Phosphorous Doping Research Articles

Effects of phosphorous doping on the superconducting properties of SmFeAs(O,F)

The systematic doping effect induced by the isovalent substitution of P for As on the superconducting properties of F-doped SmFeAsO0.88F0.12 (Sm1111) has been studied by physical and magnetic measurements. The cell volume (V) decreases with P doping and the anisotropic chemical pressure might be induced. However, the superconducting transition temperature (Tc) and the upper critical field (Hc2) are suppressed. Thermoelectric power (S) indicates the majority of electron type charge carriers in support of Hall measurements and its magnitude does not change very much for different P concentrations. The present investigation depicts that isovalent substitutions in the FeAs layer strongly deteriorate the superconducting properties of Sm1111 as a result of increase in chemical pressure. These isovalent substitution effects are comparatively discussed with hole (Mn) and electron (Ni) type substitutions in the superconducting layer of Sm1111.

Parametric investigations on proton conducting membrane by radiation induced grafting of 4-vinylpyridine onto poly(vinylidene fluoride) and phosphoric acid doping

Abstract Proton conducting membrane composed of grafted basic moiety doped with phosphoric acid (PA) was studied. The membrane denoted as PVDF-g-4-VP/PA was prepared by radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(vinylidene fluoride) (PVDF) films followed by doping with PA. The effect of grafting conditions on the degree of grafting (G%) was investigated. The acid doping conditions (G%, time and PA concentration) were also investigated with respect to doping level. The grafted precursors and the acid doped membranes were characterized by means of Fourier transform infrared (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). The membranes showed a thermal stability up to a temperature of ∼ 160 ℃, above which they undergo a multi-step degradation pattern due to decomposition of the protonated functions, poly(4VP) grafts and PVDF matrix, respectively. The proton conductivities of the membranes were found to increase with the increase in G% ( doping level) and the temperature with a maximum proton conductivity of 62 mS cm−1 achieved at 100 ℃ without any humidification. The results of the present study show that the prepared membrane has a potential to be proposed for operating polymer electrolyte membrane fuel cell above 80 ℃.

Polymer chain length, phosphoric acid doping and temperature dependence on structure and dynamics of an ABPBI [poly(2,5-benzimidazole)] polymer electrolyte membrane

The random orientations of BI units and the presence of free rotation around the single bond which connects two monomeric BI segments lead to minimal possibility of π–π interactions.

A low temperature process for phosphorous doped ZnO nanorods via a combination of hydrothermal and spin-on dopant methods

We demonstrate the fabrication of solution based low temperature-processed p-type ZnO NRs doped with phosphorous by using a spin-on-dopant method coupled with a hydrothermal process. We confirmed the incorporation of phosphorous dopants into a ZnO crystal by analyzing SIMS profiles, together with the evolution of the photoluminescence spectra. It is further revealed that the electrical properties of the p-type ZnO/n-type Si heterojunction diode exhibited good rectifying behavior, confirming that p-type ZnO NRs were successfully formed. In addition, we demonstrate that a piezoelectric nanogenerator with p-type ZnO NRs made on a glass substrate shows large enough power to drive polymer dispersed liquid crystal displays.

Green synthesis of aniline by phosphorus-doped titanium dioxide polymorphs

Phosphor doping in association with a heterostructure not only modifies the band structure of titanium dioxide (TiO2) to make it more responsive to visible light, but it also suppresses its charge recombination and causes TiO2 to have enhanced photoactivity. In this paper, we report on the controlled synthesis of phosphor-doped binary and ternary TiO2 nanostructures through a hydrothermal method. The phase and morphology of the samples can be tuned by simply changing the hydrothermal time. Also, the visible-light photoactivity of the samples was evaluated by the reduction of nitrobenzene. The as-prepared catalysts exhibit enhanced photocatalytic activity in comparison to P25 and the undoped counterpart, and the selected catalyst shows high photostability and photoactivity after reuse five times. These new TiO2 nanostructures present a promising candidate for application in photocatalysis, photochemistry, sensors, and solar cells.

