Abstract: A Silver (Ag) thin film is introduced as a template and
doping source for vertically aligned p–type ZnO nanorods. ZnO
nanorods were grown using an ammonium hydroxide based
hydrothermal process. During the hydrothermal process, the Ag thin
film was dissolved to generate Ag ions in the solution. The Ag ions can
contribute to doping in the wurzite structure of ZnO and the (111)
grain of Ag thin film can be the epitaxial temporal template for the
(0001) plane of ZnO. Hence, Ag–doped p–type ZnO nanorods were
successfully grown on the substrate, which can be an electrode or
semiconductor for the device application. To demonstrate the
potentials of this idea, p–n diode was fabricated and its electrical
characteristics were demonstrated.
Abstract: We present an analytical model for the calculation of
the sensitivity, the spectral current noise and the detective parameter
for an optically illuminated In0.53Ga0.47As n+nn+ diode. The
photocurrent due to the excess carrier is obtained by solving the
continuity equation. Moreover, the current noise level is evaluated at
room temperature and under a constant voltage applied between the
diode terminals. The analytical calculation of the current noise in the
n+nn+ structure is developed by considering the free carries
fluctuations. The responsivity and the detection parameter are
discussed as functions of the doping concentrations and the emitter
layer thickness in one-dimensional homogeneous n+nn+ structure.
Abstract: Nitrogen-doped graphene quantum dots (N-GQDs)
were fabricated by microwave-assisted hydrothermal technique. The
optical properties of the N-GQDs were studied. The luminescence of
the N-GQDs can be tuned by varying the excitation wavelength.
Furthermore, two-photon luminescence of the N-GQDs excited by
near-infrared laser can be obtained. It is shown that N-doping play a
key role on two-photon luminescence. The N-GQDs are expected to
find application in biological applications including bioimaging and
sensing.
Abstract: In the present study, we have synthesized Cr and Fe
doped zinc oxide (ZnO) nanostructures (Zn1-δCraFebO; where δ = a +
b = 20%, a = 5, 6, 8 & 10% and b = 15, 14, 12 & 10%) via sol-gel
method at different doping concentrations. The synthesized samples
were characterized for structural properties by X-ray diffractrometer
and field emission scanning electron microscope and the optical
properties were carried out through photoluminescence and UVvisible
spectroscopy. The particle size calculated through field
emission scanning electron microscope varies from 41 to 96 nm for
the samples synthesized at different doping concentrations. The
optical band gaps calculated through UV-visible spectroscopy are
found to be decreasing from 3.27 to 3.02 eV as the doping
concentration of Cr increases and Fe decreases.
Abstract: Cesiumiodide with Na doping (CsI(Na)) solution or melt is easily forming three- dimension dendrites on the free surface. The defects or bobbles form inside the CsI(Na) during the solution or melt solidification. The defects or bobbles can further effect the x-ray path in the CsI(Na) crystal and decrease the scintillation characteristics of CsI(Na). In order to enhance the CsI(Na) scintillated property we made single crystal of CsI(Na) column in the anodic aluminum oxide (AAO) template by hydraulic pressure injection method. It is interesting that when CsI(Na) melt is confined in the small AAO channels, the column grow as stable single column without any dendrites. The high aspect ratio (100~10000) of AAO and nano to sub-micron channel structure which is a suitable template for single of crystal CsI(Na) formation. In this work, a new low-cost approach to fabricate scintillator crystals using anodic aluminum oxide (AAO) rather than Si is reported, which can produce scintillator crystals with a wide range of controllable size to optimize their performance in X-ray detection.
Abstract: Computer software to calculate electron mobility with respect to different scattering mechanism has been developed. This software is adopted completely Graphical User Interface (GUI) technique and its interface has been designed by Microsoft Visual basic 6.0. As a case study the electron mobility of n-GaN was performed using this software. The behavior of the mobility for n-GaN due to elastic scattering processes and its relation to temperature and doping concentration were discussed. The results agree with other available theoretical and experimental data.
Abstract: This paper presents device simulations on the vertical silicon nanowire tunneling FET (VSiNW TFET). Simulations show that a narrow nanowire and thin gate oxide is required for good performance, which is expected even for conventional MOSFETs. The gate length also needs to be more than the nanowire diameter to prevent short channel effects. An effect more unique to TFET is the need for abrupt source to channel junction, which is shown to improve the performance. The ambipolar effect suppression by reducing drain doping concentration is also explored and shown to have little or no effect on performance.
