The invention concerns methods for preparing a nanoporous silicon nitride membrane comprising (i) ablating portions of at least one side of the membrane with an electron beam to reduce the thickness of the portions to between about 0.5 and 5 nanometers, and (ii) penetrating subportions of the ablated portions of the membrane with an electron beam to form nanopores having internal surfaces which are predominantly silicon rich compared to unablated portions of the membrane.

The invention concerns methods for preparing a nanoporous silicon nitride membrane comprising (i) ablating portions of at least one side of the membrane with an electron beam to reduce the thickness of the portions to between about 0.5 and 5 nanometers, and (ii) penetrating subportions of the ablated portions of the membrane with an electron beam to form nanopores having internal surfaces which are predominantly silicon rich compared to unablated portions of the membrane.

Methods, apparatuses, systems and software for ion beam milling or machining are disclosed. The apparatus includes a specimen holder, a table, one or more ion sources, rotatable ion optics, and an imaging device. The specimen holder is configured to hold a specimen in a stationary position during milling or machining. The table is configured to change the stationary position of the specimen holder in any of three orthogonal linear directions and an angular direction. The rotatable ion optics are configured to emit an ion beam towards a predetermined location on the specimen from any of the one or more ion sources at any angle around an axis that is orthogonal to a horizontal surface of the table when the angular direction of the table is 0. The imaging device is configured to generate an image of the specimen including the predetermined location, thereby enabling real-time monitoring of the milling or machining process.

Methods, apparatuses, systems and software for ion beam milling or machining are disclosed. The apparatus includes a specimen holder, a table, one or more ion sources, rotatable ion optics, and an imaging device. The specimen holder is configured to hold a specimen in a stationary position during milling or machining. The table is configured to change the stationary position of the specimen holder in any of three orthogonal linear directions and an angular direction. The rotatable ion optics are configured to emit an ion beam towards a predetermined location on the specimen from any of the one or more ion sources at any angle around an axis that is orthogonal to a horizontal surface of the table when the angular direction of the table is 0. The imaging device is configured to generate an image of the specimen including the predetermined location, thereby enabling real-time monitoring of the milling or machining process.