Electron source and charged particle device having same

The invention provides an electron source and charged particle device having same, wherein the electron source suitable for use in a charged-particle apparatus, in which source a beam of electrons can be extracted from an electrode that is subjected to at least one of an electric potential, thermal excitation and photonic excitation, whereby at least part of the electrode comprises semiconductor material having a conduction band that is quantized into discrete energy levels. Such a source enjoys a relatively low energy spread, typically much smaller than that of a Cold Field Emission Gun (CFEG). Said semiconductor material may, for example, comprise a semiconductor nanowire. Examples of suitable semiconductor materials for such a nanowire include InAs and GaInAs.