Contact potential difference ionization detector

• US 6,717,413 B1
• Filed: 04/21/2000
• Issued: 04/06/2004
• Est. Priority Date: 04/21/2000
• Status: Expired due to Term

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Danyluk, Steven, Zharin, Anatoly
• Primary Examiner(s): Deb, Anjan K.
• Application Number:
  US09/553,780
• Time in Patent Office: 1,446 Days
• Field of Search: 324/459, 324/455, 324/456, 324/457, 324/458, 324/464, 324/465, 324/679, 324/765, 324/470, 324/72.5, 324/461, 324/71.1, 250/282, 250/286, 250/287
• US Class Current: 324/459
• CPC Class Codes: G01N 27/62 by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
• CPC Class Codes: G01N 27/66 and measuring current or voltage

Abstract

A nondestructive testing method of condensed matter surfaces, and a sensing device for the measurement of the work function of the surface of a conducting or semiconducting sample. The sensing device includes an ionization chamber, a probe having a first surface, and a potential difference measurement circuit that is capable of measuring a difference in potential between the first surface of the probe and a surface made of another material to be tested. The ionization chamber produces ionized particles that travel out of an output of the ionization chamber and toward the probe. The probe is a non-vibrating probe having a first surface that is either a positively or negatively charged electrode. The measurement circuit of the present invention is capable of sensing the small amount of electrical current that the electrons and ions moving toward the first surface and the testing surface represent.

Claims

1. A detector capable of detecting the work function of a testing surface, said detector comprising:

a probe having a first surface, said probe having a testing position wherein said first surface is positionable proximate to the testing surface, said probe in the testing position being capable of producing an electric field between said first surface and the testing surface;

an ionization source of ionized particles, said ionization source having an ionization source output, said ionization source arranged such that a portion of the ionized particles exit said ionization source output and are capable of being influenced by an electric field generated at said first surface of said probe; and

a potential difference measurement circuit capable of measuring a difference in potential between said first surface and the testing surface when said probe is in the testing position.

2. The detector of claim 1, said first surface being a first conductive material.

3. The detector of claim 2, said first conductive material being different than material of the testing surface.

4. The detector of claim 1, said first surface being maintained at a fixed distance from the testing surface when said probe is in the testing position.

5. The detector of claim 1, said potential difference measurement circuit comprising a power supply circuit that is capable of supplying a first bias potential to said first surface.

6. The detector of claim 5, said power supply circuit capable of maintaining the testing surface at a testing bias potential approximately equal to ground.

7. The detector of claim 1, said potential difference measurement circuit comprising:

a comparator including a first comparator input, a second comparator input and comparator output, said first comparator input capable of receiving a signal indicative of a first bias potential at said first surface, said second comparator input capable of receiving a signal indicative of a testing bias potential at said testing surface, said comparator output capable of generating a signal indicative of the difference between the signals indicative of said first bias potential and said testing bias potential;

a first diode including a first diode anode and a first diode cathode, said first diode anode coupled to said first comparator input and said first diode cathode coupled to said second comparator input; and

,

a second diode including a second diode anode and a second diode cathode, said second diode anode coupled to said second comparator input and said second diode cathode coupled to said first comparator input.

8. The detector of claim 1, said probe being a non-vibrating probe.

9. A detector capable of detecting measurements reflective of the work function of a testing surface, said detector comprising:

a non-vibrating probe having a first conductive material, said probe having a testing position wherein said first conductive material is positionable proximate to the testing surface, said probe in the testing position being capable of producing an electric field between said first conductive material and the testing surface;

an ionization source of ionized particles, said ionization source having an ionization source output and said ionization source arranged such that a portion of the ionized particles exit said ionization source output and are capable of being influenced by an electric field generated at said first conductive material of said probe; and

potential difference measurement circuit capable of measuring a difference in potential between said first conductive material and the testing surface when said probe is in the testing position, said potential difference measurement circuit including a power supply circuit capable of supplying a first bias potential to said first conductive material.

10. The detector of claim 9, said first conductive material being maintained at a fixed distance from the testing surface when said probe is in the testing position.

11. The detector of claim 9, said power supply circuit capable of maintaining the testing surface at a testing bias potential approximately equal to ground.

12. The detector of claim 9, said first conductive material being a material different than the testing surface.

13. The detector of claim 9 wherein said first conductive material is selected from the group consisting of an insulator, an ionic material, a semiconductor and a covalent material.

14. A potential difference detector comprising:

a non-vibrating probe having a first surface and a second surface, said first surface being a first conductive material and said second surface being a second conductive material;

a measurement device capable of measuring the potential difference of said non-vibrating probe when said probe is provided with ionized gas particles; and

an ionization source of ionized particles, said ionization source being capable of providing ionized gas particles to said non-vibrating probe.

15. The potential difference detector of claim 14, said measurement device including a biasing element, said biasing element being capable of providing a bias potential to said non-vibrating probe.

16. The potential difference detector of claim 14, said first conductive material being different than said second conductive material.

17. A motion detector comprising:

a first conductive element for operating at a first bias potential;

a second conductive element for operating at a second bias potential;

an ionization source having an ionization source input and an ionization source output, said ionization source input for receiving gas molecules, said ionization source output capable of providing ionized gas molecules to said first conductive element and said second conductive element; and

a potential difference measurement circuit having a first potential difference input, a second potential difference input and a potential difference output, said first potential difference input capable of receiving a signal indicative of the first bias potential, said second potential difference input capable of receiving a signal indicative of the second bias potential, said potential difference output generating an output signal indicative of the difference between the signals indicative of said first bias potential and said second bias potential, said output signal being a function of motion of the gas molecules in said motion detector.

18. The motion detector of claim 17, said potential difference measurement circuit comprising:

an amplifier having a first amplifier input, a second amplifier input and an amplifier output, said first amplifier input coupled to one of said conductive elements, said second amplifier input coupled to the other of said conductive elements; and

a voltage source coupled to said amplifier output and said first amplifier input.

19. The motion detector of claim 17, said first conductive element and said second conductive element being maintained at a fixed distance with respect to one another.

20. A method of detecting the work function of a testing surface, said method comprising the following steps:

forming ionized particles;

directing said ionized particles toward a probe having a first surface being in proximity to the testing surface;

generating an electric field between said first surface and the testing surface; and

measuring a difference in potential between said first surface and the testing surface.

21. The method of detecting the work function according to claim 20, said step of forming ionized particles being provided by an ionization source, said ionization source having an ionization source input and an ionization source output.

22. The method of detecting the work function according to claim 21, said step of directing said ionized particles being provided by said ionization source arranged such that a portion of the ionized particles exit said ionization source output and are capable of being influenced by the step of generating the electric field.

23. The method of detecting the work function according to claim 20, said step of measuring a difference in potential being provided by a potential difference measurement circuit.

24. The method of detecting the work function according to claim 23, said potential difference measurement circuit comprising a power supply circuit that is capable of supplying a first bias potential to said first surface.

25. The method of detecting the work function according to claim 24, said power supply circuit capable of maintaining the testing surface at a testing bias potential approximately equal to ground.

26. The method of detecting the work function according to claim 20, further comprising a step of maintaining said first surface at a fixed distance from the testing surface.

27. The method of detecting the work function according to claim 20, said probe being a non-vibrating probe.