異質整合分子/矽電子元件：高電荷密度與電致變色分子浮動閘極記憶體之開發

Abstract

異質整合分子/矽電子元件充分利用分子電子bottom-up與矽電子top-down的互補特性，是固態電子領域未來重要且新穎的研究方向，在浮動閘極非揮發性記憶體的應用上，我們過去成功地透過一非接觸式的矽積體電路-分子接面，對整合於固態元件內的分子氧化還原能態做出精確的控制，我們也成功地驗證一分子共振穿隧能障，改善記憶體寫入/保存時間的非對稱性，目前在異質整合元件的研究上，我們在國際間享有領先的地位，上述相關結果在Nature與IEEE Spectrum上皆以專文的方式被深入的報導。 豐富的分子特性與分子工程技術提供給我們在未來異質整合元件發展上無限的可能，建立在我們過去扎實的基礎上，本計畫最主要的目的在利用更多樣性的分子種類與氧化還原特性，以分子浮動閘極提升固態記憶體的效能與功能，例如negative-U分子因獨特的電子-聲子交互作用，儲存二個電子往往比儲存一個容易，能有效增加分子浮動閘極的電荷儲存量，改善元件的微縮能力。電致變色分子在不同氧化還原狀態下有明顯的著色現象，不但可作為一固態非揮發性記憶體，亦可作為一具有非揮發性影像儲存功能的顯示器，在未來電子紙的應用上非常具有潛力。本計畫預計研究主題包含：不同的control oxide介電層材料對分子氧化還原能態的影響。深入了解介面能態在異質整合元件中所扮演的關鍵角色。探討鑭系metallofullerene與染料分子ex-TTF獨特的negative-U特性與在高電荷密度異質浮動閘極元件上的應用。以電致變色viologen分子作為浮動閘極，開發新非揮發性影像儲存元件等。

Utilizing the complementary properties of bottom-up molecular electronics and top-down silicon nanoelectronics, heterogeneous integration of both techniques represents one of the most important and exciting research fields in solid-state devices. As for the applications of floating-gate nonvolatile memory, we have successfully demonstrated the precise control on molecular redox states in an integrated solid-state device through a noncontact high-impedence interface between integrated circuit and molecules. We have also implemented a molecule-engineered resonant tunnel barrier to improve the asymmetry between the program and retention time in nonvolatile memory. We are now one of the leading research groups worldwide in the heterogeneous molecule/silicon devices. Highlights of our achievements have been reported in both Nature and IEEE Spectrum in great detail. Rich physical/chemical properties and engineering know-how of organic molecules render abundant research opportunities on the future heterogeneous devices. By leveraging our existing expertise, the main objective in this project is to improve the characteristics and functionality of conventional nonvolatile memory by integrating diverse molecules with unique redox properties as the floating gate. For instance, negative-U molecules favor two-electron reduction over one-electron one because of the strong electron-phonon interaction. The charge density that may be effectively stored in the floating gate of negative-U molecules is expected to be higher, which is beneficial for device scaling. Electrochromic molecules exhibit characteristic coloring phenomena at different redox states. The heterogeneous device with the floating gate of electrochromic molecules is not only a solid-state nonvolatile memory, but also a novel nonvolatile display device for future low-power e-paper applications. The specific research topics covered in this project are: Effect of control-oxide materials on the redox states of molecules, in-depth understanding on the critical role of interface states in the heterogeneous device, unique negative-U characteristics and applications for high charge-density heterogeneous floating-gate memory of lanthanum endohedral metallofullerene and ex-TTF dye, novel nonvolatile display device based on the electrochromic viologen floating gate.