A method of fabricating nano-tips involves placing a precursor nanotip with an apex and shank in a vacuum chamber; optionally applying an electric field to the precursor nanotip to remove oxide and other contaminant species; subsequently admitting an etchant gas to the vacuum chamber to perform field assisted etching by preferential adsorption of the etchant gas on the shank; and gradually reducing the applied electric field to confine the adsorption of the etchant gas to the shank as etching progresses.