Surface Segregation Of Phosphorus Research Articles

Extremely Low Electron Density in a Modulation-Doped Si/SiGe Two-Dimensional Electron Gases by Effective Schottky Gating

We reported an extremely low electron density (8.3 x 1010 cm-2) of a modulation-doped Si/SiGe two-dimensional electron gas by Schottky gating. Effective Schottky gating with extremely low gate leakage current was enabled by low-temperature chemical vapor deposition epitaxial growth to suppress the surface segregation of phosphorus. Furthermore, an extremely high electron mobility of ~ 504,000 cm2/V-s at 0.3 K was also reported.

Manipulation of surface energy anisotropy in iron using surface segregation of phosphorus: An atomistic simulation

The possibility of developing a {1 0 0}〈0 0 1〉 cube texture in steel sheets by altering the surface energy by phosphorus segregation has been investigated using atomistic Monte Carlo simulations. It is found that the change in order in the amount of surface energy, from (1 1 0)

The effect of hydrogen on the surface segregation of phosphorus in epitaxially grown relaxed Si0.7Ge0.3 films by rapid thermal chemical vapor deposition

The surface segregation of phosphorus in relaxed Si0.7Ge0.3 epitaxial films grown on Si (100) substrates by rapid thermal chemical vapor deposition was investigated in this letter. The effect of the growth temperature on phosphorus segregation was studied experimentally and examined using a two-state model. As the growth temperature is reduced, phosphorus segregation is greatly suppressed, and we report an extremely sharp phosphorus turn-off slope of 6 nm/dec at 500 °C. The sharper slopes at low temperatures are explained by a modified two-state model which includes the effect of increased surface coverage of hydrogen at low temperatures.

Ultra-fast grain boundary diffusion and its contribution to surface segregation on a martensitic steel. Experiments and modeling

Phosphorus surface segregation was measured by Auger Electron Spectroscopy on a 17-4 PH martensitic stainless steel at 450, 550 and 600 °C. Surface segregation was shown to be much faster than expected which was attributed to a high contribution of phosphorus diffusion along the former austenitic grain boundaries. A model of surface segregation was developed following the Darken–du Plessis approach and taking account of both bulk and grain boundary solute diffusion. The phosphorus grain boundary diffusion coefficient in 17-4 PH was estimated: D GB < = 6.2 10 4 exp(− 157 kJ mol − 1 /RT)cm 2 s − 1 . It is found to be more than three orders of magnitude higher in 17-4 PH steel than in α-iron.

Electronic properties of doped silicon nanocrystal films

The structural and electrical properties before and after laser annealing of spin-coated films of doped silicon nanocrystals (ncs) produced from the gas phase are presented. While the as-deposited films form a porous network of ncs and show only weak electrical conductivity independent of the doping level, a laser annealing step leads to sintering and melting of the particles and tremendously increases the lateral conductivity. By controlled doping of the initial particles, the conductivity can be further enhanced by seven orders of magnitude reaching values of up to 5 Ω−1 cm−1. The conductivity is found to increase with the doping concentration for highly doped samples while it is independent of the doping level below a critical concentration of 1019 cm−3. The results are discussed within a compensational model taking into account the defect concentration from electron paramagnetic resonance measurements and the activation energies of the electrical conductivity. Surface segregation of phosphorus during growth is identified as the origin of the apparently small phosphorus doping efficiency.

Investigation of phosphorus surface segregation by X-ray scattering measurements

The surface segregation of phosphorus in silicon at low temperatures is studied by using δ doping structures grown by molecular beam epitaxy. The samples are characterized by X-ray crystal truncation rod (CTR) scattering using synchrotron radiation as the light source. The 1/e decay length of P segregation and segregation barrier energy are obtained by fitting the CTR curves within kinematical approximation of X-ray diffraction theory. The surface segregation of P is strong at a growth temperature of 450 °C, with a 1/e decay length of 14 nm, while for growth temperatures below 350 °C, P segregation is negligible with a 1/e decay length not larger than 4 nm. The segregation barrier energy is determined to be 0.43 eV.

Phosphorus profile control in low-temperature silicon epitaxy by reduced pressure chemical vapor deposition

Phosphorus incorporation around 10 18 cm −3 has been studied during low-temperature (660–750 °C) silicon epitaxy by chemical vapor deposition under reduced pressure (20 torr) using silane (SiH 4) or dichlorosilane (SiH 2Cl 2) as silicon precursor. Strong surface segregation of phosphorus was observed. The phosphorous segregation could be reduced either by decreasing the growth temperature or adding HCl during growth of the undoped layer. Neither reduced growth temperature nor HCl addition was able to produce steep turn-off of the phosphorus concentration with an acceptable growth rate. Therefore, ex situ removal of the phosphorus surface layer was tested using either a chemical oxidation or a low-temperature thermal oxidation. In both cases, a dramatic reduction in surface segregation was observed with a slope less than 15 nm/decade in the resulting dopant profile. A subsequent epitaxial Si/SiGe (17%) growth on the ex situ cleaned sample was found to result in layers exhibiting high crystalline quality according to high resolution X-ray diffraction mapping.

