Trilayer Graphene as a Candidate Material for Phase-Change Memory Applications
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Trilayer Graphene as a Candidate Material for Phase-Change Memory Applications Mohamed M Atwa1, Ahmed AlAskalany1, Karim Elgammal2.3, Anderson D Smith1, Mattias Hammar1, Mikael Östling1 1
Department of Integrated Devices and Circuits, School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, SE-16440 Kista, Sweden 2
Department of Materials and Nano Physics, School of Information and Communication Technology, KTH Royal Institute of Technology, Electrum 229, SE-16440 Kista, Sweden 3 SeRC (Swedish e-Science Research Center), KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
ABSTRACT There is pressing need in computation of a universal phase change memory consolidating the speed of RAM with the permanency of hard disk storage. A potentiated scanning tunneling microscope tip traversing the soliton separating a metallic, ABA-stacked phase and a semiconducting ABC-stacked phase in trilayer graphene has been shown to permanently transform ABA-stacked regions to ABC-stacked regions. In this study, we used density functional theory (DFT) calculations to assess the energetics of this phase-change and explore the possibility of organic functionalization using s-triazine to facilitate a reverse phase-change from rhombohedral back to Bernal in graphene trilayers. A significant deviation in the energy per simulated atom arises when s-triazine is adsorbed, favoring the transformation of the ABC phase to the ABA phase once more. A phase change memory device utilizing rapid, energyefficient, reversible, field-induced phase-change in graphene trilayers could potentially revolutionize digital memory industry. INTRODUCTION As the semiconductor industry continues to push the limits of Moore’s law, fabricating transistors that are smaller, faster, and more energy-efficient than ever before, a new bottleneck in computation has arisen in the form of data storage and retrieval speed. Universal memory, corroborating the fast, non-linear data retrieval of RAM, with the retention and storage density of hard disk drives has thusly become a research topic of increasing importance in both academic and industrial contexts1–3. Current candidates for universal memory include spin-torque transfer RAM (STT-RAM)4, oxideresistance phase change memory (PCM)3 and flash memory. Each suffer shortcomings that limit their potential as universal memory devices: STT-RAM lacks low dynamic energy2, requiring inconveniently large current densities (~1-10 mA)2 to switch memory states. Existing PCMs suffer from phase drift3, limiting the number of read-write cycles they can endure (~50,000 operations5). The need for a universal memory grows ever more pressing as innovations in processing power continually overtake those in data storage and retrieval2,3. Trilayer graphene (TG) assumes one of two stable stacking orientations, corresponding to two different phases: a Bernal, ABA-stacked phase and a rhombohedral, ABC-stacked phase6. These two phases have different electrical properties by virtue of their electroni
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