scholarly journals The origin of the exceptionally low activation energy of oxygen vacancy in tantalum pentoxide based resistive memory

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ji-Hyun Hur
Keyword(s):  
Activation Energy ◽  
Oxygen Vacancy ◽  
Activation Barrier ◽  
Underlying Mechanism ◽  
Resistive Memory ◽  
Resistance Change ◽  
Switching Model ◽  
Measured Activation Energy ◽  
Practical Usefulness ◽  
Measured Activation

AbstractIt is well known that collective migrations of oxygen vacancies in oxide is the key principle of resistance change in oxide-based resistive memory (OxRAM). The practical usefulness of OxRAM mainly arises from the fact that these oxygen vacancy migrations take place at relatively low operating voltages. The activation energy of oxygen vacancy migration, which can be inferred from the operational voltage of an OxRAM, is much smaller compared to the experimentally measured activation energy of oxygen, and the underlying mechanism of the discrepancy has not been highlighted yet. We ask this fundamental question in this paper for tantalum oxide which is one of the most commonly employed oxides in OxRAMs and try the theoretical answer based on the first-principles calculations. From the results, it is proven that the exceptionally large mobility of oxygen vacancy expected by the switching model can be well explained by the exceptionally low activation barrier of positively charged oxygen vacancy within the two-dimensional substructure.

scholarly journals Temperature Effects on the Crystallization and Coarsening of Nano-CeO2 Powders

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
H. F. Lopez ◽  
H. Mendoza
Keyword(s):  
Activation Energy ◽  
Mass Transport ◽  
Ostwald Ripening ◽  
Effect Of Temperature ◽  
Transport Mechanisms ◽  
X Ray Diffraction ◽  
Measured Activation Energy ◽  
Measured Activation ◽  
Mass Transport Mechanisms ◽  
Nanoparticle Sizes

The effect of temperature on nano-CeO2 particle coarsening is investigated. The nanoceria powders were synthesized using the microemulsion method and then exposed to temperatures in the range of 373–1273 K. It was found that the nanoparticles exhibited a strong tendency to form agglomerates and through the application of ultrasound these agglomerates could be broken into smaller sizes. In addition average nanoparticle sizes were determined by powder X-ray diffraction (XRD). The outcome of this work indicates that the initial nano-CeO2 powders are amorphous in nature. Annealing promotes CeO2 crystallization and a slight shift in the (111) XRD intensity peaks corresponding to CeO2. Moreover, at temperatures below 773 K, grain growth in nano-CeO2 particles is rather slow. Apparently, mass transport through diffusional processes is not likely to occur as indicated by an estimated activation energy of 20 kJ/mol. At temperatures above 873 K, the measured activation energy shifted to 105 kJ/mol suggesting a possible transition to Ostwald-Ripening type mass transport mechanisms.

Hydrogen Incorporation in A-Si:H: Temperature and Doping Type Dependence

1990 ◽  
Vol 192 ◽  
Author(s):  
M.J.M. Pruppers ◽  
K.M.H. Maessen ◽  
F.H.P.M. Habraken ◽  
J. Bezemer ◽  
W.F. Van Der Weg
Keyword(s):  
Activation Energy ◽  
Glow Discharge ◽  
Gas Phase ◽  
Hydrogen Concentration ◽  
Hydrogen Content ◽  
Hydrogen Incorporation ◽  
Undoped Material ◽  
Measured Activation Energy ◽  
Measured Activation ◽  
The Difference

ABSTRACTPhosphorus, boron and compensation doped hydrogenated amorphous silicon films were deposited in a glow discharge at different substrate temperatures in the range 50–330°C. Gas phase doping levels were 1%. At the lower temperatures the hydrogen concentration in the B doped and compensated doped films is larger than in the P and undoped films. For higher deposition temperatures the H concentration of the B doped films appeared to be smaller than in the other materials. The difference in hydrogen content of the doped and undoped material, deposited at various temperatures, is considered as a function of the measured activation energy for conduction in these films. This difference varies in much the same way with the activation energy as the hydrogen content in films deposited at one substrate temperature, but with varying gas phase dopant levels. This represents strong evidence that, apart from the deposition temperature, the hydrogen concentration in glow discharge a-Si:H is determined by the position of the Fermi level.

