Electret element, electromechanical converter and method for manufacturing electret element

Patent metadata

Field	Value
Publication number	US-10833607-B2
Application number	US-201615550215-A
Country	US
Kind code	B2
Filing date	Feb 9, 2016
Priority date	Feb 13, 2015
Publication date	Nov 10, 2020
Grant date	Nov 10, 2020

Abstract

An electret element includes: an Si layer, an SiO2 layer formed at a surface of the Si layer; and an electret formed at the SiO2 layer near an interface of the SiO2 layer and the Si layer.

First claim

The invention claimed is:

1. An electret element, comprising:
an Si layer,
an SiO 2 layer formed at a surface of the Si layer; and
an electret formed at the SiO 2 layer near an interface of the SiO 2 layer and the Si layer,
wherein a negative charge constituting the electret is fixed in the SiO 2 layer near the interface of the SiO 2 layer and the Si layer,
wherein a positive charge is accumulated in the Si layer near the interface of the SiO 2 layer and the Si layer,
wherein an electric double layer formed with the negative charge and the positive charge is formed entirely through the interface of the SiO 2 layer and the Si layer so that no electric field is allowed to extend beyond the electric double layer, and
wherein there is no electric charge near a surface of the SiO 2 layer which is opposite the interface of the SiO 2 layer and the Si layer.

2. An electromechanical converter providing a first electrode and a second electrode disposed so as to face opposite each other, at least one of which is allowed to move, wherein:
the first electrode constitutes the electret element according to claim 1 ; and
electric energy is converted to mechanical energy and vice versa as at least either the first electrode or the second electrode moves.

3. The electromechanical converter according to claim 2 , wherein:
the Si layer constitutes an Si substrate; and
at least a part of a circuit element used to drive the electromechanical converter is formed at the Si substrate.

4. The electromechanical converter according to claim 2 , wherein:
power is generated as at least either the first electrode or the second electrode is caused to move by an external force.

5. The electromechanical converter according to claim 2 , further comprising:
a stationary unit having the first electrode disposed thereat,
a movable unit having the second electrode disposed thereat,
a voltage source that applies a voltage between the first electrode and the second electrode; and
a control unit that drives the movable unit by controlling the voltage applied by the voltage source.

6. A method for manufacturing an electret element, comprising:
applying a voltage between an Si layer, with an SiO 2 layer formed thereat, and the SiO 2 layer while sustaining the Si layer at a first temperature at which the SiO 2 layer is rendered in a semiconductor state; and
changing temperatures at the Si layer with the SiO 2 layer formed thereat from the first temperature to a second temperature at which the SiO 2 layer regains an insulating property in a state of continuous voltage application,
wherein an electret is formed at the SiO 2 layer near an interface of the SiO 2 layer and the Si layer,
a negative charge constituting the electret is fixed in the SiO 2 layer near the interface of the SiO 2 layer and the Si layer,
a positive charge is accumulated in the Si layer near the interface of the SiO 2 layer and the Si layer, and
an electric double layer formed with the negative charge and the positive charge is formed entirely through the interface of the SiO 2 layer and the Si layer so that no electric field is allowed to extend beyond the electric double layer, and
wherein there is no electric charge near a surface of the SiO 2 layer which is opposite the interface of the SiO 2 layer and the Si layer.

7. The electromechanical converter according to claim 3 , wherein:
power is generated as at least either the first electrode or the second electrode is caused to move by an external force.

8. The electromechanical converter according to claim 3 , further comprising:
a stationary unit having the first electrode disposed thereat,
a movable unit having the second electrode disposed thereat,
a voltage source that applies a voltage between the first electrode and the second electrode; and
a control unit that drives the movable unit by controlling the voltage applied by the voltage source.

Assignees

• Univ Tokyo
• Saginomiya Seisakusho Inc

Inventors

• Fujita Hiroyuki
• Hashiguchi Gen
• Ashizawa Hisayuki
• Mitsuya Hiroyuki
• Ishibashi Kazunori

Classifications

• H01G7/025 Primary

  having an inorganic dielectric · CPC title

• H02N1/008

  Laterally driven motors, e.g. of the comb-drive type · CPC title

• H02N1/10 Primary

  with non-conductive charge carrier · CPC title

• H02N1/00 Primary

  Electrostatic generators or motors using a solid moving electrostatic charge carrier · CPC title

• Y10T29/49226

  Electret making · CPC title