Ion sensor, ion concentration measurement method, and electronic component

1. An electronic component comprising:

a field effect transistor that functions as a source electrode and a drain electrode of an ion sensor;

a driving circuit that causes a potential difference between the source electrode and the drain electrode of the field effect transistor; and

a conductive diamond electrode, wherein

a reference electrode potential of the field effect transistor is fixed by the conductive diamond electrode, and

a surface of the conductive diamond electrode is fluorine-terminated.

2. The electronic component according to claim 1 , wherein

the field effect transistor has a diamond thin film disposed on a surface of a substrate of the field effect transistor, and

the source electrode and the drain electrode are disposed on the diamond thin film.

3. The electronic component according to claim 1 , wherein the field effect transistor is an Ion-Sensitive Field-Effect Transistor.

4. An ion sensor for measuring ion concentration of a measurement target liquid, based on an output from a reference electrode, a source electrode, and a drain electrode, comprising:

a field effect transistor that functions as the source electrode and the drain electrode;

a container that contains the field effect transistor and the measurement target liquid, wherein the container is fixed at a predetermined potential and functions as the reference electrode; and

a driving circuit that causes a potential difference between the source electrode and the drain electrode of the field effect transistor.

5. The ion sensor according to claim 4 , wherein

the field effect transistor has a substrate and a diamond thin film disposed on the surface of the substrate of the field effect transistor, and

the source electrode and the drain electrode are disposed on the diamond thin film.

6. The ion sensor according to claim 5 , wherein a vicinity of a surface of the diamond thin film is a p-type semiconductor.

7. The ion sensor according to claim 4 , wherein a protective film is disposed on a surface of the source electrode and the drain electrode of the field effect transistor.

8. The ion sensor according to claim 4 , wherein the field effect transistor is an Ion-Sensitive Field-Effect Transistor.

9. The ion sensor according to claim 4 , wherein the field effect transistor is an Ion-Sensitive Field-Effect Transistor that comprises a silicon substrate.

10. The ion sensor according to claim 9 , wherein a diamond thin film is disposed on a channel-side surface of the silicon substrate.

11. The ion sensor according to claim 4 , wherein an inner wall surface of the container is coated with a conductive material.

12. The ion sensor according to claim 11 , wherein the conductive material is made of at least one of metal, carbon, conductive diamond, and conductive diamond-like carbon.

13. The ion sensor according to claim 4 , wherein the container comprises an insulating container and a conductive film made of a conductive material coated on an inner wall surface of the insulating container.

14. An ion concentration measurement method using the ion sensor according to claim 4 , the ion concentration measurement method comprising:

immersing the field effect transistor in the measurement target liquid contained in the container;

generating a current between a source area and a drain area of the field effect transistor by electrochemically connecting a channel area of the field effect transistor to the container via the measurement target liquid while a potential difference is caused, by the driving circuit, between the source area and the drain area of the field effect transistor; and

measuring ion concentration in the measurement target liquid, based on the current.

15. The ion concentration measurement method according to claim 14 , wherein a voltage applied to the drain area is 0V.