Effect Of Doping Concentration Research Articles

Photoelectrocatalytic activity of immobilized Yb doped WO3 photocatalyst for degradation of methyl orange dye

Pure WO3 and Yb:WO3 thin films have been synthesized by spray pyrolysis technique. Effect of Yb doping concentration on photoelectrochemical, structural, morphological and optical properties of thin films are studied. X-ray diffraction analysis shows that all thin films are polycrystalline nature and exhibit monoclinic crystal structure. The 3at% Yb:WO3 film shows superior photoelectrochemical (PEC) performance than that of pure WO3 film and it shows maximum photocurrent density (Iph=1090µA/cm2) having onset potentials around +0.3V/SCE in 0.01M HClO4. The photoelectrocatalytic process is more effective than that of the photocatalytic process for degradation of methyl orange (MO) dye. Yb doping in WO3 photocatalyst is greatly effective to degrade MO dye. The enhancement in photoelectrocatalytic activity is mainly due to the suppressing the recombination rate of photogenerated electron-hole pairs. The mineralization of MO dye in aqueous solution is studied by measuring chemical oxygen demand (COD) values.

Optoelectronic Evaluation and Loss Analysis of PEDOT:PSS/Si Hybrid Heterojunction Solar Cells

The organic/silicon (Si) hybrid heterojunction solar cells (HHSCs) have attracted considerable attention due to their potential advantages in high efficiency and low cost. However, as a newly arisen photovoltaic device, its current efficiency is still much worse than commercially available Si solar cells. Therefore, a comprehensive and systematical optoelectronic evaluation and loss analysis on this HHSC is therefore highly necessary to fully explore its efficiency potential. Here, a thoroughly optoelectronic simulation is provided on a typical planar polymer poly (3,4-ethylenedioxy thiophene):polystyrenesulfonate (PEDOT:PSS)/Si HHSC. The calculated spectra of reflection and external quantum efficiency (EQE) match well with the experimental results in a full-wavelength range. The losses in current density, which are contributed by both optical losses (i.e., reflection, electrode shield, and parasitic absorption) and electrical recombination (i.e., the bulk and surface recombination), are predicted via carefully addressing the electromagnetic and carrier-transport processes. In addition, the effects of Si doping concentrations and rear surface recombination velocities on the device performance are fully investigated. The results drawn in this study are beneficial to the guidance of designing high-performance PEDOT:PSS/Si HHSCs.

Doping concentration effect on performance of single QW double-heterostructure InGaN/AlGaN light emitting diode

Light emitting diode (LED) employed a numerous applications such as displaying information, communication, sensing, illumination and lighting. In this paper, InGaN/AlGaN based on one quantum well (1QW) light emitting diode (LED) is modeled and studied numerically by using COMSOL Multiphysics 5.1 version. We have selected In0.06Ga0.94N as the active layer with thickness 50nm sandwiched between 0.15μm thick layers of p and n-type Al0.15Ga0.85N of cladding layers. We investigated an effect of doping concentration on InGaN/AlGaN double heterostructure of light-emitting diode (LED). Thus, energy levels, carrier concentration, electron concentration and forward voltage (IV ) are extracted from the simulation results. As the doping concentration is increasing, the performance of threshold voltage, Vth on one quantum well (1QW) is also increases from 2.8V to 3.1V.

Preparation and Luminescence Properties of Dy<sup>3+</sup> Doped Sr<sub>3</sub>Lu(PO<sub>4</sub>)<sub>3</sub> as a New Single Phase White Light Emitting Phosphor

The novel white light emitting phosphors Sr3Lu(1-x)Dyx(PO4)3 (x = 0.02, 0.04, 0.06, 0.08, 0.10) were synthesized via a conventional high-temperature solid-state reaction method at 1250°C. The excitation spectrum indicated that these phosphors had a strong absorption in near UV region in the range from 260 to 460 nm. And under 350 nm excitation, the blue emission at 483nm (4F9/2→6H15/2) and yellow emission at 576 nm (4F9/2→6H13/2) were observed in the phosphors, respectively. We studied the effect of different doping concentrations of Dy3+ activator on the luminescence properties and found that the optimum doping concentration is 6 mol%. According to the Dexter’s theory, this quenching behavior is ascribed to be electric d-d interaction. Furthermore, the chromaticity coordinate (x = 0.28, y = 0.32) of Sr3Lu (PO4)3:0.06Dy3+ phosphor was very close to the “ideal white” (x = 0.33, y = 0.33) in the chromaticity diagram. Our results indicate that the Sr3Lu (PO4)3:Dy3+ phosphor can serve as a promising candidate for single-component white light emitting phosphor under near UV excitation.

