Lower emission current was implemented in an ESCHER LEEM based on a specs P90 FE-LEEM. The electrons that are used for the imaging are provided by a cold field emitter, meaning that a voltage is...Show moreLower emission current was implemented in an ESCHER LEEM based on a specs P90 FE-LEEM. The electrons that are used for the imaging are provided by a cold field emitter, meaning that a voltage is used to extract the electrons from an metallic emitter tip. The relationship between the extractor voltage and the emission current is inherently inconsistent, and for low emission current, high noise on our measurement of the emission current prevents the use of a feedback loop as is customary for higher emission currents(above 0.6 µA). Instead a model was made that fits the relationship between emission current and extractor voltage on a day to day basis, using high emission current data points from a range where a feedback loop can be used. With this the relationship between emission current and extractor voltage can be extrapolated for emission currents below 0.6 µA, to find the right extractor voltage for a desired emission current. Then the electron detector of the LEEM, which is normally used as a camera for imaging techniques, was used to verify the model using image intensity as a measure for the emission current. Using the developed model to set extractor voltage from emission current setpoint, emission currents of down to I_emis ≈ 2.5·10^(−13) µA were observed. The obtained emission current data was in good agreement with CFE theory for many orders of magnitude, however at I_emis ≈ 0.007 µA, a negative curvature was observed that is not in agreement with CFE theory. This makes the model less precise. At I_emis ≈ 1.23·10^(−7) µA, it deviated by an order of magnitude. At I_emis ≈ 2.5·10^(−13) µA the model deviated from the emission current by a factor of approximately 5 orders of magnitude. It is not yet clear whether this negative curvature is an artifact of our measurement or a deviation form CFE theory, however it is suspected to be an artifact of our measurement caused by either the emission profile of our electron emitter changing or lensing of the extractor plate. Multiple other options exist. Until the cause of this negative curvature is found, we can not assume the model to be a precise indication of the emission current. Despite this a working model was provided that allowed us to use significantly lower emission currents. Using lower emission current we were able to image a pentacene layer grown on hBN flakes exfoliated on silicon with significantly less charging compared to using high currents.Show less