JP5669103B2 - Thermoelectric thin film device - Google Patents

Description

  The present invention relates to a structure of a thermoelectric thin film device that converts thermal energy such as solar energy and automobile waste heat into electrical energy.

  Conventionally, as a thermoelectric device using the thermoelectric effect, as shown in a paper of Non-Patent Document 1 and Patent Document 1, a plurality of p-types are interposed between a pair of insulating substrates made of a glass substrate, a silicon substrate, a ceramic substrate, or the like. The mainstream is a structure in which semiconductor elements and n-type semiconductor elements are alternately arranged. In the thermoelectric device having such a structure, one end of each of the p-type semiconductor element and the n-type semiconductor element is joined and attached to one insulating substrate through an electrode, and the other end is joined to the other through the electrode. The structure is mounted on an insulating substrate. However, the thermoelectric device having such a structure has a problem that the manufacturing process is complicated because the thermoelectric element is sandwiched between a pair of substrates provided with electrodes. In addition, since the thermoelectric element is provided in the thickness direction, the thickness of the device is increased and the miniaturization cannot be achieved. Therefore, it is conceivable to use a thin film thermoelectric element. However, since there is not much temperature difference between the front and back of the substrate, a sufficient electromotive force cannot be extracted outside.

  On the other hand, as shown in Patent Document 2, a plurality of pairs of p-type thin film patterns and n-type thin film patterns are provided in series on one surface of an insulating substrate, and electrode pads are provided at both ends thereof. A thermoelectric thin film device having a structure provided as a thermoelectric thin film element has also been proposed. In this case, a temperature difference is formed on the two-dimensional plane of the insulating substrate to extract the electromotive force to the outside. Thereby, a manufacturing process becomes simple and it becomes possible to take out sufficient electromotive force outside.

JP2004-087913 JP 09-092892 A

G. Jeffry Snyder, James R. Lim, Chen-Kuo Huang, and Jean-Pierre Fleurial, Nature Materials Vol. 2 (2003) 528-531.

  However, in the structure of the thermoelectric thin film device as described above, since the thermoelectric thin film spreads in the plane direction, there is a problem that the contact area with the substrate increases, and the thermoelectric thin film and the substrate are easily peeled off mainly due to a difference in thermal expansion. .

  Conventionally, in the case of many industrial parts having a thin film structure, adhesion has been improved by providing a buffer layer between the thin film and the substrate. As a buffer layer, in the case of a normal thin film, a metal layer is generally used. However, in the case of a thermoelectric thin film device as described above, if a metal buffer layer is introduced to improve the adhesion between the substrate and the thermoelectric thin film element, the thin film thermocouple (thermoelectric thin film) is short-circuited electrically by the metal buffer layer. It has become common sense that the metal buffer layer cannot be used because the electromotive force cannot be taken out to the outside. In the case of Patent Document 2, the buffer layer is not provided in the thin film thermocouple, and the buffer layer is provided only in the electrode pad portion to prevent peeling of the portion.

  The present invention has been made in view of such a state of the art, and can improve adhesion between the substrate and the thermoelectric thin film, effectively prevent peeling of the thermoelectric thin film, and can efficiently obtain an electromotive force. Furthermore, it is an object to provide a thermoelectric thin film device that can be reduced in thickness and size.

  In order to solve the above-described problem of peeling, the present inventors have made extensive studies to improve the adhesion of the thermoelectric thin film to the substrate, and as a buffer layer disposed at the interface between the thermoelectric thin film and the substrate. By selecting a metal thin film that has been considered meaningless by conventional common sense and controlling the ratio of the electric resistance of the thermoelectric thin film and the electric resistance of the buffer layer to be within a certain range, the thermoelectric power can be generated without causing a short circuit. It has been found that the adhesion of the thin film onto the substrate can be improved and the electromotive force can be efficiently extracted outside, and the present invention has been completed.

That is, according to the present invention, in order to solve the above-mentioned problem, first, a plurality of p-type thin film patterns and n-type thin film patterns are alternately arranged on an insulating substrate, and different types of thin film patterns adjacent to each other are formed. A thermoelectric thin film device comprising a thermoelectric thin film element that is bonded and generates a temperature difference on a two-dimensional plane, wherein a buffer layer is provided at an interface between the insulating substrate and the thermoelectric thin film element, and the thermoelectric thin film element The ratio between the electrical resistance of the buffer layer and the electrical resistance of the buffer layer is defined to be 10 ^{−5 to} 0.4 , and the thickness of the buffer layer is 0.1 nm to 1 nm. A thermoelectric thin film device is provided.

