ICMCTF 2012! - CD-Lab Application Oriented Coating Development

complexing properties with a large number of transition metal ions,
including the rare-earth ions. However, the complexes formed in this case
are tris complexes and are not very stables. On the other hand, the inclusion
of one more quinoline group stabilize the compound. Here, Li[RE(q)4]
complexes (RE 3+ = La 3+ , Lu 3+ and Y 3+ ) were synthesized in our laboratories
and then used as electron transporting and emitting layer in OLEDs. The
organic thin films were deposited in high vacuum environment by thermal
evaporation onto quartz and silicon substrates, at a base pressure of 2,0x10 -
3 Pa and with a 0,1nm/s deposition rate. The optical characterization of the
RE-complexes showed emission in the range 510-525 nm, the same
observed in the Alq3 spectra, while the absorption was observed in different
wavelengths: 382 nm for Y/La-complexes and 388 nm for Lu-complex. The
OLEDs were fabricated with indium tin oxide layer (ITO) as anode, NPB as
hole transporting layer (25nm), Li[RE(q)4] as both electron transporting and
emitting layer (40nm), and aluminum as cathode (120nm). The
electroluminescence (EL) spectra presented a broad band from 520 to
540nm and exhibited green color emission related to the 8hydroxyquinoline
ligand without intramolecular energy transfer from
quinoline to RE 3+ ions. Moreover, in the EL spectra was also observed an
interesting dependency between the maximum energy peak position and the
half-width of emission band with the atomic radius of the RE ion used. For
the fabricated OLED, the best luminance result was achieved to Li[Y(q)4]
complex, with a maximum luminance of 30 cd/m 2 taken at 11V and with a
current of 2mA. The results obtained for our devices are comparable with
similar devices based on Alq3, presenting similar optical and electrical
properties.
10:20am C2-3/F4-3-8 Effect of the deposition process and substrate
temperature on the microstructure defects and electrical conductivity
of thin Mo films, H. Köstenbauer (harald.koestenbauer@plansee.com),
Plansee SE, Austria, D. Rafaja, U. Mühle, G. Schreiber, TU Bergakademie
Freiberg, Germany, M. Kathrein, J. Winkler, Plansee SE, Austria
Thin molybdenum films are commonly used as back electrodes in
Cu(In,Ga)Se2 thin film solar cells and as contact material for thin film
transistors/liquid crystal displays. For these applications, high electrical
conductivity of the films is essential. As it follows from the classical Drude
theory of the electrical conductivity in metals, all microstructure defects are
in principle acting as scattering centres for electrons. Consequently, the
microstructure defects increase always the electrical resistance of the
material, but their “scattering cross sections” for electrons are supposed to
differ strongly. In our study, we quantified the effect of point defects,
dislocations and grain boundaries on the electrical resistivity of
molybdenum films having a constant thickness of 500 nm.
The kind and density of the microstructure defects in the Mo films were
modified by applying different physical vapour deposition methods (DC
magnetron sputtering, pulsed DC magnetron sputtering and RF magnetron
sputtering) and by depositing the thin films at different deposition
temperatures (room temperature, 150°C, 250°C and 350°C). As expected,
the electrical resistivity of the Mo films, which was measured using a 4point
probe, decreased with increasing substrate temperature. Furthermore,
the highest resistivity was observed in RF magnetron sputtered samples,
where also the effect of the substrate temperature was most pronounced.
The microstructure of the thin films was characterised by using a
combination of glancing angle X-ray diffraction (GAXRD), X-ray
reflectivity (XRR), XRD pole figure measurement, scanning electron
microscopy with electron back scattered diffraction (SEM/EBSD) and
transmission electron microscopy (TEM). GAXRD revealed residual
stresses, stress-free lattice parameters, crystallite size and microstrain in the
molybdenum films. XRR together with SEM and TEM gave information
about the morphology of the films; this information was complemented by
texture measurements performed using XRD and EBSD. The stress-free
lattice parameters were used as a measure of the density of point defects, the
microstrain as a measure of the dislocation density and the crystallite and
grain size as a measure of the distance between the grain boundaries. The
kind of the grain boundaries was deduced from the mutual orientation of
crystallites. It was concluded that the point defects have the highest impact
on the electrical conductivity of physical vapour deposited molybdenum
thin films, followed by dislocations, and grain and crystallite boundaries.
10:40am C2-3/F4-3-9 Study of the electrical performance of rf
magnetron sputtered TiO2 source and CuO drain split gate transistor,
S. Gopikishan, P. Laha, A.B. Panda, P.K. Barhai, Birla Institute of
Technology, India, AK. Das, Bhabha Atomic Research Center, India, I.
