探究新型光敏浮閘以實現非揮發性之光驅動存儲器件

Exploring Novel Photoactive Floating Gates Towards the Realization of Nonvolatile Photomemory Devices

廖明筠(Ming-Yun Liao)

指導教授 ： 闕居振

國立臺灣大學/工學院/化學工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202100096

摘要

資訊時代的來臨伴隨了物聯網、雲端技術及大數據的迅速發展，大量資料的產生帶動了資料中心的蓬勃建置，重視高傳輸、低延遲與廣域連接的5G以及邊緣計算等運用將成關鍵性技術，並引領下一波智慧科技的發展。在此基礎架構下，記憶體作為資料及程式碼的暫存空間，抑或是長期保存資料的中繼站，其需求將急遽增加且與時俱進。為滿足各界對非揮發性、低功耗、高耐用性以及高容量儲存的記憶體需求，許多研究除了從記憶體結構上進行改革，努力降低處理器與資料之間的延遲，藉以加快分析的速度外，也有突破性的研究轉而開發光記憶體，光記憶體是以光取代傳統的電驅動作為開關的記憶體元件，因具有超快的信號傳輸、寬廣頻域、電/光正交可操作性及大幅降低耗能的潛力，為記憶體與儲存解決方案帶來顛覆性的效能。
光記憶體除了提供一種新的元件應用，在應用上也提供更多新的可能性。因此，本研究致力於開發新興的光敏材料並探究其在非揮發性光驅動存儲器件的應用。有鑑於與三維鈣鈦礦材料相比，二維鈣鈦礦具有獨特的幾何結構、可調的光電性能和優異的環境穩定性等優點，使其在光電器件領域備受矚目。本研究首先選用Cs2Pb(SCN)2Br2作為研究對象並首次將其應用於光記憶體中，研究結果顯示利用Cs2Pb(SCN)2Br2與聚（4-乙烯基苯酚）之混合浮閘所建構的光記憶體可執行光致恢復行為，除了具有高達106之開/關電流比，也表現出穩定的資料保留能力和高度容錯的非易失性。此外，本研究在Cs2Pb(SCN)2Br2與聚乙烯吡咯烷酮之混合浮閘所構成的光記憶體中成功實現了完全光學驅動的光記憶行為，其中，浮閘的組成與型態及其對應之光學吸收性質是影響元件效率的關鍵因素。通過微調兩個特定的光源，完全光學驅動記憶體可成功地在沒有施加垂直電場的情況下於兩個迥異的電流態間作連續切換，展現出其重複讀寫功能之出色的數據耐久性與節能能力。
另一方面，有機材料因得益於本身分子結構的複雜性與多樣化、性能可調節性、機械柔韌性、溶液可加工性及較好的生物相容性，使有機半導體一直是方興未艾的研究領域。本研究主軸繼而聚焦在具有完美核-殼結構的共軛聚合物點，以利用有機浮閘來實現具多功能且定制化的高效光電存儲器件。研究結果發現藉由改變聚合物點的共軛結構，可有效調控光記憶體的記憶表現與光響應特性。此外，也證實了引入環鉑錯合物至聚合物主鏈能進一步將光記憶體的存儲類型從易失性存儲器轉換為非易失性閃存。最後，本研究在基於PFTBTAPtPy的光記憶體中達成非易失性多級存儲的功能，顯示出良好的數據保留能力與可靠的重複讀寫功能。值得注意的是，本研究所使用的混合浮閘均完全採用水溶液製成，所建構的光記憶體之材料與製程更為環保，為綠色元件之永續發展邁出了重要一步。

關鍵字

非易失性光記憶體 ； 多級存儲記憶體 ； 混合浮閘 ； 二維鈣鈦礦 ； 聚合物點 ； 水加工性 ； 光誘導恢復行為 ； 完全光驅動行為

並列摘要

The advent of the information age is accompanied by the rapid development of the Internet of Things, cloud technology and big data. And the generation of large amounts of data inevitably promotes the vigorous establishment of data centers. Therefore, 5G and edge computing that emphasize high transmission, low latency, and wide-area connections, will become key technologies and lead the next wave of smart technology development. In this context, memory plays an indispensable and irreplaceable role in providing temporary storage space and long-term relay stations for data. Therefore, the demand for memory will rapidly increase and keep pace with the times. To meet the high requirements of memory such as non-volatility, low power consumption, high endurance, and mass storage, numerous studies have reformed the memory structure in an effort to reduce the delay between the processor and data, thereby speeding up analysis speed. Besides, there are also many breakthrough studies that have turned to the development of photomemory. Photomemory is a storage element that utilizes light as the impetus to fully or partially substitute for traditional electrical operation. Due to its ultra-fast signal transmission, wide frequency range, electrically/optically orthogonal operability, and the potential for greatly reducing energy consumption, photomemory brings revolutionary performance to the advanced storage field.
In addition to providing a new device prototype, photomemory also opens up more new possibilities for functions and applications. Based on this, my research is devoted to developing new photosensitive materials and exploring their applications in nonvolatile light-driven storage devices. In view of the fact that compared with 3D perovskite materials, 2D perovskites with the collective advantages of unique geometric structure, adjustable photoelectric property and excellent environmental stability have received attention from all fields of optoelectronic devices. This study first selects 2D Cs2Pb(SCN)2Br2 as the research object and applies it to photomemory for the first time. The results show a demonstration of light-erasable photomemory with a hybrid floating gate composed of Cs2Pb(SCN)2Br2 and poly(4-vinylphenol), which not only exhibits superior distinguishability with an Ion/Ioff current ratio of 106 but also possesses stable data retention and highly fault-tolerant non-volatility. Moreover, an unusual fully optically driven memory behavior is achieved in the photomemory with a hybrid floating gate composed of Cs2Pb(SCN)2Br2 and polyvinylpyrrolidone. It is found that the morphological and optical properties are the key factors affecting the device performance. By fine-tuning two specific light sources, the device can be continuously switched back and forth between two distinguishable current states without an additional vertical electric field, thus showing outstanding data durability and energy-saving capability.
On the other hand, benefitting from the complexity and diversification of molecular structure, performance adjustability, mechanical flexibility, solution processability and better biocompatibility in organic materials, organic semiconductors have always been a field of research in the ascendant. This study is then focused on conjugated polymer dots with perfect core-shell structure and their derived organic floating gates to realize multifunctional and customized high-efficiency photomemories. The results show that the photomemory characteristics can be simply tuned by varying the acceptor moiety of the conjugated polymer. Moreover, forming cycloplatinated Pdots by inserting Pt complexes into the polymer backbone can further convert the storage type of derived photomemory from a volatile memory to a nonvolatile flash memory. Finally, the PFTBTAPtPy-based photomemory with the best memory performance shows a nonvolatile multilevel photo-recording capability, good data retention and reliable durability (100 WRER switching cycles with Ion/Ioff current ratio of > 103). Last but not least, all these Pdot-based floating gates are fully manufactured in water without using any toxic organic solvents. The materials and manufacturing processes of the studied photomemory are more environmentally friendly, which is an important step for the sustainable development of green technology.

並列關鍵字

Nonvolatile photomemory ； Multilevel memory ； Hybrid floating gate ； 2D perovskites ； Polymer dots ； Water processability ； Photoinduced recovery behavior ； Fully optically driven behavior

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