1
|
Parzyck CT, Galdi A, Nangoi JK, DeBenedetti WJI, Balajka J, Faeth BD, Paik H, Hu C, Arias TA, Hines MA, Schlom DG, Shen KM, Maxson JM. Single-Crystal Alkali Antimonide Photocathodes: High Efficiency in the Ultrathin Limit. PHYSICAL REVIEW LETTERS 2022; 128:114801. [PMID: 35363005 DOI: 10.1103/physrevlett.128.114801] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 02/02/2022] [Indexed: 06/14/2023]
Abstract
The properties of photoemission electron sources determine the ultimate performance of a wide class of electron accelerators and photon detectors. To date, all high-efficiency visible-light photocathode materials are either polycrystalline or exhibit intrinsic surface disorder, both of which limit emitted electron beam brightness. In this Letter, we demonstrate the synthesis of epitaxial thin films of Cs_{3}Sb on 3C-SiC (001) using molecular-beam epitaxy. Films as thin as 4 nm have quantum efficiencies exceeding 2% at 532 nm. We also find that epitaxial films have an order of magnitude larger quantum efficiency at 650 nm than comparable polycrystalline films on Si. Additionally, these films permit angle-resolved photoemission spectroscopy measurements of the electronic structure, which are found to be in good agreement with theory. Epitaxial films open the door to dramatic brightness enhancements via increased efficiency near threshold, reduced surface disorder, and the possibility of engineering new photoemission functionality at the level of single atomic layers.
Collapse
Affiliation(s)
- C T Parzyck
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - A Galdi
- Cornell Laboratory for Accelerator-Based Sciences and Education, Cornell University, Ithaca, New York 14853, USA
| | - J K Nangoi
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - W J I DeBenedetti
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - J Balajka
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - B D Faeth
- Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM), Cornell University, Ithaca, New York 14853, USA
| | - H Paik
- Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM), Cornell University, Ithaca, New York 14853, USA
| | - C Hu
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - T A Arias
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
| | - M A Hines
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - D G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
- Leibniz-Institut für Kristallzüchtung, Max-Born-Straße 2, 12489 Berlin, Germany
| | - K M Shen
- Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA
| | - J M Maxson
- Cornell Laboratory for Accelerator-Based Sciences and Education, Cornell University, Ithaca, New York 14853, USA
| |
Collapse
|
2
|
Galdi A, DeBenedetti WJI, Balajka J, Cultrera L, Bazarov IV, Maxson JM, Hines MA. The effects of oxygen-induced phase segregation on the interfacial electronic structure and quantum efficiency of Cs 3Sb photocathodes. J Chem Phys 2020; 153:144705. [PMID: 33086829 DOI: 10.1063/5.0024020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
High-performance photocathodes for many prominent particle accelerator applications, such as x-ray free-electron lasers, cannot be grown in situ. These highly reactive materials must be grown and then transported to the electron gun in an ultrahigh-vacuum (UHV) suitcase, during which time monolayer-level oxidation is unavoidable. Thin film Cs3Sb photocathodes were grown on a variety of substrates. Their performance and chemical state were measured by x-ray photoelectron spectroscopy after transport in a UHV suitcase as well as after O2-induced oxidation. The unusual chemistry of cesium oxides enabled trace amounts of oxygen to drive structural reorganization at the photocathode surface. This reorganization pulled cesium from the bulk photocathode, leading to the development of a structurally complex and O2-exposure-dependent cesium oxide layer. This oxidation-induced phase segregation led to downward band bending of at least 0.36 eV as measured from shifts in the Cs 3d5/2 binding energy. At low O2 exposures, the surface developed a low work function cesium suboxide overlayer that had little effect on quantum efficiency (QE). At somewhat higher O2 exposures, the overlayer transformed to Cs2O; no antimony or antimony oxides were observed in the near-surface region. The development of this overlayer was accompanied by a 1000-fold decrease in QE, which effectively destroyed the photocathode via the formation of a tunnel barrier. The O2 exposures necessary for degradation were quantified. As little as 100 L of O2 irreversibly damaged the photocathode. These observations are discussed in the context of the rich chemistry of alkali oxides, along with potential material strategies for photocathode improvement.
