Abstract: This paper presents a spectroscopic study on doping
of Vanadyl pathalocyanine (VOPc) by [6,6]-phenyl C61 butyric acid
methyl ester (PCBM). The films are characterized by UV/Vis/NIR
spectroscopy. A drastic increase in the absorption coefficient has
been observed with increasing dopant concentration. Optical
properties of VOPc:PCBM films deposited by spin coating technique
were studied in detail. Optical band gap decreased with the PCBM
incorporation in the VOPc film. Optical band gap calculated from the
absorption spectra decreased from 3.32 eV to 3.26 eV with a
variation of 0–75 % of PCBM concentration in the VOPC films.
Abstract: The study of the transport coefficients in electronic
devices is currently carried out by analytical and empirical models.
This study requires several simplifying assumptions, generally
necessary to lead to analytical expressions in order to study the
different characteristics of the electronic silicon-based devices.
Further progress in the development, design and optimization of
Silicon-based devices necessarily requires new theory and modeling
tools. In our study, we use the PSO (Particle Swarm Optimization)
technique as a computational tool to develop analytical approaches in
order to study the transport phenomenon of the electron in crystalline
silicon as function of temperature and doping concentration. Good
agreement between our results and measured data has been found.
The optimized analytical models can also be incorporated into the
circuits simulators to study Si-based devices without impact on the
computational time and data storage.
Abstract: Three sulphonic acid-doped polyanilines were
synthesized through chemical oxidation at low temperature (0-5 oC)
and potential of these polymers as sensing agent for O2 gas detection
in terms of fluorescence quenching was studied. Sulphuric acid,
dodecylbenzene sulphonic acid (DBSA) and camphor sulphonic acid
(CSA) were used as doping agents. All polymers obtained were dark
green powder. Polymers obtained were characterized by Fourier
transform infrared spectroscopy, ultraviolet-visible absorption
spectroscopy, thermogravimetry analysis, elemental analysis,
differential scanning calorimeter and gel permeation
chromatography. Characterizations carried out showed that polymers
were successfully synthesized with mass recovery for sulphuric aciddoped
polyaniline (SPAN), DBSA-doped polyaniline (DBSA-doped
PANI) and CSA-doped polyaniline (CSA-doped PANI) of 71.40%,
75.00% and 39.96%, respectively. Doping level of SPAN, DBSAdoped
PANI and CSA-doped PANI were 32.86%, 33.13% and
53.96%, respectively as determined based on elemental analysis.
Sensing test was carried out on polymer sample in the form of
solution and film by using fluorescence spectrophotometer. Samples
of polymer solution and polymer film showed positive response
towards O2 exposure. All polymer solutions and films were fully
regenerated by using N2 gas within 1 hour period. Photostability
study showed that all samples of polymer solutions and films were
stable towards light when continuously exposed to xenon lamp for 9
hours. The relative standard deviation (RSD) values for SPAN
solution, DBSA-doped PANI solution and CSA-doped PANI
solution for repeatability were 0.23%, 0.64% and 0.76%,
respectively. Meanwhile RSD values for reproducibility were 2.36%,
6.98% and 1.27%, respectively. Results for SPAN film, DBSAdoped
PANI film and CSA-doped PANI film showed the same
pattern with RSD values for repeatability of 0.52%, 4.05% and
0.90%, respectively. Meanwhile RSD values for reproducibility were
2.91%, 10.05% and 7.42%, respectively. The study on effect of the
flow rate on response time was carried out using 3 different rates
which were 0.25 mL/s, 1.00 mL/s and 2.00 mL/s. Results obtained
showed that the higher the flow rate, the shorter the response time.
Abstract: The threshold voltage and capacitance voltage characteristics of ultra-thin Silicon-on-Insulator MOSFET are greatly influenced by the thickness and doping concentration of the silicon film. In this work, the capacitance voltage characteristics and threshold voltage of the device have been analyzed with quantum mechanical effects using the Self-Consistent model. Reduction of channel thickness and adding doping impurities cause an increase in the threshold voltage. Moreover, the temperature effects cause a significant amount of threshold voltage shift. The temperature dependence of threshold voltage has also been observed with Self- Consistent approach which are well supported from experimental performance of practical devices.
Abstract: Films of pure tin oxide SnO2 and in presence of
antimony atoms (SnO2-Sb) deposited onto glass substrates have
shown a sufficiently high energy gap to be transparent in the visible
region, a high electrical mobility and a carrier concentration which
displays a good electrical conductivity [1]. In this work, the effects of
polycrystalline silicon substrate on the optical properties of pure and
Sb doped tin oxide is investigated.
