將太陽光能量轉換成電能的技術有很多種方式，本論文利用金屬表面電漿特性應用於金屬-絕緣層-金屬元件(metal-insulator-metal, MIM)，其可直接轉換可見光及近紅外光區的能量，並且可根據奈米光柵設計作吸收光譜調變，其光電轉換取決於以下兩種機制，第一是利用表面電漿子(Surface Plasmons, SPs)的小型電子震盪，可以與光有效的耦合，在電極上產生更高濃度的熱電子，第二是熱載子穿隧(hot carrier tunneling)理論機制。 傳統大多使用Kretschmann法耦合表面電漿，而本論文研究則將金屬層製作 成奈米光柵，如此不僅可以與其有相同的效果外，還可以縮小整體元件的尺寸， 並且使用有限時域差分法進行光柵設計，探討光柵週期性、深度等參數對表面電 漿光譜吸收趨勢。製程上，則使用雷射雙光束干涉微影法(interference lithography)製作光柵，相較於費時又昂貴的電子束微影法(E-beam Lithography, EBL)，干涉微影可以做到短時間大面積的週期性奈米結構優點。 最後在光電量測，除了觀察到表面電漿光譜吸收外，也成功量得元件在可見 光波段光電轉換現象，相較於平板MIM 元件，除了減少整體元件的大小，實驗 所得一維週期性光柵MIM 元件光電轉換效率超過平板MIM 元件三個數量級。 There are several techniques which can transit solar energy. In the study, the metal-insulator-metal device (MIM) based on the surface plasmonic effect was applied to convert solar energy with the spectrum ranges from visible to infrared into electricity. The benefit is that its absorption wavelength is tunable according to the period of its surface grating. The optoelectronic mechanism is when the light with the energy meet the surface plasmons generation, the hot carriers will be generated. These hot carriers will become photocurrent using tunneling effect or their energies are higher than the barrier. The traditional method of generating the surface plasmon resonant (SPR) was Kretschmann configuration. In the study, we developed the planar MIM device into nano-grating structure and designed the device using the Finite Difference Time Domain (FDTD) method. The advantages of the subwavelength grating structure were not only the same purpose of SPR generation but also the size reduction. We also investigated the SPR absorption spectrum resulted from the parameters of grating period, depth, duty cycle, light source angle and the thickness of MIM each layer. A two-beam-interference lithography was used to fabricate the nano-grating in the study. Compared with the expensive and time-consuming E-beam lithography, it took shorter time and achieved large-area periodic nanostructure. Finally, in the optoelectronic measurement, we observed the SPR spectrum and the optoelectronic transition phenomenon in MIM device. The efficiency of the 1D grating of MIM device was greater than planar MIM device for three orders of magnitude.
