CN105576115A - Fabrication method of double-sided junction and high-temperature super-conduction Bi<2>Sr<2>CaCu<2>O<8+Delta> (BSCCO) terahertz source - Google Patents

Abstract

The invention discloses a preparation method of a double-sided junction high-temperature superconducting BSCCO terahertz source. The upper and lower electrodes of the BSCCO single crystal are thermally evaporated separately, and then through one photolithography and ion beam etching, the thickness can reach several microns. sample. The preparation method is simple and operable, can shorten the sample preparation cycle and improve the success rate of sample preparation, and is beneficial to making ultra-thick samples. The samples prepared by this preparation process have the advantages of continuous wave, tunable, good monochromaticity and high power. When the thickness of the sample is greater than 2 μm, there is a relatively large terahertz radiation power, which can reach tens of microwatts. Compared with the traditional double-sided junction sample, the radiation power can be increased by an order of magnitude, and the adjustable frequency range of the sample can reach 500 ? GHz.

Description

Preparation method of a double-sided junction high-temperature superconducting BSCCO terahertz source

technical field

The invention relates to the technical field of BSCCO terahertz sources, in particular to a preparation method of a double-sided junction high-temperature superconducting BSCCO terahertz source.

Background technique

Terahertz (terahertz, usually abbreviated as THz) waves refer to electromagnetic waves with a frequency in the range of 0.3 THz to 10 THz (wavelength 1 mm to 0.03 mm). Terahertz waves have the advantages of low photon energy, high space-time coherence, and high signal-to-noise ratio in time-domain spectrum. Therefore, they have broad application prospects in scientific fields such as astronomy, biology, computer, and communication. However, due to the lack of effective terahertz radiation sources and detection methods, this band has not been fully studied and utilized.

The quantum tunneling effect in which electrons can pass through a thin insulating layer between two superconductors is called the Josephson effect. According to the AC Josephson effect, a DC voltage of 1mV can generate oscillations with a frequency up to 484GHz, and the frequency of supercurrent oscillations in the junction can be continuously adjusted by changing the DC voltage across the junction, so the superconducting Josephson junction is an ideal voltage- Frequency converters can be used to create terahertz sources. In 2007, researchers from the United States, Turkey and Japan cooperated to form a platform-shaped Josephson junction array with 600 junctions in series on the high-temperature superconductor Bi2Sr2CaCu2O8+δ (BSCCO) through microfabrication technology, so that the series junction array is under low current bias state, and detected a THz signal with an epitaxial power of several microwatts through a thermal radiation meter (L.Ozyuzeretal., Science318, 1291(2007)).

After several years of development, the BSCCO terahertz radiation source has developed into a new type of continuous wave tunable solid-state THz source, which has the advantages of ease of use, continuous wave, tunability, good monochromaticity, and high power (Wang et al., Phys . Rev. Lett. 105, 057002 (2010)). Improving the radiation power of the BSCCO terahertz source has always been a hot topic of research. Theoretical studies (L.N.Bulaevskiian and A.E.Koshelev, Phys.Rev.Lett.99, 057002 (2007) show that within a certain range, the radiation power of the sample is related to the formation The square of the number of junctions is proportional, so increasing the thickness of the sample is one of the effective ways to increase the radiation power. Because the traditional double-sided junction sample preparation technology requires two photolithography and two ion milling, it is difficult to prepare the thickness The double-sided junction samples up to several microns have greatly hindered the increase of the radiation power of the BSCCO terahertz source.

Contents of the invention

Purpose of the invention: In view of the deficiencies in the prior art, the purpose of the invention is to provide a preparation method of a double-sided junction high-temperature superconducting BSCCO terahertz source, which has the characteristics of simple process, high success rate, and a thickness of several microns.

Technical solution: In order to realize the above-mentioned purpose of the invention, the technical solution adopted in the present invention is as follows:

A preparation method of a double-sided junction high-temperature superconducting BSCCO terahertz source: after pretreatment of a high-temperature superconducting BSCCO single crystal, quickly put it into a gold vaporizer to thermally evaporate a layer of gold film as the bottom electrode; then transfer it to a magnesium oxide substrate On the top, the side with the gold film is pasted with the side of the magnesium oxide substrate through polyimide glue, and placed on the baking table to bake and fix; then put it into the gold steamer again to evaporate a layer of gold film as the top electrode; Photolithography technology, photoetching a rectangular pattern on the top electrode; then put it into an ion beam etching machine, argon ion milling until the bottom electrode gold film is etched; then cover it with photoresist by hand coating photoresist method Part of the bottom electrode, dry the photoresist, put it into the ion beam etching machine again to remove the bottom electrode not covered by the photoresist; remove the photoresist on the surface, use silver glue and gold wire to lead out the upper and lower electrodes to form the final High-temperature superconducting Josephson source of terahertz radiation.

The pretreatment is to cleave a fresh and clean single crystal plane with scotch tape.

The gold film thickness of the bottom electrode is 100nm.

The magnesium oxide substrate has a thickness of 0.5 mm and has been polished on both sides.

The described baking on a baking table is fixed as placing on a baking table at 90° C. for 1 hour, so that the glue is completely cured.

In the preparation method of the double-sided junction high-temperature superconducting BSCCO terahertz source, the fixed high-temperature superconducting BSCCO single crystal needs to be cleaved again with scotch tape until a flat and fresh BSCCO single crystal plane is cleaved.

The gold film thickness of the top electrode is 100nm.

The area of the rectangular figure is 280*80μm ² .

