The Electromechanical Characteristics of ZnO Grown on Poly(ethylene terephthalate) Substrates

We investigate the electromechanical properties of ZnO grown on polyethylene terephthalatePET and compare the results with those obtained from the counterparts on glass substrates. The elastic moduli of ZnO on PET measured by a microstretcher are very close to those of ZnO grown on glass substrates measured by nanoindentation: The moduli decrease then increase as the O2/Ar ratio increases. Films start to peel off from the plastic substrates when oxygen content reaches 50%. The in situ measure- ment of the ZnO resistance under uniaxial tensile stretching is influenced by the induced piezoelectric voltage, leading to a reduction in the electrical resistance for highly resistive ZnO films. The trend of the preferred orientation in relation to the oxygen content of the sputtering atmosphere is the same for ZnO films grown on either PET or glass substrates. The optical bandgap Eg of the ZnO films on both substrates exhibits crystal orientation dependence, varying from 3.18 eV with 002 preferred orientation to 3.25 eV, with a large number of 100 and 101 oriented crystals.