Particle-optical apparatus for simultaneous observing a sample with particles and photons

A particle-optical apparatus comprising:

• a vacuum chamber;
• a particle-optical column mounted on the vacuum chamber for producing a particle beam round a particle-optical axis, said particle-optical column comprising a particle source;
• a sample carrier located in the vacuum chamber for carrying a sample at a sample position, said sample position located on the particle-optical axis;
• a mirror located between the particle source and the sample position, the mirror for collecting light emitted from the sample position or focussing light on the sample position, and said mirror showing a through-hole around the particle-optical axis;
• a pump for evacuating the apparatus;
• diaphragm located between the sample position and the mirror, said diaphragm dividing a first volume within the vacuum chamber in which the sample position is located from a second volume, said diaphragm having an aperture for passing particles produced by the particle-optical column and for passing light between the mirror and the sample position, the distance between the aperture and the sample position fixed at, or capable of being adjusted to be, less than four times the diameter of the aperture;
• the aperture positioned so that said particle-optical axis passes through the aperture, and the aperture further limiting the gas flow from the first volume to the second volume to such a degree, that, when the pressure at the sample position is at the equilibrium pressure of a fluid with an equilibrium pressure above 1 mbar, the pump can evacuate the second vacuum to a pressure sufficiently low to cause negligible scattering of a particle beam passing through the second volume when compared to the scattering of a particle beam passing through the first volume.

A method of operating a particle-optical apparatus, the method comprising:

• (a) providing a particle-optical apparatus comprising:
• (i) a vacuum chamber;
• (ii) a particle-optical column mounted on the vacuum chamber for producing a particle beam round a particle-optical axis, said particle-optical column comprising a particle source;
• (iii) a sample carrier located in the vacuum chamber for carrying a sample at a sample position, said sample position located on the particle-optical axis;
• (iv) a mirror located between the particle source and the sample position, the mirror for collecting light emitted from the sample position or focussing light on the sample position, and said mirror showing a through-hole around the particle-optical axis;
• (v) a pump for evacuating the apparatus;
• (vi) diaphragm located between the sample position and the mirror, said diaphragm dividing a first volume within the vacuum chamber in which the sample position is located from a second volume, said diaphragm having an aperture for passing particles produced by the particle-optical column and for passing light between the mirror and the sample position, the distance between the aperture and the sample position fixed at, or capable of being adjusted to be, less than four times the diameter of the aperture;
• and
• (vii) the aperture positioned so that said particle-optical axis passes through the aperture, and the aperture further limiting the gas flow from the first volume to the second volume to such a degree, that, when the pressure at the sample position is at the equilibrium pressure of a fluid with an equilibrium pressure above 1 mbar, the pump can evacuate the second vacuum to a pressure sufficiently low to cause negligible scattering of a particle beam passing through the second volume when compared to the scattering of a particle beam passing through the first volume;
• (b) mounting a sample on the sample carrier at the sample position;
• (c) evacuating the first volume to a pressure between 1-50 mbar;
• (d) evacuating the second volume to a pressure below 0.1 mbar;
• (e) adjusting the distance between the sample and the aperture to a distance less than twice the diameter of the aperture;
• (f) passing a beam of particles through the aperture and onto the sample;
• and
• (g) passing a beam of photons through the aperture.