EXPERIMENTAL SECTION
Figure 1 schematically depicts the growth and processing steps
that were utilized in this work. Before sputtering, the PET
substrates were cleaned with ethanol and deionized water in an
ultrasonic cleaner, and then baked at 100 °C for 10 min to
remove moisture. AZO (Al-doped ZnO) seed layers were
deposited on PET using a RF magnetron sputtering method.
The thickness of the AZO film was approximately 50 nm. The
ZnO nanowires were hydrothermally grown at 95 °C in a
sealed beaker by immersing the PET substrates for 6 h in the
aqueous solution of 0.06 M zinc nitrate hexhydrate [Zn-
(NO3)2] and 0.06 M hexamethylenetetramine (C6H12N4). The
Zn(NO3)2/C6H12N4 molar ratio was always 1:1. Hexamethylenetetramine
(HMTA) is a highly water-soluble, nonionic
tetradentate cyclic tertiary amine. Thermal degradation of
HMT releases hydroxyl ions, which react with Zn2+ ions to
form ZnO. The crystal growth of ZnO nanowires involves the
following chemical reactions