scholarly journals Effects of Different Amounts of Nb Doping on Electrical, Optical and Structural Properties in Sputtered TiO2−x Films

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 301
Author(s):  
Daniel Dorow-Gerspach ◽  
Dieter Mergel ◽  
Matthias Wuttig
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Amorphous State ◽  
Dc Magnetron Sputtering ◽  
Transition Range ◽  
Precise Control ◽  
Consistent Model ◽  
Scattering Centers ◽  
Critical Oxygen ◽  
Nb Doping

Highly conductive TiO2 films with different Nb doping levels (up to 5 at%) were prepared by reactive DC magnetron sputtering under precise control of the oxygen partial pressure. They were deposited on unheated substrates, covered with a protective Si3N4 layer, and subsequently annealed at 300 °C. The doping efficiency of Nb is greater than 90%. Conductivity is a maximum for a partly oxidized target in the transition range. The best films exhibit a resistivity of 630 µΩ cm and a mobility of 7.6 cm2/Vs combined with a high transparency above 70%. Comparing the behavior of undoped and Nb-containing films, intrinsic limits of the conductivity in the TiO2−x:Nb system could be observed, and a consistent model explaining these findings is presented. The conductivity is limited—by decreasing electron density due to Nb oxidation—by increasing incorporation formation of Nb2O5 clusters as scattering centers with increasing oxygen partial pressure and Nb concentration, by a transition from the crystalline to the amorphous state of the films below a critical oxygen partial pressure.

scholarly journals Oxygen supply capacity breathes new life into critical oxygen partial pressure (Pcrit)

2021 ◽  
Vol 224 (8) ◽  
Author(s):  
Brad A. Seibel ◽  
Alyssa Andres ◽  
Matthew A. Birk ◽  
Alexandra L. Burns ◽  
C. Tracy Shaw ◽  
...  
Keyword(s):  
Metabolic Rate ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxygen Supply ◽  
Accurate Determination ◽  
Maximum Energy ◽  
Hypoxia Tolerance ◽  
Energy Demands ◽  
Critical Oxygen ◽  
Supply Capacity

ABSTRACT The critical oxygen partial pressure (Pcrit), typically defined as the PO2 below which an animal's metabolic rate (MR) is unsustainable, is widely interpreted as a measure of hypoxia tolerance. Here, Pcrit is defined as the PO2 at which physiological oxygen supply (α0) reaches its maximum capacity (α; µmol O2 g−1 h−1 kPa−1). α is a species- and temperature-specific constant describing the oxygen dependency of the maximum metabolic rate (MMR=PO2×α) or, equivalently, the MR dependence of Pcrit (Pcrit=MR/α). We describe the α-method, in which the MR is monitored as oxygen declines and, for each measurement period, is divided by the corresponding PO2 to provide the concurrent oxygen supply (α0=MR/PO2). The highest α0 value (or, more conservatively, the mean of the three highest values) is designated as α. The same value of α is reached at Pcrit for any MR regardless of previous or subsequent metabolic activity. The MR need not be constant (regulated), standardized or exhibit a clear breakpoint at Pcrit for accurate determination of α. The α-method has several advantages over Pcrit determination and non-linear analyses, including: (1) less ambiguity and greater accuracy, (2) fewer constraints in respirometry methodology and analysis, and (3) greater predictive power and ecological and physiological insight. Across the species evaluated here, α values are correlated with MR, but not Pcrit. Rather than an index of hypoxia tolerance, Pcrit is a reflection of α, which evolves to support maximum energy demands and aerobic scope at the prevailing temperature and oxygen level.

