An Approach to an Explanation of the Surface Work Functions of Pure Metals.

A first-principles study was performed to investigate the adsorption properties of gas molecules (CO, CO2, NO, and NO2) on carbon- (C-), nitrogen- (N-), and oxygen-doped (O) borophene. The adsorption energies, adsorption configurations, Mulliken charge population, surface work functions, and density of states (DOS) of the most stable doped borophene/gas-molecule configurations were calculated, and the interaction mechanisms between the gas molecules and the doped borophene were further analyzed. The results indicated that most of the gas molecules exhibited strong chemisorption at the VB site (the center of valley bottom B–B bond) of the doped borophene (compared to pristine borophene). Electronic property analysis of the C-doped borophene/CO2 and the NO2 adsorption system revealed that there were numerous charge transfers from the C-doped borophene to the CO2 and NO2 molecules. This indicated that C-doped borophene was an electron donor, and the CO2 and NO2 molecules served as electron acceptors. In contrast to variations in the adsorption energies, electronic properties, and surface work functions of the different gas, C-, N-, and O-doped borophene adsorption systems, we concluded that the C-, N-, and O-doped borophene materials will improve the sensitivity of CO, CO2, and NO2 molecule; this improvement of adsorption properties indicated that C-, N-, and O-doped borophene materials are excellent candidates for surface work functions transistor to detect gas molecules.

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Improve the Accuracy of Scanning Kelvin Probe Microscopy by Eliminating the Cantilever Effect

MRS Proceedings ◽

10.1557/proc-838-o11.7 ◽

2004 ◽

Vol 838 ◽

Author(s):

Zhitao Yang ◽

Michael G. Spencer

Keyword(s):

Linear Equations ◽

Kelvin Probe ◽

Probe Microscopy ◽

Kelvin Probe Microscopy ◽

Potential Source ◽

Scanning Kelvin Probe ◽

Surface Work ◽

Potential Sources ◽

Work Functions ◽

Large Capacitance

ABSTRACTScanning Kelvin probe microscopy (SKPM) is widely used to measure surface work functions and electrostatic potentials on nanoscale circuits, devices and materials. However, the accuracy of scanning Kelvin probe microscopy is reduced by a cantilever effect, which is due to a large capacitance gradient associated with the cantilever. We introduce an aperture structure to quantitatively moderate the strength of the cantilever effect. In this approach, the cantilever effect is eliminated and the true surface potential can be extracted by solving a set of linear equations. Experimental results show that this approach yields very accurate surface potentials when there is only a single potential source within the aperture. In the case of multiple potential sources, this method significantly improves accuracy as well. A mobile aperture structure mounted on a micromanipulator can make this approach more versatile.

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A High-Resolution Scanning Microscope for Surface Studies

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100064220 ◽

1971 ◽

Vol 29 ◽

pp. 34-35

Author(s):

R. K. Hart

Keyword(s):

Optical Systems ◽

Objective Lens ◽

Scanning Microscope ◽

Magnetic Lens ◽

High Brightness ◽

Surface Work ◽

Low Energy Electron ◽

Work Functions ◽

Residual Gas ◽

Tungsten Tip

There are a growing number of applications for high brightness electron optical systems which operate in non-contaminating “clean” residual gas atmospheres. These criteria are especially important if one wishes to look at, and characterize, surfaces for the purpose of following their behavior under rigorously-controlled conditions. Besides the obvious improvements to be gained in resolution and longer exposure to the electron beam, scanning electron microscopy can now be combined with other powerful techniques. These techniques include low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and field emission retarding potential (FERP) studies of surface work functions.At one end of the electron optical column shown in Figure 1, which is only 20 cm long from source to specimen, a field emitting tungsten tip is used as the electron source, while at the other end of the column a four grid LEED/AES system has been affixed to the objective lens housing. The remainder of the column consists of a cylindrical magnetic lens, stigmator, and scanning coils. The residual gas pressure in the column during operation is <10-9 torr.

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Interface dipoles, surface work functions, and Schottky-barrier formation at Au/ZnSe(100) interfaces

Physical Review B ◽

10.1103/physrevb.38.13418 ◽

1988 ◽

Vol 38 (18) ◽

pp. 13418-13421 ◽

Cited By ~ 26

Author(s):

F. Xu ◽

M. Vos ◽

J. H. Weaver ◽

H. Cheng

Keyword(s):

Schottky Barrier ◽

Barrier Formation ◽

Surface Work ◽

Work Functions

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Au Doping Effect on the Secondary Electron Emission Performance of MgO Films

Materials ◽

10.3390/ma11112104 ◽

2018 ◽

Vol 11 (11) ◽

pp. 2104 ◽

Cited By ~ 2

Author(s):

Jie Li ◽

Wenbo Hu ◽

Kang Wang ◽

Buyu Gao ◽

Yongdong Li ◽

...

