TY - JOUR

T1 - Na2KSb/CsxSb interface engineering for high-efficiency photocathodes

AU - Rozhkov, S. A.

AU - Bakin, V. V.

AU - Rusetsky, V. S.

AU - Kustov, D. A.

AU - Golyashov, V. A.

AU - Demin, A. Yu

AU - Scheibler, H. E.

AU - Alperovich, V. L.

AU - Tereshchenko, O. E.

N1 - The authors acknowledge the support from the Russian Science Foundation (Grant No. 22-12-20024, p-9), SRF SKIF Boreskov Institute of Catalysis (FWUR-2024-0042) and ISP SB RAS.

PY - 2024/8/2

Y1 - 2024/8/2

N2 - Optical and photoemission measurements were performed on alkali antimonide Na2KSb and Na2KSb/CsxSb photocathodes in order to determine their energy-band diagrams, elucidate the photoemission pathways, and explore the options for interface engineering in order to reach high quantum efficiencies of the photocathodes. This study is motivated by the recent discovery of optical orientation in Na2KSb and emission of spin-polarized electrons from Na2KSb/CsxSb photocathodes [V.S. Rusetsky et al., Phys. Rev. Lett. 129, 166802 (2022)]. We have shown that the band gap Eg of Na2KSb at T=295 K lies within the range of 1.40-1.44 eV. The Na2KSb surface activation by the deposition of Cs and Sb results in effective electron affinity decrease by approximately 0.37 eV, and in an increase of the quantum efficiency up to 0.2 electrons per incident photon. The analysis of longitudinal energy distribution curves (EDCs) proves that the surface of activated Na2KSb/CsxSb photocathodes have negative effective electron affinity of approximately -0.1 and -0.25 eV at T=295 and 80 K, respectively. EDC measurements under increasing photon energy ω demonstrate the transition of photoemission pathway from the surface states' photoionization at ωEg. EDCs measured at 80 K reveal a highly directional photoelectron emission from the Na2KSb/CsxSb photocathode, as compared to the p-GaAs(Cs,O) photocathode. This fact, along with the observed significant, by an order of magnitude, increase in the photoluminescence intensity under the Na2KSb surface activation by Cs and Sb, indicates relatively weak diffuse scattering in the "quasiepitaxial"CsxSb activation layer of a Na2KSb/CsxSb photocathode, compared to strong scattering in the amorphous (Cs,O) activation layer of a p-GaAs(Cs,O) photocathode.

AB - Optical and photoemission measurements were performed on alkali antimonide Na2KSb and Na2KSb/CsxSb photocathodes in order to determine their energy-band diagrams, elucidate the photoemission pathways, and explore the options for interface engineering in order to reach high quantum efficiencies of the photocathodes. This study is motivated by the recent discovery of optical orientation in Na2KSb and emission of spin-polarized electrons from Na2KSb/CsxSb photocathodes [V.S. Rusetsky et al., Phys. Rev. Lett. 129, 166802 (2022)]. We have shown that the band gap Eg of Na2KSb at T=295 K lies within the range of 1.40-1.44 eV. The Na2KSb surface activation by the deposition of Cs and Sb results in effective electron affinity decrease by approximately 0.37 eV, and in an increase of the quantum efficiency up to 0.2 electrons per incident photon. The analysis of longitudinal energy distribution curves (EDCs) proves that the surface of activated Na2KSb/CsxSb photocathodes have negative effective electron affinity of approximately -0.1 and -0.25 eV at T=295 and 80 K, respectively. EDC measurements under increasing photon energy ω demonstrate the transition of photoemission pathway from the surface states' photoionization at ωEg. EDCs measured at 80 K reveal a highly directional photoelectron emission from the Na2KSb/CsxSb photocathode, as compared to the p-GaAs(Cs,O) photocathode. This fact, along with the observed significant, by an order of magnitude, increase in the photoluminescence intensity under the Na2KSb surface activation by Cs and Sb, indicates relatively weak diffuse scattering in the "quasiepitaxial"CsxSb activation layer of a Na2KSb/CsxSb photocathode, compared to strong scattering in the amorphous (Cs,O) activation layer of a p-GaAs(Cs,O) photocathode.

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85200767412&origin=inward&txGid=c3a02a541efe4c71f4f4ebfea67a09ae

UR - https://www.mendeley.com/catalogue/eed476ff-4f6d-381a-86f2-f52dd783a072/

U2 - 10.1103/PhysRevApplied.22.024008

DO - 10.1103/PhysRevApplied.22.024008

M3 - Article

VL - 22

JO - Physical Review Applied

JF - Physical Review Applied

SN - 2331-7019

IS - 2

M1 - 024008

ER -