Author/Authors :
Yang, J Joshua Hewlett-Packard Laboratories, USA , Miao, Feng University of California, USA , Pickett, Matthew D Hewlett-Packard Laboratories, USA , Ohlberg, Douglas A A Hewlett-Packard Laboratories, USA , Stewart, Duncan R University of California, USA , Lau, Chun Ning University of California, USA , Williams, R Stanley Hewlett-Packard Laboratories, USA
Abstract :
Metal and semiconductor oxides are ubiquitous electronic materials. Normally insulating, oxides can change behavior under high electric fields-through electroforming or breakdown -critically affecting CMOS (complementary metal-oxide-semiconductor) logic, DRAM (dynamic random access memory) and flash memory, and tunnel barrier oxides. An initial irreversible electroforming process has been invariably required for obtaining metal oxide resistance switches, which may open urgently needed new avenues for advanced computer memory and logic circuits including ultra-dense non-volatile random access memory (NVRAM)and adaptive neuromorphic logic circuits. This electrical switching arises from the coupled motion of electrons and ions within the oxide material, as one of the first recognized examples of a memristor (memory-resistor) device, the fourth fundamental passive circuit elementoriginally predicted in 1971 by Chua. A lack of device repeatability has limited technological implementation of oxide switches, however. Here we explain the nature of the oxide electroforming as an electro-reduction and vacancy creation process caused by high electricfields and enhanced by electrical Joule heating with direct experimental evidence. Oxygen vacancies are created and drift towards the cathode, forming localized conducting channels in the oxide. Simultaneously, O^-2 ions drift towards the anode where they evolve 02 gas, causingphysical deformation of the junction. The problematic gas eruption and physical deformation are mitigated by shrinking to the nanoscale and controlling the electroforming voltage polarity. Better yet, electroforming problems can be largely eliminated by engineering the devicestructure to remove bulk oxide effects in favor of interface-controlled electronic switching.
