Effect Of Residual Impurities Research Articles

Effect of residual impurities on the behavior and laser-induced damage of oxide coatings exposed to deep space radiation

Atomic layer deposition (ALD) is an emerging coating deposition technique filled with potential that is expected to deposit coatings with high laser-induced damage threshold (LIDT). As lasers play an important role in space exploration which are gradually moving to higher orbits and longer lifetimes, a higher demand for space laser coatings has been raising. At the current state of the art, the reliability of ALD-deposited laser coatings for space applications is unclear. This work presents investigations on the stability of three ALD-deposited oxide coatings under space proton and UV radiation at values typical for space environment. Changes in the coatings containing low and high amounts of impurities under space radiation were analyzed through optical parse and composition analysis respectively. Both SiO2 and Al2O3 coatings with few impurities generated color centers after irradiation, which resulted in increased absorption loss and reduced transmittance and optical band gap, and increased probability of damage under laser irradiation. However, the changes in the ZrO2 coating were surprising, when the ZrO2 coating with a large amount of impurities was exposed to radiation, the impurity atoms bound to Zr were displaced first, and the released Zr combined with the oxygen vacancies in the coating, which reduced the number of defects, reduced the absorption loss of the coating, and led to a higher transmittance and an increased optical band-gap. This work provided a novel insight on the impact of the impurities on the stability of the ALD-manufactured oxide coatings against laser-induced damage in effect with space proton and UV radiation. Additionally, we show that high initial LIDT in ALD-prepared oxides may be compromised by the space radiation, while fine tuning of the impurities may result a mitigation approach leading to enhanced laser coatings for space applications.

Effect of residual impurities on polarization switching kinetics in atomic-layer-deposited ferroelectric Hf0.5Zr0.5O2 thin films

The ferroelectricity in fluorite-structured ferroelectrics such as HfO2 and ZrO2 has attracted increasing interest in both academia and industry. Although the polarization switching kinetics is one of the research topics which critically requires further study for the novel ferroelectric material, various factors affecting the polarization switching kinetics have not been rarely examined to date. Especially in atomic-layer-deposited films, the defects including residual impurities are expected to strongly influence the polarization switching kinetics. In this study, therefore, the effect of deposition temperature (Tdep) and impurity concentration on the physical/electrical properties and polarization switching kinetics of atomic-layer-deposited Hf0.5Zr0.5O2 thin films is reported based on physical/chemical/electrical analyses. With decreasing Tdep, the concentration of residual impurities, including carbon increased, resulting in decreased grain size. The increased defect concentration decreased the median switching time and increased the deviation of the switching time distribution. This can be attributed to the lowered energy barrier for the nucleation of oppositely polarized domains and increased spatial inhomogeneities, respectively. This result suggests that Tdep is a key process parameter for optimizing the polarization reversal behavior of fluorite-structured ferroelectrics as it has a considerable influence on the ferroelectric properties and polarization switching kinetics, which are strongly correlated to the defect concentrations and microstructure.

Effects of residual impurities in electroplated Cu on the Kirkendall void formation during soldering

Additions of bis-(sodium sulfopropyl)-disulfide (SPS) to the Cu electroplating bath strongly affected the characteristics of Kirkendall void formation when the Cu film is soldered with Sn–3.5Ag solder and subsequently aged. Voids were predominantly distributed near the Cu3Sn∕Cu interface with SPS, but randomly distributed in the Cu3Sn layer without SPS. In situ Auger electron spectroscopy of voids at the Cu3Sn∕Cu interface revealed surface segregation of S atoms, which came from SPS put into the bath as an additive. The S segregation to Cu3Sn∕Cu interface lowers the interface energy, thereby accelerating the void nucleation. Assisted by the high surface diffusivity of Cu and the presence of excess vacancies arising from the Kirkendall effect, voids tend to localize at the interface, which would result in serious degradation of the joint reliability.

