System and method for measuring conductivity on molecular level

• US 7,132,837 B1
• Filed: 08/26/2004
• Issued: 11/07/2006
• Est. Priority Date: 08/26/2004
• Status: Expired due to Fees

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Arizona Board of Regents (University of Arizona)
• Inventors: Tao, Nongjian
• Primary Examiner(s): DEB, ANJAN K
• Application Number:
  US10/929,134
• Publication Number:
  US 20060232282A1
• Time in Patent Office: 803 Days
• Field of Search: 324/693, 324/661, 324/664, 324/425, 204/556, 204/547
• US Class Current: 324/693
• CPC Class Codes: G01N 27/3278 involving nanosized elements, e.g. nanogaps or nanoparticles nanopores G01N33/48721; magnetic beads G01N27/745
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00

Abstract

A conductivity measurement system measures conductivity of molecules. A substance to be measured is applied to the first and second electrodes. A potential is applied across the electrodes. A computer-controlled motion controller moves a first electrode relative to a second electrode in discrete steps. In a first step, the electrodes are brought together in physical contact to form a plurality of molecular junctions. The electrodes are separated by a first distance which breaks a first molecular junction. The electrodes are separated by a second distance which breaks a second molecular junction. A conductivity measure is taken at each step. The process of separating the electrodes continues until conductivity measure is zero. The conductivity of one molecule corresponds to a last non-zero conductivity measurement prior to a zero conductivity measurement.

Claims

1. A method of measuring conductivity of a molecule, comprising:

providing first and second electrodes;

applying a potential between the first and second electrodes;

applying a substance to be measured to the first and second electrodes;

moving the first electrode relative to the second electrode, wherein a first step includes bringing the first and second electrodes in physical contact which forms a plurality of molecular junctions and a second step includes separating the first and second electrodes by a first distance which breaks a first molecular junction; and

measuring conductivity of the substance to be measured at a plurality of distances between the first and second electrodes.

2. The method of claim 1, wherein the first electrode is moved relative to the second electrode in discrete steps.

3. The method of claim 1, wherein the first electrode is moved relative to the second electrode in a continuous motion.

4. The method of claim 1, wherein a third step includes separating the first and second electrodes by a second distance which breaks a second molecular junction.

5. The method of claim 4, wherein a fourth step includes separating the first and second electrodes by a third distance which breaks a third molecular junction.

6. The method of claim 5, wherein a measure of conductivity is taken at each of the steps.

7. The method of claim 6, wherein the step having the last non-zero measure just previous to a conductivity measure of zero is the conductivity of one single molecule.

8. A method of measuring conductivity of a molecule, comprising:

applying a substance to be measured to first and second electrodes;

moving the first electrode relative to the second electrode, wherein a first step includes bringing the first and second electrodes in physical contact which forms a plurality of molecular junctions and a second step includes separating the first and second electrodes by a first distance which breaks a first molecular junction; and

measuring conductivity of the substance to be measured at a plurality of distances between the first and second electrodes, wherein the conductivity of one molecule corresponds to a last non-zero conductivity measurement prior to a zero conductivity measurement.

9. The method of claim 8, wherein the first electrode is moved relative to the second electrode in discrete steps.

10. The method of claim 8, wherein the first electrode is moved relative to the second electrode in a continuous motion.

11. The method of claim 8, wherein a third step includes separating the first and second electrodes by a second distance which breaks a second molecular junction.

12. The method of claim 11, wherein a measure of conductivity is taken at each step.