Oxygen‐enhanced thermionic emission pattern of hemispherical single‐crystal LaB6

摘要

With the application of Martin’s experimental arrangement for direct observation of thermionic emission patterns from a hemispherical single‐crystal LaB6 cathode, it has been determined that oxygen‐enhanced thermionic emission does occur for the (210) plane at the rather low partial pressure of oxygen, i.e., in the 10-9‐Torr region, at sample temperatures of 1050 °C. For further quantitative assessment, work‐function measurements by Richardson plots were done for different crystal planes of clean surface by attaching a photomultiplier. The result clearly shows that the values of the work function increases in order from (100), (210), (110), and (111). The measurements were also extended to the oxygen‐enhanced surface of the (210) plane and it was found that the results follow, phenomenologically, the Richardson plot as well.