A @F02366@ whose thickness is of the order of a @C00977@ or smaller. Since a @F02366@ may 'look' operationally thin or thick, according to the procedure applied, it is also recommended that the measurement procedure employed be specified (e.g. ellipsometrically thin @F02366@, optically thin @F02366@, etc.). It is recommended that the physical specification of the @F02366@ thickness be used, whenever possible (e.g. thick compared to the electron @M03778@, thin compared to the optical @W06659@, etc.)