Second, the thermoelectric thin film device according to the first invention is characterized in that the buffer layer contains 50 at% or more of Cr, Ni, Cu or Ti .

Thirdly, in the first or second invention, the buffer layer, the p-type thin film pattern, and the n-type thin film pattern are 30 in a vacuum atmosphere at 200 to 400 ° C. or in an inert gas after film formation. Provided is a thermoelectric thin film device which is heat-treated for ˜120 minutes .

The fourth, the third one of the invention from the first, the p-type thin film pattern is made of _Bi 0.5 _-Sb 1.5 -Te _3, the n-type thin film pattern is _Bi 2 -Sb _{2 The} thermoelectric thin film device is characterized by comprising _.7- Te _0.3 .

Fifth, in any one of the first to fourth inventions, there is provided a thermoelectric thin film device characterized in that condensed sunlight is used to form a temperature difference on a two-dimensional plane.

According to the present invention , the buffer layer is provided at the interface between the substrate and the thermoelectric thin film pattern so that the ratio of the electric resistance of the thermoelectric thin film and the electric resistance of the buffer layer is within a certain range, thereby enabling thin film technology and lithography. Providing a thermoelectric thin film device that can improve the adhesion between the thermoelectric thin film pattern produced by the technology and the substrate, can efficiently extract the electromotive force to the outside, and can be reduced in thickness and size. It becomes possible.
Moreover, the electrical resistance ratio can be more easily adjusted by defining the thickness of the buffer layer within a certain range.
In addition, despite the high conductivity, the adhesion to the substrate can be made more reliable by using a material containing a metal with high adhesion without short-circuiting the thermoelectric thin film element.
Further, by using the concentrated sunlight for forming the temperature difference on the two-dimensional plane, the electromotive force can be taken out to the outside at a lower cost and more efficiently.

It is a top view which shows an example of the linear thermoelectric thin film pattern of the thermoelectric thin film device by this invention. It is the XY sectional view taken on the line of FIG. It is a top view which shows an example of another radial thermoelectric thin film pattern. It is a top view which shows an example of the composite pattern of the thermoelectric thin film device which uses the some heat spot by this invention as a heat source.

  Hereinafter, embodiments of the present invention will be described in detail.

In the present invention, a plurality of p-type thin film patterns and n-type thin film patterns are alternately arranged on an insulating substrate, adjacent different thin film patterns are joined, and a temperature difference is formed on a two-dimensional plane. A thermoelectric thin film device provided with a thermoelectric thin film element for generating power, wherein a buffer layer is provided at an interface between the insulating substrate and the thermoelectric thin film element, and a ratio of an electric resistance of the thermoelectric thin film element to an electric resistance of the buffer layer is 10 It is characterized by being arranged so as to be ^{−5 to} 0.4 , and the thickness of the buffer layer is 0.1 nm to 1 nm .

  FIG. 1 is a plan view showing a thermoelectric thin film device 1 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line XY of FIG.

  The thermoelectric device 1 generates power using the thermoelectric effect and has a structure in which a thermoelectric thin film element 3 is provided on an insulating substrate 2. As shown in FIG. 1, the thermoelectric thin film element 3 includes linear p-type thin film patterns 4 and n-type thin film patterns 5 having a constant width, and the rightmost p-type thin film pattern 4 in the figure. One end 4 a and one end 5 a of the n-type thin film pattern 5 are joined to form a pair of thermoelectric thin film patterns, and the junction point is a hot junction 6. Further, the other end 5b of the n-type pattern 5 and the other end 4b of the p-type pattern 4 adjacent to the left are joined to form a pair of thermoelectric thin film patterns, and the junction point is a cold junction 7. Such a thermoelectric thin film pattern is repeatedly arranged, the electrode pad portion 8 is connected to the other end 4b of the rightmost p-type thin film pattern 4, and the electrode pad portion 9 is connected to one end 5a of the leftmost n-type thin film pattern 5. Is connected.