Effect of co doping to the optical properties of ZnO:Co Thin films deposited on glass substrate by sol-gel spray coating technique

This study aims are to analyze the effect of cobalt doping concentration to the optical properties ZnO:Co thin films deposited by using sol-gel spray coating technique. Deposition of ZnO and ZnO:Co thin films has been successfully formed on a glass substrate using sol-gel method of spray coating technique with a variation of doping Co as much as 3%, 5%, 7%, 9%, and 11%. Solution of ZnO:Co synthesized by mixing zinc acetate dehydrate (Zn (COOCH3)2.2H2O into a isopropanol ((CH3)2CHOH) then monoethanolamine (MEA) and cobalt nitrate are added as a dopant at room temperature, then ZnO:Co sprayed on a glass substrate that has been heated at a temperature of 450°C. A thin film further characterized using spectrophotometer Uv-Vis to determine the value of absorbance and transmittance. Energy band gap was determined by using tauc plot that uses the absorbance value. The results show that there has been a difference in the value of the Energy band gap of ZnO with and without of Co doping. The addition of Co doping causes the decrease of small energy band gap. The magnitude of the energy band gap of thin films of ZnO is 3.337 eV and ZnO:Co 3% is 3.129 eV. Thin film that has narrower band gap was applied for material photocatalyst

Effect of Mo doping concentration on the physical properties of ZnO studied by first principles

The experimental results of red-shift and blue-shift in absorption spectrum of Mo-doped ZnO are in mutual contradiction, and this phenomenon has not been explained rationally so far. For explaining this phenomenon, we analyze the energy band structure, state density, and absorption-spectrum distributions for each of Zn0.9583Mo0.0417O, Zn0.9375Mo0.0625O and Zn14Mo2O by first-principles calculation. The results show that within a limited doping amount range of 2.08 at%-3.13 at%, the higher Mo doping amount results in higher doping system volume, higher formation energy, lower system stability, and more difficult to dope. Meanwhile, all doping systems are converted into n-type degenerate semiconductors. Compared with the band gap of pure ZnO, the band gap of each doping system becomes narrow and the absorption spectrum shows red-shift. The higher the Mo doping amount, the weaker the narrowing of band gap becomes and the weaker the red-shift in absorption spectrum as well as the lower the electronic effective mass and the lower the electronic concentration; the lower the electronic mobility, the lower the electronic conductivity is; the lower the electronic magnetic moment is. The Curie temperature of doping system can reach a temperature higher than room temperature.

Semiconductor plasmonic gas sensor using on-chip infrared spectroscopy

In this paper, we take a novel approach in on-chip optical sensing of gases. Gases have conventionally been optically sensed using refractive index, which is a non-ideal method because of the difficulty in differentiating gases with very similar refractive indices. Infrared (IR) absorption spectra on the other hand have characteristic peaks in the fingerprint region that allow identifying the analyte. Highly doped n-type Indium Arsenide was used to design a plasmonic slot waveguide, and a dispersion analysis was carried out using the finite element method to study the effect of dopant concentration and waveguide geometry on the guided modes. Finite-difference time domain was used to simulate the transmission spectrum of the waveguide with air, methane and octane and the characteristic peaks in the IR spectra showed up strongly. This is a promising versatile method that can sense any IR-active gas.

