ICMCTF 2012! - CD-Lab Application Oriented Coating Development

dominates the characteristics of a-Si:H TFTs. The behavior of electrical
characteristics with mechanical strain can be explained by trap state
redistribution of the bandgap. The disordered bonds may generate a
redistribution of trap states, resulting in unstable electrical characteristics
such as threshold voltage, subthreshold swing, and mobility of carriers.
During mechanical strain the deep states are redistributed in a Gaussian
distribution, and are dissimilar to ordinary acceptor-like deep states which
manifest with exponential distributions. Electronic states near the Fermi
level act as recombination centers for photogenerated carries, and it may
valuable for illumination of the transistors. We conclude that the gap state
density of an a-Si:H layer under mechanical strain is fundamental to the
reliability and development of flexible electronics.
CP-25 Effects of RF power on the properties of Si thin films deposited
by an ICP CVD system with internal antennas, J.H. Hsieh
(jhhsieh@mail.mcut.edu.tw), YAN-LIANG. Lai, Ming Chi University of
Technology, Taiwan, Yuichi. Setsuhara, Osaka University, Japan
The plasma of an ICP-CVD system attached with four internal antennas was
used to deposit doped and un-doped Si thin films. Hydrogenated
microcrystalline silicon (μc-Si:H) films were prepared under various RF
power, while the flow ratio of SiH4/H2 was fixed at 1/4. During deposition,
an OES (optical emission spectrometer) and a plasma probe were used to
characterize the conditions of plasma. The crystalllinity and opto-electrical
properties of the Si:H films were investigated using Raman scattering
spectroscopy, XRD, Hall effect measurement system, and UV-Vis
photometer. It is found that the crystallinity of μc-Si:H film was
significantly affected by plasma density which was increased with the
increase of the power. This could be caused by the increase of I*SiH3/IHa. It is
also found the plasma potential would decrease with the increase of power,
while the plasma density would increase with the increase of power. The
carrier density, mobility, and photoconductivity were found related to the
plasma potential and density which might affect defect density in the films.
CP-27 The different radio-frequency powers on characteristics of
boron-doped amorphous carbon films prepared by reactive radiofrequency
chemical vapor deposition, T.S. Chen, S.E. Chiou, S.T. Shiue
(stshiue@dragon.nchu.edu.tw), National Chung Hsing University, Taiwan
Boron-doped amorphous carbon (a-C:B) films were deposited on n-type
silicon (n-Si) wafers using reactive radio-frequency (RF) chemical vapor
deposition. A boron target was used as the dopant source, and a mixture of
pure methane (CH4) and argon (Ar) gases with flow rates of 2 and 10 sccm,
respectively, was selected as the precursor gas. Five kinds of a-C:B films
were prepared with RF powers of 100, 200, 300, 400, and 500 W. The
substrate temperature and working pressure were set at 298 K and 6 Pa,
respectively. The thicknesses of a-C:B films were measured using field
emission scanning electron microscopy (FESEM). Alternatively, the
characteristics of a-C:B films were analyzed by X-ray photoelectron
spectrometer (XPS) and Raman scattering spectra (RSS). After the a-C:B/n-
Si junction was sputtered with gold (Au) and aluminum (Al) electrodes, the
current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/a-
C:B/n-Si/Al heterojunction devices were measured.
FESEM results show that all the thicknesses of a-C:B films are about 100
nm. XPS analyzed results reveal that the boron atoms are successfully
doped into amorphous carbon films, and the boron content increases from
0.02 to 28.87 at.% as the RF power increases from 100 to 500 W. The RSS
data of a-C:B films indicate that the ratio of the integrated intensity of the D
band to that of the G band (ID/IG) increases with increasing the RF power
from 100 to 300 W, but decreases with increasing the RF power from 300 to
500 W. It implies that the a-C:B film prepared with the RF power of 300 W
has a relatively higher graphitization degree. Our analyzed results also show
that all the I-V characteristics of Au/a-C:B/n-Si/Al heterojunction devices
exhibit the rectifying behavior. When the a-C:B film was prepared with the
RF power of 300 W, the Au/a-C:B/n-Si/Al heterojunction device displays
the best rectifying I-V characteristics, and its ideality factor is about 1.40.
The C-V measurement under the frequency of 1 kHz shows that as the a-
C:B film was prepared by the RF power of 300 W, the built-in voltage of
the Au/a-C:B/n-Si/Al device is about 0.2 V.
CP-28 InN/GaN Quantum Well Heterostructures: Structural
Characteristics and Strain Induced Modifications of the Electronic
Properties, -. Kioseoglou, Kalesaki, Aristoteles University of Thessaloniki,
Greece, Komninou, Aristotleles University of Thessaloniki, Greece,
Karakostas (karakost@auth.gr), Aristoteles University of Thessaloniki,
Greece
An important step towards optimization of InN/GaN based devices is the
identification of the structural characteristics of the corresponding interfaces
since the favourable bonding configurations determine the materials
polarity and consequently the direction of spontaneous polarization. We
have addressed this issue through empirical potential calculations on
Thursday Afternoon Poster Sessions 108
InN/GaN interfaces comprising misfit dislocations [1]. An appropriately
parameterized Tersoff interatomic potential [2] was implemented and
energetic calculations were performed on interfaces of III- and N- polarity,
lying at the single- or double bonds and having a wurtzite or zinc blende
stacking sequence in accordance with high resolution transmission electron
microscopy observations. Based on these results III-polarity interfaces,
cutting single bonds are energetically favourable.