How to Optimize Critical Current Performance of RE123 Materials by Controlling Oxygen Content

2001 ◽  
Vol 689 ◽  
Author(s):  
Jun-ichi Shimoyama ◽  
Shigeru Horii ◽  
Kenji Otzschi ◽  
Kohji Kishio
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Critical Current ◽  
Oxygen Content ◽  
Oxygen Nonstoichiometry ◽  
Thermodynamic Quantities ◽  
Precise Control ◽  
Oxygen Defects ◽  
Re Elements ◽  
Selection Of

ABSTRACTOxygen nonstoichiometry behaviors of REBa2Cu3Oy (RE123: RE= Nd, Sm, Eu, Gd, Dy. Ho and Y) compounds have been precisely determined by the thermogravimetric measurements. Dependence of oxygen content on temperature and oxygen partial pressure were found to slightly depend on the RE element. Thermodynamic quantities of oxygen, such as hO2 and sO2, also varied with RE element. Relationship between Tc and oxygen content is strongly dependent on the RE species. This suggests that pinnig effect due to the oxygen defects is different in each RE123 compound and, therefore, critical current properties of RE123 must be optimized by precise control of oxygen content as well as selection of suitable RE elements.

scholarly journals Breathing new life into the critical oxygen partial pressure (Pcrit): a new definition, interpretation and method of determination

2020 ◽  
Author(s):  
B. A. Seibel ◽  
A. Andres ◽  
M. A. Birk ◽  
A. L. Burns ◽  
C. T. Shaw ◽  
...  
Keyword(s):  
Metabolic Rate ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxygen Supply ◽  
Break Point ◽  
Standard Metabolic Rate ◽  
Hypoxia Tolerance ◽  
Additional Species ◽  
Critical Oxygen ◽  
Mechanistic Basis

AbstractThe critical oxygen partial pressure (Pcrit) is most commonly defined as the oxygen partial pressure below which an animal’s standard metabolic rate can no longer be maintained. It is widely interpreted as measure of hypoxia tolerance, which influences a species’ aerobic scope and, thus, constrains biogeography. However, both the physiology underlying that interpretation and the methodology used to determine Pcrit remain topics of active debate. The debate remains unresolved in part because Pcrit, as defined above, is a purely descriptive metric that lacks a clear mechanistic basis. Here we redefine Pcrit as the PO2 at which physiological oxygen supply is maximized and refer to these values, thus determined, as Pcrit-α. The oxygen supply capacity (α) is a species- and temperature-specific coefficient that describes the slope of the relationship between the maximum achievable metabolic rate and PO2. This α is easily determined using respirometry and provides a precise and robust estimate of the minimum oxygen pressure required to sustain any metabolic rate. To determine α, it is not necessary for an individual animal to maintain a consistent metabolic rate throughout a trial (i.e. regulation) nor for the metabolic rate to show a clear break-point at low PO2. We show that Pcrit-α can be determined at any metabolic rate as long as the organisms’ oxygen supply machinery reaches its maximum capacity at some point during the trial. We reanalyze published representative Pcrit trials for 40 species across five phyla, as well as complete datasets from six additional species, five of which have not previously been published. Values determined using the Pcrit-α method are strongly correlated with Pcrit values reported in the literature. Advantages of Pcrit-α include: 1) Pcrit-α is directly measured without the need for complex statistics that hinder measurement and interpretation; 2) it makes clear that Pcrit is a measure of oxygen supply, which does not necessarily reflect hypoxia tolerance; 3) it alleviates many of the methodological constraints inherent in existing methods; 4) it provides a means of predicting the maximum metabolic rate achievable at any PO2, 5) Pcrit-α sheds light on the temperature- and size-dependence of oxygen supply and metabolic rate and 6) Pcrit-α can be determined with greater precision than traditional Pcrit.

scholarly journals Kinetic decomposition of Ni2SiO4 in oxygen potential gradients

1987 ◽  
Vol 2 (3) ◽  
pp. 338-344 ◽  
Author(s):  
K. T. Jacob ◽  
A. K. Shukla
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxygen Potential ◽  
Pressure Ratio ◽  
Metallurgical Society ◽  
Low Oxygen ◽  
Critical Oxygen ◽  
Kinetic Decomposition ◽  
Potential Gradients ◽  
Partial Pressure Ratio