In the thermoelectric thin film device 1 of the present embodiment, the buffer layer 10 is disposed between the p-type thin film pattern 4 and the insulating substrate 2 and between the n-type thin film pattern 5 and the insulating substrate 2. The electric resistance of the buffer layer 10 is the ratio of the thermoelectric thin film pattern (p-type thin film pattern 4 and n-type thin film pattern 5) to the electric resistance, that is, (electric resistance of the thermoelectric thin film pattern) / (electric resistance of the buffer layer) is 10. It is specified to be ^{−5 to} 0.4. When the ratio is less than 10 ⁻⁵ , the adhesiveness with the insulating substrate 2 is not sufficient, and when it is greater than 0.4, the conductivity increases, which affects the efficient extraction of the electromotive force to the outside.

  As the buffer layer 10, a metal such as Cr, Ni, Cu, Ti or the like having strong bonding strength with the insulating substrate 2 or the thermoelectric thin film pattern, or an alloy or compound containing 50% or more of these metals can be used. In that case, it is considered that (electric resistance of thermoelectric thin film pattern) / (electric resistance of buffer layer) is within the above range. The thickness of the buffer layer 10 is preferably 0.1 nm to 100 nm, although it varies depending on the type of material. When the film thickness of the buffer layer 10 is in such a range, the adhesion with the insulating substrate 2 can be improved and the electromotive force can be efficiently taken out to the outside.

  For the film formation of the buffer layer 10, various conventionally known methods such as sputtering can be used.

In the thermoelectric thin film device 1 of the present embodiment, the thermal conductivity of the insulating substrate 2 is desirably small from the viewpoint of increasing the temperature difference between the hot junction 6 and the cold junction 7, that is, between the pn junctions, for example, 10 W / ( m · K) or less. The material of the insulating substrate 2 is not particularly limited as long as it has a small thermal conductivity as described above. For example, a SiO ₂ glass substrate or a material whose surface is made of SiO ₂ glass can be used. .

  As a material of the p-type thin film pattern 4 and the n-type thin film pattern 5, any combination of various conventionally known materials can be used as long as it exhibits a thermoelectric effect. For example, Bi-Sb-Te is used as 4 and Bi-Te-Se is used as the n-type thin film pattern 5. The film thicknesses of the p-type thin film pattern 4 and the n-type thin film pattern 5 are preferably 0.1 to 10 μm from the viewpoint of film formation time restriction, peeling, and electrical resistance. For forming these thin film patterns, various conventionally known methods such as sputtering can be used.

  The thermoelectric thin film device 1 of the present embodiment is 30 in a vacuum atmosphere of 200 to 400 ° C. or in an inert gas after forming the buffer layer 6, the p-type thin film pattern 4, and the n-type thin film pattern 5 for stress relaxation. It is preferable to perform heat treatment for about 120 minutes. If it does in this way, adhesiveness with the insulating board | substrate 2 can be improved more.

  In order to form a temperature difference between the hot junction 6 and the cold junction 7, the hot junction 6 serving as the high temperature portion is brought into a high temperature state by various methods. In order to bring the hot junction 6 into a high temperature state, a heating method is selected in consideration of the arrangement form of the hot junction 6. In this embodiment, in order to heat linearly, the method of condensing sunlight with a cylindrical lens etc. can be used, for example. When using sunlight, in order to improve the absorption efficiency of sunlight, you may make it provide a thin and linear carbon thin film etc. on the hot junction 6. FIG. The temperature difference between the high temperature part and the low temperature part is preferably 10 to 200 ° C.