The invention is based on a mature double-sided junction preparation technology, which is a mature BSCCO double-sided junction preparation technology, and the prepared sample power can reach tens of microwatts, and the frequency can reach 1THz. Using the BSCCO single crystal with gold evaporated on the upper and lower sides, a high-temperature superconducting BSCCO terahertz radiation source sample with an ideal thickness can be obtained by one-time photolithography and ion beam etching. At the same time, this technology replaces the glue-coated flipping in the original double-sided knot technology by manual mechanical flipping, which can improve the success rate of samples and shorten the sample production cycle.

Beneficial effects: Compared with the existing technology, the preparation method of the double-sided junction high-temperature superconducting BSCCO terahertz source of the present invention involves thermally evaporating the upper and lower electrodes of the BSCCO single crystal, and then passes through photolithography and ion beam etching once, that is, Samples with a thickness of several microns can be produced. The preparation process is simple and operable, which can shorten the sample preparation cycle and improve the success rate of sample preparation, and is conducive to the production of ultra-thick samples. The samples prepared by this preparation process have the advantages of continuous wave generation, tunability, good monochromaticity, and high power.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the double-sided junction high-temperature superconducting BSCCO terahertz source prepared by the present invention.

detailed description

The present invention will be further described below in conjunction with specific embodiments.

Example 1

Select a piece of high-temperature superconducting BSCCO single crystal 1, use scotch tape to cleave a fresh and clean single crystal plane, quickly put it into a gold steamer, and thermally evaporate a layer of 100nm thick gold film as the bottom electrode 3, select a flat BSCCO single crystal And transferred to a clean magnesium oxide substrate 2, the thickness of the magnesium oxide substrate is 0.5mm, and has been polished on both sides, and has a good thermal conductivity at low temperature, which is conducive to the conduction of low temperature from the cold head of the refrigerator to the sample. The sample was turned over by manual operation, and the side with the gold film was pasted together with the side of the magnesium oxide substrate through polyimide glue, and placed on a baking table at 90°C for 1 hour to fully cure the glue. Cleavage the fixed sample again with scotch tape until a flat, fresh BSCCO single crystal plane is obtained, and then put the sample into the gold steamer again to thermally evaporate a layer of gold film with a thickness of 100nm as the top electrode 4 . Then, through ultraviolet exposure lithography technology, a 280* ^80μm2 rectangular pattern is photoetched on the top electrode; then the sample is placed in an ion beam etching machine, and the sample is milled with argon ions until the bottom electrode gold film is etched; The method of hand-coating photoresist covers a part of the bottom electrode with photoresist, dries the photoresist, and puts it into the ion beam etching machine again to remove the bottom electrode not covered by the photoresist. The photoresist on the surface of the sample was removed, and the upper and lower electrodes were drawn out with silver glue and gold wire 6 to form the final high-temperature superconducting Josephson terahertz radiation source, as shown in Figure 1.

Samples with a thickness of 0.6-3.5 μm were prepared by the above method. In the experimental measurement, samples with a thickness greater than 2 μm have relatively large terahertz radiation power, which can reach tens of microwatts. Compared with traditional double-sided junction samples , the radiation power can be increased by up to an order of magnitude. The adjustable frequency range of the sample can reach 500GHz.

Claims (8)

1. a preparation method for two-sided knot high-temperature superconductor BSCCO THz source, is characterized in that: after getting the preliminary treatment of high-temperature superconductor BSCCO monocrystalline, puts into rapidly and steams golden instrument thermal evaporation one deck gold film as hearth electrode; Then transfer at magnesium oxide-based the end, have the one side of golden film to be pasted by polyimide glue and the one side at the magnesium oxide-based end, and be placed in that to dry baking on platform fixing; And then put into steaming golden instrument thermal evaporation one deck gold film as top electrode; Again by uv-exposure photoetching technique, top electrode makes rectangular graph by lithography; Then put into ion bean etcher, argon ion milling is until etch into hearth electrode gold film; Cover part hearth electrode with photoresist by the method for hand resist coating again, dry photoresist, again putting into ion bean etcher removal does not have hearth electrode covered by photoresist; Remove the photoresist on surface, draw upper/lower electrode with elargol and gold thread, form final high-temperature superconductor Josephson terahertz emission source.

2. the preparation method of two-sided knot high-temperature superconductor BSCCO THz source according to claim 1, is characterized in that: described preliminary treatment is the monocrystalline plane going out fresh clean by adhesive tape cleavage.

3. the preparation method of two-sided knot high-temperature superconductor BSCCO THz source according to claim 1, is characterized in that: the golden thickness 100nm of described hearth electrode.

4. the preparation method of two-sided knot high-temperature superconductor BSCCO THz source according to claim 1, is characterized in that: described magnesium oxide substrate thickness is 0.5mm, and through twin polishing process.

5. the preparation method of two-sided knot high-temperature superconductor BSCCO THz source according to claim 1, is characterized in that: described be placed in dry baking on platform be fixed as be placed in 90 DEG C baking platform on baking 1 hour, glue is solidified completely.

6. the preparation method of two-sided knot high-temperature superconductor BSCCO THz source according to claim 1, is characterized in that: the high-temperature superconductor BSCCO monocrystalline fixed need use adhesive tape cleavage again, until cleavage goes out smooth, fresh BSCCO monocrystalline plane.

7. the preparation method of two-sided knot high-temperature superconductor BSCCO THz source according to claim 1, is characterized in that: the thickness of the golden film of described top electrode is 100nm.

8. the preparation method of two-sided knot high-temperature superconductor BSCCO THz source according to claim 1, is characterized in that: described rectangular graph area is 280*80 μm ².