Fast hall effect measurement system
A method and system for measuring Hall effect in a material includes measuring a voltage in two test states, each state alternating the direction and orientation of a current applied across the material or the voltage measured across the material relative to a magnetic field in each state. According to an embodiment, the frequency of measurement at each state differs.
1. A method of measuring the Hall effect voltage of a material, the method comprising:
a) providing an excitation across a first pair of opposing points of a piece of the material and concurrently measuring a resulting test voltage across a second pair of opposing points of the piece of material;
b) providing an excitation across the second pair of opposing points of the piece of material and concurrently measuring a resulting test voltage across the first pair of opposing points of the piece of material;
c) providing an excitation across the first pair of opposing points of the piece of material in a direction opposite to the excitation of step (a) and concurrently measuring a resulting test voltage across the second pair of opposing points of the piece of material; and
d) providing an excitation across the second pair of opposing points of the piece of material in a direction opposite to the excitation of step (b) and concurrently measuring a resulting test voltage across the first pair of opposing points of the piece of material;
wherein a frequency between repeating steps (a) and (b) differs from a frequency between repeating steps (b) and (c).
2. The method of claim 1 , each excitation comprising a current directly applied using a current source.
3. The method of claim 1 , each excitation comprising a current generated by applying a voltage using a voltage source.
4. The method of claim 1 , further comprising the steps of:
creating a signal from a plurality of test voltages measured at steps (a)-(d);
demodulating the signal; and
amplifying the signal.
5. The method of claim 1 , wherein the material has a low carrier mobility.
6. A method of measuring the Hall effect voltage of a material, the method comprising:
providing a first test state alternating a first test parameter at a first frequency;
providing a second test state alternating a second test parameter at a second frequency;
exciting the material with a known constant current;
measuring a voltage during the first and second test states to create a signal;
demodulating the signal; and
amplifying the signal;
wherein the first test parameter is one of a test excitation, a location of the test excitation, a direction of a magnetic field and a location of the magnetic field, and the second test parameter is another of the test excitation, the location of the test excitation, the direction of a magnetic field and the location of the magnetic field.
7. The method of claim 6 , wherein the material has a low carrier mobility.
8. The method of claim 6 , wherein the first frequency and the second frequency are equal.
9. The method of claim 6 , wherein the first frequency and the second frequency are not equal.
10. A method of measuring the Hall effect voltage of a material, the method comprising:
providing a first test state alternating a first test parameter at a first frequency;
providing a second test state alternating a second test parameter at a second frequency;
exciting the material with a known constant voltage and measuring the generated current;
measuring a voltage during the first and second test states to create a signal;
demodulating the signal; and
amplifying the signal;
wherein the first test parameter is one of a test excitation, a location of the test excitation, a direction of a magnetic field and a location of the magnetic field, and the second test parameter is another of the test excitation, the location of the test excitation, the direction of a magnetic field and the location of the magnetic field.
11. The method of claim 10 , wherein the material has a low carrier mobility.
12. The method of claim 10 , wherein the first frequency and the second frequency are equal.
13. The method of claim 10 , wherein the first frequency and the second frequency are not equal.
14. A method of measuring the Hall effect voltage of a material, the method comprising:
providing a first test state alternating a first test parameter at a first frequency; and
providing a second test state alternating a second test parameter at a second frequency;
wherein the first test parameter is one of a test excitation, a location of the test excitation, a direction of a magnetic field and a location of the magnetic field, and the second test parameter is another of the test excitation, the location of the test excitation, the direction of a magnetic field and the location of the magnetic field; and
wherein the material has a low carrier mobility.
15. The method of claim 14 , further comprising:
exciting the material with a known constant current;
measuring a voltage during the first and second test states to create a signal;
demodulating the signal; and
amplifying the signal.
16. The method of claim 14 , further comprising:
exciting the material with a known constant voltage and measuring the generated current;
measuring a voltage during the first and second test states to create a signal;
demodulating the signal; and
amplifying the signal.
