scispace - formally typeset

Journal ArticleDOI

Write-Once–Read-Many-Times Memory Based on ZnO on p-Si for Long-Time Archival Storage

12 Aug 2011-IEEE Electron Device Letters (IEEE)-Vol. 32, Iss: 10, pp 1445-1447

AbstractWrite-once-read-many-times memory cells were fabricated using ZnO thin film on p-Si (111) substrate. The off- and on-state resistance ratio is over 104 and can be well sustained for more than 100 years and perfectly endure reading cycles of 108 . The conducting filaments consisting of oxygen vacancies are responsible for the switching mechanism.

Topics: Write once read many (56%)

Summary (1 min read)

Jump to:  and [Summary]

Summary

  • Write-once–read-many-times memory cells were fabricated using ZnO thin film on p-Si (111) substrate.
  • The OFFand ON-state resistance ratio is over 10 and can be well sustained for more than 100 years and perfectly endure reading cycles of 10.
  • The conducting filaments consisting of oxygen vacancies are responsible for the switching mechanism.

Did you find this useful? Give us your feedback

...read more

Content maybe subject to copyright    Report

IEEE ELECTRON DEVICE LETTERS, VOL. 32, NO. 10, OCTOBER 2011 1445
Write-Once–Read-Many-Times Memory Based on
ZnO on p-Si for Long-Time Archival Storage
Jing Qi, Qing Zhang, Jian Huang, Jingjian Ren, Mario Olmedo, and Jianlin Liu
Abstract—Write-once–read-many-times memory cells were fab-
ricated using ZnO thin film on p-Si (111) substrate. The
OFF-and
ON-state resistance ratio is over 10
4
and can be well sustained
for more than 100 years and perfectly endure reading cycles of
10
8
. The conducting filaments consisting of oxygen vacancies are
responsible for the switching mechanism.
Index Terms—Conducting mechanism, write-once–read-many-
times (WORM), ZnO.
I. INTRODUCTION
W
RITE-ONCE–READ-MANY-TIMES (WORM) mem-
ory devices, in which the data storage is permanent,
as required for archival storage of video images and for
noneditable database, have attracted a great deal of interest
[1], [2]. Even though some studies regarding the formation
and electrical properties of WORM memory devices using
organic materials [3], [4], inorganic/organic nanocomposites
[5], and inorganic/organic heterojunction [2] have been carried
out, studies on WORM memory devices fabricated using ZnO
film have not been reported yet. ZnO material is a promis-
ing candidate for WORM memory application primarily due
to its environmental friendliness, abundant availability in na-
ture, highly evolved growth technologies, compatibility with
metal–oxide–semiconductor technology, and suitability for fab-
rication of small-size devices [6], [7]. This letter reports the
switching characteristics and mechanism of WORM memory
devices fabricated using ZnO on p-Si.
II. E
XPERIMENTAL PROCEDURE
ZnO (60 nm) was deposited on p-Si (111) substrate at 400
C
with a few atomic layers of MgO as buffer in a radio-frequency
Manuscript received June 6, 2011; revised July 5, 2011; accepted
July 11, 2011. Date of publication August 11, 2011; date of current version
September 28, 2011. This work was supported in part by the Microelec-
tronics Advanced Research Corporation and its Focus Center on Function
Engineered Nano Architectonics, by the Defense Advanced Research Projects
Agency/Defense Microelectronics Activity under Agreement H94003-10-2-
1003 (3-D Electronics), and by the National Natural Science Foundation of
China under Grant number 50902065. The review of this letter was arranged by
Editor T. Wang.