N+ emitters realized using Ammonium Dihydrogen Phosphate for silicon solar cells

Phosphorous diffusion is typically derived from three sources: phosphorus oxychloride (POCl3), sprayable phosphoric acid (H3PO4), and printable dopant phosphorous paste. Aside from being costly, these sources tend to be harmful and can facilitate bulk contamination. Ammonium Dihydrogen Phosphate (NH4H2PO4:ADP) can be used in the application of doping substrate for phosphorous diffusion, which is originally introduced in this paper. ADP doping, supported by the spin-on technique, has sufficient potential to mitigate the disadvantages of other phosphorous sources. The applicability and compatibility of ADP as a phosphorous doping source in the production of silicon solar cells were demonstrated in this paper. Sheet resistance mapping shows that ADP doping generated a uniform N+ emitter. The ADP solution concentration and diffusion temperature influenced the phosphorous dopant profile and sheet resistance. The adjustment of the concentration and temperature enables the control of the phosphorous dopant profile and sheet resistance. Full aluminum back-surface field silicon solar cells with an ADP-diffused N+ emitter were realized in this paper through screen-printed front and back contacts on 154.8cm2, 180μm thick, and 1.5–3Ωcm p-type Cz–Si wafers. The highest confirmed efficiency of the investigated cells was 17.97% with an open circuit voltage of 628.40mV, short circuit current density of 36.43mA/cm2, and fill factor of 78.47%. The average efficiency (10 cells) was 17.70%, which also verified the uniformity of the ADP-diffused N+ emitter. Selective emitter solar cells with the best efficiency of 18.41% were thus fabricated.

Characteristics of silicon solar cell emitter with a reduced diffused phosphorus inactive layer

The diffusion of phosphorus using a phosphorous oxychloride (POCl3) source in silicon has been used widely in crystalline silicon solar cells. The thermal diffusion process in the furnace consists of two steps: pre-deposition and drive-in. The phosphorous doping profile via thermal diffusion often exhibits high concentrations in the surface-near emitter, which result in a recombination increase. This layer, called the dead layer, should be inhibited in order to fabricate high efficiency silicon solar cells. In this paper, the amount of the POCl3 flow rate was varied during the pre-deposition process in order to minimize the dead layer, and the characteristics of the phosphosilicate glass (PSG) and emitter were analyzed. From the secondary ion mass spectroscopy (SIMS) and electrochemical capacitance–voltage profiler (ECV) measurements, the emitter formed using a POCl3 flow rate of 1000 sccm contained the least amount of inactive dopant and resulted in reasonable performance in the silicon solar cell. As the POCl3 flow rate increased, the doped silicon wafer included electrically inactive P near the surface, which functions as a defect degrading the electrical performance of the emitter. As a result of this, the removal of the dead layer containing the inactive P was attempted through dipping the doped wafer in a HF solution. After this process, the emitter saturation current density and implied Voc were improved. The completed solar cells and their external quantum efficiencies at a short wavelength also demonstrated improved performance. A quantitative analysis of the emitter can provide a deeper understanding of methods to improve the electrical characteristics of the silicon solar cell.

Optimization and kinetics of phosphoric acid doping of poly(1-vinylimidazole)-graft-poly(ethylene-co-tetrafluorethylene) proton conducting membrane precursors

Optimization of the reaction parameters affecting phosphoric acid (PA) doping behavior of poly(1-vinylimidazole), P(VIm), grafted poly(ethylene-co-tetrafluoroethylene) (ETFE) proton conducting membrane precursors obtained by radiation induced grafting was studied using the Taguchi method. The reaction parameters such as degree of grafting (G%) in the precursors, PA concentration, temperature and doping time were selected as independent parameters while doping level was the response. The optimum parameters for achieving the maximum doping level (7.45mmolrepeat polymer unit−1) were: G% of 54%, PA concentration of 60%, temperature of 100°C and reaction time of 5 days. The kinetics of the acid doping reaction was also studied and the doping rate was found to be a function of reaction parameters and followed a first order reaction. The PA doping was verified by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis of the membranes. The proton conductivity and thermal stability of the membranes were also evaluated. It can be concluded that the Taguchi method provides an effective tool for prediction of acid doping level and optimization of reaction parameters. The kinetics of acid doping is also suggested to be a diffusion-driven reaction following a multi-layers adsorption model.

