Focused electron emission from planar quantum point contacts

A planar quantum-point-contact device is proposed capable of producing focused electron beams. This solid-state device consists of a tunnel barrier attached to a quantum point contact. By solving the time-independent and time-dependent Schrödinger equation of the 2D system, it is shown that the angular spread of the emitted beam can be reduced to less than 10°, is coherent and collimated in energy, and is able to produce interferences. By applying a magnetic field for which electron orbits have a radius of 2 m, it should then be possible to focus the beam down to 0.15 m. © 1989 The American Physical Society.