THESIS
2018
xx, 71 pages : illustrations ; 30 cm
Abstract
With strikingly high speed, data retention ability and memory density, Resistive RAMs
have emerged as a forerunning non-volatile memory. In this work, we report an ultra-fast
switching electron-transport-assisted ECM (E
2CM) cell using three-dimensional arrays of
quantum wires (QWs) made of methyl ammonium lead iodide (MAPbI
3) perovskite as solid
electrolyte and silver (Ag) as AE. The QWs have diameter ~ 10 nm approaching exciton Bohr
radius thus demonstrating optical band-gap widening due to quantum confinement. The
mechanistic study has confirmed that the electrical switching behavior in MAPbI
3 QWs and
nanowires (NWs) originates from electrochemical reduction of Ag cation at aluminum (Al) CE
and in body of QWs assisted by electron transport, leading to fast formation of Ag fila...[
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With strikingly high speed, data retention ability and memory density, Resistive RAMs
have emerged as a forerunning non-volatile memory. In this work, we report an ultra-fast
switching electron-transport-assisted ECM (E
2CM) cell using three-dimensional arrays of
quantum wires (QWs) made of methyl ammonium lead iodide (MAPbI
3) perovskite as solid
electrolyte and silver (Ag) as AE. The QWs have diameter ~ 10 nm approaching exciton Bohr
radius thus demonstrating optical band-gap widening due to quantum confinement. The
mechanistic study has confirmed that the electrical switching behavior in MAPbI
3 QWs and
nanowires (NWs) originates from electrochemical reduction of Ag cation at aluminum (Al) CE
and in body of QWs assisted by electron transport, leading to fast formation of Ag filament in
material resulting in drastic conductivity increase. Intriguingly, it was also discovered that
when downscaling the wire diameter from NW to QW, the device ON/OFF ratio was increased
by 1,000 times rendering QWs much more energy efficient than NW and TF devices. Careful
switching speed measurement shows that the QW device has ~ 1.5 ns ultra-fast switching speed,
which is 20,000 times faster than the commercially available Phase–Change Memory (PCM)
based R-RAM system and also much faster than many conventional oxide, sulphide and
selenide based ECM devices. The devices made with the electrically isolated QWs with density up to 2×10
11 /cm
2 demonstrated unprecedented scalability down to 14 nm memory cell lateral
dimension and 76.5 nm
2 effective device area for single bit storage, which is even smaller than
the effective single bit storage area of the state-of-the-art tri-layered-cell (TLC) based 3D
NAND and PCMs. Moreover, the QW based device exhibited multi-bit storage and hence the
unparalleled ultra-high storage density of 13.07 Giga-bit (Gb) /mm
2 is potentially achievable.
The memory device also demonstrated optical response to light illumination, thus enabling
device optical programmability among different levels of LRSs.
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