In our present study, additional calculations are performed on subcritical
thickness InN/GaN QWs, which exhibit lower dislocation densities as well
as reduced InN decomposition and are currently implemented in the
fabrication of near-UV light emitting diodes [3,4]. Ab initio calculations are
performed under modified pseudopotentials, accurately reproducing the InN
and GaN band gap values, on supercells comprising 1 monolayer (ML)
thick InN elastically strained in 5 nm thick GaN barriers having a wurtzite
or zinc blende stacking at the interface. The former is found to be
energetically favourable. Subsequent calculations on supercells comprising
1 ML thick InN in 8 and 11 nm thick GaN barriers as well as 3 ML InN in
11 nm thick GaN having a wurtzite stacking, depicted a variation in III-N
bond lengths. This variation become more significant as the barrier
thickness decreases or the QW thickness increases. Hence the strain and
consequently piezoelectric polarization are modified. The latter is attested
by density of states calculations, which show a vast decrease of the band
gap when 5 nm thick barriers are considered, while a significant decrease is
also recorded at the 3 ML InN / 11 nm GaN barrier heterostructure in
comparison with the 1 ML InN supercell. Our results scrutinize recent
experimental observations [3,4] and could prove beneficial for tailoring the
optoelectronic properties of InN/GaN QWs.
[1] J. Kioseoglou et al., J. Mater. Sci. 43, 3982 (2008)
[2] J. Kioseoglou et al., Phys. Stat. Sol. (b) 245, 1118 (2008)
[3] E. Dimakis et al., Phys. Stat. Sol. (a) 205, 1070 (2008)
[4] A. Yoshikawa et al., J. Vac. Sci. Technol. B 26, 1071 (2008)
[5] Work supported by EC under the 7 th European Framework Project
DOTSENSE (Grant No.
STREP 224212)
CP-29 Optical properties of AlN:Ag and Al-Si-N:Ag nanostructured
films and the effect of thermal annealing, A. Siozios, E. Lidorikis, P.
Patsalas (ppats@cc.uoi.gr), University of Ioannina, Greece
Aluminum Nitride (AlN) is a wide bandgap semiconductor that has been
studied extensively because of its remarkable optical, mechanical, physical
and chemical properties that make it suitable for a variety of applications
such as optoelectronic devices, protective coatings, wave-guides, etc. The
incorporation of Ag into an AlN matrix can provide additional functionality
through the localized surface plasmon resonance (LSPR): a collective
oscillation of conduction electrons, fueled by light illumination at the proper
frequency. In this work we investigate under which circumstances LSPR is
manifested. In particular, we have grown nanostructured films consisting of
an AlN matrix and Ag inclusions in the form of nanospheres, nanosheets
and atomic dispersions, by sputtering and pulsed laser deposition (PLD).
The refractive index of the matrix was varying by controlling the matrix
microstructure and density (amorphous or wurtzite AlN, a-AlN and w-AlN,
respectively) and the optical absorption in the visible range was controlled
by the incorporation of Si in to the AlN matrix. The refractive index of the
films is correlated with the films’ density measured by X-Ray Reflectivity
(XRR). The optical properties of the films were studied using Optical
Reflectivity Spectroscopy (ORS) in vertical incidence in the 1.5-5.25 eV
spectral range. The spectroscopic data are critically compared to Finite
Difference Time Domain (FDTD) calculations of the optical response. The
effect of the thermal annealing to the plasmonic behavior of the AlN:Ag
and Al-Si-N:Ag has been studied systematically by repeating the ORS
measurement after annealing in inert Ar atmospheres cycles at various
temperatures as high as 800 o C.
CP-30 Investigation of photoluminescent characteristics and optical
properties of thin film zinc silicate doped with manganese, K.H. Yoon,
J.H. Kim (joohan@cbnu.ac.kr), Chungbuk National University, Republic
of Korea
The photoluminescent characteristics and optical properties of manganesedoped
zinc silicate (Zn2SiO4:Mn) thin films were investigated. The
Zn2SiO4:Mn films were deposited by radio frequency magnetron sputtering,
followed by post-deposition annealing at temperatures of 600 – 1200 °C.
The Zn2SiO4:Mn films exhibited a pronounced optical absorption edge in
the near ultraviolet wavelength region and a high optical transparency in the
visible spectral range. The maximum transmittance reached 0.922 at 597
nm, which was very close to the transmittance of the fused quartz substrate
alone. The refractive index of the Zn2SiO4:Mn films showed normal
dispersion behavior. X-ray diffraction and atomic force microscopy
measurements revealed that the as-deposited Zn2SiO4:Mn films had an