Linear-accelerator-based applications like x-ray free electron lasers, ultrafast electron diffraction, electron beam cooling, and energy recovery linacs use photoemission-based cathodes in photoinjectors for electron sources. Most of these photocathodes are typically grown as polycrystalline materials with disordered surfaces. In order to understand the mechanism of photoemission from such cathodes and completely exploit their photoemissive properties, it is important to develop a photoemission formalism that properly describes the subtleties of these cathodes. The Dowell–Schmerge (D–S) model often used to describe the properties of such cathodes gives the correct trends for photoemission properties like the quantum efficiency (QE) and the mean transverse energy (MTE) for metals; however, it is based on several unphysical assumptions. In the present work, we use Spicer’s three-step photoemission formalism to develop a photoemission model that results in the same trends for QE and MTE as the D–S model without the need for any unphysical assumptions and is applicable to defective thin-film semiconductor cathodes along with metal cathodes. As an example, we apply our model to Cs3Sb thin films and show that their near-threshold QE and MTE performance is largely explained by the exponentially decaying defect density of states near the valence band maximum.

1.
P.
Emma
,
R.
Akre
,
J.
Arthur
,
R.
Bionta
,
C.
Bostedt
,
J.
Bozek
,
A.
Brachmann
,
P.
Bucksbaum
,
R.
Coffee
,
F.-J.
Decker
,
Y.
Ding
,
D.
Dowell
,
S.
Edstroma
,
A.
Fisher
,
J.
Frisch
,
S.
Gilevich
,
J.
Hastings
,
G.
Hays
,
P.
Hering
,
Z.
Huang
,
R.
Iverson
,
H.
Loos
,
M.
Messerschmidt
,
A.
Miahnahri
,
S.
Moeller
,
H.-D.
Nuhn
,
G.
Pile
,
D.
Ratner
,
J.
Rzepiela
,
D.
Schultz
,
T.
Smith
,
P.
Stefan
,
H.
Tompkins
,
J.
Turner
,
J.
Welch
,
W.
White
,
J.
Wu
,
G.
Yocky
, and
J.
Galayda
, “
First lasing and operation of an ångstrom-wavelength free-electron laser
,”
Nat. Photonics
4
,
641
647
(
2010
).
2.
S. M.
Gruner
,
D.
Bilderback
,
I.
Bazarov
,
K.
Finkelstein
,
G.
Krafft
,
L.
Merminga
,
H.
Padamsee
,
Q.
Shen
,
C.
Sinclair
, and
M.
Tigner
, “
Energy recovery linacs as synchrotron radiation sources
,”
Rev. Sci. Instrum.
73
,
1402
(
2002
).
3.
T. V.
Oudheusden
,
E. F.
de Jong
,
S. B.
van der Geer
,
W. O.
‘t Root
,
O. J.
Luiten
, and
B. J.
Siwick
, “
Electron source concept for single-shot sub-100 fs electron diffraction in the 100 keV range
,”
J. Appl. Phys.
102
,
093501
(
2007
).
4.
P.
Musumeci
,
J. G.
Navarro
,
J. B.
Rosenzweig
,
L.
Cultrera
,
I. V.
Bazarov
,
J. M.
Maxson
,
S.
Karkare
, and
H. A.
Padmore
, “
Advances in bright electron sources
,”
Nucl. Instrum. Methods Phys. Res., Sect. A
907
,
209
220
(
2018
).
5.
J.
Feng
,
J.
Nasiatka
,
W.
Wan
,
S.
Karkare
,
J.
Smedley
, and
H. A.
Padmore
, “
Thermal limit to the intrinsic emittance from metal photocathodes
,”
Appl. Phys. Lett.
107
,
134101
(
2015
).
6.
D. H.
Dowell
,
F. K.
King
,
R. E.
Kirby
,
J. F.
Schmerge
, and
J. M.
Smedley
, “
In situ cleaning of metal cathodes using a hydrogen ion beam
,”
Phys. Rev. Spec. Top. Accel. Beams
9
,
063502
(
2006
).
7.
D. H.
Dowell
and
J. F.
Schmerge
, “
Quantum efficiency and thermal emittance of metal photocathodes
,”
Phys. Rev. ST Accel. Beams
12
,
074201
(
2009
).
8.
W. E.
Spicer
, “
Photoemissive, photoconductive, and optical absorption studies of alkali-antimony compounds
,”
Phys. Rev.
112
,
1
(
1958
).
9.
M.
Kiziroglou
,
X.
Li
,
A.
Zhukov
,
P.
De Groot
, and
C.
De Groot
, “
Thermionic field emission at electrodeposited Ni–Si Schottky barriers
,”
Solid-State Electron.
52
,
1032
1038
(
2008
).
10.
S.
Karkare
,
G.
Adhikari
,
W.
Schroeder
,
J.
Nangoi
,
T.
Arias
,
J. M.
Maxson
, and
H. A.
Padmore
, “
Ultracold electrons via near-threshold photoemission from single-crystal Cu(100)
,”
Phys. Rev. Lett.
125
,
054801
(
2020
).
11.
C. M.
Pierce
,
J. K.
Bae
,
A.
Galdi
,
L.
Cultrera
,
I. V.
Bazarov
, and
J. M.
Maxson
, “
Beam brightness from Cs–Te near the photoemission threshold
,”
Appl. Phys. Lett.
118
,
124101
(
2021
).
12.
L.
Cultrera
,
I.
Bazarov
,
A.
Bartnik
,
B.
Dunham
,
S.
Karkare
,
R.
Merluzzi
, and
M.
Nichols
, “
Thermal emittance and response time of a cesium antimonide photocathode
,”
App. Phys. Lett.
99
,
152110
(
2011
).
