交互作用對於螢光奈米鑽石光學特性之影響

Abstract

本論文在研究操作奈米鑽石中的發光缺陷、與其他缺陷和鑽石晶格間的交互作用關係。鑽石中的氮原子與碳空缺形成原子尺度的缺陷十分重要，如NV0、NV-、N3、 以及H3等等缺陷中心。這些聚合的缺陷在室溫下存在獨特的光學與自旋特性。在這裡我們研究不同型態之缺陷、發光缺陷以及鑽石經格彼此間的電荷轉移方法。我們首先研究不同粒徑大小之螢光奈米鑽石的光學性質，我們發現發光缺陷的密度將被較小粒徑的表面缺陷所增強。 接著，NV 缺陷中心的電荷態之光游離和複合過程在532奈米的光激發下被觀察到。而N3缺陷中心僅觀察到雙光子解離的游離過程而沒有復合過程。這機制上的不同點，可應用具於有堅韌性以及重現性之可區隔多重態性質的非揮發性單寫多讀記憶體(WORM)。 為了更深入研究注入電荷與光游離電子的交互作用，我們製作了導電的氫端奈米鑽石裝置。我們注意到在裝置上施加偏壓不只調控了鑽石的費米能階、更提供了額外的自由電子，加速N3缺陷中心的光解離速率與NV0缺陷中心的複合速率。這顯示出不同發光缺陷間彼此電荷訊息可交換的巨大淺力。 奈米鑽石中的表面缺陷，在發光缺陷中心與其能級間、提供電子新的鬆弛路徑。我們展示一個利用NV缺陷中心裡，電子自旋與微波彼此交互作用的遙控微波偵測技術。震盪的磁場增加了自旋多重性發生的機率，因此、電子自旋的系統間跨越將趨於發生。並且，在塊材鑽石中未曾觀察到的、發光缺陷與表面缺陷的電荷傳遞，將使奈米鑽石之光激螢光的強度淬滅或增強。我們同時也藉由微波強度掃描的方法觀察到未知的NV+存在之證據。這新穎的物理效應對於偵測微波信號，提供一個不需走線連結、且敏感度與可信度高的新方向。更詳細的遠程微波偵測器特性研究，顯示出高品質的表現，並且具有重建材料介電常數影像、無關入射光強的高解析度之能力。 在我們研究中，我們展示了奈米鑽石中、不同電荷態缺陷與不同缺陷間的操作機制。顯示出在高複雜性的奈米鑽石缺陷中，控制電荷傳輸的潛力。

The properties of color centers in nanodiamonds and their modification through interactions with other defects and the diamond lattice are investigated in this thesis. Atomic-scale defects in diamond that comprise nitrogen atoms and carbon vacancies produce important color centers such as NV0, NV-, N3, and H3 centers. Such defect aggregates exhibit unique optical and spin properties at room temperature. Here we investigate several methods of charge transfer between nuclear states, between different types of defects, and between color centers and diamond lattice. We first investigate the optical properties of fluorescent nanodiamond with different sizes. We notice that the enhanced contribution of surface defects in smaller nanoparticles affects the densities of color centers. Second, the photoionization and recombination processes of NV charge centers are observed with 532 nm excitation. We observe a two-photon-assisted dissociation photoionization process in N3 center but recombination process. The difference in mechanisms was applied to nonvolatile write-once read many (WORM) memory with multiple distinct memory levels, which exhibited high robustness and reproducibility. To investigate the interaction between injected charges and photoionized electrons, conductive hydrogen terminated nanodiamond electronics are fabricated. We notice that the bias of the device would not only tune the Fermi level of nanodiamond but also supply additional free charges, resulting in faster photoionized rate in N3 and higher recombination rate in NV0. It reveals a huge potential for charge communication between different colorful defect states. Surface defects on nanodiamond provide new relaxation pathways between surface defect levels and colorful defect centers for electrons. We demonstrate a technique for remote microwave (MW) detection based on an unexpected interaction effect between spins and microwaves in NV centers. An oscillating magnetic field increases the probability for the spin multiplicity occurrence. Thus, intersystem crossing process tends to occur and charge transfer between colorful defect centers and surface defects results in PL quenching and enhancement which have not been observed for bulk diamond. We also discover evidence for the existence of the previously unexplored NV+ state during MW sweeping. This novel physical effect provides a sensitive and reliable route to detect microwave signals without an electrical connection. A detailed characterization of this remote microwave sensor shows high performance and the ability to reconstruct the dielectric constant independent of light intensity with high-resolution. Using our approach, unique mechanisms of defect and charge manipulations in nanodiamonds are demonstrated, revealing the potential for charge transfer between complex diamond defects.