Banerjee, SK. Mahapatra (skmahapatra@bitmesra.ac.in), Birla Institute of
Technology, India
We have fabricated split-gate field effect transistor based on Si/Al2O3
substrate. TiO2 thin film (n-type) used as source, CuO thin film (p-type) as
drain and platinum thin film as gate of the transistor. The separation
between the two platinum gates was ~ 0.1 µm and confirmed by Scanning
Electron Microscope (SEM). The crystallinity of the Al2O3, TiO2 and CuO
Tuesday Morning, April 24, 2012 30
films was confirmed by the GIXRD. Resistance (RS), conductance (G), and
I-V measurement of the split-gate field effect transistor were performed by
Impedance analyzer and source meter respectively. The field effect on the
transistor current was studied by applying different bias voltage between the
splitting gate thin films of platinum. It was found that the conductance and
current were varied in a quantized step of 2e 2 /h with varying gate voltage.
The Shubnikov-de Haas effect in channel resistance (Rc) vs B at different
reverse bias of the transistor was also studied.
11:00am C2-3/F4-3-10 Characteristics and photocatalytic reactivity of
TiO2 beads synthesized using a microwave-assisted hydrothermal
method, W. Wu (wanyu@mdu.edu.tw), Y. Tsou, S. Huang, MingDao
University, Taiwan
In this study, a two-step process involving sol-gel and microwave
hydrothermal techniques are used to synthesis a novel TiO2 structure, so
called as TiO2 beads. It exhibits the required characteristics for
photocataysis such as large surface area and well anatase crystallinity.
Various synthesis parameters were investigated to evaluate the proper
processing window of TiO2 beads such as the complex amount in the sol-gel
process, temperature and heating time in the microwave hydrothermal
process. It was found that microwave hydrothermal techniques can much
reduce the process time and the size of TiO2 nanocrystalline. The texture
and morphology of obtained nanoporous TiO2 beads were examined using
scanning electron microscopy (SEM) and transmission electron microscopy
(TEM). The crystalline phase was analyzed using x-ray diffractometer
(XRD) and Raman spectroscopy. The surface chemical bonding state was
examined using x-ray photoelectron spectroscopy (XPS). The specific
surface, pore diameter and pore volume of beaded TiO2 was examined using
BET. UV-visible diffuse reflectance spectra were achieved using a UVvisible
spectrophotometer. The photocatalytic reactivity was obtained by
degradation the Methylene blue.
11:20am C2-3/F4-3-11 Effect of growth parameters and annealing on
some properties of sputtered ZnO thin films, R. Chander
(rcohri@yahoo.com), GPC Bhikhiwind, India
ZnO thin films were deposited by RF magnetron sputtering technique onto
silicon (001) and fused quartz substrates. The X-ray diffraction studies
revealed (002) plane oriented growth of ZnO nano-grains. Grain size and
surface roughness analysis performed onto AFM scans showed that av.
grain size of film ~75 nm and r.m.s. roughness of film ~ 7nm. The effect of
oxygen partial pressure during deposition was studied. Optical studies
revealed ~ 12% increase in transmittance in the visible range for thin films
grown in oxygen partial pressure than films grown without oxygen during
deposition. Films exhibited direct optical band gap ~3.2 to 3.37 eV for films
grown at different oxygen partial pressure as obtained from transmittance
data. The observed change in optical band gap is corroborated with
compositional analysis that showed deficiency of oxygen in ZnO matrix,
which decreases for films grown at higher oxygen partial pressure.
Refractive index and extinction coefficient was calculated by fitting the
spectroscopic ellipsometery data obtained for 0.5 oxygen partial pressure
film. Post deposition annealing of thin films in ambient environment led to
surface reconstruction and change in the morphology of grains along with
their growth during annealing at higher temperature.
Fundamentals and Technology of Multifunctional Thin
Films: Towards Optoelectronic Device Applications
Room: Pacific Salon 3 - Session C4-1
Transparent Conductive Films: Inorganic Oxides,
Organic Materials, Metals
Moderator: P. Kelly, Manchester Metropolitan University,
UK, S. Lim, Lawrence Berkeley National Laboratory, US
8:00am C4-1-1 ZnO films deposited from a filtered cathodic vacuum
arc: characterization and device applications, J.G. Partridge
(jim.partridge@rmit.edu.au), E.H. Mayes, M.R. Field, D.G. McCulloch,
RMIT University, Australia, H-S Kim, R. Heinhold, S. Elzwawi, G.C.
Turner, R.J. Reeves, M.W. Allen, University of Canterbury, New Zealand
Existing applications for zinc oxide thin films include transparent electronic
devices, transparent conducting electrodes and ultraviolet photonics.
Deposition methods such as molecular beam epitaxy and pulsed laser
deposition are normally required to achieve films with sufficient quality for
electronic device applications. Unfortunately, these methods typically incur
high cost and provide limited scalability. The filtered cathodic vacuum arc
(FCVA) deposition technique offering both low cost and high throughput is
routinely employed to produce aluminium doped ZnO for degenerate