  Although the present invention has been described based on one embodiment, the thermoelectric thin film pattern according to the present invention may be configured as shown in FIGS. The pattern of FIG. 3 is effective when a temperature difference is generated radially from a certain point on the substrate, and the pattern of FIG. 4 is effective when a plurality of heat spots are present on the substrate. Moreover, it is good also as a pattern which combined linear form and radial form.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[ Examples 1-2 , Reference Examples 1-2 , Comparative Example]
In order to pattern a thermoelectric thin film on a SiO ₂ glass substrate (thickness 1 mm, length 20 mm, width 26 mm), a p-type thermoelectric thin film Bi is formed by sputtering using a resist pattern (thickness 15 μm) produced by a lithography process as a mask. _{When 0.5-} Sb _1.5 -Te ₃ was formed to a thickness of 1 μm, the thermoelectric thin film was also peeled off when the resist was peeled off. Even if the n-type thermoelectric thin film Bi ₂ -Te _2.7 -Se _0.3 was formed to a thickness of 1 μm, it was peeled off in the same manner. Therefore, after providing a resist pattern made of the same material as described above for the mask using a lithography process, a Cr thin film is formed as a buffer layer to a thickness of 0.1 nm, 1 nm, 18 nm, 100 nm, and 1 μm, respectively. A p-type thermoelectric thin film (Bi _0.5 -Sb _1.5 -Te ₃ ) and an n-type thermoelectric thin film (Bi ₂ -Te _2.7 -Se _0.3 ) are sequentially formed to a thickness of 1 μm by sputtering. As a result, the film could be formed without peeling. It was found that even if annealing was performed in a vacuum atmosphere at 300 ° C. for 60 minutes, the thermoelectric thin film did not peel off and a thermoelectric thin film with high adhesion could be formed. The electrode pad portions themselves at both ends of the thermoelectric thin film patterns connected in series were also p-type or n-type thin films, and were produced at the same time as the thermoelectric patterns. When the electromotive force of these thermoelectric thin film devices was measured, the values shown in Table 1 were obtained. Table 1 also shows the relationship between the ratio between the electric resistance of the thermoelectric thin film and the electric resistance of the buffer layer and the characteristics. The temperature difference was 40 ° C. with a hot plate.

[Examples 3 to 5 ]
In the example described above, an example in which Cr is used as the buffer layer has been shown, but the case where Ni, Cu, and Ti are used in the buffer layer was also examined. Except for the type of buffer layer, both the thermoelectric thin film device and the fabrication process were the same as in the above example. When any buffer layer was used, the thermoelectric thin film was not peeled off, and a thermoelectric thin film with high adhesion was obtained. When the electromotive force of these thermoelectric thin film devices was measured, the values shown in Table 2 were obtained. The ratio of the resistance of the thermoelectric thin film and the resistance of the buffer layer estimated from the physical properties is shown in Table 2 as the resistance ratio. A temperature difference of about 70 ° C. was generated by heating the high temperature side with a hot plate.

  The present invention is a thermoelectric element for converting thermal energy such as solar energy and automobile waste heat into electric energy, and since it is a thin film, it leads to miniaturization and weight reduction, and has excellent portability. Can provide. Furthermore, it can also be used for power supply, temperature sensors, etc. using heat generated by the human body to mobile devices.

DESCRIPTION OF SYMBOLS 1 Thermoelectric thin film device 2 Insulating substrate 3 Thermoelectric thin film element 4 P type thin film pattern 5 N type thin film pattern 6 Hot junction 7 Cold junction 8, 9 Electrode pad part 10 Buffer layer

Claims (5)

A thermoelectric thin film in which a plurality of p-type thin film patterns and n-type thin film patterns are alternately arranged on an insulating substrate, adjacent different kinds of thin film patterns are joined, and a temperature difference is formed on a two-dimensional plane to generate power. A thermoelectric thin film device provided with an element, wherein a buffer layer is provided at an interface between the insulating substrate and the thermoelectric thin film element, and a ratio of an electric resistance of the thermoelectric thin film element to an electric resistance of the buffer layer is 10 ^{−5 to} 0 And a buffer layer having a thickness of 0.1 nm to 1 nm . The thermoelectric thin film device according to claim 1, wherein the buffer layer contains 50 at% or more of Cr, Ni, Cu, or Ti . The buffer layer, the p-type thin film pattern and the n-type thin film pattern are heat-treated for 30 to 120 minutes in a vacuum atmosphere at 200 to 400 ° C. or in an inert gas after film formation. The thermoelectric thin film device according to claim 1 or 2, characterized by the above. From claim 1, wherein the p-type thin film pattern is made of _Bi 0.5 _-Sb 1.5 -Te _3, the n-type thin film pattern is characterized in that it consists of _Bi 2 _-Sb 2.7 _{-Te 0.3} 4. The thermoelectric thin film device according to any one of 3 above. The thermoelectric thin film device according to any one of claims 1 to 4, wherein condensed sunlight is used for forming a temperature difference on a two-dimensional plane.

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