On the determination of the substrate effective doping concentration of irradiated HV-CMOS sensors using an edge-TCT technique based on the Two-Photon-Absorption process

We introduce a new method based on the transient-current technique (TCT) for the radiation tolerance assessment of an n-in-p junction with a deep n-well on a relatively low-resistivity p-type substrate commonly used for HV-CMOS pixel sensors. The transient-current method here employed uses a femtosecond laser to generate excess carriers via a two-photon-absorption (TPA) process. Special attention has been paid to overcome the limitations of the conventional transient-current method based on single-photon-absorption carrier generation when applied to the HV-CMOS sensors. Specifically, we tackle the precise determination of the depletion region boundaries, including the deep-n-well spatial location, needed to calculate the effective doping concentration of the substrate. As illustration, we have applied this new TPA-based method to both a fresh and a neutron irradiated single-pixel deep-n-well diode manufactured in a 180 nm high-voltage CMOS process. In the irradiated device, concurrent with the expected effective acceptor removal in the p-type substrate, an indication of an effective donor removal in the DNW implant was also observed.

Effect of Doping Concentration on the Optical Properties of Indium-Doped Gallium Arsenide Thin FILMS

Effects of indium doping (concentration 0.2, 0.3 and 0.4%) on the optical properties of GaAs thin films were studied. Thin films of 600 nm were grown onto chemically and ultrasonically cleaned glass substrate by thermal evaporation method in high vacuum (~10-4 Pa) at 50°C fixed substrate temperature. The samples were annealed for 15 minutes at a fixed temperature of 200°C. The thicknesses of films were being measured in situ by a quartz crystal thickness monitor during deposition. The transmittance and reflectance data were found using UV-VIS-NIR spectrophotometer in the photon wavelength range of 310 ~ 2500 nm. These data were utilized to compute the absorption coefficient, refractive index, extinction co-efficient and band gap energy of the studied films. Here transmittance was found 78 for 0.2% indium doping concentration. The band gap energy decreased with the increase of doping concentration.Journal of Bangladesh Academy of Sciences, Vol. 40, No. 2, 179-186, 2016

Effect of lithium-ion doping concentration on structural and optical properties of NiO films fabricated by magnetron sputtering

In the present work, we report the dependence of lithium-ion (Li+) doping concentration on structure, optical and electrical properties of NiO films fabricated by radio frequency (rf) magnetron sputtering. It was found that the NiO grains were increased with increase in lithium-ion concentration from an anomalous state to a cubic shape following the NaCl-type structure. The NiO films presented highly c-axis preferred orientation with significant (111) diffraction. The samples marked A-C under the lithium-ion concentration of 1 at.%, 3 at.%, and 5 at.% respectively have optical band gap values of 3.72 eV, 3.61 eV and 3.47 eV, respectively. Comparatively, the controllable electrical properties of NiO films can be achieved by the variations of crystal quality arise from the lithium-ion doping concentration.

Effects of Zn doping concentration on resistive switching characteristics in Ag /La1−x Zn x MnO 3 / p + $_{3}/\textit {p}^{\mathrm {+}}$ -Si devices

Ag /La 1 −x Zn x MnO\(_{\mathbf {3}}\boldsymbol {/}\textit {p}^{\boldsymbol {+}}\)-Si devices with different Zn doping contents were fabricated through sol–gel method. The effects of Zn doping concentration on the microstructure of La 1 −x Zn x MnO 3 films, as well as on the resistance switching behaviour and endurance characteristics of Ag /La 1 −x Zn x MnO\(_{\mathbf {3}}\boldsymbol {/}\textit {p}^{\boldsymbol {+}}\)-Si were investigated. After annealing at 600∘C for 1 h, the La 1 −x Zn x MnO 3 (x = 0.1, 0.2, 0.3, 0.4, 0.5) are amorphous and have bipolar resistance characteristics, with R H R S / R L R S ratios >103. However, the endurance characteristics show considerable differences; x= 0 . 3 shows the best endurance characteristics in more than 1000 switching cycles. The conduction mechanism of the Ag /La 1 −x Zn x MnO\(_{\mathbf {3}}\boldsymbol {/}\textit {p}^{\boldsymbol {+}}\)-Si is the Schottky emission mode at high resistance state. However, the conduction mechanism at low resistance state varies with Zn doping concentration. The dominant mechanism at x= 0 . 1 is filamentary conduction mechanism, whereas that at x ≥ 0 . 2 is space-charge-limited current conduction.

