過去數年中雖然以「熱電子」(hot electrons)為基礎之光電轉換機制與元件製作已得到極大的關注，然而藉由奈米金屬異質接面耦合表面電漿子以提升光電轉換效率之研究尚未被提出，且奈米金屬中熱電子在表面電漿子作用下其傳輸(transport)行為與特性仍尚未被理解;相關之實驗結果與機制探討似仍付之闕如。本研究計畫擬以我們已建構之金屬內部光輻射理論、元件之設計、奈米製程與單波長光電量測為基礎，進一步以超短雷射脈衝光探討奈米金屬結構於異質接面電漿子耦合增強之光電轉換中，載子之時間解析動態行為。主要之研究項目包含轉換效率與結構對稱性、共振激發、共振耦合間之關聯;載子於奈米尺度金屬中之傳輸理論以計算載子之弛豫時間，及以自製之創新奈米金屬光電轉換元件作為平台，運用激發-探測(pump-probe)技術進行載子動態行為之研究。理論研究中將以電子波包與極短之交互作用時間為基礎，建構適於具極高載子濃度之材料於奈米尺度下之載子傳輸理論，並冀以弛豫時間之量測值進行理論之修正。此外於計畫之後期，亦將探究「光-電-熱」間之交互作用對熱電子之產生與非彈道(non-ballistic)傳輸之影響，以進一步釐清奈米金屬熱電子元件之效率極限因子。本計畫預期不僅將拓展學界對具極高載子濃度材料於奈米尺度下，載子動態行為之知識，研究所得之資訊亦可同時評估此一元件應用於非傳統光通訊波長進行短距離、超高速光連結之可行性。 ;While metallic, hot-electron-based photoelectric conversion has been drawing much attention in the past few years, enhanced photon energy conversion via heterogeneously-coupled surface plasmon plaritons (SPPs) and carrier transport in nano-metallic films/structures in the presence of SPPs remains relatively unexplored. On the basis of what we have developed in theoretical formalism and experimental demonstrations, the proposed research will explore the time-resolved carrier dynamics in nano-metallic films/structures using a novel hot-electron-based device enhanced by heterogeneously-coupled SPPs. Key areas to be investigated are the dependence of conversion efficiency enhancement on structural symmetry and resonant excitations/coupling, carrier transport formalism for carrier relaxation time in nano-metallic structures, novel device design and nanofabrications, transition from the localized surface plasmons (LSPs) to the interference of SPPs. Carrier transport theory based on an electron wavepacket and extremely short interaction time will be developed and shall be modified using empirical data acquired from time-resolved pump-probe measurements. In addition, opto-electro-thermal interactions in the photon energy conversion process will also be investigated in order to reveal the limiting factors of the conversion efficiency. All the effort leads to extending the knowledge of non-ballistic transport in nano-metallic, hot-electron-based devices and of optimum device designs in favor of minimum inelastic collision losses. The results will also provide sufficient data for assessing potential applications of such devices in non-telecom-window, short-reach, ultra-high-speed optical interconnects.