Synthesis and properties of phenylindane-containing polybenzimidazole (PBI) for high-temperature polymer electrolyte membrane fuel cells (PEMFCs)

A thermally stable and organo-soluble phenylindane-containing polybenzimidazole (phenylindane-PBI) was synthesized from 3,3′,4,4′-tetraaminobiphenyl and 1,1,3-trimethyl-3-phenylindan-4′,5-dicarboxylic acid using polyphosphoric acid (PPA) as both solvent and dehydrating agent. Polymerization conditions were carefully investigated to achieve high molecular weight polymers (IV = 1.00 dL g−1). To study the effects of backbone structure on properties, meta-PBI was also synthesized in PPA. It was found the introduction of rigid bent phenylindane moiety into the polymer backbone greatly improved the polymer solubility in polar aprotic solvents. The fabrication of acid-doped phenylindane-PBI membranes was attempted by both sol–gel and acid imbibing processes. The membranes prepared by the latter method showed a maximum proton conductivity of 0.061 S cm−1 at 180 °C with a phosphoric acid doping level of 10.0 PA/RU. Both phenylindane-PBI and meta-PBI membranes were fabricated into membrane electrode assemblies (MEAs) and tested to evaluate their fuel cell performance. The phosphoric acid doped phenylindane-PBI membrane exhibited comparable fuel cell performance as meta-PBI under similar testing conditions, demonstrating that it is a promising polymer electrolyte membrane candidate for high-temperature fuel cell applications.

Atomic layer doping of strained Ge-on-insulator thin films with high electron densities

We demonstrate that phosphorous atomic layer doping in ultra-high vacuum is a viable method to obtain n-type doping of strained germanium-on-insulator thin films. By engineering single and multiple, closely-spaced P δ-layers, we obtain high active electron concentrations (∼1 × 1020 cm−3) and low electrical resistivity (∼120 Ω/square) whilst keeping control over doping profile, structural integrity, and tensile strain levels (e = 0.35%). Investigation of magnetotransport over a large temperature range (1.7-290 K) allows observation of two-dimensional electrons' weak localization up to 30 K.

Etching Paste for Innovative Solar-Cell Applications

This paper reports the development of an etching paste for selective etching of a phosphor silicate glass (PSG) layer, which is used as a mask in processing of solar cells. The etching paste should thoroughly open a thick PSG layer that has high oxygen content in 2 minutes. Moreover, the paste must be completely water based and etch the PSG layer at room temperature without damaging the silicon surface. One of the applications for this kind of etching paste is making solar cells with a selective emitter structure. In this study, a selective structure with a double diffusion process is considered. The first PSG layer is created by adding oxygen and POCl3 gases into the diffusion furnace. By using the ETCH-TEC. Ox etching paste, this oxide-rich PSG layer is locally opened and the second diffusion without oxygen is carried out. Light and heavy phosphorous doping of silicon leads to locally doped areas with sheet resistances of 100 and 50 Ω/□, respectively. The opened structures were characterized microscopically and physically. An experiment with 800 wafers in a solar cell production line of the company MAGI Solar was carried out. Compared to the wafers with a homogeneous emitter, an average increase of +0.52% in absolute efficiency was measured.

NMOS SiP Epitaxy Process - Optimizing Facet Growth

Phosphorous doped selective epitaxial technology has gained interest recently as the source / drain for NMOS. High, >1E20 atm./cc., Phosphorous doping is required to ensure low contact resistance when metal contacts are formed. The study of contact resistance as a function of temperature and chemical composition of reactants is presented in this paper. Additionally, the phosphorous growth needs to have a facet to prevent any nitride residue during the remaining process flows. In this paper, the faceted growth of high Phosphorous doped Silicon epitaxy using various process schemes is explored.

