  Most graphene nanoribbons in the experimental literature are patterned using
plasma etching. Various etching processes induce different types of defects and
do not necessarily result in the same electronic and structural ribbon
properties. This study focuses on two frequently used etching techniques,
namely oxygen plasma ashing and oxygen/argon reactive ion etching (RIE). Oxygen
plasma ashing represents an alternative to RIE physical etching for sensitive
substrates, as it is a more gentle chemical process. We find that plasma ashing
creates defective graphene in the exposed trenches, resulting in instabilities
in the ribbon transport. These are probably caused by more or larger localized
states at the edges of the ashed device compared to the RIE defined device.
