Roll-to-Roll Atmospheric Atomic Layer Deposition of Al_2O_3 Thin Films on PET Substrates

摘要

The conventional atomic layer deposition (ALD) technologies are capable of fabricating supreme quality thin films of a wide variety of materials, but sequential introduction and purging of precursors and inert gases prevent its application in the mass production of thin films under atmospheric conditions. In this study, we introduce a novel technique of roll-to-roll atmospheric (R2R-A)ALD using a multiple-slit gas source head. Thin films of Al_2O_3 are developed on a movable web of polyethylene terephthalate (PET) substrate at 50 °C. The Al_2O_3 deposition is carried out under a working pressure of 740 Torr, which is very near to atmospheric pressure (760 Torr). An appreciable growth rate of 0.98 ? per cycle is observed at a carefully optimized web velocity of 7 mm s~(-1). Good morphological, chemical, electrical, and optical characteristics are shown by the Al_2O_3 films produced at a large scale. Low root mean square roughness (R_q) values of 1.85nm and 1.75nm are recorded for the Al_2O_3 films deposited at 50 °C over 75 and 125 ALD cycles, respectively. The appearance of Al 2p, Al 2s, and O 1s peaks at the binding energies of 74 eV, 119 eV, and 531 eV, respectively, in the X-ray photoelectron spectroscopy (XPS) analysis confirms the fabrication of Al_2O_3 films, which is also supported by Fourier transform infrared spectroscopy (FTIR). The films show excellent insulating properties, and optical transmittance of more than 85% is recorded in the visible region.