17. The method of claim 14 , wherein the first frequency and the second frequency are equal.
18. The method of claim 14 , wherein the first frequency and the second frequency are not equal.
19. A method of measuring the Hall effect voltage of a material, the method comprising:
providing a first test state alternating a first test parameter at a first frequency; and
providing a second test state alternating a second test parameter at a second frequency;
wherein the first test parameter is one of a test excitation, a location of the test excitation, a direction of a magnetic field and a location of the magnetic field, and the second test parameter is another of the test excitation, the location of the test excitation, the direction of a magnetic field and the location of the magnetic field; and
wherein the first frequency and the second frequency are not equal.
20. The method of claim 19 , further comprising:
exciting the material with a known constant current;
measuring a voltage during the first and second test states to create a signal;
demodulating the signal; and
amplifying the signal.
21. The method of claim 19 , further comprising:
exciting the material with a known constant voltage and measuring the generated current;
measuring a voltage during the first and second test states to create a signal;
demodulating the signal; and
amplifying the signal.
22. The method of claim 19 , wherein the material has a low carrier mobility.
23. A system for measuring the Hall effect voltage of a material, the system comprising:
a magnet;
a test excitation mechanism;
a voltage measuring device;
a demodulator and an amplifier; and
a controller configured to:
provide a first test state alternating a first test parameter at a first frequency; and
provide a second test state alternating a second test parameter at a second frequency,
wherein the first test parameter is one of a test excitation, a location of the test excitation, a direction of a magnetic field and a location of the magnetic field, and the second test parameter is another of the test excitation, the location of the test excitation, the direction of a magnetic field or the location of the magnetic field.
24. The system of claim 23 , the test excitation mechanism comprising a source of current.
25. The system of claim 23 , the test excitation mechanism comprising a voltage source and a current measuring device.
26. The system of claim 23 , wherein the material has a low carrier mobility.
27. The system of claim 23 , wherein first frequency and second frequency are equal.
28. The system of claim 23 , wherein the first frequency and the second frequency are not equal.
29. The system of claim 23 , wherein the piece of material has a substantially square shape.
30. The system of claim 23 , wherein the shape of the material is one of a square, a Hall bar, or a Greek cross.
31. A system for measuring the Hall effect voltage of a material, the system comprising:
a magnet;
a test excitation mechanism;
a voltage measuring device; and
a controller configured to:
provide a first test state alternating a first test parameter at a first frequency; and
provide a second test state alternating a second test parameter at a second frequency,
wherein the first test parameter is one of a test excitation, a location of the test excitation, a direction of a magnetic field and a location of the magnetic field, and the second test parameter is another of the test excitation, the location of the test excitation, the direction of a magnetic field or the location of the magnetic field; and
wherein the material has a low carrier mobility.
32. The system of claim 31 , the test excitation mechanism comprising a source of current.
33. The system of claim 31 , the test excitation mechanism comprising a voltage source and a current measuring device.
34. The system of claim 31 , further comprising a demodulator and an amplifier.
35. The system of claim 31 , wherein first frequency and second frequency are equal.
36. The system of claim 31 , wherein the first frequency and the second frequency are not equal.
37. The system of claim 31 , wherein the piece of material has a substantially square shape.
38. The system of claim 31 , wherein the shape of the material is one of a square, a Hall bar, or a Greek cross.
39. A system for measuring the Hall effect voltage of a material, the system comprising:
a magnet;
a test excitation mechanism;
a voltage measuring device; and
a controller configured to:
provide a first test state alternating a first test parameter at a first frequency; and
provide a second test state alternating a second test parameter at a second frequency,
wherein the first test parameter is one of a test excitation, a location of the test excitation, a direction of a magnetic field and a location of the magnetic field, and the second test parameter is another of the test excitation, the location of the test excitation, the direction of a magnetic field or the location of the magnetic field; and
wherein the first frequency and the second frequency are not equal.
40. The system of claim 39 , the test excitation mechanism comprising a source of current.
41. The system of claim 39 , the test excitation mechanism comprising a voltage source and a current measuring device.
42. The system of claim 39 , further comprising a demodulator and an amplifier.
43. The system of claim 39 , wherein the material has a low carrier mobility.
44. The system of claim 39 , wherein the piece of material has a substantially square shape.
45. The system of claim 39 , wherein the shape of the material is one of a square, a Hall bar, or a Greek cross.