Novel Polybenzimidazole-Phosphoric Acid Membranes for Fuel Cell Applications

Polybenzimidazole-phosphoric acid membranes have been used extensively in high temperature fuel cell applications. They are generally prepared either by copolymerization of tetramines and dicarboxylic acids (AA/BB copolymers) or by homopolymerization of diaminoacids (AB homopolymers). We describe the preparation of 4-(3,4-diaminophenylsulfonyl) benzoic acid, a diamino acid useful for the synthesis of novel AB polybenzimidazoles having excellent thermal and thermal-oxidative stability. The polymer, readily cast from polar aprotic solvents, when imbibed with phosphoric acid produces polymer electrolyte membranes exhibiting proton conductivities ranging from 0.06-0.12 S/cm at 80-160 {degree sign}C (20% RH) at a phosphoric acid doping level of 6.1.

Influence of phosphorous doping on silicon nanocrystal formation in silicon-rich silicon nitride films

Phosphorus-doped silicon nanocrystals (Si-NCs) embedded in a silicon nitride matrix were fabricated by post-annealing of silicon-rich silicon nitride (SRN) films deposited by electron cyclotron resonance chemical vapour deposition. The effects of phosphorus addition on the Si crystallization behaviour in SRN films were investigated. From the experimental results, the existence of phosphorus enhances phase separation in SRN and thus Si crystallization rate. As the phosphorus content increases, the Si-NC size increases under the same annealing conditions. The x-ray photoelectron spectroscopy P 2p signal attributed to Si–P or P–P bonds indicates that the phosphorus may exist inside Si-NCs. It was also found that the crystallization temperature decreases when phosphorus concentration is increased, and could be as low as 800 °C.

Benzimidazole grafted polybenzimidazoles for proton exchange membrane fuel cells

High molecular weight polybenzimidazole (PBI) was synthesized and grafted with benzimidazole pendant groups. The high molecular weight of PBI resulted in good film-forming properties and superior tensile strength. With a phosphoric acid doping level (ADL) of 13.1, a tensile strength of 16 MPa was achieved at room temperature. Grafting of benzimidazole moieties onto the PBI macromolecular chain introduced additional basic sites which allowed the membrane to achieve higher phosphoric acid uptakes. A molar acid conductivity, defined as the specific conductivity of each mole of doping acid, was proposed to evaluate the effective conductivity contributed from the doping acids. With a grafting degree of 5.3% and an ADL of 13.1, the PBI membranes exhibited a total conductivity of 0.15 S cm−1. A H2–air fuel cell based on this membrane showed a peak power density of 378 mW cm−2 at 180 °C without humidification.

Multifunctional PECVD Layers: Dopant Source, Passivation, and Optics

In this study, the feasibility of creating one dielectric layer system acting simultaneously as antireflection coating, phosphorous doping source, masking against metal plating, and surface passivation is presented. Moreover, a similar layer stack is described, which behaves as rear-side surface passivation, boron dopant source, and internal reflection mirror. The optical characteristics of these layers are especially investigated and optimized for a solar cell's front- and rear-side coating. By consequent use of the multifunctional layers, a totally diffused solar cell with rear-side passivation and local rear contacts can be produced using only one wet chemical bath sequence, one multilayer vacuum step, and one high-temperature process. We present the first proof of concept for such a solar cell production using multifunctional plasma-enhanced chemical vapor deposition layers resulting already in a conversion efficiency of 18.3%.

Analysis of Voltage Losses in High Temperature Proton Exchange Membrane Fuel Cells with Properties of Membrane Materials and Fluent Software

The mass and charge transport significantly affect the performance of fuel cells. A numerical model of high temperature proton exchange membrane fuel cells is developed. Ohmic losses and activation losses of both anode and cathode are analyzed at different design and operating condition. The polarization curve predicted by the model is in a reasonable agreement with published experimental data. The results of the model indicate that increasing the phosphoric acid doping level or operating temperature is helpful to decrease ohmic losses. The operating temperature has negligible impact on activation losses. Increasing the operating pressure can decrease activation losses.

