TUNABLE CHARGED PARTICLE VORTEX BEAM GENERATOR AND METHOD

Abstract

The present invention refers to a device for generating charged particle beams with tunable orbital angular momentum. The device firstly includes one or more components for providing a charged particle beam. It is further characterized by an electrical arrangement for imparting a tunable orbital angular momentum to the charged particle beam during operation. The orbital angular momentum of the produced charged particle vortex beam is tunable by adjusting the amount of electrical current. The chirality of the produced charged particle vortex beam is switchable by reversing the direction of the electrical current. The generation of the charged particle vortex beam from the present invention does not depend on the energy of the charged particle beams. The generation of the charged particle vortex beams from the present invention is predictable and reproducible.

Claims

1. Charged particle vortex beam generator comprising one or more components (7) for providing a charged particle beam (1) characterized by an electrical arrangement which imparts an orbital angular momentum to the charged particle beam (1) during operation.

2. Generator according to the preceding claim, wherein the electrical arrangement comprises at least one electrical conductor for providing a first electrical current flowing in a first direction and a second electrical current flowing in a second opposite direction, wherein the first direction is antiparallel to the second direction.

3. Generator according to the preceding claim, wherein the electrical conductor or section (4) of an electrical conductor for said first electrical current makes an acute angle (a) with the charged particle beam path and wherein the electrical conductor or section (5) of an electrical conductor for said second electrical current makes an acute angle (a) with the charged particle beam path.

4. Generator according to one of the two preceding claims, wherein the electrical conductor or section (4) of an electrical conductor for said first electrical current and the electrical conductor or section (5) of an electrical conductor for said second electrical current both extend until, or at or at least nearby, the center of the charged particle beam (1).

5. Generator according to one of the three preceding claims, wherein a first electrical conductor or section (4) of an electrical conductor for the first electrical current is arranged on one side of the center of the charged particle beam (1) and a second electrical conductor or section (5) of an electrical conductor is arranged on an opposite side of the center of the charged particle beam (1).

6. Generator according to one of the four preceding claims, wherein the first electrical current flowing in the first direction flows along a straight line and the second electrical current flowing in the second direction also flows along a straight line during operation.

7. Generator according to one of the preceding claims, comprising only one single electrical conductor (4, 5, 6) which provides an electrical current imparting an orbital angular momentum to the charged particle beam (1) during operation.

8. Generator according to the preceding claim, wherein the single electrical conductor (4, 5, 6) is U-shaped.

9. Generator according to one of the two preceding claims, wherein the single electrical conductor (4, 5, 6) comprises a first leg (4) on one side of the center of charged particle beam path (1) and a second leg (5) on an opposite side of the center of the charged particle beam path (1), each of which makes an angle () of less than 90 degrees with the charged particle beam path.

10. Generator according to one of the preceding claims, wherein an acute angle () is less than 80, preferably less than 60 and/or wherein the acute angle () is more than 20, preferably more than 30 and wherein the angle is formed between an electrical conductor or a section of an electrical conductor (4, 5) of the electrical arrangement and the charged particle beam (1).

11. Generator according to one of the preceding claims, wherein the electrical arrangement comprises a substrate (14) and/or a film (15) and at least one electrical conductor disposed on a surface (14) and/or the film (15), wherein the charged particle beam (1) flows nearby two legs (4, 5) of the electrical conductor during operation, and wherein the surface is tilted to make an acute angle with the charged particle beam path (1) during operation.

12. Generator according to the preceding claim, wherein the substrate (14) is formed from Si and/or the film (15) is formed from SiN.

13. Generator according to one of the two preceding claims, wherein the length of the legs (4, 5) disposed on the film (15) is less than 100 m, preferably less than 50 m and/or wherein the gap between the two legs (4, 5) is less than 1 m, preferably less than 0.5 m, and/or wherein the width of the legs (4, 5) is less than 1 m, preferably less than 0.5 m.

14. Generator according to one of the three preceding claims, wherein the electrical arrangement comprises one or more electrical conductors (4, 5, 6) formed by metal, preferably by Pt or Au.

15. Generator according to one of the preceding claims, wherein the generator comprises an electron microscope.

16. Generator according to one of the preceding claims, comprising a specimen holder (2), wherein the electrical arrangement is arranged between the specimen holder (2) and the components (7) for providing a charged particle beam (1).

17. Generator according to one of the preceding claims, comprising a detection and/or evaluation unit (3) for detecting a charged particle vortex beam (9) and/or for characterizing properties of a specimen.

18. Method for generating a charged particle vortex beam comprising the steps generating a charged particle beam (1), providing an electrical arrangement so that a first electrical current flows in a first direction and a second electrical current flows in a second opposite direction, wherein the first direction is antiparallel to the second direction, directing the charged particle beam (1) through the first electrical current and the second electrical current so that the electrical arrangement imparts an orbital angular momentum to the charged particle beam (1).

19. Method according to the preceding claim, wherein the first electrical current and the second electrical current flow within the charged particle beam (1) in a tilted manner relative to the particle beam path (1).

20. Method according to the preceding claim, wherein the diameter of the charged particle beam (1) is greater than the distances between the outer boundaries of the first electrical current and the second electrical current.

Description

[0046] FIG. 1 shows a charged particle vortex beam generator of a first embodiment.

[0047] FIG. 2 is a side view on parts of the charged particle vortex beam generator shown in FIG. 1.

