Abstract
We developed an angle-resolved photoemission spectroscopy system for the analysis of conduction-band electrons. By forming a negative electron affinity surface on a semiconductor surface, electrons in conduction bands are emitted into a vacuum and measured by using an analyzer. This method enables us to determine the energy and momentum of the conduction electrons. Furthermore, it can be used to determine unoccupied conduction band structures. The main challenges of this method are that the energies of the emitted electrons are extremely low and the trajectories of the electrons change due to various influences. We overcame these problems by placing the shielding mesh close to the sample and parallel to the sample surface. The entire chambers, including the shielding mesh, were grounded, and a negative bias voltage was applied only to the sample. This configuration realizes the acceleration of electrons while preserving the momentum component parallel to the sample surface. Another problem is the establishment of a method for converting a detected angle into the corresponding wavevector. We focused on the emission angle of electrons emitted from a sample and their minimum energy and then established an analytical method for converting detected angles into corresponding wavevectors on the basis of the minimum energy.
Highlights
University, Hamamatsu 432-8561, Japan.vacuum level by using a probe light
One of the difficulties in performing angle-resolved measurement is that the kinetic energy of the conduction electrons emitted from the negative electron affinity (NEA) surface is too low to reach the analyzer without acceleration by an applied bias voltage
We developed a measurement system capable of ARPES of the low-energy electrons emitted from the NEA surface to determine the wavevector and the energy of the conduction electrons
Summary
In the analysis of semiconductors, the electrons are excited from the valence band to the conduction band by photon absorptions, transported in the conduction band, and emitted into a vacuum by passing through the NEA surface.. In the analysis of semiconductors, the electrons are excited from the valence band to the conduction band by photon absorptions, transported in the conduction band, and emitted into a vacuum by passing through the NEA surface.17 In this method, it is possible to determine which part of the band structure the electron has transported. One of the difficulties in performing angle-resolved measurement is that the kinetic energy of the conduction electrons emitted from the NEA surface is too low to reach the analyzer without acceleration by an applied bias voltage. We established an analytical method to derive the wavevector from the detected angle
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