J. Qi is with the Quantum Structures Laboratory, Department of Electrical
Engineering, University of California, Riverside, CA 92521 USA, and also
with the Department of Physics, School of Physical Science and Technology,
Lanzhou University, Lanzhou 730000, China (e-mail: qijing@lzu.edu.cn).
Q. Zhang, J. Huang, J. Ren, M. Olmedo, and J. Liu are with the Quan-
tum Structures Laboratory, Department of Electrical Engineering, Univer-
sity of California, Riverside, CA 92521 USA (e-mail: zq2000@hotmail.
com; jian.huang002@email.ucr.edu; jren004@student.ucr.edu; molmedo@
ee.ucr.edu; jianlin@ee.ucr.edu).
Color versions of one or more of the figures in this letter are available online
at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/LED.2011.2162219
(RF) plasma-assisted molecular beam epitaxy system. An ex-
periment on a reference sample with only MgO layer indicated
that MgO is too thin to have similar memory performance (not
shown here). The Si substrates were cleaned using standard
RCA method to remove contamination and native oxide layer.
High-purity Mg (6 N) and Zn (6 N) sources were evaporated
from conventional low-temperature effusion cells. Atomic oxy-
gen was provided by an RF plasma source. Ti (10 nm)/Au
(90 nm) square-shaped metal patterns of different areas, which
act as top electrodes, were deposited on ZnO by electron-beam
evaporation after photolithography, followed by a standard
lift-off process. Al was evaporated also by electron-beam evap-
oration as back contact onto p-Si (111). The electrical charac-
teristics of the Au/Ti/ZnO/p-Si/Al structure were measured by
an Agilent 4155 C semiconductor analyzer. Current maps for
the surface of ZnO film were measured by a conductive atomic
force microscope (C-AFM). A scanning electron microscope
(SEM) was utilized to observe surface morphology change of
top electrodes after electrical characterization.
III. R
ESULTS AND DISCUSSION
Fig. 1(a) shows a typical current–voltage (IV ) curve of a
memory cell [device structure with electrodes of different areas
shown as the bottom right inset in Fig. 1(a)]. First, an external
applied voltage (V
ext
) was swept from 1.5 to 1.5 V to obtain
the IV curve for high-resistance state (OFF), as shown in
Fig. 1(a) as black square curve. Then, as V
ext
(0 20 V) in
sweeping mode increased to approximately the writing voltage
(V
w
) of 14 V, the current increased suddenly, which switched
the memory cell to low-resistance state (ON), as shown in
the right inset of Fig. 1(a). This phenomenon is similar to an
electroforming process, which is a soft breakdown due to the
protection of current compliance, in resistive random access
memory (RRAM), where the sudden current increase is caused
by the formation of the conducting filaments [8]. Finally, V
ext
swept from 1.5 to 1.5 V again to obtain the IV curve for
ON state, as shown in Fig. 1(a) as red circle curve. Probability
of resistance ratio (R-ratio, R
OFF
/R
ON
) obtained at a reading
voltage of 1 V from 100 devices with an area of 30 × 30 μm
2
[left inset of Fig. 1(a)] shows that the R-ratio for most devices
is between 10
5
and 10
6
. Fig. 1(b) shows the dependence of R-
ratio and writing power on the current compliance during the
writing process. A WORM memory effect can still be clearly
observed even if the writing power is lowered to be smaller
than 1 mW. Furthermore, R-ratio decreases to 10
3
with the
writing power lowered to 1 mW. This ratio is large enough to
distinguish two different states.
0741-3106/$26.00 © 2011 IEEE