[0048] FIG. 3 shows a circuit path formed on a flat surface of a substrate for a charged particle vortex beam generator.

[0049] FIG. 4 is a top view on the particle vortex beam and an electrical arrangement for imparting an orbital momentum to the charged particle beam.

[0050] FIG. 1 illustrates the path of a charged particle beam 1 flowing towards a holder 2 for holding a specimen and detection and evaluation unit 3 during operation. During operation, there is an electrical current flowing in a first direction along the first section 4 of an electrical conductor. There is an electrical current flowing in a second opposite direction along the second section 5 of the electrical conductor. The electrical current flowing direction flowing along the first section 4 is thus antiparallel with the electrical current flowing direction flowing along the second section 5. Each flowing direction is tilted with respect to the charged particle beam 1. Thus, there is an electrical arrangement which imparts an orbital angular momentum to the charged particle beam 1 during operation due to the sections 4 and 5 of the electrical conductor.

[0051] A third section 6 connects the first section 4 with the second section 5. The sections 4, 5 and 6 of the electrical conductor are shaped in a U-like manner. As a result, the end of a first electrical current flowing along the first section 4 is situated adjacent to the start of a second electrical current flowing along the second section 5. The end of the second electrical current is situated adjacent to the start of the first electrical current. The center of the charged particle beam 1 is arranged nearby the section 6 of the electrical conductor and thus nearby the corresponding ends of the first section 4 and the second section 5 of the electrical conductor.

[0052] The charged particle vortex beam generator comprises components 7 for providing the charged particle beam 1. The first electrical conductor section 4 in the form of a leg is arranged on one side of the center of the charged particle beam 1 and the second electrical conductor section 5 in the form of a leg is arranged on the other side of the center of the charged particle beam 1. There is an electrical power supply 8 connected with the ends of the first section 4 and the second section 5 opposite to the third section 6.

[0053] Such an electrical arrangement imparts an orbital angular momentum to the charged particle beam 1 during operation. The angular momentum depends on the electrical current flowing through the first and second sections 4 and 5 but not on the energy of the charged particle beam. A charged particle vortex beam 9 will be generated.

[0054] An angle of less than 90 degrees is formed between each electrical conductor section 4 or 5 and the charged particle beam 1. The electrical conductor which is composed of the three sections 4, 5 and 6 is connected to a DC voltage source 8 so that there is a component of an electrical current flow parallel to the charged particle beam 1 on one side and a component of an electrical current flow antiparallel to the charged particle beam 1 on the other side during operation. As a result, there will be a charged particle vortex beam 9. Thus, the device can be realized by setting two parallel conductive lines 4, 5 having flowing currents in opposite directions and having a tilt angle with respect to the direction of the charged particle beam 1.

[0055] FIG. 2 is a side view on parts of the particle vortex beam generator shown in FIG. 1. FIG. 2 illustrates the presence of an acute angle of less than 90 degrees which is formed between the electrical conductor section 5 and the charged particle beam 1. The electrical conductor section 5 and the electrical conductor section 4 are located at the same height. Further, the two conductor sections 4 and 5 are parallel. Thus, there is a corresponding acute angle of less than 90 degrees which is formed between the electrical conductor section 4 and the charged particle beam 1.

[0056] The charged particle vortex beam 9 of the charged particle vortex beam generator illustrated by FIG. 1 and FIG. 2 is tunable by varying the electrical current. The chirality of the charged particle vortex beam 9 of the charged particle vortex beam generator is switchable by varying the direction of the electrical current. The vortex beam 9 of the charged particle vortex beam generator does not depend on the energy of the charged particle beam 1.

[0057] In order to realize the effects, a charged particle vortex beam generator has been constructed as follows. A substrate 14 formed from Si comprising a thin film 15 on a flat surface has been provided. A circuit path was formed on the flat surface by deposition as shown in FIG. 3. The circuit path comprises the above mentioned sections 4, 5 and 6 in the form of a U. The circuit path was formed by Pt. The distance between the sections 4 and 5 of the electrical conductor and thus the length of the section 6 were 200 nm. The circuit path comprise two pins 17 for a power supply. The width of the sections 4 and 5 on the film 15 was 200 nm.

[0058] The substrate has been placed in an electron microscope in a tilted manner so that there is an angle of about 60 to 70 between the sections 4 and 5 and the electron beam 1 of the electron microscope for providing a tunable and predictable electron vortex beam which does not depend on the energy of the electron beam of the electron microscope. The energy of the electron beam could be varied between 50 keV and 300 keV. An electrical current of a few mA is sufficient for providing the electron vortex beam 9. At least in connection with an electron microscope, an angle of 60 to 70 is preferred.

[0059] FIG. 4 is a top view on the particle vortex beam and an electrical arrangement for imparting an orbital momentum to the charged particle beam. FIG. 4 shows the cross section of the charged particle beam 1.

[0060] A first electrical current and the second electrical current flow along the sections 4 and 5 within the charged particle beam 1 in a tilted manner relative to the particle beam path. FIG. 4 illustrates that the diameter of the charged particle beam (1) is greater than the distances between the outer boundaries of the first electrical current and the second electrical current. The electron beam illumination area 1 is approximately restricted to the apex of the two electrical currents respectively the apex of the two sections 4 and 5 of the electrical conductor. The center of illumination area 1 and thus the center of the electron beam may cross the section 6 of the electrical conductor or may at least be arranged nearby the section 6 as shown in FIG. 4.