Angle-resolving photoelectron spectrometer and method

A method for an angle-resolving photoelectron spectrometer comprising:

• an electrostatic lens system having a first end and a second end, and comprising at the first end, a first lens element having a lens aperture, which is to be arranged facing a sample surface of a solid sample, and
• at the second end, a measurement region for analysing the electrons,
• wherein the electrostatic lens system comprises an optical axis extending through the lens aperture from the first end to the second end,
• wherein the electrostatic lens system is arranged to form a beam of electrons emitted from a measurement area on the sample surface, and entering through the lens aperture,
• wherein the electrostatic lens system is arranged to transport the electrons to the second end, and
• wherein the method comprises the step of
• applying, on the first lens element, a positive voltage in relation to the sample,
• characterized in that the method comprises the steps of
• providing at least a first shielding electrode with a limiting aperture, between the sample and the first lens element, with the limiting aperture within a distance from the sample surface of no more than a fifth of the distance between the sample surface and the first lens element, with the limiting aperture surrounding the optical axis, wherein the size of the limiting aperture and the distance between the sample surface and the limiting aperture are such that the angle between the optical axis and any point on the limiting aperture is larger than 45° and smaller than 70°, seen from a point on the sample surface at the optical axis, and
• providing at least one compensation electrode which is arranged around the optical axis, and
• arranging the compensation electrode at a negative voltage in relation to the particle emitting sample, to achieve a lower electric field at the measurement area on the sample surface in comparison to the electric field caused by the voltage on the first lens element.