ICMCTF 2012! - CD-Lab Application Oriented Coating Development

proposed memory device exhibits excellent resistance switching with a high
resistance state/ low resistance state ration of 2.5 order, write/erase
endurance of about 2 order, and long retention time of 10 4 s at 85 �. In
addition, the device was investigated to achieve multilevel operation, which
could increase storage density for next generation memory application. It
was also found that the polarity of the forming process would not influence
the resistive switching characteristic but influence the first reset process
behavior. The switching behavior could be regarded as the oxygen redox
near the TiN interface. However, the first reset behavior of negative
forming process was related with the oxygen concentration gradients near
the Pt electrode and the Joule heating enhanced oxidation.
FP-13 Switching mechanism transition induced by annealing
treatment in ZnO/Ru/ZnO resistive memory, L.C. Chang
(lcchang@mail.mcut.edu.tw), Y.H. Wei, Ming Chi University of
Technology, Taiwan, K.H. Liu, Chang Gung University, Taiwan
ZnO/Ru/ZnO trilayer films sandwiched between Ru electrodes were
prepared for nonvolatile resistive memory applications. These structures
show resistance switching under electrical bias both before and after a rapid
thermal annealing treatment, while it is found that the resistive switching
effects in the two cases exhibit distinct characteristics. The ZnO devices
after RTA treatment demonstrates remarkable device parameter
improvements including lower threshold voltages and lower write current.
Furthermore, the RTA treatment has triggered a switching mechanism
transition from a carrier trapping/de-trapping type to an electrochemicalredox-reaction-controlled
conductive filament formation/rupture process, as
indicated by different features in current-voltage characteristics.
FP-14 Bismuth Oxide thin films grown by RF reactive magnetron
sputtering, P. Lunca Popa, P. Eklund (perek@ifm.liu.se), Linköping
University, Sweden
Bismuth oxide has five known crystalline phases: alpha, beta, gamma, delta
and omega, each with its distinct properties and stability domains. The delta
phase exhibits ionic conductivity 1-2 orders of magnitude higher than yttriastabilized
zirconia, the compound widely used in solid oxide fuel cells. In
bulk, the delta-Bi2O3 phase is not stable at room temperature but from 750
C to 825 C, the melting point of bismuth oxide. Outside this temperature
range, other phases are stable but their conductivities are up to three orders
of magnitude lower than that of the delta phase. The stability of the delta
phase stability can be extended to lower temperatures by doping, but this
process yields a severe reduction in ionic conductivity.
In the present work, we have synthesized Bi2O3 films by RF reactive
magnetron sputtering using a Bismuth target in an Ar/O2 gas discharge. We
investigate how the structure of the films is influenced by substrate
temperature, source power, and oxygen flow rate/total gas flow rate ratio.
As expected, the substrate temperature influences the initial nucleation
process and growth kinetics. Deposition at ambient temperature yields
mainly amorphous films while higher temperature yields crystalline films.
Different stoichiometric compositions can be obtained by varying the
source power and the oxygen flow ratio. By tuning all these parameters we
obtain Bi2O3 with cubic structure, with thickness of hundreds of
nanometers. XRD shows crystalline films with peaks around 27 and 55 two
theta degrees corresponding to (111) and (222) planes for cubic structure.
Pole figures XRD analysis was also performed for those peaks and
diffractions rings were observed near phi angle of 70 degree which
corresponds to the angle between (1 1 1) and (1 1 -1) planes in a cubic
structure, consistent with the delta phase. SEM showed a columnar structure
of our films with very good uniformity of the films. Electrical and optical
measurements have also been performed; ellipsometry yields a value of the
band gap around 2.5eV while for optical constants values of n≈2.5 and
k≈0.5 are obtained for UV-Vis wavelength interval.
FP-15 Electromechanical reliability of ITO-coated polymer substrates
after exposure to acrylic acid, K. Burrows, University of Birmingham,
UK, A. Hoover, D. Cairns, K. Sierros, West Virginia University, US, S.
Kukureka (s.n.kukureka@bham.ac.uk), University of Birmingham, UK
This paper considers the electromechanical reliability of ITO-coated
polymer substrates, for use in flexible display applications, after exposure to
acrylic acid (a common constituent of display structures). Due to the
mechanical mismatch of properties between the organic polymer substrate
and the inorganic transparent conducting oxide, it is important to investigate
the electro-mechanical response to a number of stresses commonly seen in
general use.
