Atomic layer-controlled growth of transparent conducting ZnO on plastic substrates

Highly transparent (T > 80%) and conductive (rho similar to 10(-3) Ohm cm) zinc oxide thin films were deposited by atomic layer-controlled growth on a wide variety of substrates, including glass Sapphire and flexible polyethylene terephthalate (PET) at temperatures of 100-210 degrees C using diethylzinc (DEtZn) and water. This is the first example of atomic layer-controlled growth or atomic layer epitaxy on a polymer substrate. The growth was accomplished by separating the CVD reaction, Zn(CH2CH3)(2) + H2O --> ZnO + 2CH(3)CK(3), into the following half reactions: (A) Zn-OH* + Zn(CH2CH3)(2) --> Zn-O-Zn-CH2CH3* + CH3CH3 (B) Zn-CH2CH3* + H2O --> Zn-OH* +CH3CH3. The reactions were self-terminating and growth rates from 1.5-1.9 Angstrom/cycle were observed. In order to grow films at higher temperatures and to improve him adhesion, alumina buffer layers were deposited before the ZnO films on PET substrates. The resistivity of the films improved by doping gallium into the films and with increasing temperature. The best film grown on PET had a resistivity of 1.4 x 10(-3) Ohm cm, while the best film grown on glass had a resistivity of 8 x 10(-4) Ohm cm. (C) 1999 Elsevier Science S.A. All rights reserved.