Concentrations Of Phosphorus Atoms Research Articles

Identifying the effects of phosphorus on the magnetism of WS2 nanosheets

To identify the effects of phosphorus on the magnetism of WS2, the magnetic properties of phosphatized WS2 (P-WS2) nanosheets with varying phosphorus concentrations are studied by experimental research and first-principle calculations. Our experimental findings demonstrate that all P-WS2 samples exhibit distinct ordered-magnetic signatures (ferromagnetic and antiferromagnetic), and the saturation magnetization varies with the phosphorus concentration. First-principle calculations reveal that phosphorus atoms preferentially occupy sulfur vacancies, inducing magnetic moments in WS2 nanosheets. Phosphorus atoms occupying sulfur vacancies in the same sulfur atom layer exhibit ferromagnetic coupling, while those in two sulfur atom layers of a monolayer exhibit antiferromagnetic coupling. The magnetic properties of P-WS2 can be tuned by controlling the position and concentration of phosphorus atoms. Increasing the concentration of phosphorus atoms occupying sulfur vacancies in the same sulfur atom layer is a viable approach to enhance the magnetism of P-WS2. This study clarifies the effects of phosphorus on the magnetism of WS2 nanosheets and will promote its application in spintronics.

Periodic Arrays of Dopants in Silicon by Ultralow Energy Implantation of Phosphorus Ions through a Block Copolymer Thin Film.

In this work, block copolymer lithography and ultralow energy ion implantation are combined to obtain nanovolumes with high concentrations of phosphorus atoms periodically disposed over a macroscopic area in a p-type silicon substrate. The high dose of implanted dopants grants a local amorphization of the silicon substrate. In this condition, phosphorus is activated by solid phase epitaxial regrowth (SPER) of the implanted region with a relatively low temperature thermal treatment preventing diffusion of phosphorus atoms and preserving their spatial localization. Surface morphology of the sample (AFM, SEM), crystallinity of the silicon substrate (UV Raman), and position of the phosphorus atoms (STEM- EDX, ToF-SIMS) are monitored during the process. Electrostatic potential (KPFM) and the conductivity (C-AFM) maps of the sample surface upon dopant activation are compatible with simulated I-V characteristics, suggesting the presence of an array of not ideal but working p-n nanojunctions. The proposed approach paves the way for further investigations on the possibility to modulate the dopant distribution within a silicon substrate at the nanoscale by changing the characteristic dimension of the self-assembled BCP film.

The improvement of Mo/4H-SiC Schottky diodes via a P2O5 surface passivation treatment

Molybdenum (Mo)/4H-silicon carbide (SiC) Schottky barrier diodes have been fabricated with a phosphorus pentoxide (P2O5) surface passivation treatment performed on the SiC surface prior to metallization. Compared to the untreated diodes, the P2O5-treated diodes were found to have a lower Schottky barrier height by 0.11 eV and a lower leakage current by two to three orders of magnitude. Physical characterization of the P2O5-treated Mo/SiC interfaces revealed that there are two primary causes for the improvement in electrical performance. First, transmission electron microscopy imaging showed that nanopits filled with silicon dioxide had formed at the surface after the P2O5 treatment that terminates potential leakage paths. Second, secondary ion mass spectroscopy revealed a high concentration of phosphorus atoms near the interface. While only a fraction of these are active, a small increase in doping at the interface is responsible for the reduction in barrier height. Comparisons were made between the P2O5 pretreatment and oxygen (O2) and nitrous oxide (N2O) pretreatments that do not form the same nanopits and do not reduce leakage current. X-ray photoelectron spectroscopy shows that SiC beneath the deposited P2O5 oxide retains a Si-rich interface unlike the N2O and O2 treatments that consume SiC and trap carbon at the interface. Finally, after annealing, the Mo/SiC interface forms almost no silicide, leaving the enhancement to the subsurface in place, explaining why the P2O5 treatment has had no effect on nickel- or titanium-SiC contacts.