Three films of varying ITO thicknesses were examined: sheet resistance and
optical transmission were monitored and tensile testing performed before
and after exposure to acrylic acid. Also the tribological properties of the
coated films were examined under a specially-modified fretting rig.
It appears that even low concentrations of acrylic acid that would often go
unnoticed, may cause failure to occur more readily. In both tensile testing
and the monotonic bending test where the film is subjected to tension, high
concentrations of acrylic acid would normally be a cause of failure.
Nevertheless, even low concentrations such as 0.1M can also cause the
critical onset strain to occur more readily due to stress-corrosion cracking.
However when the films are subjected to stresses in compression, the
exposure to acrylic acid shows little or no effect.
FP-16 Observation of amorphous to crystalline phase transformation
in Te substituted Sn-Sb-Se chalcogenide thin films for memory
applications, R. Chander (rcohri@yahoo.com), R. Thangaraj, GNDU,
India
Thin films of Sn Sb Se Te (x = 10, 12, 14) chalcogenide system were
prepared by thermal evaporation technique using melt quenched bulk
samples. The as-prepared thin films were found amorphous as evidenced
from X-ray diffraction studies. Resistivity measurement showed an
exponential decrease with temperature upto critical temperature (transition
temperature) beyond which a sharp decrease was observed and with further
increase in temperature showed an exponential decrease in resistivity with
different activation energy. The transition temperature showed a decreasing
trend with tellurium content in the sample. The resistivity measurement
during cooling run showed no abrupt change in resistivity. The resistivity
measurements of annealed films did not show any abrupt change revealing
the structural transformation occurring in the material. The transition width
showed an increase with tellurium content in the sample. The resistivity
ratio showed two order of magnitude improvements for sample with higher
tellurium content. The observed transition temperature in this system was
found quite less than already commercialized Ge Sb Te system for optical
and electronic memories.
FP-17 Investigating the degradation behavior under Hot Carrier
Stress for InGaZnO TFT with symmetric and asymmetric structure,
M.Y. Tsai (baxiatwice@yahoo.com.tw), NSYSU, Taiwan
This letter studies the hot-carrier effect in indium–gallium–zinc oxide
(IGZO) thin film transistors with symmetric and asymmetric source/drain
structures. The different degradation behaviors after hot carrier stress in
symmetric and asymmetric source/drain device indicate that different
mechanisms dominate the degradation. Since the C-V measurement is
highly sensitive to the trap state compared with the I-V characteristics, thus,
the C-V curves are utilized to analyze the hot carrier stress induced trap
state generation. Furthermore, the asymmetric C-V measurements (gate-todrain
capacitance, gate-to-source capacitance) are useful to analyze the trap
state location. For asymmetric device structure, different source/drain
structure under hot carrier stress will induce asymmetric electrical field and
cause different degradation behaviors. In this work, the on-current and
subthreshold swing (S.S) degrade under low electrical field, whereas the
apparent Vt shift occurs under large electrical field. The different
degradation behavior indicates that the trap state generates under low
electrical field and channel-hot-electron (CHE) effect occurs under large
electrical field.
FP-18 Investigating the Drain Bias stress of InGaZnO TFTs under
Dark and Light Illumination for AMOLED application, S.Y. Huang
(aramis88888@gmail.com), T.C. Chang, L.W. Lin, M.C. Yang, National
Sun Yat-Sen University, Taiwan, K.H. Yang, University of Toronto,
Canada, M.H. Wu, M.C. Chen, National Sun Yat-Sen University, Taiwan,
F.Y. Jian, National Tsing Hua University, Taiwan
The degradation mechanism of the drain bias stress for a-IGZO TFT under
dark and light illumination are investigated in this paper. The current
crowding effect, on current decreased of current-voltage, and a stretch-out
of capacitance-voltage indicate that an additional barrier increased near the
drain region by the oxygen molecules adsorbed model after the drain-bias
stress under the dark (DBS) . This result induces the carrier transport is
impeded from source terminal to drain terminal. In addition, the recovery
characteristics show that all degradation behaviors significant disappear,
which can be regarded as the O2 desorption from the active back channel.
However, the unusual stretch-out phenomenon for the subthreshold
capacitance after the drain bias stress under light illumination (DBIS) can
not recover to the initial in the dark. This is attributed to the additional fix
charge generated near the drain region by the photo-leakage current.
Furthermore, an obvious negative threshold voltage shift after the DBIS
indicates the charge trapping mechanism simultaneously occurred. Finally,
this work also employs the gate and source floating conditions during the
DBIS to further clarify the mechanism of degradation behaviors.
119 Thursday Afternoon Poster Sessions