1), the visible transmittance (at lambda = 550 nm) was 90%, and optical direct band gap energy 3.8 eV. (C) 2000 Published by Elsevier Science B.V. All rights reserved.