1446 IEEE ELECTRON DEVICE LETTERS, VOL. 32, NO. 10, OCTOBER 2011
Fig. 1. (a) Switching characteristics of the WORM memory. (Black squares)
Current–voltage (IV ) characteristic of the WORM memory before writ-
ing (
OFF state). (Red circles) Data for the WORM memory after writing
(
ON state). (Bottom right inset) Device structure of the WORM memory. (Top
right inset) IV characteristic for the writing process. (Left inset) Probability
of the resistance ratio between
OFF and ON states for 100 devices of 30 μm ×
30 μm. (b) Dependence of
ON-andOFF-state resistances and writing power on
current compliance during the writing process.
The typical retention and endurance performances of
Au/Ti/ZnO/p-Si WORM memory measured at room tempera-
ture and higher temperature (85
C) are shown in Fig. 2(a) and
(b), respectively, in which the
ON- and OFF-state resistances
were measured at 1 V in sampling mode. The
ON state ex-
hibited little degradation after 1 × 10
5
s, while the OFF state
showed no degradation. However, the two states can still be
well distinguished by high
OFF/ON resistance ratio of over 10
4
,
as the data trends are extrapolated to 100 years. It should be
noted that the extrapolation method was extensively utilized
by other researchers [9], [10]. This result indicates excellent
retention. For endurance, as shown in Fig. 2(b), both
ON and
OFF states with a large resistance ratio of over 10
5
exhibited
little degradation after reading cycles of 1 × 10
8
. The relation
between the resistances of both
ON and OFF states and the
measurement temperature is shown in Fig. 2(c). As the mea-
surement temperature increases, the
OFF-state resistance de-
creases slightly, while the
ON-state resistance increases, which
originates from the dependence of resistance on temperature for
semiconductor/insulator and metal materials, respectively.
IV characteristics were measured on 100 devices for all six
different metal contact areas to obtain the statistic information
for this kind of memory. As shown in the inset of Fig. 3,
when the area of the device decreases from 600 × 600 μm
2
to
30 × 30 μm
2
, V
w
increases to the range of 12–20 V. The writing
voltage of over 12 V ensures reliability of the memory states.
The dependence of average resistance for both
ON and OFF
states on the device area is shown in Fig. 3. The OFF-state resis-
tance increases linearly with the decrease of the area. However,
there is no obvious relationship between
ON-state resistance
and device area, similar to the reported results in RRAM [11],
where resistive switching was caused by formation/rupture
Fig. 2. (a) Retention and (b) endurance characteristics of the ZnO WORM
memory device in the
ON and OFF states at a read voltage of 1.0 V.
(c) Dependence of resistance on measurement temperature.
Fig. 3. Dependence of resistance for ON and OFF states on the area of the
device. (Inset) Cumulative probability of writing voltage for different device
areas [(noted as “1” in the inset) 30 × 30, (2) 50 × 50, (3) 100 × 100, (4) 200 ×
200, (5) 400 × 400, and (6) 600 × 600 μm
2
].
of conducting filaments. In this conducting filament model,
the effective cell area is attributed to the conducting filament
density and diameter rather than to the geometrical size of the
electrode [12]. Voltage sweeping of larger range (5 5V)
was performed at different current compliance. Typical results
are shown in Fig. 4, which shows that the memory cell can be
reset slightly at negative bias. The IV curves for the RESET
process are not linear in the low-voltage region, indicating the
formation of tunneling barrier at the MgO–Si interface during
the SET process due to the existence of a few MgO monolayers.
The formation of this barrier prevents the device from being
totally reset [13]. These larger range voltage sweeping results
mean that WORM memory and RRAM can coexist in one
memory cell and the switching mechanism is controlled by
the conducting filament. In the ZnO WORM memory case, the
formed conducting filaments cannot be totally ruptured. For
OFF state, the device is a heterojunction diode consisting of ZnO
and Si substrate, which leads to diodelike IV characteristics.
After the formation of the conducting filaments in ZnO, the
device becomes a metal/semiconductor contact, in which the
top electrode and conducting filaments act as metal while
the Si substrate is a semiconductor part of the device. This

