Electron spectroscopy apparatus and methods

A method of electron spectroscopy, comprising:

• setting, by a controller, one or more parameters of pulses of a laser based on composition information about a sample;
• ablating material from an area on a surface of the sample by irradiating the area of the sample with one or more pulses of the laser, wherein the parameters of the pulses of the laser have been set by the controller;
• irradiating at least part of the area with an excitation beam of electrons or electromagnetic radiation;
• measuring intensities and energies of electrons emitted from the at least part of the area of the sample as a result of the excitation beam;
• adjusting the one or more parameters of the pulses of the laser based on measured or predicted composition information about the sample at a depth following the ablation;
• repeating the steps of ablating material, irradiating with the excitation beam and measuring electron intensities and energies using the adjusted one or more parameters of the pulses of the laser;
• and
• determining a chemical composition of the surface based on the measured intensities and energies of the emitted electrons.

An electron spectroscopy apparatus for determining a chemical composition of a sample, the apparatus comprising:

• a vacuum chamber;
• a sample stage mounted in the vacuum chamber, the sample stage configured for receiving a sample to be analysed;
• a laser source configured to generate and direct laser pulses at a target area of the sample to ablate a surface of the sample;
• an excitation beam source configured to generate and direct an excitation beam of electrons or electromagnetic radiation at the target area of the sample;
• and
• an electron analyser and detector configured to measure energies and intensities of electrons emitted from the sample surface in response to the excitation beam and to determine a quantitative surface depth profile of the chemical composition of the sample.