Patent ID: 9613779
Date: 2017-04-04
CPC Classifications: H01J

Claim:
1. A scanning transmission electron microscope (STEM) comprising: an electron source for emitting a primary electron beam; a detector for receiving the electron beam, wherein a reference axis is defined by the straight line connecting the electron source and the detector; a specimen plane located between the electron source and the detector, wherein the reference axis is perpendicular to the specimen plane; a first redirector that redirects the electron beam to a path not in alignment with the reference axis; a magnetic lens for making an immersion lens field comprising two in-lens deflectors including a first in-lens deflector and a second in-lens deflector, a variable axis objective lens having a central axis, and a variable axis collection lens having a central axis, between the objective lens and the collection lens being the specimen plane, wherein the variable axis objective lens is located between the electron source and the specimen plane for focusing the electron beam redirected by said first redirector to a focusing spot on the specimen plane, wherein the variable axis collection lens is located between the specimen plane and the detector for collecting the electron beam that has passed through the specimen plane, wherein the variable axis objective lens and the variable axis collection lens are symmetrical about the specimen plane, wherein the central axis of the variable axis objective lens is varied by the first in-lens deflector; and wherein the central axis of the variable axis collection lens is varied by the second in-lens deflector; and a second redirector that redirects the electron beam that has been collected by the variable axis collection lens back to a path in alignment with the reference axis, before the beam reaches the detector.