選擇性雷射燒結摻雜鋁的氧化鋅奈米顆粒及其熱電元件應用

Abstract

技蓬勃發展的現代，能量的需求持續上升，如何利用廢熱發電是一個重要的議題。熱電薄膜材料可有效的在生活中收集廢熱來產生電能；其中摻雜鋁的氧化鋅材料高導電性、低成本、對環境友善的材料特性，是其為具潛力的熱電材料。有別於高真空製程導致成本高、耗費時間多，本研究利用波長532 nm、脈衝波時間8 ns的雷射，利用雷射高能量密度以及極短的加熱時間，搭配2D振鏡系統，高效和低成本的方式。將摻雜鋁的氧化鋅(1.5 at%)燒結沉積在石英上。 透過研究不同表面質量密度以及不同雷射參數的影響，得出最優化摻雜鋁的氧化鋅薄膜。表面質量密度 3.52 mg/cm2，其燒結出來的薄膜有較佳導電率。從不同掃描次數的實驗，可觀察到第一次雷射掃描主要是將材料能燒結成薄膜，可使薄膜附著力上升；後幾次的掃描是將薄膜進行退火，多次掃描會使薄膜連續性下降；再經過X光繞射儀的量測，可觀察到雷射燒結/退火會使得摻雜鋁的氧化鋅結晶變差。最終在表面質量密度 3.52 mg/cm2、脈衝重疊率98.5%、雷射能量794 mW、掃描一次時，可獲得最佳功率因子0.128 μWcm-1K-2。

The demand of energy rises, with increasing popularity and technology development. It is important to utilize waste heat to recycle the energy. Thermoelectric material films can effectively collect waste heat in life to generate electricity. Aluminum-doped zinc oxide(AZO) has suitable properties, like high conductivity, low cost, and environmentally friendly, and has been investigated for application of thermoelectric device. Different from the high cost and time-consuming high-vacuum process, this work use a nanosecond pulsed laser with a wavelength of 532 nm and a pulse duration of 8ns, to successfully sinter AZO nanoparticles on quartz, owing to laser’s high energy density and flexible patterning capability via galvanometer scanner system. Surface mass densities and laser process parameters, different results has been studied. The optimal surface mass density is founded to be 3.52 mg/cm2, which shows better conductivity. In the experiments of multiple laser scanning times, it can be observed that the first time of laser scanning is mainly to sinter AZO nanoparticles into a film, which can increase the adhesion of nanoparticles. The next few scans are to anneal the film, however, it is observed multiple scans will reduce film continuity. Moreover, X-ray diffractometer(XRD) measurement shows that multiple laser scan decrease the crystal peaks which implies worse crystal quality of AZO films. Finally, the maximum power factor of 0.128 μWcm-1K-2 can be obtained when the surface mass density is 3.52 mg/cm2, the overlap ratio is 98.5%, the laser energy is 794 mW, and one scan is performed.