QI et al.: WORM MEMORY BASED ON ZnO ON p-Si FOR LONG-TIME ARCHIVAL STORAGE 1447
Fig. 4. Coexistence of WORM memory and RRAM in one cell.
Fig. 5. (a) C-AFM image of the surface of ZnO thin film. (b) Spot of
5 nm corresponding to the black square area in (a). (c) Typical SEM images
of blown-off and bubble areas on top of contact for
ON-state WORM memory.
(d) Magnified images of the bubble in the rectangular area of (c).
results in much higher current for ON state than that of OFF state
at a positive external applied voltage. The error bars plotted
in Fig. 3 are indicative of the variability of
OFF- and ON-state
resistances from one memory element to the other.
Fig. 5 shows the C-AFM current map for the surface of
ZnO thin film and typical SEM images for
ON-state devices.
The current maps shown in Fig. 5(a) and (b) suggest that con-
ducting filaments are responsible for the switching mechanism
and the diameter of the filaments can be as small as 5 nm,
indicating good potential of scaling down. Some blown-off and
bubble areas are observed on the surface of the top contacts,
as shown in the SEM images [Fig. 5(c) and (d)]. These areas
were caused by the production of oxygen gas because of the
oxidation reaction that happened during the writing process,
corresponding to the positions with the strongest filaments.
Similar bubble phenomenon caused by redox reaction during
the filament-forming process was also reported by Szot et al.
[14]. These results again indicate that conducting filaments con-
sisting of oxygen vacancies are responsible for the switching
behavior.
IV. C
ONCLUSION
WORM memories fabricated using a ZnO epitaxial thin film
have shown excellent performance of suitable writing voltage
(12–20 V), high resistance ratio of
OFF and ON states (mainly
in the range of 10
5
10
6
), good retention (100 years), and ex-
cellent endurance (> 10
8
cycles). The characteristics of writing
process, the dependence of
ON- and OFF-state resistances on
the device area, current maps for the surface of ZnO thin film,
and morphology change of the contact area for
ON-state devices
show that conducting filaments consisting of oxygen vacancies
are responsible for the conduction mechanism.
R
EFERENCES
[1] S. Moller, C. Perlov, W. Jackson, C. Taussig, and S. R. Forrest, A
polymer/semiconductor write-once read-many-times memory,” Nature,
vol. 426, no. 6963, pp. 166–169, Nov. 2003.
[2] S. Smith and S. R. Forrest, A low switching voltage organic-on-inorganic
heterojunction memory element utilizing a conductive polymer fuse on a
doped silicon substrate,” Appl. Phys. Lett., vol. 84, no. 24, pp. 5019–5021,
Jun. 2004.
[3] Y. Yang, J. Ouyang, L. Ma, R. J.-H. Teseng, and C.-W. Chu, “Electrical
switching and bistability in organic/polymeric thin films and memory
devices,” Adv. Funct. Mater., vol. 16, no. 8, pp. 1001–1014, May 2006.
[4] Q. D. Ling, D. J. Liaw, E. Y. H. Teo, C. Zhu, D. S. H. Chan, E. T. Kang,
and K. G. Neoh, “Polymer memories: Bistable electrical switching and
device performance,” Polymer, vol. 48, no. 18, pp. 5182–5201, Aug. 2007.
[5] D. Y. Yun, J. K. Kwak, J. H. Jung, T. W. Kim, and D. I. Son, “Electrical
bistabilities and carrier transport mechanisms of write-once–read-many-
times memory devices fabricated utilizing ZnO nanoparticles embedded
in a polystyrene layer,” Appl. Phys. Lett., vol. 95, no. 14, pp. 143 301-1–
143 301-3, Oct. 2009.
[6] L. M. Kukreja, A. K. Das, and P. Misra, “Studies on nonvolatile resistance
memory switching in ZnO thin films,” Bull. Mater. Sci., vol. 32, no. 3,
pp. 247–252, Jun. 2009.
[7]Üzgür,Y.I.Alivov,C.Liu,A.Teke,M.A.Reshchikov,S.Do
˘
gan,
V. Avrutin, S. J. Cho, and H. Morkoç, A comprehensive review of ZnO
materials and devices,” J. Appl. Phys., vol. 98, no. 4, pp. 041 301-1–
041 301-103, Aug. 2005.
[8] K. Nagashima, T. Yanagida, K. Oka, M. Taniguchi, T. Kawai, J. Kim, and
B. H. Park, “Resistive switching multistate nonvolatile memory effects in
a single cobalt oxide nanowire,” Nano Lett., vol. 10, no. 4, pp. 1359–1363,
Apr. 2010.
[9] Q. Ling, Y. Song, E. Teo, S. Lim, C. Zhu, D. Chan, D. Kwong,
E. Kang, and K. Neoh, “WORM-type memory device based on a con-
jugated copolymer containing europium complex in the main chain,”
Electrochem. Solid-State Lett., vol. 9, no. 8, pp. G268–G271, Aug. 2006.
[10] L. Li, Q. Ling, S. Lim, Y. Tan, C. Zhu, D. Chan, E. Kang, and K. Neoh, A
flexible polymer memory device,” Org. Electron., vol. 8, no. 4, pp. 401–
406, Aug. 2007.
[11] Y. Wang, Q. Liu, S. Long, W. Wang, Q. Wang, M. Zhang, S. Zhang, Y. Li,
Q. Zuo, J. Yang, and M. Liu, “Investigation of resistive switching in Cu-
doped HfO
2
thin film for multilevel non-volatile memory applications,”
Nanotechnology, vol. 21, no. 4, pp. 045202-1–045202-6, Jan. 2010.
[12] R. Waser and M. Aono, “Nanoionics-based resistive switching memo-
ries,” Nat. Mater., vol. 6, no. 11, pp. 833–840, Nov. 2007.
[13] S. S. Chung and Y. H. Tseng, “The static and dynamic behaviors of resis-
tive random access memory and its potential application as a memristor,”
in Proc. 10th IEEE ICSICT, 2010, pp. 1069–1072.
[14] K. Szot, W. Speier, G. Bihlmayer, and R. Waser, “Switching the electrical
resistance of individual dislocations in single-crystalline SrTiO
3
,” Nat.
Mater., vol. 5, no. 4, pp. 312–320, Apr. 2006.
Citations
More filters

