Poly(styrene-b-4-vinylpyridine)自組裝塊式高分子薄膜應用於非揮發性記憶體的研究

Abstract

將Poly(styrene-b-4-vinylpyridine)自組裝塊式高分子薄膜材料應用在非揮發性記憶體上，製備元件結構分別為Al/Polymer/Al和ITO/Polymer/Al的三明治元件結構，量測其電性的差異。Poly(styrene-b-4-vinylpyridine)為單層的薄膜時(約30 nm)，薄膜的形貌會和塊材有所不同，Poly(styrene-b-4-vinylpyridine)塊式高分子因為相分離自組裝產生奈米結構，具有大面積週期性規則的排列，可製備高密度的資料儲存元件。用不同的儀器分析結果發現Al/Polymer/Al和ITO/Polymer/Al兩種不同的元件結構有不同的傳導的過程，但是主要都歸類在導線機制(filament mechanism)。 對Al/Polymer/Al元件結構而言，實驗所得之I-V特性曲線與空間電荷場和歐姆定律有關，on/off ratio可達到104，並且記憶時間可達到1.5小時；另外地，對ITO/Polymer/Al元件而言，當驅動電壓施加之後，金屬因為電場作用而進入到P4VP中而產生金屬導線，使元件導通，調控on state的限制電流，on/off ratio最高可以達到106，寫入和抹除的時間可達到微秒(us)的狀態，有超過4個小時的記憶時間。此兩種元件屬於兩種不同的傳導機制，分別使用不同的方法證明。另外還分別比較PS-b-P4VP自組裝塊式高分子和P4VP高分子之間的I-V特性曲線有什麼不同的差異。

Studying on a Nonvolatile Memory Device based on poly(4-vinylpyridine) nanodomains of a poly(styrene-b-4-vinylpyridine) diblock copolymer thin films. We fabricated Al/Polymer/Al and ITO/Polymer/Al sandwiched structure to examine the electrical behavior, respectively. The PS-b-P4VP monolayer thin film (ca. 30 nm) develops hexagonally structure, which is different from its cylindrical bulk morphology. Block copolymers have unique associative properties that facilitate self-assembly into a variety of ordered structures with nanoscale periodicities. The block copolymer domains are useful as fabrication of high density information storage media. Studies proposed that the ON/OFF switching of the devices is mainly governed by a filament mechanism. For the Al/Polymer/Al device structure, the I-V curve can be simulated by a combination of the space charge limited model and the ohmic model. This device show on/off ratio (104), and retention time(1.5 hours). For the ITO/Polymer/Al device structure, the switch voltage applied, the metal atom drifted into the P4VP domains to form the metal filament. The device show high on/off ratio (106), fast programming speed (us), and long retention time (>4 hours). Additional, we compared the P4VP nanodomains of PS-b-P4VP block copolymer and P4VP homo-polymer with current-voltage (I-V) of the memory behavior.