Interaction of cesium and oxygen on W(110) I. Cesium adsorption on oxygenated and oxidized W(110)

Desplat, J.‐L.; Papageorgopoulos, C.A.

doi:10.1016/0167-2584(80)90709-4

Cited by 3 publications

(5 citation statements)

References 14 publications

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“…Our limited investigation of the post-submonolayer deposition of Cs does not rule out the possibility of the formation of three dimensional islands of Cs on the sapphire surface. This growth mode has been observed for Cs on Nit(100) (Kennou et al 1991) and oxidized W(110) (Desplat et al 1980). 1 1 I I I I I I I I I I 0 150 300 450 600 Kinetic Energy (eV) It is clear from the adsorption data presented above that the rapid decay in the initial sticking coefficient, demonstrated in the deposition profiles, occurs within the submonolayer coverage regime.…”

Section: Cs Adsorptionmentioning

confidence: 52%

Adsorption and Desorption Studies of Cesium on Sapphire Surfaces

Zavadil¹,

Ing²

1994

AIP Conference Proceedings

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The adsorption/desorptioncharacteristicsof Cs on sapphiresurfaces have been studied using a combinationof surface analytical techniques. An approximateinitial sticking coefficient for Cs on sapphire has been measured using a reflection mass spectrometric technique and has been found to be 0.9. Thermal Desorption Mass Spectrometry(TDMS) and Auger El_tron Spectroscopy(AES) have been used to verify that a significant decrease in sticking coefficient occurs as ,e Cs coverage reaches a critical submonolayer value. TDMS analysis demonstrates that Cs is stabilized on a clean sapphire surface at temperatures (1200 K) in excess of the temperatures experiencedby sapphire in a TOPAZ-IIthermionic fuel element (TFE). Surface contaminants on sapphire can enhance Cs adsorptionrelative to the clean surface.C contamination eliminates the high temperature state of Cs desorptionfoundon clean sapphirebut shifts the bulk of the Cs desorption from 400 to 620 K. Surface C is a difficult contaminant to remove from sapphire, requiringannealing temperatures in excess of 1400 K. Whether Cs is stabilized on sapphirein a TFE environment will most likely dependon the relationship between surface contaminationand surface structure. I]Ib-'TRtBUTION 0F THISOOCUMEN1 IS ll_k.li_likll 4' DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government.

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Section: Cs Adsorptionmentioning

confidence: 52%

Adsorption and Desorption Studies of Cesium on Sapphire Surfaces

Zavadil¹,

Ing²

1994

AIP Conference Proceedings

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“…Although we have chosen In 0.53 Ga 0.47 As as a cathode material for this study due to its low energy bandgap (0.74 eV) and high melting temperature (∼1400 K), hightemperature behaviors of this material and III-IV compounds in general still remain in question. Moreover, cesium-coated surfaces may become unstable at high temperatures by evaporating excessive cesium ions (Cs + ), leading to the unstable electron affinity of the cathode [46,57,58]. Several groups have investigated the thermophysical properties of InGaAs alloys for various compositions up to the temperature of ∼1500 K and found no phase change or peculiar material behaviors at high temperatures.…”

Section: Resultsmentioning

confidence: 99%

“…Alkali or alkali-earth metals, mostly cesium (Cs), have been widely used to lower the work function of a material. For example, cesiated tungsten has a much lower work function (∼1.7 eV) than that of pure tungsten (∼4.5 eV) [45], and even can be lowered to ∼1 eV by interacting cesium and oxygen on tungsten [46]. Besides tungsten, other materials also have been examined in efforts to achieve a low work function.…”

Section: Resultsmentioning

confidence: 99%

Near-field enhanced thermionic energy conversion for renewable energy recycling

Ghashami

Cho

Park

2017

Journal of Quantitative Spectroscopy and Radiative Transfer

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This article proposes a new energy harvesting concept that greatly enhances thermionic power generation with high efficiency by exploiting the nearfield enhancement of thermal radiation. The proposed near-field enhanced thermionic energy conversion (NETEC) system is uniquely configured with a low-bandgap semiconductor cathode separated from a thermal emitter with a subwavelength gap distance, such that a significant amount of electrons can be photoexcited by near-field thermal radiation to contribute to the enhancement of thermionic current density. We theoretically demonstrate that the NETEC system can generate electric power at a significantly lower temperature than the standard thermionic generator, and the energy conversion efficiency can exceed 40%. The obtained results reveal that near-field photoexcitation can enhance the thermionic power output by more than 10 times, making this hybrid system attractive for renewable energy recycling.

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“…For instance, the optimal anode work function in TECs would be approximately 0.5 eV at room temperature [5]. Over the last few decades, many experimental and theoretical works have been devoted to find materials with extremely low work function [9][10][11][12][13][14][15][16][17]. The lowest value theoretically predicted to date is 1.16 eV in Ba-Sc-O adsorbed on W (1 0 0) surface [9].…”

Section: Introductionmentioning

confidence: 99%

“…Combination of AMs and oxygen is also tested to control the work function utilizing the high electronegativity of oxygen. Among them, Cs/O-covered surfaces show the lowest work function of 1.1-4 eV [14,15]. AMs and chalcogen atoms have strong tendencies to be ionized by donating or accepting electron and work as efficient elements for the charge transfer to or from adsorbents.…”

Section: Introductionmentioning

confidence: 99%

Super low work function of alkali-metal-adsorbed transition metal dichalcogenides

Kim

Lee

et al. 2017

J. Phys.: Condens. Matter

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Discovering the materials that have work functions less than 1 eV is essential for efficient thermionic energy converter (TEC). The lowest work function of materials reported so far is in a range of about 1 eV. Here, to design low work function materials, we perform first-principles calculations on selected materials of transition metal dichalcogenide as substrates and alkali metals as adsorbates. The work function of our selected materials has a dip ubiquitously independent of the true binding distances of the adsorbates and exhibits contrasting behavior between empty d-shell elements (K, Rb, and Cs) and the others (Li and Na). We show that the interaction of empty d-orbitals of alkali metals and lone pair electrons of chalcogen is a key to the behavior of the work function. From calculated key parameters that determine the work function, we find that, regardless of the amount of charge transfer, K on WTe induces the largest surface dipole moment, which consequently makes the surface work function of as small as 0.8 eV, the smallest reported to date, and that the work function is lowered further to 0.7 eV by lattice strains. We demonstrate that the thermal efficiency of TEC using the low work function material exceeds that of thermoelectric materials with figure of merit of 5-10 in temperature range of 880-1200 K.

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Interaction of cesium and oxygen on W(110) I. Cesium adsorption on oxygenated and oxidized W(110)

Cited by 3 publications

References 14 publications

Adsorption and Desorption Studies of Cesium on Sapphire Surfaces

Adsorption and Desorption Studies of Cesium on Sapphire Surfaces

Near-field enhanced thermionic energy conversion for renewable energy recycling

Super low work function of alkali-metal-adsorbed transition metal dichalcogenides

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