- 學位論文
鋯鈦酸鉛(PZT)壓電厚膜在雷射激發產生的壓電及焦電現象
Piezoelectric and pyroelectric effects on PZT template under laser
摘要
近期內施教授已經成功開發出壓電性/非壓電性雙層結構，可使用於微小分子與細胞的探測，如同使用手指探測有彈性的紙巾。這種結構受到外來的應力而變形時亦可產生電壓。本論文中，我使用了雷射光束作用於此雙層結構而產生電壓。我們假設雷射把雙層結構加熱，由於不同的膨脹係數會造成不同的收縮，而由壓電材料產生電的訊號。這種雙層結構在把熱能轉換成電力會有很大的潛力。 而在論文中，我們將探討這激發電壓的訊號可能的兩個機制，並試著去分離他們的影響。第一，當我們開啟雷射時，因為這種雙層結構有不同的膨脹係數，所以當雷射照到樣品時會造成，結構的形變或彎曲而產生壓電的訊號。另一種機制就是所謂的焦電效應，當鋯鈦酸鉛(PZT)受熱時，這壓電材料本身的極化量會產生改變，即可量到所謂的焦電電流。為了要清楚的分離這兩個機制對激發電壓的影響，我們將鋯鈦酸鉛(PZT)樣品上面兩層的鎳(Ni)都移除，然後度上一層薄薄的金(Au)，然後測得大約幾mV的電壓訊號。我們發現鍍一層薄薄金(Au)所得的激發訊號較以鎳(Ni)來的小，因為它對的光的反射較強，因此金(Au)可以擋掉較多的雷射使得激發電壓訊號變小。雖然我們成功的測得不同電極的激發電壓訊號，我們仍不能清楚的分離這兩個機制對激發電壓的影響，但可以確定有這兩個機制參雜其中。同時我們可以確定壓電性/非壓電性雙層結構是明顯的壓電現象。
並列摘要
Recently Prof. Shih’s group has developed a piezoelectric-nonpiezoelectric bilayer structure that can be used as a sensor for small molecules and cells as well as a finger to probe elastic properties of soft tissues. The same structure can also generate voltage when it is deformed by a mechanical force. In this thesis, I describe the generation of voltage by applying a laser beam to the bilayer structure. It is hypothesized that the laser can heat the sample and the differential shrinkage of piezoelectric and nonpiezoelectric layers can result in the stress of the piezoelectric layer causing charge generation. This type of device will have tremendous application potential in converting heat into electricity The induced voltage comes from two possible mechanisms. First, the laser heats up the PZT layer and the Ti layer and the difference in thermal expansion coefficient causes the cantilever to bend. Another possible mechanism is the pyroelectric effect. As the PZT is heated, the polarization changes resulting in the generation of induced voltage. In order to investigate whether the signal is due to the piezoelectricity effect, we examined the PZT layer only and removed the Ni electrodes on both sides of PZT layer. We then sputtered a thin Au layer as the electrodes on both sides and focused the laser beam on the new sample. We found only a few mV of induced voltage, much smaller than that obtained with the Ni electrodes. However, due to the similarity of thermal expansion coefficient of Ni and Au, and the lower reflectivity of Ni than Au, both pyroelectric effect and piezoelectric effect are possible mechanism for the observed behavior. More future study is needed to reach a clear conclusion about the mechanism. On the other hand, for the PZT layer with Ni electrodes bonded to a Ti layer, the mechanism is clearly piezoelectric.