Relaxing the electrostatic screening effect by patterning vertically-aligned silicon nanowire arrays into bundles for field emission application

Top-down fabrication strategies are proposed and demonstrated to realize arrays of vertically-aligned silicon nanowire bundles and bundle arrays of carbon nanotube-silicon nanowire (CNT-SiNW) heterojunctions, aiming for releasing the electrostatic screening effect and improving the field emission characteristics. The trade-off between the reduction in the electrostatic screening effect and the decrease of emission sites leads to an optimal SiNW bundle arrangement which enables the lowest turn-on electric field of 1.4 V/μm and highest emission current density of 191 μA/cm2 among all testing SiNW samples. Benefiting from the superior thermal and electrical properties of CNTs and the flexible patterning technologies available for SiNWs, bundle arrays of CNT-SiNW heterojunctions show improved and highly-uniform field emission with a lower turn-on electric field of 0.9 V/μm and higher emission current density of 5.86 mA/cm2. The application of these materials and their corresponding fabrication approaches is not limited to the field emission but can be used for a variety of emerging fields like nanoelectronics, lithium-ion batteries, and solar cells.