Temperature Effect of CO2 Reduction Electrocatalysis on Copper: Potential Dependency of Activation Energy

2020 ◽  
Vol 17 (4) ◽  
Author(s):  
Yixu Zong ◽  
Pongkarn Chakthranont ◽  
Jin Suntivich
Keyword(s):  
Activation Energy ◽  
Activation Barrier ◽  
Co2 Reduction ◽  
Underlying Mechanism ◽  
Reduction Reaction ◽  
Hydrogen Electrode ◽  
Proton Coupled Electron Transfer ◽  
Ch4 Production ◽  
Electrochemical Co2 Reduction ◽  
Surface Adsorbates

Abstract The electrochemical CO2 reduction reaction (CO2RR) has gathered widespread attention in the past decade as an enabling component to energy and fuel sustainability. Copper (Cu) is one of the few electrocatalysts that can convert CO2 to higher-order hydrocarbons. We report the CO2RR on polycrystalline Cu from 5 °C to 45 °C as a function of electrochemical potential. Our result shows that selectivity shifts toward CH4 at low temperature and H2 at high temperature at the potential values between −0.95 V and −1.25 V versus reversible hydrogen electrode (RHE). We analyze the activation energy for each product and discuss the possible underlying mechanism based on their potential dependence. The activation barrier of CH4 empirically obeys the Butler–Volmer equation, while C2H4 and CO show a non-trivial trend. Our result suggests that the CH4 production proceeds via a classical electrochemical pathway, likely the proton-coupled electron transfer of surface-saturated COad, while C2H4 is limited by a more complex process, likely involving surface adsorbates. Our measurement is consistent with the view that the adsorbate–adsorbate interaction dictates the C2+ selectivity.

scholarly journals GaN Decomposition in Ammonia

2000 ◽  
Vol 5 (S1) ◽  
pp. 273-279 ◽  
Author(s):  
D.D. Koleske ◽  
A.E. Wickenden ◽  
R.L. Henry
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Decomposition Rate ◽  
Flow Conditions ◽  
Growth Pressure ◽  
Growth Environment ◽  
Similar Role ◽  
Measured Activation Energy ◽  
Movpe Growth ◽  
Measured Activation

GaN decomposition is studied as a function of pressure and temperature in mixed NH3 and H2 flows more characteristic of the MOVPE growth environment. As NH3 is substituted for the 6 SLM H2 flow, the GaN decomposition rate at 1000 °C is reduced from 1×1016 cm−2 s−1 (i.e. 9 monolayers/s) in pure H2 to a minimum of 1×1014 cm−2 s−1 at an NH3 density of 1×1019 cm−3. Further increases of the NH3 density above 1×1019 cm−3 result in an increase in the GaN decomposition rate. The measured activation energy, EA, for GaN decomposition in mixed H2 and NH3 flows is less than the EA measured in vacuum and in N2 environments. As the growth pressure is increased under the same H2 and NH3 flow conditions, the decomposition rate increases and the growth rate decreases with the addition of trimethylgallium to the flow. The decomposition in mixed NH3 and H2 and in pure H2 flows behave similarly, suggesting that surface H plays a similar role in the decomposition and growth of GaN in NH3.

Electromigration and 1/ƒ Noise in Single-Crystalline, Bamboo and Polycrystalline Al Lines

1997 ◽  
Vol 473 ◽  
Author(s):  
Marc J.C. Van Den Homberg ◽  
P.F.A. Alkemade ◽  
A. H. Verbruggen ◽  
A. G. Dirks ◽  
E. Ochs ◽  
...  
Keyword(s):  
Activation Energy ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Pipe Diffusion ◽  
Single Crystalline ◽  
Interface Diffusion ◽  
Measured Activation Energy ◽  
Noise Measurements ◽  
Measured Activation ◽  
Groove Pattern