Abstract: The porous silicon (PS), formed from the anodization
of a p+ type substrate silicon, consists of a network organized in a
pseudo-column as structure of multiple side ramifications. Structural
micro-topology can be interpreted as the fraction of the interconnected
solid phase contributing to thermal transport. The
reduction of dimensions of silicon of each nanocristallite during the
oxidation induced a reduction in thermal conductivity. Integration of
thermal sensors in the Microsystems silicon requires an effective
insulation of the sensor element. Indeed, the low thermal conductivity
of PS consists in a very promising way in the fabrication of integrated
thermal Microsystems.In this work we are interesting in the
measurements of thermal conductivity (on the surface and in depth)
of PS by the micro-Raman spectroscopy. The thermal conductivity is
studied according to the parameters of anodization (initial doping and
current density. We also, determine porosity of samples by
spectroellipsometry.
Abstract: The “conveyor belt" as a product represents a
complex high performance component with a wide range of different
applications. Further development of these highly complex
components demands an integration of new technologies and new
enhanced materials. In this context nanostructured fillers appear to
have a more promising effect on the performance of the conveyor
belt composite than conventional micro-scaled fillers.
Within the project “DotTrans" nanostructured fillers, for example
silicon dioxide, are used to optimize performance parameters of
conveyor belt systems. The objective of the project includes
operating parameters like energy consumption or friction
characteristics as well as adaptive parameters like cut or wear
resistance.
Abstract: This article summarizes ways to verify neutron
fluence for neutron transmutation doping of silicon with phosphorus
on the LVR-15 reactor. Neutron fluence is determined using
activation detectors placed along the crystal in a strip or encapsulated
in a rod holder. Holders are placed at the centre of a water-filled
capsule or in an aluminum or silicon ingot that simulates a real single
crystal. If the diameter of the crystal is significantly less than the
capsule diameter and water from the primary circuit enters the free
space in the capsule, neutron interaction in the water changes neutron
fluence, affecting axial irradiation homogeneity. The effect of
moving the capsule vertically in the channel relative to maximum
neutron fluence in the reactor core was also measured. Even a small
shift of the capsule-s centre causes great irradiation inhomogeneity.
This effect was measured using activation detectors, and was also
confirmed by MCNP calculation.
Abstract: Aggressive scaling of MOS devices requires use of ultra-thin gate oxides to maintain a reasonable short channel effect and to take the advantage of higher density, high speed, lower cost etc. Such thin oxides give rise to high electric fields, resulting in considerable gate tunneling current through gate oxide in nano regime. Consequently, accurate analysis of gate tunneling current is very important especially in context of low power application. In this paper, a simple and efficient analytical model has been developed for channel and source/drain overlap region gate tunneling current through ultra thin gate oxide n-channel MOSFET with inevitable deep submicron effect (DSME).The results obtained have been verified with simulated and reported experimental results for the purpose of validation. It is shown that the calculated tunnel current is well fitted to the measured one over the entire oxide thickness range. The proposed model is suitable enough to be used in circuit simulator due to its simplicity. It is observed that neglecting deep sub-micron effect may lead to large error in the calculated gate tunneling current. It is found that temperature has almost negligible effect on gate tunneling current. It is also reported that gate tunneling current reduces with the increase of gate oxide thickness. The impact of source/drain overlap length is also assessed on gate tunneling current.
Abstract: A major challenge in biomaterials research is the
regulation of protein adsorption which is a key factor for controlling
the subsequent cell adhesion at implant surfaces. The aim of the
present study was to control the adsorption of fibronectin (FN) and
the attachment of MG-63 osteoblasts with an electronic
nanostructure. Shallow doping line lattices with a period of 260 nm
were produced for this purpose by implantation of phosphorous in
silicon wafers. Protein coverage was determined after incubating the
substrate with FN by means of an immunostaining procedure and the
measurement of the fluorescence intensity with a TECAN analyzer.
We observed an increased amount of adsorbed FN on the
nanostructure compared to control substrates. MG-63 osteoblasts
were cultivated for 24h on FN-incubated substrates and their
morphology was assessed by SEM. Preferred orientation and
elongation of the cells in direction of the doping lattice lines was
observed on FN-coated nanostructures.
Abstract: Carriers scattering in the inversion channel of n-
MOSFET dominates the drain current. This paper presents an effective
electron mobility model for the pocket implanted nano scale
n-MOSFET. The model is developed by using two linear pocket
profiles at the source and drain edges. The channel is divided into
three regions at source, drain and central part of the channel region.
The total number of inversion layer charges is found for these three
regions by numerical integration from source to drain ends and the
number of depletion layer charges is found by using the effective
doping concentration including pocket doping effects. These two
charges are then used to find the effective normal electric field,
which is used to find the effective mobility model incorporating the
three scattering mechanisms, such as, Coulomb, phonon and surface
roughness scatterings as well as the ballistic phenomena for the
pocket implanted nano-scale n-MOSFET. The simulation results show
that the derived mobility model produces the same results as found
in the literatures.
