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Photolithography Free Ge-Se Based Memristive Arrays Material Characterization and Devices Testing. M. R. Latif 1 , I. Csarnovics 1,2 , T. Nichol 1 , S. Kökényesi 2 , A. Csik, 3 M. Mitkova 1 1.Department of Electrical and Computer Engineering Boise State University, Boise, ID - USA - PowerPoint PPT Presentation
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M. R. Latif1, I. Csarnovics1,2, T. Nichol1, S. Kökényesi2, A. Csik,3 M. Mitkova1 1. Department of Electrical and Computer Engineering Boise State University, Boise, ID - USA
2.Department of Experimental Physics, University of Debrecen, Debrecen - Hungary3.Institute of Nuclear Research (ATOMKI), Debrecen - Hungary
Photolithography Free Ge-Se Based Memristive Arrays Material Characterization and Devices Testing
Acknowledgment: This work was supported by the IMI-NFG under NSF Grant # DMR 0844014, TAMOP 4.2.2./B-10/1-2010-0024 and TAMOP 4.2.2.A-11/2/KONV-2012-0032 projects, which are co-financed by the European Union and European Social Fund. The financial support of the Czech Science Foundation (under the project No. P106/11/0506) is also acknowledged.
I. Motivation
II. Experimental Details
III. EDS Mapping EDS mapping of the data provides evidence of compositional distribution of different elements in the array stack.
IV. Film Characterization - AFM
RMS value of surface roughness in 25µm2 area of cells # 1, 10 and 20 in the array.
The result shows that the SNMP method is suitable for via formation. Quality of the surface depends upon the films’ structure.
SampleCell No.
RMS Surface Roughness in the ChG film after ion bombardment by AFM
Ge20Se80
1 21.710 4.5220 2.31
Ge30Se70
1 5.1510 7.2120 8.67
Ge40Se60
1 1.9710 1.7820 1.89
VI. Electrical Testing The IV curves for cells # 20 in the arrays are presented in the following
figures. It is obvious that ChG surface with higher roughness results in a poorer device performance.
Devices threshold voltages (Vth) and the resistance plots are shown below:
The array allows individual device addressing. Devices show six orders of magnitude difference between the low
resistive state (LRS) and high resistive state (HRS). Vth of Ge30Se70 and Ge40Se60 shows excellent repeatability. Increase in Ge concentration results in improvement of the devices’
performance which is attributed to the formation of Ge-Ge bonds. Devices performance depends on the film roughness which results in
voids occurrence that obstructs bridge formation. The devices showed good endurance at over 103 cycles.
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-10n
0
10n
20n
30n
40n
50n
60n
Cur
rent
(A)
Voltage (V)
Cell 20 100 Cycles
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-10n
0
10n
20n
30n
40n
50n
60n
Cur
rent
(A)
Voltage (V)
Cell 20 100 Cycles
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-10n
0
10n
20n
30n
40n
50n
60n
Cur
rent
(A)
Voltage (V)
100 CyclesCell 20
Ge20Se80 Device Ge30Se70 Device Ge40Se60 Device
0.00.20.40.60.81.01.21.4
Vth HRS LRS
100 Cycles/Cell
Thre
shol
d Vo
ltage
(V)
10k100k1M10M100M1G10G100G1T
Resistance
()
Cell 1 Cell 8 Cell 16 Cell 200.2
0.4
0.6
0.8
1.0
1.2
Vth HRS LRS
100 Cycles/Cell
Thre
shol
d Vo
ltage
(V)
Cell 1 Cell 4 Cell 8 Cell 12 Cell 16 Cell 20 10k100k1M10M100M1G10G100G1T
Resistance
()
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
Cell 20Cell 16Cell 12Cell 8Cell 4Cell 1
Vth HRS LRS
100 Cycles/Cell
Thre
shol
d Vo
ltage
(V)
1k10k100k1M10M100M1G10G100G
Resistance
()
Ge20Se80 Device Ge30Se70 Device Ge40Se60 Device
VII. Conclusion
V. Raman Spectroscopy Analysis
A memristive array with devices build by Ge-Se thin films and Ag bridging the two device electrodes is demonstrated.
SNMP method for array formation shows excellent yield with stable ON/OFF ratio.
The individual devices demonstrate reliable performance. Additional improvement in the cells can be achieved by formation of
smoother layers within the vias and filling them homogeneously with thick Ag films.
SNMS Setup Profilometer Image Profilometer Scan SNMS Measurement
100
101
102
103
104
105
Inte
nsity [cps]
0 20 40 60 80 100 120 140 160 180 200 220 240 260Time [s]
Ge40Se60/W//Si - #6, sputtering 800 nm deep crater (sput. time: 275 sec)
File: DT06379.SADDate: 2/25/2013 1:59:37 PM
Si [29]GeSeW [186]
DT06379.SAD
0 20 40 60 80 100 120140 160 220200180 260240Time [s]
Inte
nsit
y [
cp
s]
100
101
104
105
102
103
Success already achieved at the single cell level suggests that conductive bridge memristor is well positioned for ultra high performance memory, neuromorphic computing and logic applications.
A high density conductive bridge memristor arrays on thin films metal/insulator/metal (MIM) stack is demonstrated in this work.
ChG ChG Ag ChG ChG Ag1µm 150nm 150nm
20nm - 30nm 20nm - 30nm 20nm - 30nm
Ag
W electrode 100nm1µm150nm
Si <100> SiO2 100nm
ChG
Vias filled with Ag
ChGAg
ChG
ESSe-SeES
Outside Via
Coun
ts (a
rb.)
Inside Via
CS
ETH
Coun
ts (a
rb.)
Outside Via
Inside Via
150 200 250 300 350 400 Wavenumber (cm-1)
Coun
ts (a
rb.)
Inside Via
Outside Via
Ge24.8 ± 0.51 Se75.2 ± 0.51
Ge30.7 ± 0.15 Se69.3 ± 0.15
Ge38.8 ± 0.14 Se61.2 ± 0.14
Ge25.6 ± 0.061 Se74.4 ± 0.061
Ge31.2 ± 0.037 Se68.8 ± 0.037
Ge39.9 ± 0.19 Se60.1 ± 0.19
Sour
ce co
mpos
ition:
Ge20
Se80
Ge30
Se70
Ge40
Se60
Ge30Se70 Virgin Ge30Se70 Via0.0
0.5
14
21
ETH ES/CS
Coun
ts (a
rb.)
Ge40Se60 Virgin Ge40Se60 Via
0.32
0.40
ETH ES/CS
Coun
ts (a
rb.)
Ge40Se60
Ge30Se70
Virgin Via
Area
s (a
rb.)
Area
s (a
rb.)
Area
s (a
rb.)
CS ES Se-Se
Ge20Se80
Ge30Se70
Ge40Se60
Area
s (Ar
b.)
Area
s (Ar
b.)
Area
s (Ar
b.)
Virgin Via
Coun
ts (A
rb.)
Coun
ts (A
rb.)
Coun
ts (A
rb.)
Coun
ts (A
rb.)
Coun
ts (A
rb.)
Ge40
Se60
Ge30
Se70
Ge20
Se80