Alkali deposition
Last updated
Last updated
Deposition of sub-atomic layers of alkali metals provides a method of continuous charge doping of the sample surface. In certain cases it allows to reach otherwise unaccesible in photoemission electronic states above the Fermi level (but not too far above, usually ~0.1-0.3 eV).
There is a permanently installed evaporator of potassium from the side of the wobble-stick. Other alkali metals, such as Na, Li and Cs are also available, but their installation should be discussed with the beamline scientist in advance.
There are two SAES Getters K dispensers installed inside the evaporator, their common point is grounded. Evaporator feedthrough has 3 contact pins: one on top and two at the bottom. The top contact is not used! Lower two correspond to two dispensers (K1 and K2). You need to connect "+" cable of the power supply to one of the lower contacts and "-" cable to the ground (e.g. any screw on the chamber).
Standard current is 5.7 A, which corresponds to a rate of ca. 1 monolayer in 2-3 min. Exact rate can be monitored by placing quartz microbalance close to the sample during deposition, this should be done very carefully to avoid collision!