以氧化鈷/氧化鋅製作p-n型壓電換能器之研究

Abstract

近年來，而由於生態環境的監測、災害預警系統的構建及智慧型生活空間的發展，多點分佈無線監測網路的佈置已成必然。然而，成熟的無線通訊技術和低功率消耗電路的發展，使得感測器的用電量大幅降低。且許多微機電系統結構與遠紅外線裝置因有電池更換不易、使用壽命不長等問題。故期望能夠將這些裝置整合為自給供電裝置。 本研究開發一可操作於低頻下之氧化鋅壓電換能器，氧化鋅薄膜採用射頻濺鍍法沉積於80μm厚度的軟性鈦基板上。藉由XRD、SEM、EDS及AFM之量測可得知，氧化鋅薄膜及氧化鈷薄膜皆分別成功的沉積於鈦基板及ZnO/Ti上，且利用本實驗的濺鍍參數，沉積於鈦基板上之氧化鋅呈現完美的c軸(002)優選取向，亦呈現緻密的表面結構。 另一方面，本研究亦利用n型氧化鋅半導體(ZnO)及p型氧化鈷半導體(Co3O4)之結合來製作一p-n型壓電換能器。兩者之接合使其介面形成一p-n 接面(p-n junction)，可想像成兩電容串聯，其阻抗降低，而使其電壓增加。並可藉由兩者能階之不同，使其壓電換能器在操作時於兩電極間形成一能階差，利用這樣的方式，可以有效的增加其發電效率。由實驗結果可得知，在相同應變下，p-n型壓電換能器的輸出電壓約為氧化鋅壓電換能器之1.5倍，最大功率輸出則約為10.6倍。

Enabling technologies for wireless sensor networks have gained considerable attention in research communities over the past few years. With the development of the low powered small wireless electronic devices, it is highly desirable, even necessary in certain situations, for wireless sensor nodes to be self-powered. This research develops a ZnO piezoelectric transducers that can be operated in low frequency. A ZnO films and Co3O4 films were well-deposited on flexible titanium (Ti) foil of 80 μm and ZnO/Ti structure. The ZnO deposited on Ti foil performed a best piezoelectric coefficient at the specific sputtering parameters, and showed a good textured structure via XRD, SEM, EDS and AFM measurements. However, we utilize n-type zinc oxide (ZnO) and p-type cobalt oxide (Co3O4) to develop a p-n type piezoelectric transducers. The Co3O4-ZnO interface forms a p-n junction. When two capacitors are connected in series, their overall capacitance is less than that of either. It can reduce the impedance to enhance the output voltage. Also, it can increase the difference in Fermi levels between two electrodes. This structure enhances the output power efficiently. From the experiment results, the output voltage and power of the p-n type piezoelectric transducer is around 1.5 times and 10.6 times of ZnO piezoelectric transducers at the same strain respectively.