A new method to determine the work function of powdery samples

To develop a new method to determine the work function (f) of powdery samples, saline hydride deposited on a molybdenum ribbon was heated up to 1000 K at a constant rate in vacuum. The thermal electron current directly emitted from the hydride was measured simultaneously with the ion current of H2‡ detected by mass spectrometry of H2 liberated from the hydride. Theoretical analysis of temperature-programmed desorption spectra thus obtained yields that (1) f of NaH at 740±800 K is 2:3 0:1 eV, where the percentage of thermal decomposition (NaH ! Na‡1 2H2) creating active spot (Na) is 5±20%, (2) f of NaH increases by up to 0.1 eV with a temperature increase up to 870 K ( 80%), and (3) f of LiH at 860±900 K ( 60±65%) is 5:5 0:5 eV, but this value is increased by up to 0.2 eV by a temperature increase up to 940 K ( 80%). In conclusion, our method makes it possible to determine f as a function of the decomposition percentage. # 2001 Elsevier Science B.V. All rights reserved.