According to an aspect of the present disclosure there is provided a method for forming an EUVL pellicle, the method comprising: coating a carbon nanotube, CNT, membrane, and mounting the CNT membrane to a pellicle frame, wherein coating the CNT membrane comprises: pre-coating CNTs of the membrane with a seed material, and forming an outer coating on the pre-coated CNTs, the outer coating covering the pre-coated CNTs, the forming of the outer coating comprising depositing a coating material on the pre-coated CNTs by atomic layer deposition.