An electron optical system with an array of columns was developed for an electron-beam addressable data storage device that has the form factor of Compact Flash and a capacity > 10 GB. The electron optical column occupies an area. < 2500 mu m(2) and produces a focused beam with current < 100. nA and a diameter < 40 nm. An extended-area electron source that consists of an array of randomly distributed hemispherical-grain polysilicon nodules was developed. The field at the nodules is enhanced by a factor of 3-5 compared with metal-insulator-semiconductor structures with smooth cathodes. Electron emission consequently occurs predominantly at the nodules. A maximum current density of similar to 20 A/cm(2) was achieved with this electron source. The multiplicity of emission sites helps us to reduce significantly the emission current noise. An electron optical column to focus the emission from this extended source into a diameter < 30 nm was also developed. The column consists of a single main lens and an array of auxiliary nanolenses. The main lens has a diameter of similar to 3 mu m. The distance between the main lens and the electron source is similar to 3 mu m. Each electron emission nodule has a self-aligned extraction electrode and a nanolens whose diameters are similar to 0.03-0.1 mu. The nanolenses collimate the electron emission from the nodules. The main lens then focuses the collimated beams into a diameter of similar to 30 nm at an image distance of similar to 3 mu m. Without the nanolenses, the main lens alone can only focus the beam into a diameter of similar to 300 nm. (c) 2006 American Vacuum Society.