Journal ArticleDOI
TL;DR: This work presents the first presentation of fully degradable biomimetic synaptic devices based on a W/MgO/ZnO/Mo memristor on a silk protein substrate, which show remarkable information storage and synaptic characteristics including long-term potentiation (LTP), long- term depression (LTD) and spike timing dependent plasticity (STDP) behaviors.
Abstract: Physically transient electronic devices that can disappear on demand have great application prospects in the field of information security, implantable biomedical systems, and environment friendly electronics. On the other hand, the memristor-based artificial synapse is a promising candidate for new generation neuromorphic computing systems in artificial intelligence applications. Therefore, a physically transient synapse based on memristors is highly desirable for security neuromorphic computing and bio-integrated systems. Here, this is the first presentation of fully degradable biomimetic synaptic devices based on a W/MgO/ZnO/Mo memristor on a silk protein substrate, which show remarkable information storage and synaptic characteristics including long-term potentiation (LTP), long-term depression (LTD) and spike timing dependent plasticity (STDP) behaviors. Moreover, to emulate the apoptotic process of biological neurons, the transient synapse devices can be dissolved completely in phosphate-buffered saline solution (PBS) or deionized (DI) water in 7 min. This work opens the route to security neuromorphic computing for smart security and defense electronic systems, as well as for neuro-medicine and implantable electronic systems.

39 citations


Journal ArticleDOI
Abstract: In this letter, we report the dependence of memory characteristics on electroforming polarity based on TiN/HfO2/Pt devices. Bipolar resistive switching (BRS) and write-once-read-many-times memory (WORM) behaviors were obtained after the negative and positive electroforming process, respectively. Analysis of conduction mechanisms of high resistance state confirms that BRS and WORM were dominated by Schottky emission and trap-controlled space charge limited current, respectively. These phenomena can be explained by the filamentary model with the assistance of interfacial role. Moreover, this letter also indicates that the TiN/HfO2/Pt devices have promising application in both RRAM and non-editable WORM.

