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得到極大的關注，然而金屬中熱電子在表面電漿子存在與作用下之載子傳輸行為與特性尚未被徹底理解，其相關之實驗結果與機制探討仍付之闕如。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、奈米製程與光電量測為基礎，以超短雷射脈衝光探討熱電子於多層「週期奈米金屬多邊構型-介電質-金屬」結構中之時間解析載子動態(time-resolved carrier dynamics)行為；包括外加電場與入射光強度對暫態吸收之影響、侷域表面電漿子致發表面電漿波之干涉行為、熱電子於不同外力激發作用下之弛豫時間、以及熱電子對光偏振之相依性等。除了以激發-探測(pump-probe)技術取得載子動態行為之理解外，我們亦將基於金屬三維能帶結構及晶體動量空間解析(k-resolved)與能量解析(energy-resolved)之群速度，建構熱電子於外力作用下之傳輸理論，並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，以進一步釐清金屬熱電子元件之效率極限因子。本計畫預期不僅將延伸學界對熱電子於表面電漿子存在或外力作用下，載子動態行為之知識，其結果亦同時評估金屬熱電子元件應用於超高速光通訊之可行性。 ;While metallic, hot-electron-based photoelectric conversion has been drawing much attention in the past few years, hot-electron carrier transport in periodically nanostructured metal in the presence of surface plasmons (SPs) or an applied electric field remains in negligence from the experimental standpoint. 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 nanostructured metal in multilayered metal-insulator-metal configuration using ultrashort laser pulses. Key areas to be investigated are field/light intensity effects in transient absorptance, transition from the localized surface plasmon (LSP) to the interference of SP waves, electron relaxation time, and polarization dependence of hot electron generations. Carrier transport theory based on quantum treatment using three-dimensional, realistic energy bandstructure and k-/energy-resolved group velocity in the presence of perturbed Hamiltonian will be developed and modified using empirical data acquired from time-resolved pump-probe measurements. In addition, opto-electro-thermal interactions in photoelectric conversion will also be investigated in order to reveal the potential limitation of the conversion efficiency. All the effort leads to extend the knowledge of non-ballistic transport of hot electrons in metallic, hot-electron-based devices and optimum device designs in favor of minimum inelastic collision losses. The research results will also provide sufficient data for assessing the potential application of such devices in ultra-high-speed optical communications.
