Morphology, Mechanical Stability, and Protective Propertiesof Ultrathin Gallium Oxide Coatings.

Ultrathin gallium oxide layers witha thickness of 2.8 ± 0.2nm were transferred from the surface of liquid gallium onto solidsubstrates, including conjugated polymer poly(3-hexylthiophene) (P3HT).The gallium oxide exhibits high mechanical stability, withstandingnormal pressures of up to 1 GPa in contact mode scanning force microscopyimaging. Moreover, it lowers the rate of photodegradation of P3HTby 4 orders of magnitude, as compared to uncovered P3HT. This allowsus to estimate the upper limits for oxygen and water vapor transmissionrates of 0.08 cm3m–2day–1and 0.06 mg m–2day–1, respectively.Hence, similar to other highly functional coatings such as graphene,ultrathin gallium oxide layers can be regarded as promising candidatesfor protective layers in flexible organic (opto-)electronics and photovoltaicsbecause they offer permeation barrier functionalities in conjunctionwith high optical transparency. [ABSTRACT FROM AUTHOR]