Surface segregation of phosphorus, carbon, and sulfur in commercial low-carbon grades of steel

Surface segregation behavior of solute atoms has been studied on low-carbon steels used in producing galvannealed sheet steels for automotive body panel applications. Samples of cold-rolled low-carbon steels with different amounts of carbon and phosphorus in solution were heated in a vacuum chamber and their surface chemistries analyzed by Auger electron spectroscopy. For the steels studied here, one or more of the elements carbon, phosphorus, and sulfur accumulated significantly at the surface within a temperature window of 300 to 973 K. As the temperature was increased, carbon appeared on the surface first, followed by phosphorus, and then sulfur. Each succeeding segregating element displaced the previous one from the surface. The free solute concentration in the bulk and the temperature were critical factors controlling the amount of solute accumulation at the surface. Once segregated, the solute atoms remained on the surface as the samples cooled. Carbon and/or boron in steels retarded the transport of phosphorus to the surface. The implications of these findings in understanding the galvannealing behavior of these steels are discussed.

Segregation of n-dopants on SiGe surfaces

We have investigated the surface segregation of phosphorus in comparison to antimony on Si and SiGe(001) in molecular beam epitaxy. The segregation was measured with electrochemical capacitance voltage and secondary ion mass spectroscopy. Phosphorus doping is used to achieve high carrier concentrations in complementary double-sided modulation-doped n-Si and p-Ge channel (CMOD) structures on SiGe graded buffers.

Segregation and diffusion on semiconductor surfaces.

The surface segregation of phosphorus, antimony, and boron in Si molecular-beam epitaxy is investigated experimentally at low temperatures. Rate and temperature dependent measurements are explained by a segregation model, which connects surface segregation with surface diffusion. The model is found to explain quantitatively many available data of segregation on different semiconductor surfaces, explicitly: Si, Ge, and GaAs. \textcopyright{} 1996 The American Physical Society.

Influence of phosphorus addition on the surface tension of liquid iron and segregation of phosphorus on the surface of Fe-P alloy

This article presents a study of the surface tension and phosphorus surface segregation in Fe-P alloys. The surface tension was measured by the sessile drop technique. The result of the dynamic surface tension for the low phosphorus content alloys shows that the alloy surface vaporization has a clear effect on the surface tension and causes a positive surface tension temperature coefficient. However, from this article, it is evident that phosphorus in liquid iron acts as a surface active element similar to arsenic. The surface segregation was determined using Auger electron spectroscopy. The result on the surface analysis of as-solidified sample indicates that the adsorption of impurity elements, such as oxygen, carbon, and nitrogen, can conceal phosphorus segregation on the free surface. Phosphorus segregation was also examined in the samples as-cleaned by Ar+ and then treated 30 minutes at 650°C. Phosphorus was found to segregate extensively on the surface of the alloys. On the basis of the analysis of the published data, the surface active intensity sequence of some nonmetallic elements was arrayed, and the surface active intensity of fluorine and boron in liquid iron was estimated.

Phase Evolution in Galvanneal Coatings on Steel Sheets.

The evolution of the phases in galvanneal coatings on IF and IFP steel sheets is studied by combining optical microscopy (OM), scanning electron microscopy (SEM) with X-ray microanalysis (EDS) and transmission electron microscopy (TEM). The early stage of galvannealing is dominated by the formation of intermetallic compounds, particularly δ phase by constitutional supercooling except the region near the steel substrate where rapid formation of a thin alloy layer, the nature of which depends strongly on surface segregation of minor elements such as phophorus in a steel substrate. The Γ phase, which shows a well-defined columnar structure, grows at the expense of the Γ1 phase. The thickness of the Γ1 phase decreases, while maintaining the total thickness of (Γ+Γ1) constant, 2 μm, during galvannealing, Three different grain morphologies of δ phase have been observed. The surface segregation of phosphorus in steel was found to promote the nucleation of the Γ1 phase at the solid-liquid interface in the very beginning of galvannealing. The formation of the Γ phase was retarded accordingly. The hot-dip simulator was found to reproduce the microstructures of galvanneal coatings obtained by the in-line production and to facilitate the investigation of the phase evolution during hot-dip galvanizing and galvannealing.

Kinetics of sulfur and phosphorus surface segregation competition in copper

Surface segregation of impurities in metals may lead to significant enrichment in a monolayer. The segregation kinetics are usually described in terms of bulk diffusion; measurements of the segregation kinetics in single crystals have been used to determine the respective bulk diffusion coefficients. On the other hand, sulfur segregation in ferrous alloys has been reported to be accelerated via pipe diffusion. Moreover, segregation induced phase transitions may modify the segregation kinetics. The present paper deals with the kinetics of the segregation competition of sulfur and phosphorus in copper. On the basis of earlier measurements by Frech, a segregation model is developed, which takes into account bulk and pipe diffusion as well as structural phase transitions in the surface layer.