CALCULATION OF THE THERMODYNAMIC CHARACTERISTICS OF Fe – P SYSTEM BY METHOD OF MOLECULAR DYNAMICS

The problem of dephosphorization of iron-carbon alloys is relevant for the metallurgical industry, since a high concentration of phosphorus contributes to the appearance of a number of extremely undesirable phenomena. A lot of experimental work has been devoted to solving this problem, but it has still not been completely possible to cope with it. Any field experiments aimed at studying the process of phosphorus removal, require considerable material and time costs, but at the same time do not guarantee getting the desired result. Therefore, to search for new approaches to solving this problem, it is much more rational to use numerical simulation methods involving the computational capabilities of modern computers. At present, computer experiments are the same recognized research method as theoretical research and real experiment. To study the behavior of phosphorus atoms in iron using a numerical experiment, it is necessary to build a computational model and test it by calculating various characteristics whose values are known in advance. In this paper, the method of molecular dynamics was chosen as the method of computer simulation. Using this method, one can conduct experiments with given atomic velocities and describe dynamics of the studied processes. To describe the interparticle interaction, we used the potential calculated in the framework of the immersed atom method. The study was conducted on a computational cell simulating α-iron crystal with phosphorus substitution atoms. The constructed model demonstrated satisfactory results when calculating the known characteristics of the simulated system. Dependences of changes in such characteristics as temperature coefficient of linear expansion, melting point, latent heat of melting and heat capacity on the concentration of phosphorus atoms, as well as in some cases on magnitude of the applied external pressure were established. Calculations showed that, for example, the phosphorus concentration of 0.5 % leads to an increase in the average thermal coefficient of linear expansion by 9 %, a decrease in temperature and latent heat of fusion by 5 % and a heat capacity by 7 %.

Calculation of the Thermodynamic Characteristics of Fe–P System by the Molecular Dynamics Method

The problem of dephosphorization of iron-carbon alloys is relevant for the metallurgical industry, since a high concentration of phosphorus contributes to the appearance of a number of extremely undesirable phenomena. A lot of experimental work has been devoted to solving this problem, but it has still not been completely possible to cope with it. Any field experiments aimed at studying the process of phosphorus removal require considerable material and time costs, but at the same time do not guarantee getting the desired result. Therefore, to search for new approaches to solving this problem, it is much more rational to use numerical simulation methods involving the computational capabilities of modern computers. At present, computer experiments are the same recognized research method as theoretical research and real experiment. To study the behavior of phosphorus atoms in iron using a numerical experiment, it is necessary to build a computational model and test it by calculating various characteristics whose values are known in advance. In this paper, the method of molecular dynamics was chosen as the method of computer simulation. Using this method, one can conduct experiments with given atomic velocities and describe dynamics of the studied processes. To describe the interparticle interaction, we used the potential calculated in the framework of the immersed atom method. The study was conducted on a computational cell simulating α-iron crystal with phosphorus substitution atoms. The constructed model demonstrated satisfactory results when calculating the known characteristics of the simulated system. Dependencies of changes in such characteristics as temperature coefficient of linear expansion, melting point, latent heat of melting and heat capacity on the concentration of phosphorus atoms, as well as in some cases on magnitude of the applied external pressure, were established. Calculations showed that, for example, the phosphorus concentration of 0.5% leads to an increase in the average thermal coefficient of linear expansion by 9%, a decrease in temperature and latent heat of fusion by 5% and a heat capacity by 7%.