17 citations


Journal ArticleDOI
Abstract: Write-once-read-many-times memory (WORM) devices were fabricated using ZnO and ZnO/MgO as active layers on Si. Devices fabricated with ZnO show a different memory effect at different current compliances such as WORM at 100 $\mu \text{A}$ , 500 $\mu \text{A}$ , and 1 mA, resistive switching (RS) instead of WORM at 5 and 10 mA, and WORM and RS coexisting at 20, 50, and 100 mA, while devices fabricated with ZnO/MgO show WORM only at all current compliances. A few nanometers of MgO layer play a major role in preventing devices from reset at all current compliances because the much lower drift velocity of oxygen vacancy in MgO and accumulation of negatively charged O2− ions at the interface between ZnO and MgO prevent the conducting filaments composed of oxygen vacancies from breaking.

7 citations


Cites background from "Write-Once–Read-Many-Times Memory B..."

  • ...ZnO on Si was found to exhibit WORM characteristics, and further inclusion of a MgO thin layer between ZnO and Si led to enhanced memory performance [24], [25]....

    [...]

  • ...In previous publication [24], it is reported that the conduct-...

    [...]


Journal ArticleDOI
Abstract: TaN/ZrTiOx/Pt metal-insulator-metal structure was employed as the platform to evaluate the eligibility for antifuse one-time programmable (OTP) memory applications, and the impact of O2 plasma on device performance was also discussed. Owing to the oxygen radicals that enhance the dielectric integrity, the voltage for state switching increases with O2 plasma treatment. Memory cells without plasma treatment demonstrate promising characteristics for OTP memory applications in terms of a low dc switching voltage of 2 V, high programming speed of 60 ns, high read endurance up to 106 reading cycles, and desirable retention time and low switching power density of 6.4 mW/cm2. The memory cell technology not only exhibits the prominent performance which is advantageous over other dielectrics reported in the literature, but it also possesses the capability to from stackable 3-D architecture.

6 citations


Cites background or result from "Write-Once–Read-Many-Times Memory B..."

  • ...Although these newly developed dielectrics exhibit promising characteristics, there is still plenty of room to improve their performance since most dielectrics show dc program voltage higher than 4 V [10], [11] and program speed longer...

    [...]

  • ...Recently, dielectrics such as SiNx [6], Ta2O5 [7], Al2O3 [8], ZrO2 [9], ZnO [10], and BZN [11] have also been explored to investigate their feasibility for use in antifuse applications....

    [...]

  • ...This result compares favorably to other dielectrics [6]–[8], and [10], [11] in terms of low programming voltage along with high operation speed....

    [...]


Journal ArticleDOI
Abstract: Write-onceread-many-times memory (WORM) devices were fabricated using Ti/Au and Au as top contacts on ZnO thin films on Si. Electrical characterization shows that both types of WORM devices have large resistance OFF/ON ratio (R ratio), small resistance distribution range, long retention and good endurance. WORM devices with Au top contact have better performance of higher R ratio because of a larger work function of Au compared to Ti. ((c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

4 citations


References
More filters

Journal ArticleDOI
Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

9,486 citations


Additional excerpts

  • ...rication of small-size devices [6], [7]....

    [...]


Journal ArticleDOI
TL;DR: A coarse-grained classification into primarily thermal, electrical or ion-migration-induced switching mechanisms into metal-insulator-metal systems, and a brief look into molecular switching systems is taken.
Abstract: Many metal–insulator–metal systems show electrically induced resistive switching effects and have therefore been proposed as the basis for future non-volatile memories. They combine the advantages of Flash and DRAM (dynamic random access memories) while avoiding their drawbacks, and they might be highly scalable. Here we propose a coarse-grained classification into primarily thermal, electrical or ion-migration-induced switching mechanisms. The ion-migration effects are coupled to redox processes which cause the change in resistance. They are subdivided into cation-migration cells, based on the electrochemical growth and dissolution of metallic filaments, and anion-migration cells, typically realized with transition metal oxides as the insulator, in which electronically conducting paths of sub-oxides are formed and removed by local redox processes. From this insight, we take a brief look into molecular switching systems. Finally, we discuss chip architecture and scaling issues.