Effect of biogenic fermentation impurities on lactic acid hydrogenation to propylene glycol

The effect of residual impurities from glucose fermentation to lactic acid (LA) on subsequent ruthenium-catalyzed hydrogenation of LA to propylene glycol (PG) is examined. Whereas refined LA feed exhibits stable conversion to PG over carbon-supported ruthenium catalyst in a trickle bed reactor, partially refined LA from fermentation shows a steep decline in PG production over short (<40 h) reaction times followed by a further slow decay in performance. Addition of model impurities to refined LA has varying effects: organic acids, sugars, or inorganic salts have little effect on conversion; alanine, a model amino acid, results in a strong but reversible decline in conversion via competitive adsorption between alanine and LA on the Ru surface. The sulfur-containing amino acids cysteine and methionine irreversibly poison the catalyst for LA conversion. Addition of 0.1 wt% albumin as a model protein leads to slow decline in rate, consistent with pore plugging or combined pore plugging and poisoning of the Ru surface. This study points to the need for integrated design and operation of biological processes and chemical processes in the biorefinery in order to make efficient conversion schemes viable.

분말사출성형한 W-15 wt%Cu 나노복합분말의 고상소결에 미치는 잔류불순물의 영향

The effects of residual impurities on solid state sintering of the powder injection molded (PIMed) W-15wt%Cu nanocomposite powder were investigated. The W-Cu nanocomposite powder was produced by the mech-ano-chemical process consisting of high energy ball-milling and hydrogen reduction of W blue powder-cuO mixture. Solid state sintering of the powder compacts was conducted at <TEX>$1050^{\circ}C$</TEX> for 2~10 h in hydrogen atmosphere. The den-sification of PIM specimen was slightly larger than that of PM(conventional PM specimen), being due to fast coalescence of aggregate in the PIM. The only difference between PIM and PM specimens was the amount of residual impurities. The carbon as a strong reduction agent effectively reduced residual W oxide in the PIM specimen. The <TEX>$H_2O$</TEX> formed by <TEX>$H_2$</TEX> reduction of oxide disintegrated W-Cu aggregates during removal process, on the contrary to this, micropore volume rapidly decreased due to coalescence of the disintegrated W-Cu aggregates during evolution of CO.It can be concluded that the higher densification was due to the earlier occurred Cu phase spreading that was induced by effective removal of residual oxides by carbon.

Effects of residual impurities on Zn electrical activity in Zn-doped InGaAlP grown by metalorganic chemical vapor deposition

The effects of residual impurities, such as hydrogen and oxygen, on Zn electrical activity have been studied for Zn-doped In 0.5(Ga 1− x Al x ) 0.5P grown by low-pressure metalorganic chemical vapor deposition. Zn electrical activity with a p-type cap l ayer grown on Zn-doped InGaAlP was found to be quite low and a high concentration of hydrogen was detected in Zn-doped InGaAlP. Zn electrical activity with an n-type cap layer was relatively high and no hydrogen was detected. The difference in Zn electrical activity with the conduction type of the cap layer may be a result of hydrogen passivation of Zn acceptors. The oxygen concentration in the InGaAlP increased abruptly for x > 0.4. The decrease in Zn electrical activity with increasing x correlated strongly with the increase in oxygen concentration with x, while Si electrical activity was unchanged with varying x. Oxygen might act as a deep donor in InGaAlP, compensating for Zn acceptors. It was thus demonstrated that Zn electrical activity in InGaAlP was significantly affected by the presence of hydrogen and oxygen.

Development of Cryogenic Sealed Cells as Temperature Standards: Their Filling System and the Purification of CO2

Design considerations for the NRC sealed cryogenic triple point cells are discussed, together with their filling system. The versatility of the filling system is illustrated by the purification of CO2. Finally, it is shown that the effects of residual impurities upon the realized liquidus points of high-purity cryogenic substances may be demonstrated by observing the dependence of the liquidus points on the fraction of sample condensed.

