sin

, 3-2

Keywords:ThermoelectricPeltierSeebeckBiSeTe

edals.plic

from each other. The current dependence of the stage temperature of the NN-type Peltier device was

irect cthe t

of the

perature performance of semiconductor devices such as semicon-

cesses, which has led to circuit chips and small infrared sensorsthat require cooling using Peltier modules to increase their perfor-mance and improve their S/N ratio [6,7]. Miniaturized Peltier mod-ules can remove heat directly from an electronic component,preventing it from overheating and allowing higher operating per-formance. This improves the reliability and lifetime of electronicdevices.

peratures, typically 54, 72, and 94 C [9,10]. Transitions betweenapid temperature

type thermtric materials [1,2]: the use of bipolar materials leads to theof materials that can be used being limited to those withP-type or N-type conductivity; both types of electrical conduare seldom found in the same material.

In this paper, we report the development of a novel NN-typePeltier device with a temperature gradient using a pair of N-typethermoelectric materials, which may solve the above problem.We have targeted the application of our NN-type Peltier deviceas a PCR thermal cycler. No devices with a stage on which a tem-perature gradient can occur at a specic location have previously

Corresponding author. Tel./fax: +81 45 481 5661/7915.E-mail address: yamags18@kanagawa-u.ac.jp (S. Yamaguchi).

Microelectronic Engineering 129 (2014) 7780

Contents lists availab

ic

.eductor lasers for optical communication [35]. Moreover, therecent miniaturization of Peltier modules used in optical compo-nents has made them suitable for high-density packaging pro-

these temperatures must be conducted with a rgradient.

These Peltier modules use both P-type and N-http://dx.doi.org/10.1016/j.mee.2014.07.0210167-9317/ 2014 Elsevier B.V. All rights reserved.oelec-rangeeitherctivitymance of many compounds with the aim of improving theirthermoelectric properties for use in power generation and environ-mentally friendly cooling [1,2].

As an application of thermoelectrics, in ber optics andintegrated circuits, Peltier modules are used to stabilize the tem-

cycle for the polymerase chain reaction (PCR) [9]. The PCR is anextremely important and well-established technique for DNAamplication and is widely used in genome sequencing, forensics,and the diagnosis of various diseases [9]. For a successful PCR, pre-cise temperature control is required between three different tem-1. Introduction

Thermoelectricity refers to the delectricity or vice versa. Research inexpanded to include the analysisinvestigated and the temperature difference on the stage was 21.4 C at a current of 24 A. To analyzethe device performance, the heat balance for the Peltier device composed of two N-type bulks wasobtained by considering the effects of the electric resistance and thermal conductance of the central elec-tric wire between the two N-type materials. The Seebeck coefcient, total resistance, total thermalconductance, and heat absorption were obtained by tting to be 4.24 104 V/K, 2.55 104X,0.159 W/K, and 1.13 W, respectively, which were in good agreement with those estimated using litera-ture values. Moreover, we fabricated an NN-type thermoelectric power device with a temperature differ-ence of 70 K, an open voltage of 16 V, and a maximum power of 8 mW at a current of 0.9 A.

2014 Elsevier B.V. All rights reserved.

onversion of heat intohermoelectric eld hasthermoelectric perfor-

The miniaturization of devices, including microuidics andmicro electrophoresis devices, has also attracted interest in theelds of analytical chemistry and bioengineering [8]. These devicesare particularly suitable for deoxyribonucleic acid (DNA) analysis.In these devices, Peltier modules are used, especially in the thermalAvailable online 1 August 2014ference can be induced by altering the current, targeting a rapid amplication system for deoxyribonu-cleic acid (a thermal cycler for the polymerase chain reaction). The currents in the two circuits differFabrication of a unipolar Peltier device uthermoelectric materials

Shigeo Yamaguchi , Hideyuki HommaDepartment of Electrical, Electronic, and Information Engineering, Kanagawa University

a r t i c l e i n f o

Article history:Received 1 May 2014Received in revised form 27 June 2014Accepted 24 July 2014

a b s t r a c t

We proposed and fabricatthermoelectric bulk materibulks. We introduce an ap

Microelectron

journal homepage: wwwg a pair of N-type

7-1 Rokkakubashi, Kanagawa-ku, 221-8686 Yokohama, Japan

an NN-type Peltier device composed of two small N-type Bi2Se0.37Te2.36This structure includes an additional electric wire between the two N-typeation of the NN-type Peltier device as a stage on which a temperature dif-

le at ScienceDirect

Engineering

l sevier .com/locate /mee

been reported. This feature is useful for preparing rapid and precisescreening conditions such as the temperature conditions for thePCR: PCR thermal cyclers in general include a conventional Peltierdevice that is required to change the temperature rapidly betweenthree different temperatures. However, it is ideal for the PCR pro-cedure if these different temperatures are xed. Our proposedNN-type Peltier stage is suitable for this application.