4,263 citations


"Write-Once–Read-Many-Times Memory B..." refers background in this paper

  • ...the effective cell area is attributed to the conducting filament density and diameter rather than to the geometrical size of the electrode [12]....

    [...]


Journal ArticleDOI
TL;DR: It is demonstrated that the switching behaviour is an intrinsic feature of naturally occurring dislocations in single crystals of a prototypical ternary oxide, SrTiO3, and to be related to the self-doping capability of the early transition metal oxides.
Abstract: The great variability in the electrical properties of multinary oxide materials, ranging from insulating, through semiconducting to metallic behaviour, has given rise to the idea of modulating the electronic properties on a nanometre scale for high-density electronic memory devices. A particularly promising aspect seems to be the ability of perovskites to provide bistable switching of the conductance between non-metallic and metallic behaviour by the application of an appropriate electric field. Here we demonstrate that the switching behaviour is an intrinsic feature of naturally occurring dislocations in single crystals of a prototypical ternary oxide, SrTiO(3). The phenomenon is shown to originate from local modulations of the oxygen content and to be related to the self-doping capability of the early transition metal oxides. Our results show that extended defects, such as dislocations, can act as bistable nanowires and hold technological promise for terabit memory devices.

1,483 citations


Journal ArticleDOI
13 Nov 2003-Nature
TL;DR: The results indicate that the hybrid organic/inorganic memory device is a reliable means for achieving rapid, large-scale archival data storage for ultralow-cost permanent storage of digital images, eliminating the need for slow, bulky and expensive mechanical drives used in conventional magnetic and optical memories.
Abstract: Organic devices promise to revolutionize the extent of, and access to, electronics by providing extremely inexpensive, lightweight and capable ubiquitous components that are printed onto plastic, glass or metal foils1,2,3. One key component of an electronic circuit that has thus far received surprisingly little attention is an organic electronic memory. Here we report an architecture for a write-once read-many-times (WORM) memory, based on the hybrid integration of an electrochromic polymer with a thin-film silicon diode deposited onto a flexible metal foil substrate. WORM memories are desirable for ultralow-cost permanent storage of digital images, eliminating the need for slow, bulky and expensive mechanical drives used in conventional magnetic and optical memories. Our results indicate that the hybrid organic/inorganic memory device is a reliable means for achieving rapid, large-scale archival data storage. The WORM memory pixel exploits a mechanism of current-controlled, thermally activated un-doping of a two-component electrochromic conducting polymer.

709 citations


"Write-Once–Read-Many-Times Memory B..." refers background in this paper

  • ...noneditable database, have attracted a great deal of interest [1], [2]....

    [...]


Journal ArticleDOI
Abstract: Recently, films created by incorporating metallic nanoparticles into organic or polymeric materials have demonstrated electrical bistability, as well as the memory effect, when subjected to an electrical bias. Organic and polymeric digital memory devices based on this bistable electronic behavior have emerged as a viable technology in the field of organic electronics. These devices exhibit fast response speeds and can form multiple-layer stacking structures, demonstrating that organic memory devices possess a high potential to become flexible, ultrafast, and ultrahigh-density memory devices. This behavior is believed to be related to charge storage in the organic or polymer film, where devices are able to exhibit two different states of conductivity often separated by several orders of magnitude. By defining the two states as “1” and “0”, it is now possible to create digital memory devices with this technology. This article reviews electrically bistable devices developed in our laboratory. Our research has stimulated strong interest in this area worldwide. The research by other laboratories is reviewed as well.

526 citations


"Write-Once–Read-Many-Times Memory B..." refers background in this paper

  • ...and electrical properties of WORM memory devices using organic materials [3], [4], inorganic/organic nanocomposites [5], and inorganic/organic heterojunction [2] have been carried...

    [...]