films as an example the same approach can be used for preparation of straight well defined pores in other inorganic films e g silica alumina and similar materials the production process starts with the product which is well described in the literature and can be bought or easily made we used homemade starting materials all the dimensions in the following figures are not to scale and just serve as an example as shown in fig1 a 1c using standard lithography techniques supported patterned membranes 10 are made on a silicon wafer 12 covered or supported on its upper and lower surfaces with desired dielectric layer 14 si x n y for example the supported patterned membranes 10 are then irradiated with energetic ions 16 diagrammatically illustrated in fig1 b the irradiation can be done from different sides of the membrane 10 fig1 b shows an example in which the irradiation is performed from the patterned side of the wafer 12 fig1 c is a scanning electron microscope image of the prepared patterned membrane 10 after the irradiation with energetic ions 16 the damaged tracks can be etched using various well known agents formation of pores using h 3 po 4 and hf as the etching agents are demonstrated here only as examples conical pores 18 as shown in fig2 a and double conical pores 18 in fig2 c were prepared using conventional latent track etching steps cylindrical geometry of the pores.