Hollow ring arrays with an outer and inner diameter of 33 and 11 nm, respectively, are formed from a thin film of poly(styrene-b-ferrocenylethylmethylsilane-b-2-vinyl pyridine) (PS-b-PFS-b-P2VP) triblock terpolymer with a core/shell cylindrical morphology. The PS minority block forms a core surrounded by a PFS shell in a P2VP matrix; the core/shell structure is oriented perpendicularly to the film surface. The PS core and P2VP matrix blocks are partly removed using oxygen reactive ion etching, leaving ring patterns made from oxidized PFS.