Stable organic static random access memory from a roll-to-roll compatible vacuum evaporation process

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  • J.A. Avila-Niño
  • E.R. Patchett
  • D.M. Taylor
  • H.E. Assender
  • S.G. Yeates
  • Z. DIng
  • J.J. Morrison
An organic Static Random Access Memory (SRAM) based on p-type, six-transistor cells is demonstrated. The bottom-gate top-contact thin film transistors composing the memory were fabricated on flexible polyethylene naphthalate substrates. All metallization layers and the p-type semiconductor dinaphtho[2,3-b:2',3'-f] thieno[3,2-b]thiophene were deposited by thermal evaporation. The gate dielectric was deposited in a vacuum roll-to-roll environment at a web speed of 25 m/min by flash-evaporation and subsequent plasma polymerisation of tripropyleneglycol diacrylate (TPGDA). Buffering the TPGDA with a polystyrene layer yields hysteresis-free transistor characteristics with turn-on voltage close to zero. The static transfer characteristic of diode-connected load inverters were also hysteresis-free with maximum gain >2 and noise margin ∼2.5 V. When incorporated into SRAM cells the time-constant for writing data into individual SRAM cells was less than 0.4 ms. Little change occurred in the magnitude of the stored voltages, when the SRAM was powered continuously from a −40 V rail for over 27 h testifying to the electrical stability of the threshold voltage of the individual transistors. Unencapsulated SRAM cells measured two months after fabrication showed no significant degradation after storage in a clear plastic container in normal laboratory ambient.
Original languageEnglish
Pages (from-to)77-81
JournalOrganic Electronics
Volume31
DOIs
Publication statusPublished - 20 Jan 2016

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