ESCA study of the oxidation of DHP copper

AbstractThe surface composition of deoxidized high phosphorus (DHP) copper sheets was investigated by ESCA with the aim of verifying the role of phosphorus in oxide formation. While no surface segregation of phosphorus was observed on samples cleaned by ion bombardment and annealing in ultrahigh vacuum, the presence of large amounts of phosphorus was found after the formation of the oxide by exposure to 0.1 Torr oxygen at 770 K. The surface enrichment in P with the same binding energy was found after annealing a sheet of DHP copper coated with a layer of Cu2O deposited by sputtering. The binding energy of the P 2p peak as well as the analysis of the components of O 1s can be interpreted with the formation of a metaphosphate. Experiments performed at intermediate temperatures showed that the segregation of phosphorus is appreciable above 600 K and appears to be related to oxygen diffusion into the bulk.

リン青銅スズめっき材の熱はく離について

Tin-coated phosphor-bronze with good adhesion as deposited sometimes shows an almost complete lack of adhesion at the interface of the tin layer and the phosphor bronze substrate after aging at 100-200°C. In this paper, this adhesion failure is called“thermal peeling”, since peeling accompanies metallurgical changes caused by such thermal processes as diffusion and segregation. Main findings are summarized as follows.1. Tin-coated phosphor-bronze with no copper undercoat is much less sensitive to thermal peeling than that with a thin (about 0.5μm) copper undercoat.2. Plastic bending prior to aging increases thermal peeling: thermal peeling appears after aging for 4000 hours at 85°C even for tin-coated phosphor-bronze with no copper undercoat.3.ε-Cu3Sn and η-Cu6Sn5 are formed between the tin layer and the surface of the phosphor-bronze.4. Accumulations of phosphorus and the formation of Kirkendall voids having concentrated amounts of phosphorus and oxygen are found along the ε-Cu3Sn/phosphor-bronze interface.5. It is suggested that surface segregation of phosphorus accelerates the formation of the Kirkendall voids, which in turn causes the thermal peeling.

Surface segregation of phosphorus in titanium stabilized and cold-worked austenitic stainless steel

Auger Electron Spectroscopy (AES) is applied to examine the surface segregation activity of phosphorus in AISI 321 titanium stabilized and cold-worked austenitic stainless steel which was annealed at temperatures ranging from 400° to 1000°C. An increase in deformation is found for the temperature interval 400–600°C which corresponded to a pronounced surface segregation of phosphorus. This was not observed in the undeformed state of the material. A gradual reversal of segregation pattern is observed when the specimens are reheated successively to higher temperatures. Such information can be useful for the better understanding of the gradual deterioration of austenitic stainless steel exposed to service temperatures.

Effect of cold work on the surface segregation of phosphorus in AISI 321 austenitic stainless steel

On utilise la spectrometrie Auger pour determiner comment differents degres de deformation a froid affectent la segregation du phosphore dans un acier inoxydable austenitique stabilise au titane de type AISI 321

Observation of phosphorus segregation onto the free surface of an amorphous Fe44Ni36P14B6 alloy

Phosphorus segregation to the free surface of an amorphous Fe44Ni36P14B6 alloy during annealing in the temperature range 180 to 300° C has been studied by Auger electron spectroscopy. The phosphorus concentration increased with annealing temperature with an abrupt change appearing at about 250° C. At 276° C the phosphorus Peak Height Ratio on the surface was three times as high as that of a sputtered surface. A step-heating scheme has been employed to observe the surface segregation of phosphorus in the temperature range 25 to 290° C. On heating, the segregation behaviour can be correlated with a degradation in toughness properties. It is concluded that the segregation of phosphorus onto the free surface of this amorphous alloy is an indication of some local atomic migration processes, for example clustering, occurring inside the bulk.

Radiation induced phosphorus segregation in austenitic and ferritic alloys

The radiation induced surface segregation (RIS) of phosphorus in stainless steel attained a maximum at a dose of 0.8 dpa then decreased continually with dose. This decrease in the surface segregation of phosphorus at high dose levels has been attributed to removal of the phosphorus layer by ion sputtering. Phosphorus is not replenished since essentially all of the phosphorus within the irradiation zone has been segregated to the surface. Sputter removal can explain the previously reported absence of phosphorus segregation in ferritic alloys irradiated at high doses 1,2 (>1 dpa) since irradiation of ferritic alloys to low doses has shown measurable RIS. This sputtering phenomenon places an inherent limitation to the heavy ion irradiation technique for the study of surface segregation of impurity elements. The magnitude of the segregation in ferritics is still much less than in stainless steel which can be related to the low damage accumulation in these alloys.

Hydrogen embrittlement of cast 13% Cr 6% NiMo steel

This paper reports on a study of the hydrogen embrittlement resistance of cast 13Cr6NiMo steel after various alternative tempering treatments. The threshold levels of the stress intensity factor, K ISH , ascertained in this work are examined as they relate to the residual austenite content in the structure of lath martensite, the type of fracture found on the specimens and the surface segregation of phosphorus observed on them.