Highly Conducting Phosphorous Doped nc-Si:H Thin Films Deposited at High Deposition Rate by Hot-Wire Chemical Vapor Deposition Method

In this paper, we report the synthesis of highly conducting phosphorous doped hydrogenated nanocrystalline silicon (nc-Si:H) films at substantially low substrate temperature (200 degrees C) by hot-wire chemical vapor deposition (HW-CVD) method using pure silane (SiH4) and phosphine (PH3) gas mixture without hydrogen dilution. Structural, optical and electrical properties of these films were investigated as a function of PH3 gas-phase ratio. The characterization of these films by low-angle X-ray diffraction, Raman spectroscopy and atomic force microscopy revealed that, the incorporation of phosphorous in nc-Si:H induces an amorphization in the nc-Si:H film structure. Fourier transform infrared spectroscopy analysis indicates that hydrogen predominately incorporated in phosphorous doped n-type nc-Si:H films mainly in di-hydrogen species (Si-H2) and poly-hydrogen (Si-H2)n bonded species signifying that the films become porous, and micro-void rich. We have observed high band gap (1.97-2.37 eV) in the films, though the hydrogen content is low (< 1.4 at.%) over the entire range of PH3 gas-phase ratio studied. Under the optimum deposition conditions, phosphorous doped nc-Si:H films with high dark conductivity (sigma Dark -5.3 S/cm), low charge-carrier activation energy (E(act) - 132 meV) and high band gap (- 2.01 eV), low hydrogen content (- 0.74 at.%) were obtained at high deposition rate (12.9 angstroms/s).

Optical absorbance of doped Si quantum dots calculated by time-dependent density functional theory with partial electronic self-interaction corrections

The optical properties of Si quantum dots (QDs) with phosphorous and aluminum dopants have been calculated with the recently tested Heyd-Scuseria-Ernzerhof (HSE) density functionals to ascertain the effect of functional corrections to electronic self-interaction. New results have been obtained for 20 crystalline and amorphous structures of Si(29) and Si(35) quantum dots and are compared to our previous results obtained using the PW91∕PW91 functionals. The bandgaps are greater in magnitude and shifted to higher energies in HSE calculations compared to PW91 calculations, and the absorption spectrum is blueshifted in HSE. Trends in the shifts of absorbances due to doping are similar for both sets of calculations, with doped QDs absorbing at lower photon energies than undoped QDs. Consistent with previous results, the bandgaps of QDs are found to decrease as the size of the QD increases, and the absorption spectra of amorphous QDs are redshifted compared to those of crystalline structures. The molecular orbitals involved in the transitions with the largest oscillator strengths show that the electron density moves towards the surface of the quantum dot as the structure is excited. The lifetimes of photoexcited states were found to differ substantially between the two functionals due to their sensitivity to the overlaps of initial and final orbitals. Comparison with available experimental and independent theoretical results supports the conclusion that the HSE functional better matches experimental results due to the partial inclusion of Hartree-Fock exchange.

Composite proton conducting membrane by radiation-induced grafting of 1-vinylimidazole onto poly(ethylene-co-tetrafluoroethylene) and phosphoric acid doping

Composite membrane containing phosphoric acid (PA) for possible use in a fuel cell was prepared by radiation-induced grafting of 1-vinylimidazole (1-VIm) onto poly(ethylene- co-tetrafluoroethylene) (ETFE) films followed by protonation with PA doping. The preparation procedure involved three steps: (i) irradiation of ETFE films by an electron beam, (ii) grafting of 1-VIm onto the irradiated films under selected conditions and (iii) doping the grafted film with PA. The membrane composition, thermal properties and thermal stability were evaluated using Fourier-transformed infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry, respectively. The obtained membrane was found to have a degree of grafting of 54% and 6.6 mmol PA per poly-VIm repeating unit with ionic conductivity of 140 mS cm−1 at 120°C and ∼20% relative humidity. The overall results suggest that the membrane has a promising combination of physicochemical properties appealing for possible application in polymer electrolyte membrane fuel cell above 100°C.