Fabrication of an invertedly poled domain structure from a ferroelectric crystal

A method of fabricating an invertedly poled domain structure having alternating sections of opposite electric polarities, from a ferroelectric crystal wafer having two opposite polar surfaces, the method comprising:

• (a) patterning at least one of said two polar surfaces of the wafer to comprise a plurality of alternating discrete regions, of which first regions are adapted for, and second regions are protected from, the direct application thereto of an electric contact;
• (b) applying to both polar surfaces of the wafer electrically conducting electrodes so that the first regions are in direct contact with the electrodes and the second regions are protected from such a contact;
• (c) applying to the electrodes a switching electrical field of the intensity E which satisfies the condition Ebr>E≧Ec, Ec being the coercive field of the ferroelectric crystal and Ebr being the breakdown field of the ferroelectric crystal;
• wherein
• a time interval τdur, during which the switching electric field is applied to the ferroelectric crystal wafer, meets the condition
• (1:3)τsw≦τdur≦(0.1:0.3)τres
• where τsw and τres are, respectively, a switching time at the intensity E of the switching electric field and a dielectric response time of the ferroelectric crystal wafer.

A method of determining parameters for fabricating an invertedly poled domain structure having alternating sections of opposite electric polarities, from a ferroelectric crystal wafer having two opposite polar surfaces, the wafer being patterned at least at one of said two polar surfaces of said wafer to comprise a plurality of alternating discrete regions, of which first regions are adapted for, and second regions are protected from, the direct application thereto of an electric contact, to enable the applications to both of its polar surfaces of electrically conducting electrodes so that the first regions are in direct contact with the electrodes and the second regions are protected from such a contact;

• the method comprising:
• (a) choosing an intensity E of an electric field for applying to said electrodes, which satisfies the condition Ebr>E≧Ec, Ec being the coercive field of said ferroelectric crystal and Ebr being the breakdown field of said ferroelectric crystal wafer;
• (b) determining the dependency of a switching time τsw of said ferroelectric crystal wafer on temperature at the chosen intensity E of the electric field;
• (c) determining a temperature Tx at which said switching time τsw of the ferroelectric crystal wafer at the chosen intensity E of the electric field equals a dielectric response time τres of the ferroelectric crystal wafer;
• and
• (d) determining a working temperature Tw at which said switching electric field applied to the wafer satisfies the condition Tmin<Tw<Tx, where the temperature Tmin is the minimum temperature at which the intensity E of the switching electric field still satisfies the condition Ebr>E>Ec.

A method of fabricating an invertedly poled domain structure having alternating sections of opposite electric polarities, from a ferroelectric crystal wafer having two opposite polar surfaces, the method comprising:

• (a) providing said wafer made of a ferroelectric material whose dielectric response time τres is shorter than the switching time τsw at room temperature, and is equal to said switching time at a temperature Tx lower than room temperature, at an intensity E of a switching electrical field which satisfies the condition Ebr>E>Ec, Ec being the coercive field of the ferroelectric crystal and Ebr being the breakdown field of the ferroelectric crystal;
• (b) patterning at least one of said two polar surfaces of said wafer to comprise a plurality of alternating discrete regions, of which first regions are adapted for, and second regions are protected from, the direct application thereto of an electric contact;
• (c) applying to both polar surfaces of the wafer electrically conducting electrodes so that the first regions are in direct contact with the electrodes and the second regions are protected from such a contact;
• (d) applying to the electrodes a switching electrical field of said intensity E wherein
• said switching electrical field is applied to the wafer at a working temperature Tw which satisfies the condition Tmin<Tw<Tx, where the temperature Tmin is the minimal temperature at which the intensity E of the switching electric field still satisfies the condition Ebr>E≧Ec.

A method of fabricating an invertedly poled domain structure having alternating sections of opposite electric polarities, from a ferroelectric crystal wafer having two opposite polar surfaces, the method comprising:

• (a) providing said wafer made of a ferroelectric crystal having at room temperature a dielectric response time τres shorter than its switching time τsw;
• (b) modifying said crystal to change its conductivity so as to increase the dielectric response time τres to meet the condition τres>τsw;
• (c) patterning at least one of said two polar surfaces of the wafer to comprise a plurality of alternating discrete regions, of which first regions are adapted for, and second regions are protected from, the direct application thereto of an electric contact;
• (d) applying to both polar surfaces of the wafer electrically conducting electrodes so that the first regions are in direct contact with the electrodes and the second regions are protected from such a contact;
• (e) applying to the electrodes a switching electrical field of the intensity E which satisfies the condition Ebr>E≧Ec, Ec being the coercive field of the ferroelectric crystal and Ebr being the breakdown field of the ferroelectric crystal;
• wherein
• said switching electrical field is applied to the wafer at a working temperature Tw which satisfies the condition Tmin<Tw<Tx, where the temperature Tmin is the minimal temperature at which the intensity E of the switching electric field still satisfies the condition Ebr>E≧Ec and where Tx is the temperature at which said dielectric response time τres equals said switching time τsw of the ferroelectric crystal at the chosen intensity E of the electric field.