A tunable photo-electric co-excited point electron source: low-intensity excitation emission and structure-modulated spectrum-selection

The development of a point electron source requires an efficient excitation mode with low energy consumption, flexible tunability, and high performance. In particular for traditional electron emission cathode materials, it is necessary to expand the function of this aspect to meet application demands in many emerging fields. In this study, we propose a photo-electric co-excited scheme to drive a tungsten (W) needle nano-cold-cathode. The developed W needle cathode has been demonstrated to show electron emission performance with a narrow energy spread of 0.76 eV and a high brightness of 4 × 10⁹ A m^-2 sr^-1 V^-1. This could be achieved through low-intensity co-excitation, including an electrostatic field below ∼0.5 V μm^-1 and a laser intensity at ∼10 W cm^-2 level. Based on this co-excitation, the electron emission further exhibited a tunable property relative to the intrinsic properties of the incident light, such as optical frequency and polarization, which is shown to be directly modulated by the structure of the W needle nano-cold-cathode. This work provides a choice to achieve tunable, miniaturized and integrated vacuum micro- and nano-electronic devices.