To realize rapid PCR systems, their miniaturization has so farbeen performed using a microreactor, capillary, or silicon technol-ogy [1114]. Although lm-based Peltier devices are important inelectronics, they have not yet been employed in commercial use.We consider that lm-based devices can be developed as an exten-sion of bulk devices. Thus, we provide a new technique for usingbulk devices that can be applied to lm-based devices.

tacted with the electrode bridging the two NN-type bulks. This

DTch c 2 tKt 3

The tting parameters a, Rt, Kt, and Q were obtained to be4.24 104 V/K, 2.55 104X, 0.159 W/K, and 1.13 W, respec-tively. To verify these values, they were estimated using somevalues in the literature and calculated values [18]: a, Rt, and Ktwereestimated to be 4.20 104 V/K, 1.65 104X, and 0.0712W/mK, respectively. For the N-type material, a/2 (the Seebeck coef-cient) was 2.10 104 V/K, q (electric resistivity) was1.0 105Xm, and j (thermal conductivity) was 1.4 W/mK [18];for the copper wire, q was 1.68 109Xm and j was 401W/km,where the copper wire was 100 mm in length and 3.5 mm in dia-meter. For the heat absorption, a value of 1.6 Wwas experimentallyobtained for a PN-type Peltier device at a current of 24 A and a tem-perature difference of 10 K. These parameters are summarized in

78 S. Yamaguchi, H. Homma /MicroelectroFig. 1(a). Structure of proposed NN-type Peltier device.structure reduces the electric resistance of the device. Moreover,as described below, two independent currents are used to providetemperature difference on the electrode itself. Using this structure,the top metal stage can be cooled or heated by changing the cur-rent polarity. The amounts of heat absorption and heat dissipationcan be changed by varying the current I. Each N-type bulk is Bi2Se0.37Te2.36 (3.2 3.2 1.7 mm). The thickness of the metal stageon which both N-type bulks were set was 0.2 mm. The contactbetween the stage and the wire was formed using solder. As shownin Fig. 1(b), through-holes were made in the hot-side electrodesmade from copper, through which water ows to enhance heat dis-sipation. The temperatures on the cold and hot sides were mea-sured when the current was changed from 0 to 24 A inincrements of 2 A.

3. Results and discussion

Fig. 2 shows the current dependence of the stage temperature ofthe NN-type Peltier device shown in Fig. 1(a). The temperature ofthe cold side of the metal stage, Tc (circles), and that of the hot side(the electrode through which water ows), Th (squares), were 17and 10 C, which corresponded to room temperature and the2. Experimental

Fig. 1(a) shows the proposed unipolar Peltier device fabricatedwith only N-type materials. This structure features an additionalelectric wire between two N-type bulks. The PN-sandwich struc-ture, which we previously developed [1517], gave us the inspira-tion for this NN-type structure. In this device, unlike the device in[17], the central electric wire in the actual device is directly con-Fig. 1(b). Detailed structure of electrodes and heat dissipation in Fig. 1(a).temperature of the owing water, respectively. The stage tempera-ture reached 1.9 C at a current of 24 A, and the temperature differ-ence between the cold side and the hot side (triangles) was10.4 C. Here, the temperature difference DTch is dened asDTch Tc Th.

Analogous to the heat balance for a PN-type Peltier device [1,2],the heat balance for a Peltier device composed of two N-type bulksis given by

Q aTcI 12RI2 KTh Tc; 1

where Q , a 2aN, Tc , R 2RN, and K 2KN are the heat absorp-tion, the Seebeck coefcient for the two thermoelectric materials,the temperature of the cold side, the internal resistance of thedevice, and the thermal conductance between the cold and thehot sides, respectively. The subscript N represents an N-type mate-rial, and the properties of the two N-type materials are assumed tobe the same here. Moreover, we must consider the effects of theelectric resistance and thermal conductance of the central electricwire between the two N-type materials. After some modicationof Eq. (1), we obtain the expression

Q aTcI 12RtI2 KtTh Tc; 2

where 1=Rt 1=R 1=Rwire and Kt K Kwire. Here, Rwire and Kwireare the electric resistance and thermal conductance of the centralwire, respectively.