RESURF Model and Electrical Characteristics of Finger-Type STI Drain Extended MOS Transistors

Finger-type shallow trench isolation (finger STI) drain extended MOS transistors are fabricated and its electrical characteristics is studied. Polyplate on a finger STI served as a reduced surface field is adopted to enhance breakdown voltage (BV) by reducing the effective doping concentration of the drain extension (DE) finger. The conformal mapping method, which relates the reduction of the doping concentration to the width ( $z_{o}$ ) of the DE finger, the gap ( $z_{d}$ ) between the polyplate and the DE finger, and the STI depth $y_{s}$ , is used to estimate the reduction of the doping concentration theoretically. Based on this reduced doping concentration, a BV model is derived. The predictions of this model agree very well with the experimental data.

Analytical modeling of subthreshold characteristics of ion-implanted symmetric double gate junctionless field effect transistors

This paper reports a 2D analytical model for the subthreshold current and subthreshold swing (SS) of ion-implanted Double-Gate Junctionless Field Effect Transistors (DG-JLFETs) with a vertical Gaussian-like doping profile. The effects of gate length, straggle parameter, oxide thickness, channel thickness, and peak doping concentration on subthreshold current and subthreshold swing have been demonstrated. The model results are validated with the simulation data obtained by 2-D TCAD ATLASTM device simulator. Finally, the performance of a CMOS inverter using the DG-JLFET device has been investigated through ATLASTM TCAD mixed mode circuit simulations.

Effects of drain doping concentration on switching characteristics of tunnel field-effect transistor inverters

In order to investigate the effects of the modulation of drain doping concentration (Ndrain) on alternating current (AC) switching characteristics of a tunnel filed-effect transistor (TFET) inverter, the characteristics of TFETs with various Ndrains are analyzed rigorously through mixed-mode device and circuit TCAD simulations. As the Ndrain gets decreased, the drain current (ID) becomes reduced and the gate-to-drain capacitance (CGD) reflects the entire gate capacitance (CGG) at a lower gate voltage (VG), which leads to the degradation of falling/rising delay in TFET inverters. These phenomena are explained successfully by the change of quasi-Fermi energy in the drain (EF_drain) as a function of VG. The EF_drain rises dramatically from when tunneling current starts to flow from the source in the n-type TFET with low Ndrain. As a result, drain-side channel inversion occurs at a lower VG due to the reduction of the energy barrier between the EF_drain and the conduction band edge of the channel.

First observation of sol-gel derived Al:CsZnO/CsZnO bilayer thin film for solar cells application

In this research, we fabricated CsZnO and Al:CsZnO/CsZnO bilayer thin films grown by the spin-coating-assisted sol-gel method on ITO substrate. The influence of diverse velocity of spin-coating (500, 1000, 1500, 2000, 2500 and 3000RPM) and also annealing times (30, 60, 90, 120, 150 and 180min) on the characteristics of the ZnO thin film was examined. The samples were examined by X-ray diffraction, scanning electron microscopy, Uv-Vis spectrometer and conductivity measurement. With the optimization of the velocity of spin-coating (2500RPM) and annealing times (60min), we fabricated Al:CsZnO/CsZnO bilayer thin films with diverse dopant concentration. By comparing the effect of dopant concentration with different dopant ratio (0, 0.5, 1.0 and 2%), 0.5% of CsZnO and Al:CsZnO/CsZnO bilayer was found as the most effective doping level with the best conductivity properties among the selected doping concentrations.

Fabrication and characterization of Sr-doped PbS thin films grown by CBD

In this work, undoped and Strontium-doped lead sulfide (PbS) thin films were deposited on glass substrates by chemical bath deposition (CBD) technique. The effect of Sr doping concentration on the structural, morphological and optical properties of the PbS thin films was studied. Changing in crystallite size, microstrain, dislocation density and band gap energy values of the PbS thin films as a function of Sr concentration were investigated by scanning electron microscopy (SEM), X-Ray diffraction (XRD) and UV–visible spectroscopy measurements. Energy dispersive X-Ray analysis (EDS) results indicated that nanostructured PbS films is doped with Sr without causing much lattice strain. According to XRD experiments crystallite size of the films is decreasing from 17.90 to 9.14nm with increasing Sr-doping. UV–visible analysis showed that the band gap value of PbS thin films increased from 1.73ev to 2.19eV by changing Sr doping concentration from 0% to 5%.

