Precision volt--ampere measurements of tungsten point field emission

Electric field electron emission from etched tungsten points was measured with maximum errors of +-0.05 percent in potential and +-2 percent in current. Precision pulse generation and differential oscillography removed usually observed charging current errors. Emitter surface cleanliness was achieved by 20000K flashing in 10-11 torr vacuum preceding each data point determination in an automatically timed sequence. The measured standard deviation of the emission current common logarithm was 0.019, inclusive of all process and measurement uncertainties. All data runs showed a hitherto unreported upward-then-downward deviation from linearity on conventional log I vs 1/V plots. Changing the dependent variable to log (I/V2) removed the double inflection and extended linearity to current density 1--3 x 106 A/cm2. A well defined monotonically downward deviation from linearity occurred at all larger current densities. Appropriateness of the log (I/V2) variable was interpreted as experimental verification of a corresponding dependency in the Fowler--Nordheim theoretical equation. The general data trends were slightly but significantly different from those of Dyke and Trolan (Phys. Rev. 89, 799 (1953)). Current densities at critical points were smaller and the downward deviations from linearity were better defined