The interaction of water with surfaces of Pt and Ir field emitters

Błaszczyszyn, R.; Ciszewski, A.; Blaszczyszynowa, M.; Bryl, Robert; Zuber, S.

doi:10.1016/0169-4332(93)90314-2

Cited by 14 publications

(6 citation statements)

References 12 publications

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“…As it could be expected [2,3], high electric field significantly affected the water adsorbate. Therefore, the field was applied only for short periods (about 2 seconds) necessary to record the emission current.…”

Section: Adsorption Of H20 On Pt Field Emitter: 513mentioning

confidence: 68%

“…[3]. A glass, ultrahigh vacuum (UΗV) system based on mercury diffusion pumps and equipped with a small, glass titanium pump provided a final pressure far below 1 x 10 -10 torr.…”

Section: Methodsmentioning

confidence: 99%

“…reduces the total FE current, Fig. 2) [3]. Although this statement should be conflned to the atomically rough region of the emitter (including high index planes which contribute to the total emission current), the result is quite different from what could be expected on the basis of the results obtained in various adsorption experiments for the (111), (110), (100) planes of a large single crystal of platinum as well as for Pt polycrystalline substrate and film, which were carried out by using other methods [1,4,5,19].…”

Section: Work Function Changesmentioning

confidence: 99%

“…Information on the magnitude of the diffusion barrier for adsorbed 12O is derived from the theoretical prediction: (i) the height of the diffusion barrier is approximately 10% to 40% of the value for the desorption barrier [3,17]; (ii) the differences in binding energy between various types of sites should correspond rather closely to the diffusion barrier. This consideration leads to the conclusion that the energy barrier for the surface diffusion of I12O molecules on metals should range from 3 to 27 kJ/mol [1].…”

Section: Surface Diffusionmentioning

confidence: 99%

“…An attempt is undertaken to explain the reduction of the total FE current (i.e., the increase in the work function Φ) which was found during the adsorption of water on the emitter surface [3]. This result is quite different from the work function results reported for the adsorption of H2O on the low index planes of the Pt large single crystal or a Pt polycrystal surface, which are obtained using other methods [1,4,5]; in the latter cases a distinct lowering of Φ occurs.…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of H₂O on Pt Field Emitter: Surface Diffusion and Field-Induced Effects

1995

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Adsorption of an Η2 O layer onto a Pt field emitter tip under the influence of an electric field and the surface dichusioii of water were studied by using the field electron microscopy method. The presence of a negative field (field electron microscopy mode of operation), examined in the range of 33-44 MV/cm, significantly reduced the water coverage on the emitter at temperatures above 120 K. The reduction could also occur upon drawing a high density field emission current when the emitter was kept at 78 K. Surface dichusion of water, which was observed in the temperature range 120-132 K, corresponded to the "unrolling the carpet" mechanism and started from a water multilayer to a surface region water-and/or hydrogeri-submonolayer covered. This was accompanied by the transitioii process from the state of the current-and field-induced redistribution of Η2O to the state of thermal equilibrium. The activatioii energy of the dichusioii was found to be 19 and 25 kJ/mol depending oii the crystallographic direction. A positive electric field of 44 MV/cm, which was applied at temperatures of the substrate in excess of 121 K, decreased the field emission of the system and raised the desorptioii temperature of the layer over 720 K. It is assumed that the negative electric field causes reorientation of Η2 O molecules at the surface of platinum tip. The positive as well as negative electric fields promote the field desorption of water, which is in accordance with the results reported before.

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Section: Adsorption Of H20 On Pt Field Emitter: 513mentioning

confidence: 68%

“…[3]. A glass, ultrahigh vacuum (UΗV) system based on mercury diffusion pumps and equipped with a small, glass titanium pump provided a final pressure far below 1 x 10 -10 torr.…”

Section: Methodsmentioning

confidence: 99%