Thermoelectric Power Devices Based on InN Thin Films
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0973-BB04-09
Thermoelectric Power Devices Based on InN Thin Films Takayuki Matsumoto1, Shigeo Yamaguchi1, and Atsushi Yamamoto2 1 Kanagawa University, Yokohama, 221-8686, Japan 2 AIST, Tsukuba, 305-8568, Japan
ABSTRACT We have studied the temperature dependence of thermoelectric properties of amorphous InN thin films prepared by reactive radio-frequency sputtering. We fabricated 60-pair and 120-pair InN-chromel films, which were deposited on polyimide films. For the 120-pair device, the maximum open output voltage and the maximum output power were 210 mV and 65 nW, respectively, at temperature difference of 168 K. INTRODUCTION We have studied the thermoelectric properties and fabricated thermoelectric devices based on InN thin films targeting a mobile power generator using body-heat [1-3]. The use of unused thermal energy such as wasted heat in the environment is important from a viewpoint of energy and environmental problems. Thermoelectric conversion can directly change heat energy into electric energy, and does not need movable parts and not produce radiation such as radioactive material. On the other hand, nitrides are one of appropriate materials since they are sufficiently thin to be easily embedded in device. Moreover, they do not constitute toxic elements, which render them acceptable for a wide range of general uses. Therefore, we have studied the thermoelectric properties of nitride films. In addition, many electric devices have been integrated and downsized, and the technology to achieve low power supplies will be necessary. To operate such small-size devices, the power source is very important. In particular in terms of use of human body heat, we have studied thermoelectric power devices. In this study, we fabricated 60-pair and 120 pair InN-chromel thermoelectric roll devices. We have focused on the properties the thermoelectric device using InN thin films.
EXPERIMENT Thermoelectric materials can be evaluated with Pf=α2/ρ. Here, Pf, α, and ρ, are power factor, Seebeck coefficient, and electrical resistivity, respectivity. Pf is an important criterion, and value of 10-3 W/mK2 is a standard for practical use. InN thin films were prepared at room temperature or low temperature (100K) using liquid nitrogen on SiO2 substrate. Preparation method was reactive radio-frequency sputtering. The two films are referred to InN-1 and InN-2, respectively, below. We measured the temperature
dependences of electric resistivity (ρ), Seebeck coefficient (α), mobility, and carrier concentration of InN-1 and InN-2, and estimated Power factor (Pf). Furthermore, we have fabricated 60-pair and 120-pair thermoelectric InN-chromel device of Swiss-roll-type. Those devices were also prepared by means of reactive radio-frequency sputtering. They were deposited on polyimide film substrate. The patterns of the devices were fabricated using stainless-use- steel (SUS) masks prepared by photo-etching. The pairs of InN and chromel are in a serial line electrically. The device was setup such that both sides were on blocks made from st
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