First principles study on the resistive switching of cu x o based memory device
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First principles study on the resistive switching of cu x o based memory device

Introduction

Recently, transition metal oxides(TMOs) based resistive change random access memory (ReRAM) has attracted great attention due to their significant potential as the next generation memory device to replace Flash memory. These devices can be easily made and have a good scaling capacity down into the sub-20 regime. Among them, Cu2O metal-insulator-metal memory device has been studied a lot. Several models are proposed, among which the filament model is well accepted. But the micro-mechanism of this kind of switching remains unclear.

A general filament model: typical I-V behavior of such a device

Set:

low resistive state(LRS)

Reset:

high resistive state(HRS)Applied Physics Letters 91, 123517 (2007)

  • Defect properties of Cu2O

  • PHYSICAL REVIEW B 79, 035205 (2009) PRL 103, 096405 (2009)

  • Different theoretical methods show the same fact that in Cu2O, VCu is really easy to form and Cu2O is a natural p-type semiconductor.

  • We believe that VCu plays an important role in the switching process and the motion of Cu ion in this material is critically related to the formation and broken of the filament.

Cu2O

Cu

M

connected

First-principles study on the resistive switching of CuxO based memory device

Cu2O

disconnected

M

Cu

III. The migration potential of VO

I. The migration potential of VCu and V-1Cu

1.39

0.25

The migration potential is estimated to be about 1.39 eV for VO, which means the

oxygen vacancy is difficult to walk in Cu2O and this is different from the case in

ZnO and In2O3, etc.

IV. The migration potential of Cu ions from Cu2O to Cu electrode (Cu (111)/Cu2O(111) interface

Ji-Hui Yang, Shiyou Chen, and X.G. Gong

Department of Physics and MOE laboratory for computational physical sciences, Fudan University, 200433

Su-Huai Wei

National Renewable Energy Laboratory, Golden, Colorado 80401, USA

The migration potential is estimated to be

about 0.25 eV for VCu and 0.30 eV for

V-1Cu ,which means copper vacancy is

very easy to move in Cu2O.

0.30

0.11

0.92

II. The migration potential of Cuio and Cu+1io

A Cu ion needs to overcome a barrier of 0.92 eV to move from Cu bulk to Cu2O

while the barrier is only 0.11 eV for It moves from Cu2O to Cu bulk.

0.25

V. Proposed model based on the above understanding

The migration potential is estimated to be

about 0.25 eV for Cuio and 0.38 eV for

Cu+1io, which shows Cu ion is also very

easy to move along the octahedral

interstitial sites. However, the formation

energy of defect Cu+1io is relative large

compared to that of VCu and this will let

us exclude the possibility that Cu ions

move between octahedral interstitial sites.

0.38

  • The switching between HRS and LRS is based on VCu (Cu atom or ion) migration:

  • When the Cu ions are driven under a positive voltage to move to the Cu electrode,

  • many VCu are created in Cu2O and they form a conductivity path between BE and

  • TE, the film exhibits LRS;

  • When the Cu ions are driven under a negative voltage to leave the Cu electrode and enter into Cu2O, VCu are filled by Cu ions, then the conductivity path breaks and the film exhibits HRS.

Thanks for your attention!


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