Metal Hexaboride Work Functions: Surface Configurations and the Electrical Double Layer from First‐Principles

Abstract

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Work Function Trends and New Low-Work-Function Boride and Nitride Materials for Electron Emission Applications

“…The work functions of (001)-metal-terminated rare-earth hexaborides from our calculations are shown in Figure , along with experimental work function values for each material, where available. For the most studied hexaboride, LaB 6 , our DFT-calculated work function is generally lower than experimentally measured values, and the work function of LaB 6 from our calculation (2.01 eV) is consistent with previous computational studies, which found values of 2.07 and 2.27 eV . The observed discrepancy between the calculated and experimental LaB 6 work function may be caused by factors related to the measurement method or method of data analysis ( e.g.…”

“…For the most studied hexaboride, LaB 6 , our DFT-calculated work function is generally lower than experimentally measured values, and the work function of LaB 6 from our calculation (2.01 eV) is consistent with previous computational studies, which found values of 2.07 60 and 2.27 eV. 61 The observed discrepancy between the calculated and experimental LaB 6 work function may be caused by factors related to the measurement method or method of data analysis (e.g., fitting work function or work function and Richardson constant in thermionic emission experiments) or materialrelated factors such as different stoichiometries, defect concentrations, and surface conditions determined by sample preparation. In addition, it is possible that errors in DFT play a role, as previous studies benchmarking the accuracy of DFTcalculated work functions suggest that DFT−GGA level work functions are ∼0.3 eV lower than experimental values for metals, 69,70 and a separate study of DFT−HSE level work functions has a ∼0.2 eV deviation, on average, from experiments for SrTiO 3 .…”

“…For thermionic In addition to the experimental LaB 6 work function data, there are also computational studies on LaB 6 predicting work functions of 2.07 60 and 2.27 eV. 61 Given the observed spread in the experimental data, it is difficult to make one-to-one comparisons between calculation and experiment; however, the computational results are generally lower than the experimental results. The origin of this discrepancy is not clear but discussed further in Section 3.2.…”

Morphology Control of Tantalum Carbide Nanoparticles through Dopant Additions

“…Strain effects have also been explored as parameters for morphological modification of copper and nickel particles, and doping has been applied for obtaining nanorods of magnesium . In addition, modeling − and experimental techniques − have been applied for exploring the behavior of borides of cubic and other morphologies. Moreover, experimental efforts have investigated shape change in cubic carbides as a function of carbon stoichiometry, which influences the relative growth rate of the dominant {111} and {100} facets. − …”