Endurance study of switching characteristics in NiO films

Article abstract of DOI:10.1016/j.jmmm.2006.11.075

Bi-stable switching effect has been studied in nickel oxide films with three different thicknesses. The best sample of our experiments was 150-nm NiO film. Its resistance ratio between high and low states was 3.6 in endurance measurement. The maximum resistance ratio in I-V curve could reach two orders of magnitude, and it could endure over 200 times of reverse processes with the ratio remaining about 1.46. This indicates that the nickel oxide has potential to be a promising material on resistance random access memory.

Full text of DOI:10.1016/j.jmmm.2006.11.075

ARTICLE IN PRESS
Journal of Magnetism and Magnetic Materials 310 (2007) e1030–e1031
www.elsevier.com/locate/jmmm
Endurance study of switching characteristics in NiO films
a,
M.D. Lee , C.K. Lo , T.Y. Peng , S.Y. Chen , Y.D. Yao
Ã
b
a
a
a,c
a
Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
b
Electronics Research & Service Organization, Industrial Technology Research Institute (ITRI), Hsinchu 310, Taiwan
c
Institute of Physics, Academia Sinica, Taipei 115, Taiwan, ROC
Available online 27 November 2006
Abstract
Bi-stable switching effect has been studied in nickel oxide films with three different thicknesses. The best sample of our experiments
was 150-nm NiO film. Its resistance ratio between high and low states was 3.6 in endurance measurement. The maximum resistance ratio
in I–V curve could reach two orders of magnitude, and it could endure over 200 times of reverse processes with the ratio remaining about
1.46. This indicates that the nickel oxide has potential to be a promising material on resistance random access memory.
r 2006 Elsevier B.V. All rights reserved.
Keywords: Nickel oxide; RRAM; Bi-stable memory switching effect
Non-volatile memory (NVM) plays an important role in
semiconductor industry. Besides the flash memory, others
such as magnetic random access memory (MRAM), phase
change random access memory (PCRAM) and resistance
random access memory (RRAM) are very interesting
research topic. The bi-stable memory switching effect of
RRAM has been reported in metal–oxide–metal (MOM)
structure with Nb O [1], TiO [2], ZrO [3], Ta O [4],
voltage was supplied by Agilent 81110A and switching
bridge was controlled by Keithley 707A.
Bi-stable memory switching effect of poly-crystal nickel
oxide (not show here) has been studied in this report. Fig. 1
shows the typical current–voltage measurement (I–V curve)
of bi-stable memory switching effect NiO film with
different thickness. In order to facilitate the use of a
semi-log scale, we plot the absolute value of current (jIj). It
is obvious to observe that the hysteresis phenomenon with
two states in the electrical property measure process. In this
measurement, we defined these bi-stable states as set (low
resistance:high induction current) and reset (high resistan-
ce:low induction current) states that were controlled by
voltage. In this process, we could see the resistance change
from reset state to set state when we poured a positive
voltage. Similarly, we poured a negative voltage, resistance
changes from reset state to set state. An asymmetric shape
of the I–V curve might be attributed to the different
work functions of Ti/NiO and NiO/W interfaces [11]. In
addition, we found that the thicker films need more voltage
to change the state, and the ratio of two states was bigger
on thicker films. For 30-nm NiO film, the resistance ratio
was very small and the two states were not obvious. When
we increased the thickness, it is obvious that the ratio
increased. And the maximum ratio of our samples is about
one to one hundred of 150 nm.
2
5
2
2
2
5
Al O [5], NiO [6], Cr-doped SrZrO [7], (Pr,Ca)MnO [8]
3
2
3
3
and Fe oxides [9]. Much works have been done in this field,
starting already in the late 1960s. Recently, NiO has been
reported to be a promising material due for RRAM to its
high resistivity ratio and simple constituents [10]. In this
study, we reported the electrical and endurance properties
with different thickness of NiO films.
The ion beam sputtering system with 99.95% nickel
target was used to prepare our films at room temperature.
In the deposit processes, we controlled the oxygen partial
pressure to the working pressure about 56%. NiO films
with different thickness from 30 to 150 nm were deposited
in a 300 ꢀ 300 nm pattern area using Ti and W for top and
bottom electrodes. Electrical properties were measured by
Agilent 4156C semiconductor parameter analyzer, pulse
Ã
Corresponding author. Tel.: +886 35912878; fax: +886 35912933.
E-mail address: mingdaou@gmail.com (M.D. Lee).
0304-8853/$ - see front matter r 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jmmm.2006.11.075

ARTICLE IN PRESS
M.D. Lee et al. / Journal of Magnetism and Magnetic Materials 310 (2007) e1030–e1031
e1031
1
1
1
1
1
1
E-4
E-5
E-6
E-7
E-8
E-9
4
3
3
2
2
.0
.5
.0
.5
.0
150nm
5nm
7
3
0nm
75nm
50nm
1.5
1
1
1
E-10
E-11
E-12
1
0
.0
.5
1
-
7
-6 -5 -4 -3 -2 -1
0
1
2
3
4
5
6
7
0
50
100
150
200
Voltage (V)
Times
Fig. 1. The current–voltage measurement of different thickness NiO films.
Fig. 3. The resistance ratio of different thickness NiO films in the
endurance measurement.
obvious that the resistance increased. It might be attributed
to the localized ‘‘burned’’ pits with create-like geometry
generated and the structure shorted [12].
In Fig. 3, it is obvious to observe that the ratio decreased
in the endurance measurement. This time dependence can
be well fitted by a double exponential decay function of the
form R(t) ¼ R +A exp(ꢁt/t1)+A exp(ꢁt/t2). In fitted
1
E8
0
1
2
1
1
7
7
50nm Set
50nm Reset
5nm Set
program, we found the ultimate ratio was 1.29 (0.437) of
150 (75)-nm NiO film when we fixed the constants of A1,
A , t , t , and defined t to infinite.
2
1
2
5nm Reset
In summary, bi-stable switching effect in nickel oxide
films has been studied with three different thicknesses. Its
maximum resistance ratio can reach one hundred in I–V
curve and it can endure over 200 times of reverse processes
with the ratio remaining about 1.46. So, the nickel oxide
has potential to be a promising material on resistance
random access memory.
1E7
0
50
100
150
200
Times
Fig. 2. The endurance of NiO films using pulse voltage to reverse the
states with different thickness.
About the endurance of NiO films, we poured a pulse
voltage to reverse the states. Fig. 2 shows the endurance of
NiO films with different thickness. Because the two states
almost overlap in 30-nm NiO film, we just showed the
endurance about 75 and 150 nm. In this figure, we found
that the films could endure the set and reset processes
about 200 times without overlap. Then we defined the value
of (RresetꢁR )/R as resistance ratio in order to observe
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set
set
the influence with switching processes. The resistance ratio
of these two samples did not reach the same level as Fig. 1
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