Evaluation of electron energy spread in CsBr based photocathodes

Maldonado, Juan R.; Sun, Yun; Li, Zhi; Li, Xuefeng; Tanimoto, Sayaka; Pianetta, P.; Pease, Fabian

doi:10.1116/1.2976572

Cited by 9 publications

(10 citation statements)

References 6 publications

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“…For a good material in the lithography application, the number of secondary electrons should be low to maximize the contrast between reflective electrodes at low voltages. 4 The size of the beam on the sample measured along two perpendicular directions with a pinhole and a Faraday cup is shown in Fig. Figure 2 shows the behavior of a machined and unpolished flat surface of a Cu rod with about 1 in.…”

Section: Descriptionmentioning

confidence: 99%

Apparatus to measure electron reflection

Maldonado

Sun

Tsai

et al. 2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Articles you may be interested inHigh-current electron optical design for reflective electron beam lithography direct write lithography Controlling reflection of electrons from an array of electrodes is a key feature of an electron lithography system currently under development. Here the authors describe a technique for characterizing this control. The apparatus is only 30 mm long, features simple colinear electron optics and a photocathode that emits a well-directed, monochromatic beam. The overall energy resolution is better than 1 eV.

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Section: Descriptionmentioning

confidence: 99%

Apparatus to measure electron reflection

Maldonado

Sun

Tsai

et al. 2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…Robust CsBr photoemitters have been demonstrated and characterized, and they show significant promise for multiple electron-beam systems. [2][3][4][5] The virtual source size of an electron source is determined by the size of the emission area. Therefore, the laser spot, which controls the size of the photoemission area, determines the virtual source size.…”

Section: Introductionmentioning

confidence: 99%

Analysis of surface electromagnetic wave resonant structures for potential application in an array of compact photoelectron sources

Choi

Groves

2010

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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“…CsBr on InGaN, for example, produces an energy spread less than 0.5 eV FWHM with CsBr thicknesses well above 100Å (Ref. 17) in measurements with the sample illuminated from the rear, and CsBr on copper substrates produce a FWHM of 0.77 eV in measurements performed using the same equipment and technique as this work. 18 Therefore, it seems unlikely that CsBr directly increases the energy spread.…”

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“…17,18 However, we have demonstrated the ability of diamondoids to reduce the energy spread of these types of devices, and it should be possible to add the diamondoid monolayers onto the other, more desirable substrates if a suitable monolayer attachment method can be found.…”

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Photocathode device using diamondoid and cesium bromide films

Clay

Maldonado

Pianetta

et al. 2012

Applied Physics Letters

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A photocathode structure is presented that shows promise for use in high brightness electron sources. The structure consists of a metal substrate, a monolayer of a diamondoid derivative, and a thin film of cesium bromide. Diamondoid monolayers reduce the energy spread of electron emitters, while cesium bromide increases the yield and stability of cathodes. We demonstrate that the combined structure retains these properties, producing an emitter with lower energy spread than the corresponding cesium bromide emitter (1.06 eV versus 1.45 eV) and higher yield and stability than un-coated diamondoid emitters. 3 An ideal emitter for these devices would have high intensity, small physical size, good stability under operating conditions, and low energy spread. One method for achieving high yield and small physical size is to use a focused laser beam to create photoelectrons. However, performance of such devices is limited by the quantum yield and the energy spread. In this work, we present a photocathode structure that improves on the quantum yield and reduces the energy spread of laser photoemission devices without sacrificing the other desirable properties. This device consists of a monolayer of diamondoid combined with a thin film of cesium bromide.Diamondoids are hydrocarbon molecules with the same carbon-lattice structure as bulk diamond. They inherit many of the superior properties of diamond 4,5 and possess emergent properties relating to their small size and high surface area ratio. [6][7][8][9][10][11][12] One unique property of these diamondoids is their behavior in photoemission devices. A monolayer of diamondoids on a metal substrate can largely monochromatize the photoemission, with the majority of the electrons emitting in a single peak with a full-width half-max (FWHM) of around 0.3 eV.6,7 This low energy spread is ideal for many cathode applications, but the diamondoid monolayers that have been studied are not stable enough for use in most devices. In order to correct this problem, we have added cesium bromide as a protective over-layer to provide mechanical stability and protection.Cesium bromide provides more than just protection, however. CsBr coatings on photocathodes have been extensively studied [13][14][15][16][17][18] and have desirable properties. They greatly enhance the quantum yield of the emitter by reducing the effective work function and are robust and capable of operation under the demanding conditions of ultra bright FEL sources. 19 Our objective is to combine these attractive properties with the reduced energy spread of diamondoids by creating a device that contains both films using a thiolated diamondoid to create a self-assembled monolayer (SAM).We tested these devices using ultra-violet (UV) laser photoemission, as shown in Figure 1. We measured the quantum yield, the energy spread, and lifetime of devices with and without the diamondoid present with varying thicknesses of CsBr. Through these investigations, we demonstrate that the high quantum yield of the CsBr emitter is preserved ...

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Evaluation of electron energy spread in CsBr based photocathodes

Cited by 9 publications

References 6 publications

Apparatus to measure electron reflection

Apparatus to measure electron reflection

Analysis of surface electromagnetic wave resonant structures for potential application in an array of compact photoelectron sources

Photocathode device using diamondoid and cesium bromide films

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