We used the APCVD (atmospheric pressure chemical vapour
deposition) technique, which is a low-cost and simple technique,
under nitrogen ambient, for growing this material. A series of SnO2
and SnO2-Sb have been deposited onto polycrystalline silicon
substrates with different contents of antimony atoms at the same
conditions of deposition (substrate temperature, flow oxygen,
duration and nitrogen atmosphere of the reactor). The effect of the
substrate in terms of morphology and nonlinear optical properties,
mainly the reflectance, was studied. The reflectance intensity of the
device, compared to the reflectance of tin oxide films deposited
directly on glass substrate, is clearly reduced on the overall
wavelength range. It is obvious that the roughness of the poly-c
silicon plays an important role by improving the reflectance and
hence the optical parameters.
A clear shift in the minimum of the reflectance upon doping level
is observed. This minimum corresponds to strong free carrier
absorption, resulting in different plasma frequency. This effect is
followed by an increase in the reflectance depending of the antimony
doping. Applying the extended Drude theory to the combining
optical and electrical obtained results these effects are discussed.
Abstract: Highly ordered TiO2 nanotube (TNT) arrays were
fabricated onto a pre-treated titanium foil by anodic oxidation with a
voltage of 20V in phosphoric acid/sodium fluoride electrolyte. A pretreatment
of titanium foil involved washing with acetone,
isopropanol, ethanol and deionized water. Carbon doped TiO2
nanotubes (C-TNT) was fabricated 'in-situ' with the same method in
the presence of polyvinyl alcohol and urea as carbon sources. The
affects of polyvinyl alcohol concentration and oxidation time on the
composition, morphology and structure of the C-TN were studied by
FE-SEM, EDX and XRD techniques. FESEM images of the
nanotubes showed uniform arrays of C-TNTs. The density and
microstructures of the nanotubes were greatly affected by the content
of PVA. The introduction of the polyvinyl alcohol into the electrolyte
increases the amount of C content inside TiO2 nanotube arrays
uniformly. The influence of carbon content on the photo-current of
C-TNT was investigated and the I-V profiles of the nanotubes were
established. The preliminary results indicated that the 'in-situ'
doping technique produced a superior quality nanotubes compared to
post doping techniques.
Abstract: The effect of the number of quantum dot (QD) layers
on the saturated gain of doped QD semiconductor optical amplifiers
(SOAs) has been studied using multi-population coupled rate
equations. The developed model takes into account the effect of
carrier coupling between adjacent layers. It has been found that
increasing the number of QD layers (K) increases the unsaturated
optical gain for K
Abstract: Nowadays, doping is an intricate dilemma. Wrestling
is the nationally popular sport in Iran. Also the prevalence of doping
may be high, due to its power demanding characteristics. So, we
aimed to assess the knowledge and attitudes toward doping among
the club wrestlers. In a cross sectional study, 426 wrestlers were
studied. For this reason, a researcher made questionnaire was used. In
this study, researchers selected the clubs by randomized clustered
sampling and distributed the questionnaire among wrestlers.
Knowledge of wrestlers in three categories of doping definitions,
recognition of prohibited drugs and side effects was poor or moderate
in 70.8%, 95.8% and 99.5%, respectively. Wrestlers have poor
knowledge in doping. Furthermore, they believe some myths which
are unfavorable. It seems necessary to design a comprehensive
educational program for all of the athletes and coaches.
Abstract: The present work deals with the calculation of
transport properties of Hg0.8Cd0.2Te (MCT) semiconductor in
degenerate case. Due to their energy-band structure, this material
becomes degenerate at moderate doping densities, which are around
1015 cm-3, so that the usual Maxwell-Boltzmann approximation is
inaccurate in the determination of transport parameters. This problem
is faced by using Fermi-Dirac (F-D) statistics, and the non-parabolic
behavior of the bands may be approximated by the Kane model. The
Monte Carlo (MC) simulation is used here to determinate transport
parameters: drift velocity, mean energy and drift mobility versus
electric field and the doped densities. The obtained results are in
good agreement with those extracted from literature.
Abstract: A computational study at the level density functional theory (DFT) was carried out to investigate the influences of Si and C-doping on the 14N and 27Al quadrupole coupling constant in the (10, 0) zigzag single ? walled Aluminum-Nitride nanotube (AlNNT). To this aim, a 1.16nm, length of AlNNT consisting of 40 Al atoms and 40 N atoms were selected where the end atoms are capped by hydrogen atom. To follow the purpose, three Si atoms and three C atoms were doped instead of three Al atoms and three N atoms as a central ring in the surface of the Si and C-doped AlNNT. At first both of systems optimized at the level of BLYP method and 6-31G (d) basis set and after that, the NQR parameters were calculated at the level BLYP method and 6-311+G** basis set in two optimized forms. The calculate CQ values for both optimized AlNNT systems, raw and Si and C-doped, reveal different electronic environments in the mentioned systems. It was also demonstrated that the end nuclei have the largest CQ values in both considered AlNNT systems. All the calculations were carried out using Gaussian 98 package of program.