Nickel orthosilicate (Ni2SiO4) has been found to decompose into its component binary oxides in oxygen potential gradients at 1373 K. Nickel oxide was formed at the high oxygen potential boundary, while silica was detected at the low oxygen potential side. Significant porosity and fissures were observed near the Ni2SiO4/SiO2 interface and the SiO2 layer. The critical oxygen partial pressure ratio required for decomposition varied from 1.63 to 2.15 as the oxygen pressures were altered from 1.01 ⊠ 105 to 2.7X 10−4 Pa, well above the dissociation pressure of Ni2SiO4. Platinum markers placed at the boundaries of the Ni2SiO4 sample indicated growth of NiO at the higher oxygen potential boundary, without any apparent transport of material to the low oxygen potential side. However, significant movement of the bulk Ni2SiO4 crystal with respect to the marker was not observed. The decomposition of the silicate occurs due to the unequal rates of transport of Ni and Si. The critical oxygen partial pressure ratio required for decomposition is related both to the thermodynamic stability of Ni2SiO4 with respect to component oxides and the ratio of diffusivities of nickel and silicon. Kinetic decomposition of multicomponent oxides, first discovered by Schmalzried, Laqua, and co-workers [H. Schmalzried, W. Laqua, and P. L. Lin, Z. Natur Forsch. Teil A 34, 192 (1979); H. Schmalzried and W. Laqua, Oxid. Met. 15, 339 (1981); W. Laqua and H. Schmalzried, Chemical Metallurgy—A Tribute to Carl Wagner (Metallurgical Society of the AIME, New York, 1981), p. 29] has important consequences for their use at high temperatures and in geochemistry.

The Influence of Total and Oxygen Partial Pressures on Structure and Hydrophilic Property of TiO2 Thin Films Deposited by Reactive DC Magnetron Sputtering

2008 ◽  
Vol 55-57 ◽  
pp. 465-468 ◽  
Author(s):  
Surasing Chaiyakun ◽  
A. Buranawong ◽  
T. Deelert ◽  
N. Witit-Anun
Keyword(s):  
Thin Films ◽  
Magnetron Sputtering ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Total Pressure ◽  
Dc Magnetron Sputtering ◽  
Tio2 Thin Films ◽  
Rutile Structure ◽  
Hydrophilic Property ◽  
Partial Pressures

TiO2 thin films have been deposited by reactive DC magnetron sputtering technique to study the effect of total pressure and oxygen partial pressure on structure and hydrophilic properties. The crystal structure and hydrophilic property was measured by XRD and contact angle meter, respectively. The results showed that the films were composed of pure rutile and mixed of anatase/rutile structure dependent on the total pressure and oxygen partial pressure. It was found that all films can perform hydrophilic property. In case of high total pressure, the films showed superhydrophilic property, whereas the films deposited under various oxygen partial pressures with fixed total pressure were all films exhibit superhydrophilic property.

Effect of Oxygen Partial Pressure on Properties of ZnO Films Deposited on Freestanding Diamond Films

2013 ◽  
Vol 544 ◽  
pp. 230-233
Author(s):  
Ke Tang ◽  
Lin Jun Wang ◽  
Jian Huang ◽  
Bing Ren ◽  
Jie Zhou ◽  
...  
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Diamond Films ◽  
Flux Ratio ◽  
Zno Films ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
X Ray ◽  
Effect Of Oxygen ◽  
Ar Gas

Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of freestanding diamond (FSD) films by the direct current (DC) magnetron sputtering method in an oxygen (O2) + argon (Ar) gas mixture. The effect of oxygen partial pressure on properties of ZnO films was investigated by X-ray diffraction (XRD). The results showed that when flux ratio of argon to oxygen was 1, the ZnO films had a better crystalline quality.

Sign in / Sign up

Export Citation Format

Share Document