The effects of cerium doping concentration on the properties and photocatalytic activity of bimetallic Mo/Ce catalyst

In this study, the characterization and photocatalytic activity of MoO3 nanoparticles doped with various doping concentrations of cerium have been investigated. The Fourier transform infrared (FT-IR) spectra of the prepared catalysts confirmed that MoO3 particles have been successfully doped by cerium. Field emission scanning electron microscopy (FESEM) was performed to visualize the surface morphology of the obtained catalysts. The XRD patterns suggested that the crystallinity of the sample with the lowest doping concentration of 15 mol % was higher in comparison with samples of higher doping concentrations. The volume-averaged crystal sizes of the obtained catalysts were calculated to be 25, 28, and 32 nm for 15, 35, and 60 mol % samples, respectively. The photocatalytic activity along with the reaction kinetics of Ce-doped MoO3 nanoparticles have also been investigated through the dye degradation of methyl orange. The synthesized Ce-doped MoO3 particles with the lowest dopant concentration of 15 mol % exhibited the highest photocatalytic activity for methyl orange dye degradation. It was observed that photo-degradation activity decreased with an increase in the doping concentration of cerium. The predicted rate constants for samples with 15, 35, and 60 mol % doping concentrations were found to be 0.0432, 0.035, and 0.029 min–1, respectively.

Na doping effects on the structural, conduction type and optical properties of sol–gel ZnO thin films

In this work we report on the sol–gel deposition of Na doped ZnO thin films on quartz substrates. The effects of Na doping concentrations (0, 3, 6 and 9 at.%) on structural, morphological, electrical and optical properties of the synthesized films were systematically investigated by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), Hall-effect measurements, UV–Vis–NIR spectrophotometry and photoluminescence (PL) spectroscopy. XRD patterns showed that the prepared films were highly c-axis oriented exhibiting hexagonal wurtzite structure of ZnO. Raman spectra of All the ZnO films exhibited similar scattering peaks corresponding to the Raman active modes of ZnO wurtzite hexagonal structure. AFM images indicated that grain size and surface roughness of the films were affected by Na doping. From the Hall-effect measurements, it was found that carrier type is dependent on Na content. The UV–Vis–NIR spectroscopy analyses revealed that all the films were highly transparent in the visible region. Room temperature PL spectra demonstrated that UV emission of the Na-doped ZnO thin films depends on the Na concentration. In particular, the undoped sample shows the highest emission intensity, while the p-type Na doped ZnO film at 3 at.% exhibits the lowest one.

Synthesis, characterization and photoluminescence property of La-doped ZnO nanoparticles

La-doped ZnO nanoparticles were synthesized via a facile and surfactant-free chemical precipitation route, and the effects of lanthanum doping concentration on the structures, morphologies and photoluminescence properties were investigated by XRD, TEM, EDX, PL and UV–Vis absorption spectra. The results showed that the La3+ ions were successfully incorporated into the ZnO host, and the products were well-crystalline. The average size and band gap of La-doped ZnO nanoparticles were varied with the lanthanum doping concentration. The average size of doped nanoparticles was much smaller as compared to that of undoped ZnO. The increasing of lanthanum doping concentration increased the defects in ZnO and resulted in a red shift of UV emission, indicating the narrow band gap in doped nanoparticles. This was probably attributed to the impurity energy levels in band gap introduced by substitutional La3+ ions.

Dopant-induced modifications in structural and optical properties of ZnO thin films prepared by PLD

The objective of the present work is to study the effect of yttrium doping concentration on the microstructure and optical behavior of ZnO thin films, deposited by pulsed laser deposition on silicon (001) substrates. The microstructural analysis of doped ZnO thin films shows columnar growth of the ZnO (002) plane under tensile stress, confirmed by Raman shifts of the E2 (high) mode. The optical properties are investigated by using a spectroscopic ellipsometer. Undoped and yttrium-doped ZnO films show high transparency in the visible region, and the estimated optical band gap energy is randomly shifted in the range 2.93–3.1 eV by increasing the yttrium doping level. Yttrium doping in ZnO is limited, which means that at doping concentrations higher than 3 wt.% of yttrium, the structural and optical properties show a shift towards those of undoped ZnO.