Synthesis, surface chemical analysis, lifetime studies and degradation mechanisms of Cs-K-Sb photocathodes

Panuganti, H.; Chevallay, E.; Fedosseev, V. N.; Himmerlich, Marcel

doi:10.1016/j.nima.2020.164724

Cited by 9 publications

(3 citation statements)

References 45 publications

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“…From the experimental perspective, the routinely adopted deposition methods [19][20][21], together with the propensity of multi-alkali antimonides to be contaminated by atmospheric pollutants [11], demand ultrahigh vacuum conditions for both growth and characterization [22,23] which minimize opportunities for thorough analysis. In light of these limitations, results of ab initio calculations represent a valuable source to obtain information about the properties of these systems.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure and optical properties of Na₂KSb and NaK₂Sb from first-principles many-body theory

Amador

Saßnick

Cocchi

2021

J. Phys.: Condens. Matter

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In the search for novel materials for vacuum electron sources, multi-alkali antimonides and in particular sodium-potassium-antimonides have been recently regarded as especially promising due to their favorable electronic and optical properties. In the framework of density-functional theory and many-body perturbation theory, we investigate the electronic structure and the dielectric response of two representative members of this family, namely Na2KSb and NaK2Sb. We find that both materials have a direct gap, which is on the order of 1.5 eV in Na2KSb and 1.0 eV in NaK2Sb. In either system, valence and conduction bands are dominated by Sb states with p- and s-character, respectively. The imaginary part of the dielectric function, computed upon explicit inclusion of electron–hole interactions to characterize the optical response of the materials, exhibits maxima starting from the near-infrared region, extending up to the visible and the ultraviolet band. With our analysis, we clarify that the lowest-energy excitations are non-excitonic in nature and that their binding energy is on the order of 100 meV. Our results confirm the potential of Na2KSb and NaK2Sb as photoemissive materials for vacuum electron sources, photomultipliers, and imaging devices.

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Section: Introductionmentioning

confidence: 99%

Electronic structure and optical properties of Na₂KSb and NaK₂Sb from first-principles many-body theory

Amador

Saßnick

Cocchi

2021

J. Phys.: Condens. Matter

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“…In terms of preparation, various recipes have been proposed based on co-evaporation [7][8][9] or sequential growth [10,11]. The analysis of the produced photocathodes has focused both on their operando performance in accelerators [12][13][14][15][16] as well as on their physical properties [17][18][19]. These experimental efforts have been recently complemented by several theoretical studies aiming at an in-depth understanding of the fundamental characteristics of the materials [20][21][22][23][24][25][26][27][28] and their photoemission performance [29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic stability and vibrational properties of multi-alkali antimonides

Santana-Andreo,

Saßnick,

Cocchi

2024

J. Phys. Mater.

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Modern advances in generating ultrabright electron beams have unlocked unprecedented experimental advances based on synchrotron radiation. Current challenges lie in improving the quality of electron sources with novel photocathode materials such as alkali-based semiconductors. To unleash their potential, a detailed characterization and prediction of their fundamental properties is essential. In this work, we employ density functional theory combined with machine learning techniques integrated into the hiphive package to probe the thermodynamic stability of various alkali antimonide crystals, emphasizing the role of the approximations taken for the exchange-correlation potential. Our results reveal that the SCAN functional offers an optimal trade-off between accuracy and computational costs to describe the vibrational properties of these materials. Furthermore, it is found that systems with a higher concentration of Cs atoms exhibit enhanced anharmonicities, which are accurately predicted and characterized with the employed methodology.

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“…However, these materials are unsuitable for the next generation of electron sources: their characteristic absorption in the ultra-violet region requires power-expensive frequency conversion, and their tendency to heat up represents an additional source of inefficiency [ 6 ]. New classes of semiconductors [ 7 ], such as Cs

Te [ 8 , 9 ] and multi-alkali antimonides [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ], have therefore emerged in the last decade as photocathode materials.…”

Section: Introductionmentioning

confidence: 99%

Ab Initio Quantum-Mechanical Predictions of Semiconducting Photocathode Materials

Cocchi

Saßnick

2021

Micromachines

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Ab initio quantum–mechanical methods are well-established tools for material characterization and discovery in many technological areas. Recently, state-of-the-art approaches based on density-functional theory and many-body perturbation theory were successfully applied to semiconducting alkali antimonides and tellurides, which are currently employed as photocathodes in particle accelerator facilities. The results of these studies have unveiled the potential of ab initio methods to complement experimental and technical efforts for the development of new, more efficient materials for vacuum electron sources. Concomitantly, these findings have revealed the need for theory to go beyond the status quo in order to face the challenges of modeling such complex systems and their properties in operando conditions. In this review, we summarize recent progress in the application of ab initio many-body methods to investigate photocathode materials, analyzing the merits and the limitations of the standard approaches with respect to the confronted scientific questions. In particular, we emphasize the necessary trade-off between computational accuracy and feasibility that is intrinsic to these studies, and propose possible routes to optimize it. We finally discuss novel schemes for computationally-aided material discovery that are suitable for the development of ultra-bright electron sources toward the incoming era of artificial intelligence.

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Synthesis, surface chemical analysis, lifetime studies and degradation mechanisms of Cs-K-Sb photocathodes

Cited by 9 publications

References 45 publications

Electronic structure and optical properties of Na₂KSb and NaK₂Sb from first-principles many-body theory

Electronic structure and optical properties of Na₂KSb and NaK₂Sb from first-principles many-body theory

Thermodynamic stability and vibrational properties of multi-alkali antimonides

Ab Initio Quantum-Mechanical Predictions of Semiconducting Photocathode Materials

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Synthesis, surface chemical analysis, lifetime studies and degradation mechanisms of Cs-K-Sb photocathodes

Cited by 9 publications

References 45 publications

Electronic structure and optical properties of Na2KSb and NaK2Sb from first-principles many-body theory

Electronic structure and optical properties of Na2KSb and NaK2Sb from first-principles many-body theory

Thermodynamic stability and vibrational properties of multi-alkali antimonides

Ab Initio Quantum-Mechanical Predictions of Semiconducting Photocathode Materials

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Product

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Electronic structure and optical properties of Na₂KSb and NaK₂Sb from first-principles many-body theory

Electronic structure and optical properties of Na₂KSb and NaK₂Sb from first-principles many-body theory