Keyword(s):

Electron Emission ◽

Secondary Electron ◽

Electrical Characteristic ◽

Secondary Electron Emission ◽

Doping Effect ◽

Principle Calculation ◽

First Principle Calculation ◽

Surface Work ◽

Work Functions ◽

Characteristic Measurement

Au-doped MgO films were prepared by reactive sputtering of individual Mg and Au targets, and the Au doping effect on the electron-induced secondary electron emission (SEE) performance was explored by means of surface analysis, first-principle calculation, and electrical characteristic measurement. The results show that the size enlargement of MgO grains and the reduction of surface work functions induced by Au doping are the main reasons for the increase of the SEE coefficient (δ). Additionally, the superior SEE degradation property of the Au-doped MgO film under continuous electron bombardment results from the improvement of electrical conductivity. Through the optimization of Au doping concentration (x), Au-doped MgO film with an x value of 3.0% was found to have the best SEE performance due to its highest SEE coefficient and longest duration of maintaining a relatively high SEE coefficient; its maximum δ value reached 11.5—an increase of 32.2% in comparison with the undoped one.

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First Principle Research on Ga Rich GaAs0.5P0.5(001) β2(4×2) and As(P) rich β2(2×4) Reconstruction Surfaces With and Without Cs Adsorption

10.21203/rs.3.rs-265102/v1 ◽

2021 ◽

Author(s):

Siyi He ◽

Mingzhu Yang ◽

Shixin Pei

Keyword(s):

Dipole Moments ◽

Mulliken Charge ◽

First Principle ◽

Surface Work ◽

Exothermic Process ◽

Charge Analysis ◽

Average Variation ◽

Topmost Layer ◽

Work Functions ◽

Adsorption Energies

Abstract Based on first principle calculations, Ga rich and As(P) rich clean GaAs0.5P0.5(001) reconstruction surfaces and adsorbed surfaces with 0.125ML coverage of Cs at different sites are researched. Formation energy of Ga rich GaAs0.5P0.5(001) β2(4×2) reconstruction surface is smaller than that of As(P) rich one, and the work functions of Ga rich β 2 (4×2) and As(P) rich β2(2×4) surfaces are 4.657 eV and 5.187 eV, respectively. The adsorption energies of Cs adatoms on both surfaces are negative, showing that Cs adsorption is a stable exothermic process. The work functions of two surfaces both decrease after Cs adsorption, and the average variation of As(P) rich β2(2×4) surface is larger. Mulliken charge analysis shows that Cs adatoms transfer electrons to GaAsP substrate, resulting in Cs-GaAsP dioples which lower the work functions. When Cs atoms are located at D 2 of Ga rich surface and D 2 ' of As(P) rich surface, work function values of the two reconstruction surfaces reach the minimums, which are 2.834eV and 2.859eV, respectively. By calculating dipole moments, it can be found that Cs adatoms on the topmost layer form larger effective dipole moments with GaAsP substrate than the Cs atoms located in the trench.

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Recommended values of clean metal surface work functions

Journal of Vacuum Science & Technology A Vacuum Surfaces and Films ◽

10.1116/1.4934685 ◽

2015 ◽

Vol 33 (6) ◽

pp. 060801 ◽

Cited By ~ 79

Author(s):

Gregory N. Derry ◽

Megan E. Kern ◽

Eli H. Worth

Keyword(s):

Metal Surface ◽

Surface Work ◽

Clean Metal Surface ◽

Work Functions ◽

Clean Metal

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Theoretical Insights into Effect of Surface Composition of Pt-Ru Bimetallic Catalysts on CH3OH Oxidation: Mechanistic Considerations

10.21203/rs.3.rs-1134900/v1 ◽

2022 ◽

Author(s):

Lihui Ou

Keyword(s):

Bimetallic Catalysts ◽

Surface Composition ◽

Experimental Studies ◽

Theoretical Studies ◽

Lower Electrode ◽

Electrode Potentials ◽

Surface Work ◽

Optimal Surface ◽

Work Functions ◽

Effect Of Surface

Abstract A deeper mechanistic understanding on CH3OH oxidation on Pt-Ru alloys with different Ru surface compositions is provided by DFT-based theoretical studies in this paper. The present results show that alloying and surface compositions of Ru can change CH3OH oxidation pathway and activity. The optimal surface composition of Ru is speculated to be ca. 50% since the higher Ru surface composition can lead to formation of carbonaceous species that can poison surface. Our present calculated Ru surface composition of ca. 50% exhibits excellent consistency with experimental studies. The origin of enhanced catalytic activity of Pt-Ru alloys is determined. The significantly decreased surface work functions after alloying suggest more electrons are transferred into adsorbates. The calculated lower electrode potentials after alloying imply that lower overpotentials are required for CH3OH oxidation. The excellent inconsistency with experimental study on decreased onset potentials after alloying further confirms accuracy of our present calculated results.

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