Effect of doping profile on sheet resistance and contact resistance of monocrystalline silicon solar cells

This paper presents the preparation and characterization of phosphorous-doped silicon solar cells based on screen-printed technique with systematically changing the phosphorous doping concentration. In the work, P-type monocrystalline (100) oriented Czochralski Si wafers of the thickness of 200 μm were textured using wet alkaline solution. Phosphorous was doped on Si wafers employing the diffusion technique with a fixed flow rate of liquid phosphorus oxychloride (POCl3) at the changing diffusion time of 10 min, 15 min and 20 min, respectively. Four-point probe method was adopted to measure the sheet resistance of doped wafers that resulted in significant decrease in the sheet resistance. Moreover, the doping concentration of phosphorus atoms estimated by energy-dispersive x-ray spectroscopy (EDS) analysis as well as Hall Effect measurement found to increase with increasing doping time. Furthermore, the increasing and decreasing of the front contact and back contact resistance with increasing doping concentration was confirmed by the measured contact resistance for different doping densities of the cells using transmission line method (TLM). Thus, the study on the controllable sheet resistance and contact resistance by varying the doping concentration may assist in the commercialization of efficient crystalline Si solar cell.

Impact of Phosphorus superlattices on charge and spin dependent transport properties of zigzag silicene nanoribbons

To investigate charge and spin dependent conductance properties of Phosphorus doped zigzag silicene nanoribbons (ZSiNRs), we utilize recursive Green's function method and Landauer-Büttiker formalism. Our calculations are performed in the absence and presence of exchange magnetic fields with both parallel and antiparallel configurations. Considering a supperlattice of Phosphorus substituents in a periodic distribution at the edge of nanoribbon, the effect of increasing number of dopants and period of the distribution on transport properties are studied. It is found that transport properties of doped ZSiNRs vary with doping concentration according to being odd or even of number of dopants. For parallel configuration, doped ZSiNR with various concentrations works as a controllable spin filter with Fermi energy. Increasing doping concentration leads to increasing size of conductance gap and improvement of controlling quality of spin-filtering property while increasing period of Phosphorus atomic distribution has destructive effect on size of conductance gap and destroys spin-filtering property. Moreover, we show that although the same results are obtained for transport properties of doped ZSiNR with various concentrations of Phosphorus atoms in presence of antiparallel exchange magnetic fields, a completely controllable spin-filtering property cannot be achieved by Fermi energy changes.

Kelvin Probe Force Microscope Observation of Donors’ Arrangement in Si Transistor Channel

Further development of dopant-atom-based transistors requires investigation of the effects of discrete dopant distribution on device operation. Hence, it is important to monitor dopants’ arrangement inside transistor channels. We used Kelvin Probe Force Microscope (KPFM) to measure surface potential profiles of field-effect transistor (FET) channels doped with different concentrations of phosphorus atoms. We observed three basic configurations of dopants: solitary donors, “clusters” of a few coupled donors, and “clusters” of many donors. Our systematic observation provides information about the formation of quantum dots consisting of a single donor or a number of coupled donors.

Sensitivity of CoSi2 precipitation in silicon to extra-low dopant concentrations. II. First-principles calculations

The paper is the second part of the study on the influence of very low dopant content in silicon on CoSi2 precipitation during high-temperature cobalt ion implantation into transmission electron microscope samples. It deals with the computational justification of various assumptions used in Paper I when rationalizing the kinetics of cobalt clustering in ion-implanted intrinsic silicon (both undoped and containing low concentrations of phosphorus atoms). In particular, it is proven that divacancies are efficient nucleation centers for the new Co-Si phase. It is shown that the capture of vacancies and divacancies on phosphorus atoms increases their lifetime in silicon matrix, but practically does not affect the mechanism of their interaction with interstitial cobalt atoms. Finally, it is demonstrated that the mobility of phosphorus interstitials at temperatures of our experiment is orders of magnitude higher than might be expected from the published literature data.