The solid line shown in Fig. 2 was obtained by tting the plotteddata to Eq. (3), which was derived from Eq. (2), where Tc was set to282 K, which was the average temperature for currents from 0 to24 A.

aT I 1R I2 Q

0 5 10 15 20 25-15

-10

-5

0

5

10

15

20

Current [A]

Tem

pera

ture

[oC

]

: Cold side: Hot side: Temperature difference

Tc

Th

Tc-h=Tc-Th

Fig. 2. Current dependence of temperature of NN-type Peltier device.

nic Engineering 129 (2014) 7780Table 1.On the whole, the tted and estimated values are in relatively

good agreement. However, the deviation between the tted and

estimated values is larger for Rt and Kt. This strongly indicates thatthe serial contact resistance and the heat passing through the cen-tral electric wire affect the performance of the NN-type Peltierdevice.

Next, we describe another application of the NN-type Peltierdevice, varying the temperature on the metal stage itself, as shownin Fig. 3.

In this type of Peltier device, the currents I1 and I2 in the two cir-cuits differ from each other as shown in Fig. 4(a). If the current isdifferent in each N-type material, a temperature difference isinduced on the metal stage. Moreover, the temperature differenceon the stage, DT12 T1 T2, i.e., the temperature gradient, can bealtered by changing the current. We experimentally investigatedthe current dependence of DT12.

The experimental data for the device shown in Fig. 4(a) isdepicted in Fig. 4(b).

Current I1 was xed to 24 A for the heating operation and cur-rent I2 was varied from 0 to 24 A for the cooling operation. In spiteof I1 being xed at 24 A, the temperature on the hot side of thestage decreased with increasing current I2, suggesting the transferof heat. Generally, DT12 gradually increased with increasing cur-rent I1.

With increasing current I1, the temperatures on both the hotside (T1) and the cold side (T2) decreased, while DT12 increased.This indicates that the decrease in temperature on the cold sideis larger than that on the hot side. Consequently, using this effect,a temperature difference can be induced on the stage. DT12 was21.4 C at a current I1 of 24 A.

In the next experiment, current I2 was xed at 24 A and I1 wasvaried from 0 to 24 A as shown in Fig. 5(a). The experimental data

are plotted in Fig. 5(b). At a current of 0 A on the hot side, the tem-perature on the hot side (T1) was 10.2 C and that on the cold side(T2) was 2.8 C. With increasing current I2, both temperaturesincreased and DT12 simultaneously increased. DT12 was a maxi-mum of 21.7 C at a current I1 of 24 A.

Finally, we introduce an application of our NN-type Peltierdevice as a thermoelectric device, where a temperature differenceof 70 K was induced between the top stage and the electrodes (notshown here). From the temperature dependences of the outputvoltage and output power of an NN-type thermoelectric powerdevice employing the NN-type Peltier device, the maximum powerwas 8 mW at a current of 0.9 A and the open voltage was 16 V.

4. Conclusion

Peltier device shown in (a).

Fig. 5(a). NN-type Peltier device with temperature difference on top stage. I2 wasxed to 24 A, and I1 was varied from 0 to 24 A.

0 5 10 15 20 250

20

40

60

80

Current [A]

Tem

pera

ture

[oC] : Cold side

: Hot side

: T1-2=T1-T2 T1

T2

T1-2

Fig. 5(b). Current (I1) dependence of temperature difference on stage for NN-typePeltier device shown in (a).

S. Yamaguchi, H. Homma /MicroelectroTable 1Pamareters obtained by tting and estimation.

a [V/K] Rt [X] Kt [W/K] Q [W]

Fitted 4.24 104 2.55 104 0.159 1.13Estimated 4.20 104 1.65 104 0.0712 1.6

Fig. 3. NN-type Peltier device with temperature difference on top stage.Fig. 4(a). NN-type Peltier device with temperature difference on top stage. I1 wasxed to 24 A and I2 was varied from 0 to 24 A.0 5 10 15 20 250

20

40

60

80

Current [A]

Tem

pera

ture

[oC]

: Cold side: Hot side

: T1-2=T1-T2

T1

T2

T1-2

Fig. 4(b). Current (I2) dependence of temperature difference on stage for NN-type

nic Engineering 129 (2014) 7780 79We proposed and fabricated an NN-type Peltier device com-posed of two N-type thermoelectric materials. We also fabricated

a stage on which a temperature difference was realized that couldbe changed by altering the current. Our results demonstrated thateven thermoelectric materials with either N-type or P-type electri-cal carriers can be used to fabricate thermoelectric Peltier andSeebeck devices.

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80 S. Yamaguchi, H. Homma /Microelectronic Engineering 129 (2014) 7780

Fabrication of a unipolar Peltier device using a pair of N-type thermoelectric materials1 Introduction2 Experimental3 Results and discussion4 ConclusionReferences