ABSTRACTThe relation between electromigration and microstructure for three types of Al lines with different microstructures has been studied. The lines were made by recrystallization of Al in a SiO2 groove pattern. They were either truly bamboo with grains of on average 3 μm long or distorted (i.e. with dislocations) single-crystals. In addition, conventional, polycrystalline Al lines with grains of on average 230 nm were made. The lines were lifetime-tested (200 °C,j=2, 5 and 8 MA/cm2) and subjected to l/f noise measurements (from 200 to 500 K).The bamboo and single-crystalline Al lines showed the same, although weak, 1/ƒ noise. This observation demonstrates that other mechanisms than thermal motion of atoms at grain boundaries can cause noise. It is suggested that dislocations are the sources for noise in our samples. The measured activation energy (0.8 eV) is in agreement with the activation energy for pipe diffusion along dislocation lines.The lifetime-tests showed significantly higher times to failure for the single-crystalline and bamboo lines as compared to polycrystalline lines. Preliminary results indicate slightly higher lifetimes for the bamboo than for the single-crystalline lines. It is concluded that interface diffusion is the main mechanism for electromigration in truly bamboo or single-crystalline lines. Our measurements demonstrated that dislocations are important in the formation of l/ƒ noise and interfaces in the formation of electromigration damage.

Electromigration and 1/f Noise in Single-Crystalline, Bamboo and Polycrystalline Al Lines

1997 ◽  
Vol 472 ◽  
Author(s):  
Marc J.C. Van Den Homberg ◽  
P.F.A. Alkemade ◽  
A.H. Verbruggen ◽  
A.G. Dirks ◽  
E. Ochs ◽  
...  
Keyword(s):  
Activation Energy ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Pipe Diffusion ◽  
Single Crystalline ◽  
Interface Diffusion ◽  
Measured Activation Energy ◽  
Noise Measurements ◽  
Measured Activation ◽  
Groove Pattern

ABSTRACTThe relation between electromigration and microstracture for three types of Al lines with different microstructures has been studied. The lines were made by recrystallization of Al in a SiO2 groove pattern. They were either truly bamboo with grains of on average 3 μm long or distorted (i.e. with dislocations) single-crystals. In addition, conventional, polycrystalline Al lines with grains of on average 230 nm were made. The lines were lifetime-tested (200 °C,j=2, 5 and 8 MA/cm2) and subjected to 1/f noise measurements (from 200 to 500 K).The bamboo and single-crystalline Al lines showed the same, although weak, 1/f noise. This observation demonstrates that other mechanisms than thermal motion of atoms at grain boundaries can cause noise. It is suggested that dislocations are the sources for noise in our samples. The measured activation energy (0.8 eV) is in agreement with the activation energy for pipe diffusion along dislocation lines.The lifetime-tests showed significantly higher times to failure for the single-crystalline and bamboo lines as compared to polycrystalline lines. Preliminary results indicate slightly higher lifetimes for the bamboo than for the single-crystalline lines. It is concluded that interface diffusion is the main mechanism for electromigration in truly bamboo or single-crystalline lines. Our measurements demonstrated that dislocations are important in the formation of 1/f noise and interfaces in the formation of electromigration damage.

Annealing Kinetics of Neutron?Irradiated Aluminium and Copper

1960 ◽  
Vol 13 (2) ◽  
pp. 347 ◽  
Author(s):  
TH Blewitt ◽  
RR Coltman ◽  
CE Klabunde
Keyword(s):  
Activation Energy ◽  
Activation Energies ◽  
Slope Method ◽  
Measured Activation Energy ◽  
Measured Activation ◽  
Kinetics Of ◽  
Constant Activation Energy

Activation energies for the annealing of copper and aluminium following reactor bombardment near 4 OK have been measured in the range from 10 to 40 OK. Both the change in slope method and the isothermal technique method were utilized with the assumption that a constant activation energy existed. Computations of the number of jumps involved from the measured activation energy result in an impossibly small number. It is obvious that the method for determination of the activation energies is not applicable, probably because of the non-uniqueness of the activation energy.