Phosphorus in-diffusion from a surface source by millisecond flash lamp annealing for shallow emitter solar cells

We have investigated in-diffusion of phosphorus into monocrystalline silicon by depositing a phosphorus source on the surface followed by millisecond flash lamp annealing (FLA) to form shallow emitters for solar cells. By varying both the energy density of a 20 ms flash in the range from 62 to 132 J/cm2 and the sample preheating, it is observed that FLA treatments can in-diffuse a high concentration of phosphorus atoms becoming electrically active. The most promising emitters are obtained after FLA in the energy range from 110 to 128 J/cm2 including preheating at 300 °C with a peak concentration of 4−6×1020cm−3. The emitter junction depth for these treatments is in the range of 100 nm to 200 nm, respectively.

Fracture Behaviour and Temper Embrittlement Induced by NGS of Phosphorus

The non-equilibrium grain-boundary segregation (NGS) isotherms and its kinetics serve to provide a more complete understanding of inter-granular segregation behavior in relation to mechanical properties, not only for the engineering steels but also for a wide range of structural alloys. The NGS of phosphorus and temper embrittlement dynamics on the same heat treatment condition at the same isothermal holding time in two Cr-Mo steels, 12Cr1MoV and 2.25Cr1Mo, was experimentally studied. The fracture behaviour was also observed by tensile tests in situ in a scanning electron microscope (SEM). Results show that both the concentration of phosphorus atoms in grain boundaries and the degree of embrittlement reaches a maximum at the critical time. It can be satisfactorily elucidated by the temper embrittlement mechanism of NGS caused by cooling from solution temperature to isothermal holding temperature.

Surface Reactions of Molecular and Atomic Oxygen with Carbon Phosphide Films

The surface reactions of atomic and molecular oxygen with carbon phosphide films have been studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Carbon phosphide films were produced by ion implantation of trimethylphosphine into polyethylene. Atmospheric oxidation of carbon phosphide films was dominated by phosphorus oxidation and generated a carbon-containing phosphate surface film. This oxidized surface layer acted as an effective diffusion barrier, limiting the depth of phosphorus oxidation within the carbon phosphide film to < 3 nm. The effect of atomic oxygen (AO) exposure on this oxidized carbon phosphide layer was subsequently probed in situ using XPS. Initially AO exposure resulted in a loss of carbon atoms from the surface, but increased the surface concentration of phosphorus atoms as well as the degree of phosphorus oxidation. For more prolonged AO exposures, a highly oxidized phosphate surface layer formed that appeared to be inert toward further AO-mediated erosion. By utilizing phosphorus-containing hydrocarbon thin films, the phosphorus oxides produced during exposure to AO were found to desorb at temperatures >500 K under vacuum conditions. Results from this study suggest that carbon phosphide films can be used as AO-resistant surface coatings on polymers.

Temper embrittlement dynamics induced by non-equilibrium segregation of phosphorus in steel 12Cr1MoV

Abstract Temper embrittlement dynamics were experimentally studied in an industrial steel 12Cr1MoV. Results showed that both the concentration of phosphorus atoms in grain boundaries and the degree of embrittlement reaches a maximum at the critical time. It can be satisfactorily elucidated by the temper embrittlement mechanism of non-equilibrium grain boundary segregation caused by cooling from solution temperature to isothermal holding temperature. An embrittlement prediction method for steel in service is proposed based on this mechanism.

Development of an interatomic potential for phosphorus impurities inα-iron

We present the derivation of an interatomic potential for the iron–phosphorus system basedprimarily on ab initio data. Transferability in this system is extremely problematic, and thepotential is intended specifically to address the problem of radiation damage and pointdefects in iron containing low concentrations of phosphorus atoms. Some preliminarymolecular dynamics calculations show that P strongly affects point defect migration.

The formation and properties of surface phosphide on (100)W

Adsorption of PCl3 molecules on the (100)W surface has been studied over a wide temperature range from 300 to 2000 K. It is shown that adsorption at T>1100 K results in the formation of a surface tungsten phosphide with the WP composition and a surface concentration of phosphorus atoms of (1±0.15)×1015 cm−2. Adsorption of silicon atoms on the surface phosphide at 1300 K results in the displacement of phosphorus atoms from the surface and their replacement by silicon atoms.