13.
L.
Cultrera
,
C.
Gulliford
,
A.
Bartnik
,
H.
Lee
, and
I. V.
Bazarov
, “
Ultra low emittance electron beams from multi-alkali antimonide photocathode operated with infrared light
,”
Appl. Phys. Lett.
108
,
134105
(
2016
).
14.
T.
Vecchione
,
D. H.
Dowell
,
W.
Wan
,
J.
Feng
, and
H. A.
Padmore
, “Quantum efficiency and transverse momentum from metals,” in Proceedings of FEL 2013 (JACoW Publishing, New York, NY, 2013).
15.
S.
Hüfner
, Photoelectron Spectroscopy—Principles and Applications (Springer, 2003).
16.
C. N.
Bergund
and
W. E.
Spicer
, “
Photoemission studies of copper and silver: Theory
,”
Phys. Rev.
136
,
A1030
(
1964
).
17.
W. E.
Spicer
and
A.
HerreraGómez
, “Modern theory and applications of photocathodes,” Proc. SPIE 2022, 18–35 (1993).
18.
S.
Karkare
,
D. A.
Dimitrov
,
W.
Schaff
,
L.
Cultrera
,
A.
Bartnik
,
X.
Liu
,
E.
Sawyer
,
T.
Esposito
, and
I. V.
Bazarov
, “
Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes
,”
J. Appl. Phys.
113
,
104904
(
2013
).
19.
P.
Gupta
,
L.
Cultrera
, and
I. V.
Bazarov
, “
Monte Carlo simulations of electron photoemission from cesium antimonide
,”
J. Appl. Phys.
121
,
215702
(
2017
).
20.
O.
Chubenko
,
S.
Karkare
,
D. A.
Dimitrov
,
J. K.
Bae
,
L.
Cultrera
,
I. V.
Bazarov
, and
A.
Afanasev
, “
Monte Carlo modeling of spin-polarized photoemission from p-doped bulk GaAs
,”
J. Appl. Phys.
130
,
063101
(
2021
).
21.
S.
Karkare
and
I. V.
Bazarov
, “
Effects of surface nonuniformities on the mean transverse energy from photocathodes
,”
Phys. Rev. App.
4
,
024015
(
2015
).
22.
K. L.
Jensen
,
J. J.
Petillo
,
E. J.
Montgomery
,
Z.
Pan
,
D. W.
Feldman
,
P. G.
O’Shea
,
N. A.
Moody
,
M.
Cahay
,
J. E.
Yater
, and
J. L.
Shaw
, “
Application of a general electron emission equation to surface nonuniformity and current density variation
,”
J. Vac. Sci. Technol. B
26
,
831
837
(
2008
).
23.
J. M.
Maxson
,
P.
Musumeci
,
L.
Cultrera
,
S.
Karkare
, and
H. A.
Padmore
, “
Ultrafast laser pulse heating of metallic photocathodes and its contribution to intrinsic emittance
,”
Nucl. Instrum. Methods Phys. Res., Sect. A
865
,
99
(
2017
).
24.
J.
Bae
,
I.
Bazarov
,
L.
Cultrera
,
J.
Maxon
,
P.
Musumeci
,
X.
Shen
,
S.
Karkare
, and
H.
Padmore
, “Multi-photon Photoemission and Ultrafast Electron Heating in Cu Photocatholds at Threshold,” in the 9th International Particle Accelerator Conference (JACoW Publishing, 2018)
25.
L.
Cultrera
,
S.
Karkare
,
H.
Lee
,
X.
Liu
,
I. V.
Bazarov
, and
B.
Dunham
, “
Cold electron beams from cryocooled, alkali antimonide photocathodes
,”
Phys. Rev. Spec. Top. Accel. Beams.
18
,
113401
(
2015
).
26.
J.
Feng
,
S.
Karkare
,
J.
Nasiatka
,
S.
Schubert
,
J.
Smedley
, and
H. A.
Padmore
, “
Near atomically smooth alkali antimonide photocathode thin films
,”
J. Appl. Phys.
121
,
044904
(
2017
).
27.
G. S.
Gevorkyan
,
S.
Karkare
,
S.
Emamian
,
I. V.
Bazarov
, and
H. A.
Padmore
, “
Effects of physical and chemical surface roughness on the brightness of electron beams from photocathodes
,”
Phys. Rev. Accel. Beams
21
,
093401
(
2018
).
28.
J. K.
Nangoi
,
M.
Gaowei
,
A.
Galdi
,
J. M.
Maxson
,
S.
Karkare
,
J.
Smedley
, and
T. A.
Arias
, “Ab initio study of the crystal and electronic structure of mono- and bi-alkali antimonides: Stability, Goldschmidt-like tolerance factors, and optical properties,” arXiv:2205.14322 (2022).
29.
V.
Sa-yakanit
and
H.
Glyde
, “
Urbach tails and disorder
,”
Comments Matter Phys.
13
(
1
),
35
48
(
1987
).
30.
T. H.
Nguyena
and
S. K.
O’Leary
, “
The dependence of the Fermi level on temperature, doping concentration, and disorder in disordered semiconductors
,”
J. Appl. Phys.
88
,
3479
(
2000
).
31.
P.
Saha
,
O.
Chubenko
,
G. S.
Gevorkyan
,
A.
Kachwala
,
C. J.
Knill
,
C.
Sarabia-Cardenas
,
E.
Montgomery
,
S.
Poddar
,
J. T.
Paul
,
R. G.
Hennig
,
H. A.
Padmore
, and
S.
Karkare
, “
Physically and chemically smooth cesium-antimonide photocathodes on single crystal strontium titanate substrates
,”
Appl. Phys. Lett.
120
,
194102
(
2022
).
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