Temperature-dependent Degradation Modes in CdS/CdTe Devices

2007 ◽  
Vol 1012 ◽  
Author(s):  
David Albin ◽  
Samuel H Demtsu ◽  
Anna M Duda ◽  
Wyatt K Metzger
Keyword(s):  
Activation Energy ◽  
Space Charge ◽  
Open Circuit ◽  
Temperature Dependent ◽  
Measured Activation Energy ◽  
Measured Activation ◽  
Accelerated Lifetime ◽  
Lifetime Testing ◽  
Stressed Cells ◽  
Recombination Current

AbstractA set of 24 identically made CdS/CdTe devices were subjected to accelerated lifetime testing (ALT) under open-circuit bias, 1 sun illumination, and temperatures of 60, 80, 100, and 120 °C. A total of 6 identical devices were tested for statistical purposes at each temperature. Current density-voltage (JV) measurements were made on stressed cells for up to 2000+ hours. Device performance parameters were calculated as a function of temperature and stress time using discrete element circuit models. Forward current behavior was represented by two parallel diodes to simulate recombination currents in the quasi-neutral (QNR) and space-charge (SCR) regions. Backcontact behavior was studied using a parallel combination blocking diode and shunt conductance. A systematic pattern of degradation was apparent with increased stress temperature. At 60 °C, degradation associated with the CdTe/backcontact dominates. At temperatures above 80 °C, greater losses in fill factor (FF) and open-circuit voltage (Voc) were observed. Recombination current modeling of JV data attributes this to increased space-charge recombination. Calculated diffusion lengths based upon an Arrhenius-derived activation energy of 0.63 eV in this temperature-range suggests Cu diffusion into the SCR is mechanistically responsible for the observed increased recombination, and decreased Voc and FF. At lower temperatures (60 to 80 ºC), degradation was considerably slower with a measured activation energy of 2.9 eV.

scholarly journals Water-ion permselectivity of narrow-diameter carbon nanotubes

2020 ◽  
Vol 6 (38) ◽  
pp. eaba9966 ◽  
Author(s):  
Yuhao Li ◽  
Zhongwu Li ◽  
Fikret Aydin ◽  
Jana Quan ◽  
Xi Chen ◽  
...  
Keyword(s):  
Activation Energy ◽  
Water Transport ◽  
Lipid Membranes ◽  
High Performance ◽  
High Water ◽  
Chloride Ions ◽  
Experimental Conditions ◽  
Measured Activation Energy ◽  
Water Salt ◽  
Measured Activation

Carbon nanotube (CNT) pores, which mimic the structure of the aquaporin channels, support extremely high water transport rates that make them strong candidates for building artificial water channels and high-performance membranes. Here, we measure water and ion permeation through 0.8-nm-diameter CNT porins (CNTPs)—short CNT segments embedded in lipid membranes—under optimized experimental conditions. Measured activation energy of water transport through the CNTPs agrees with the barrier values typical for single-file water transport. Well-tempered metadynamics simulations of water transport in CNTPs also report similar activation energy values and provide molecular-scale details of the mechanism for water entry into these channels. CNTPs strongly reject chloride ions and show water-salt permselectivity values comparable to those of commercial desalination membranes.

GaN Decomposition in Ammonia

1999 ◽  
Vol 595 ◽  
Author(s):  
D.D. Koleske ◽  
A.E. Wickenden ◽  
R.L. Henry
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Decomposition Rate ◽  
Flow Conditions ◽  
Growth Pressure ◽  
Growth Environment ◽  
Similar Role ◽  
Measured Activation Energy ◽  
Movpe Growth ◽  
Measured Activation

AbstractGaN decomposition is studied as a function of pressure and temperature in mixed NH3 and H2 flows more characteristic of the MOVPE growth environment. As NH3 is substituted for the 6 SLM H2 flow, the GaN decomposition rate at 1000 °C is reduced from 1x1016 cm-2s-1 (i.e. 9 monolayers/s) in pure H2 to a minimum of 1x1014 cm-2s-1 at an NH3 density of 1x1019 cm-3. Further increases of the NH3 density above 1x1019 cm-3 result in an increase in the GaN decomposition rate. The measured activation energy, EA, for GaN decomposition in mixed H2 and NH3 flows is less than the EA measured in vacuum and in N2 environments. As the growth pressure is increased under the same H2 and NH3 flow conditions, the decomposition rate increases and the growth rate decreases with the addition of trimethylgallium to the flow. The decomposition in mixed NH3 and H2 and in pure H2 flows behave similarly, suggesting that surface H plays a similar role in the decomposition and growth of GaN in NH3.

Sign in / Sign up

Export Citation Format

Share Document