Photoemission of spin-polarized electrons from GaAs

Abstract

The spin polarization of electrons photoemitted from (110) GaAs by irradiating with circularly polarized light of energy 1.5 & heu & 3.6 eU was measured by Mott scattering. The GaAs surface was treated with cesium and oxygen to obtain a negative electron af6nity (NEA), The spectrum of spin polarization P(hem) exhibits a peak (P = 40%) at threshold arising from transitions at I, and positive (P = 8%) and negative (P = -8%) peaks at 3.0 and 3.2 eV, respectively, arising from transitions at L (A). Anomalous behavior, consisting of a depolarization at threshold and an increase and shift in the peak polarization to 54% at 1.7 eV, is attributed to a small positive electron a%nity (PEA) characteristic of some samples. Restriction of the photoelectron emission angle by the PEA leads directly to the anomalously high P. Results of calculations show that P cannot be increased above 50% for emission arising from transitions at I in NEA GaAs. Our detailed interpretation of the spectra indicates how spin-polarized photoemission can be used to study the spindependent aspects of electronic structure. The outstanding qualities of NEA GaAs as a source of spinpolarized electrons are discussed and compared with other sources.

Exchange-split interface state at h-BN/Ni(111)

“…[5,[21][22][23][24] A GaAs photocathode irradiated by circularly polarized laser light is used as a source for spin-polarized electrons. [25,26] The spin polarization of the electron beam is P e = 33 ± 3%. [23,27] The electrons impinge on the sample with well defined energy, momentum and spin polarization.…”

Search for spin-polarized photoemission from GaAs using light with orbital angular momentum

“…1. 2 The ground state valence-band states possess p-symmetry at the Г-point, with the 2 p1/2 and 2 p3/2 states being split by spin-orbit interaction. The standard technique for the production of spin-polarized electrons by photoemission from GaAs relies on the absorption of circularly-polarized light with SAM of, e.g., +1ħ, where electrons make transitions to the conduction band states of 2 s symmetry proportional to the respective transition strengths indicated by the labels "1", "2", and "3" in Fig.…”

“…1 GaAs has long been used to generate spin-polarized electron beams via photoemission using light with SAM. 2 These electron beams are created using atomically clean GaAs in an ultrahigh vacuum environment. Photoemission is obtained when chemicals (e.g., Cs and NF3) are applied to the surface to produce a negative electron affinity (NEA) condition.…”

Investigation of transient linear and circular birefringence in metallic thin films

“…However, in certain semiconductors, due to the spin-orbit splitting of the valence band, a circularly polarized pump can selectively excite spin-polarized electrons. For example, spin-polarized electrons have been excited from GaAs to the vacuum level and used in inverse photoemission experiments [3]. By pumping close to the band gap, non-equilibrium spin polarizations may be created that persist for times in excess of 1 ns and hence give rise to long-lived circular birefringence [4].…”