Status of device-qualified GaAs substrate technology for GaAs integrated circuits

A review is presented of the current technical status of large-diameter GaAs crystal growth, the effects of residual impurities, stoichiometric defects and crystalline imperfections on the electrical properties of undoped semi-insulating GaAs, and the effectiveness of Group III and V isovalent, lattice-hardening dopants in yielding dislocation-free, semi-insulating GaAs crystals. Factors related to crystal growth, postgrowth annealing, and the preparation of ultraflat, damage-free GaAs wafers, which can significantly improve the performance and yields of directly implanted devices and monolithic circuits are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thermal stability of polyacrylamide solutions: effect of residual impurities in the molecular-weight-degradation process upon heating

We have investigated the effect of temperature on the chemical (hydrolysis) and thermal (molecular weight) stability of purified polyacrylamide solution.From viscosity and light scattering data we show that no polymer degradation due to oxygen contamination results from heating polymer solutions although higher temperature is responsible for hydrolysis of amide groups.

The influence of chemical interactions between metallic and metalloid solutes on their segregation in α-Fe I: Co-segregation at free surface studied by Auger electron spectroscopy

The segregation of metallic additives M and metalloid impurities I to the free surface of iron was studied by Auger electron spectroscopy in dilute binary and ternary iron-based alloys (FeM, FeI, FeMI). Both M and I were chosen for their known behaviour in the temper embrittlement of steels: M ≡ Ni, Cr, V, Ti, Mo; I ≡ Sb, P. The effect of residual impurities I′ ≡ S, C, N was also considered. Quantitative measurements of the equilibrium segregation of M and I as a function of temperature allowed the interaction parameter β MI S between M and I at the surface and the interaction parameter β MI B in the bulk to be determined with the help of segregation and precipitation equations in ternary systems. The results are in qualitative agreement with the interactive behaviour of these elements in the bulk solid solution of the same alloys, as deduced from solid solubility data and solid state physics properties.

Electrons and holes in HgTe and Hg 0.82Cd 0.18Te with controlled deviations from stoichiometry

The deviations from the stoichiometric composition of HgTe and Hg 0.82Cd 0.18Te crystals have been controlled by heat treatment under Hg vapor pressure. The magnetic field dependence of the Hall coefficient always shows the presence of two different sets of electrons and one set of holes. A low mobility electron is shown to belong to the conduction band. Vapor pressure dependence of hole concentration in HgTe shows that the concentration of nonstoichiometric defects decreases with increasing Hg vapor pressure, but the hole concentration is always higher than the electron concentration. In the case of Hg 0.82Cd 0.18Te, the electron concentration exceeds the hole concentration at high Hg vapor pressures. The dependence of the conduction band electron mobility in HgTe upon carrier density shows that the scattering by holes and impurities is predominant. In Hg 0.82Cd 0.18Te, however, optical phonon scattering is dominant when the deviation from stoichiometry is small and the effect of residual impurities can be neglected, and scattering by holes is dominant when the hole concentration is over 10 17 cm 3 .

Electrons and holes in HgTe and Hg 0.82Cd 0.18Te with controlled deviations from stoichiometry

Abstract The deviations from the stoichiometric composition of HgTe and Hg 0.82 Cd 0.18 Te crystals have been controlled by heat treatment under Hg vapor pressure. The magnetic field dependence of the Hall coefficient always shows the presence of two different sets of electrons and one set of holes. A low mobility electron is shown to belong to the conduction band. Vapor pressure dependence of hole concentration in HgTe shows that the concentration of nonstoichiometric defects decreases with increasing Hg vapor pressure, but the hole concentration is always higher than the electron concentration. In the case of Hg 0.82 Cd 0.18 Te, the electron concentration exceeds the hole concentration at high Hg vapor pressures. The dependence of the conduction band electron mobility in HgTe upon carrier density shows that the scattering by holes and impurities is predominant. In Hg 0.82 Cd 0.18 Te, however, optical phonon scattering is dominant when the deviation from stoichiometry is small and the effect of residual impurities can be neglected, and scattering by holes is dominant when the hole concentration is over 10 17 cm 3 .