Collapse
Affiliation(s)
- Alice Galdi
- Cornell Laboratory for Accelerator-Based Sciences and Education and Department of Physics, Cornell University, Ithaca New York 14853, USA
| | - William J I DeBenedetti
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca New York 14853, USA
| | - Jan Balajka
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca New York 14853, USA
| | - Luca Cultrera
- Cornell Laboratory for Accelerator-Based Sciences and Education and Department of Physics, Cornell University, Ithaca New York 14853, USA
| | - Ivan V Bazarov
- Cornell Laboratory for Accelerator-Based Sciences and Education and Department of Physics, Cornell University, Ithaca New York 14853, USA
| | - Jared M Maxson
- Cornell Laboratory for Accelerator-Based Sciences and Education and Department of Physics, Cornell University, Ithaca New York 14853, USA
| | - Melissa A Hines
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca New York 14853, USA
| |
Collapse
|
3
|
Karkare S, Adhikari G, Schroeder WA, Nangoi JK, Arias T, Maxson J, Padmore H. Ultracold Electrons via Near-Threshold Photoemission from Single-Crystal Cu(100). PHYSICAL REVIEW LETTERS 2020; 125:054801. [PMID: 32794833 DOI: 10.1103/physrevlett.125.054801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 06/16/2020] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
Achieving a low mean transverse energy or temperature of electrons emitted from the photocathode-based electron sources is critical to the development of next-generation and compact x-ray free electron lasers and ultrafast electron diffraction, spectroscopy, and microscopy experiments. In this Letter, we demonstrate a record low mean transverse energy of 5 meV from the cryo-cooled (100) surface of copper using near-threshold photoemission. Further, we also show that the electron energy spread obtained from such a surface is less than 11.5 meV, making it the smallest energy spread electron source known to date: more than an order of magnitude smaller than any existing photoemission, field emission, or thermionic emission based electron source. Our measurements also shed light on the physics of electron emission and show how the energy spread at few meV scale energies is limited by both the temperature and the vacuum density of states.
Collapse
Affiliation(s)
- Siddharth Karkare
- Physics Department, Arizona State University, Tempe, Arizona 85282, USA
| | - Gowri Adhikari
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - W Andreas Schroeder
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - J Kevin Nangoi
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Tomas Arias
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Jared Maxson
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Howard Padmore
- Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| |
Collapse
|
4
|
Karkare S, Feng J, Chen X, Wan W, Palomares FJ, Chiang TC, Padmore HA. Reduction of Intrinsic Electron Emittance from Photocathodes Using Ordered Crystalline Surfaces. PHYSICAL REVIEW LETTERS 2017; 118:164802. [PMID: 28474903 DOI: 10.1103/physrevlett.118.164802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Indexed: 06/07/2023]
Abstract
The generation of intense electron beams with low emittance is key to both the production of coherent x rays from free electron lasers, and electron pulses with large transverse coherence length used in ultrafast electron diffraction. These beams are generated today by photoemission from disordered polycrystalline surfaces. We show that the use of single crystal surfaces with appropriate electronic structures allows us to effectively utilize the physics of photoemission to generate highly directed electron emission, thus reducing the emittance of the electron beam being generated.
Collapse
Affiliation(s)
- Siddharth Karkare
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, California 94720, USA
| | - Jun Feng
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, California 94720, USA
| | - Xumin Chen
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, California 94720, USA
| | - Weishi Wan
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, California 94720, USA
| | - F Javier Palomares
- Instituto de Ciencia de Materiales de Madrid (CSIC), Sor Juana Ines de la Cruz, 3, 28049 Madrid, Spain
| | - T-C Chiang
- Department of Physics, University of Illinois, Urbana, Illinois 61801 USA and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 USA
| | - Howard A Padmore
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, California 94720, USA
| |
Collapse
|
5
|
Feist A, Bach N, Rubiano da Silva N, Danz T, Möller M, Priebe KE, Domröse T, Gatzmann JG, Rost S, Schauss J, Strauch S, Bormann R, Sivis M, Schäfer S, Ropers C. Ultrafast transmission electron microscopy using a laser-driven field emitter: Femtosecond resolution with a high coherence electron beam. Ultramicroscopy 2016; 176:63-73. [PMID: 28139341 DOI: 10.1016/j.ultramic.2016.12.005] [Citation(s) in RCA: 123] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 11/30/2016] [Accepted: 12/02/2016] [Indexed: 10/20/2022]
Abstract
We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the Göttingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode. Using this emission mechanism, we achieve record pulse properties in ultrafast electron microscopy of 9Å focused beam diameter, 200fs pulse duration and 0.6eV energy width. We illustrate the possibility to conduct ultrafast imaging, diffraction, holography and spectroscopy with this instrument and also discuss opportunities to harness quantum coherent interactions between intense laser fields and free-electron beams.
Collapse
Affiliation(s)
- Armin Feist
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Nora Bach
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Nara Rubiano da Silva
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Thomas Danz
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Marcel Möller
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Katharina E Priebe
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Till Domröse
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - J Gregor Gatzmann
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Stefan Rost
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Jakob Schauss
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Stefanie Strauch
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Reiner Bormann
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Murat Sivis
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany
| | - Sascha Schäfer
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany.
| | - Claus Ropers
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Göttingen, Germany.
| |
Collapse
|