Abstract: Microbial contamination, most of which are fecal born in drinking water and food industry is a serious threat to humans. Escherichia coli is one of the most common and prevalent among them. We have developed a sensor for rapid and an early detection of contaminants, taking E.coli as a threat indicator organism. The sensor is based on co-polymerizations of aniline and formaldehyde in form of thin film over glass surface using the vacuum deposition technique. The particular doping combination of thin film with Fe-Al and Fe-Cu in different concentrations changes its non conducting properties to p- type semi conductor. This property is exploited to detect the different contaminants, believed to have the different surface charge. It was found through experiments that different microbes at same OD (0.600 at 600 nm) have different conductivity in solution. Also the doping concentration is found to be specific for attracting microbes on the basis of surface charge. This is a simple, cost effective and quick detection method which not only decreases the measurement time but also gives early warnings for highly contaminated samples.
Abstract: This paper presents the doping profile measurement
and characterization technique for the pocket implanted nano scale
n-MOSFET. Scanning capacitance microscopy and atomic force
microscopy have been used to image the extent of lateral dopant
diffusion in MOS structures. The data are capacitance vs. voltage
measurements made on a nano scale device. The technique is nondestructive
when imaging uncleaved samples. Experimental data from
the published literature are presented here on actual, cleaved device
structures which clearly indicate the two-dimensional dopant profile
in terms of a spatially varying modulated capacitance signal. Firstorder
deconvolution indicates the technique has much promise for
the quantitative characterization of lateral dopant profiles. The pocket
profile is modeled assuming the linear pocket profiles at the source
and drain edges. From the model, the effective doping concentration
is found to use in modeling and simulation results of the various
parameters of the pocket implanted nano scale n-MOSFET. The
potential of the technique to characterize important device related
phenomena on a local scale is also discussed.
Abstract: This paper presents a threshold voltage model of pocket implanted sub-100 nm n-MOSFETs incorporating the drain and substrate bias effects using two linear pocket profiles. Two linear equations are used to simulate the pocket profiles along the channel at the surface from the source and drain edges towards the center of the n-MOSFET. Then the effective doping concentration is derived and is used in the threshold voltage equation that is obtained by solving the Poisson-s equation in the depletion region at the surface. Simulated threshold voltages for various gate lengths fit well with the experimental data already published in the literature. The simulated result is compared with the two other pocket profiles used to derive the threshold voltage models of n-MOSFETs. The comparison shows that the linear model has a simple compact form that can be utilized to study and characterize the pocket implanted advanced ULSI devices.
Abstract: In realizing devices using ZnO, a key challenge is the
production of p-type material. Substitution of oxygen by a group-V
impurity is thought to result in deep acceptor levels, but a candidate
made up from a complex of a group-V impurity (P, As, Sb) on a Zn
site coupled with two vacant Zn sites is widely viewed as a candidate.
We show using density-functional simulations that in contrast to such
a view, complexes involving oxygen interstitials are energetically
more favorable, resulting in group-V impurities coordinated with four,
five or six oxygen atoms.
Abstract: This paper presents a physics-based model for the
high-voltage fast recovery diodes. The model provides a good
trade-off between reverse recovery time and forward voltage drop
realized through a combination of lifetime control and emitter
efficiency reduction techniques. The minority carrier lifetime can be
extracted from the reverse recovery transient response and forward
characteristics. This paper also shows that decreasing the amount of
the excess carriers stored in the drift region will result in softer
characteristics which can be achieved using a lower doping level. The
developed model is verified by experiment and the measurement data
agrees well with the model.
Abstract: In metal cutting industries, mathematical/statistical
models are typically used to predict tool replacement time. These
off-line methods usually result in less than optimum replacement
time thereby either wasting resources or causing quality problems.
The few online real-time methods proposed use indirect measurement
techniques and are prone to similar errors. Our idea is based on
identifying the optimal replacement time using an electronic nose to
detect the airborne compounds released when the tool wear reaches
to a chemical substrate doped into tool material during the
fabrication. The study investigates the feasibility of the idea, possible
doping materials and methods along with data stream mining
techniques for detection and monitoring different phases of tool
wear.
Abstract: Carrier mobility has become the most important
characteristic of high speed low dimensional devices. Due to
development of very fast switching semiconductor devices, speed of
computer and communication equipment has been increasing day by
day and will continue to do so in future. As the response of any
device depends on the carrier motion within the devices, extensive
studies of carrier mobility in the devices has been established
essential for the growth in the field of low dimensional devices.
Small-signal ac transport of degenerate two-dimensional hot
electrons in GaAs quantum wells is studied here incorporating
deformation potential acoustic, polar optic and ionized impurity
scattering in the framework of heated drifted Fermi-Dirac carrier
distribution. Delta doping is considered in the calculations to
investigate the effects of double delta doping on millimeter and submillimeter
wave response of two dimensional hot electrons in GaAs
nanostructures. The inclusion of delta doping is found to enhance
considerably the two dimensional electron density which in turn
improves the carrier mobility (both ac and dc) values in the GaAs
quantum wells thereby providing scope of getting higher speed
devices in future.