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.

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.

Energetics and structural effects in the fragmentation of protonated esters in the gas phase

1981 ◽  
Vol 59 (14) ◽  
pp. 2133-2145 ◽  
Author(s):  
Jan A. Herman ◽  
Alex. G. Harrison
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Methyl Formate ◽  
Carbonyl Oxygen ◽  
Original Structure ◽  
Proton Affinities ◽  
Acetate Methyl ◽  
Ether Oxygen ◽  
The Difference ◽  
Tertiary Alkyl

A series of formate (methyl through butyl) and acetate (methyl through pentyl) esters have been protonated in the gas phase by the Brønsted acids H3+, N2H+, CO2H+, N2OH+, and HCO+. Carbonyl oxygen protonation is 87–97 kcal mol−1 exothermic for H3+ and 47–57 kcal mol−1 exothermic for the weakest acid HCO+, permitting a study of the effect of protonation exothermicity on the decomposition modes of the protonated esters. With the exception of protonated methyl formate, three decomposition modes, (a) to (c) are observed.[Formula: see text]Reaction (a) is unimportant for formates; for acetates it is the sole decomposition channel for the methyl ester, but is less important for higher acetates. The dependence of the relative importance of this reaction mode on the protonation exothermicity indicates an activation energy considerably in excess of ΔH0, presumably because the reaction involves a symmetry-forbidden 1,3-H shift for the carbonyl protonated ester. For the higher acetates where the difference in the proton affinities of the carbonyl and ether oxygens is less, acyl ion formation results, in part, from protonation at the ether oxygen. For protonated methyl formate the major fragmentation reaction yields CH3OH2+ + CO; this reaction also appears to have an activation energy considerably in excess of the ΔH0. For the remaining esters either reaction (b) or (c) is the major decomposition mode. The competition between these two channels depends strongly on the protonation exothermicity and the relative activation energies. From the reaction competition we conclude that 1,2-H shifts occur in the case of primary alkyl esters yielding more stable secondary or tertiary alkyl ions. This rearrangement appears to occur after the excess energy has been partitioned between the alkyl ion and the neutral acid since the extent of further fragmentation of the alkyl ion reflects the original structure of the alkyl group.

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.

Hydrogen Content and the Optical Bandgap in Amorphous Silicon

1987 ◽  
Vol 95 ◽  
Author(s):  
K. M. H. Maessen ◽  
M. J. M. Pruppers ◽  
J. Bezemer ◽  
F. H. P. M. Habraken ◽  
W. F. van der Weg
Keyword(s):  
Glow Discharge ◽  
Amorphous Silicon ◽  
Hydrogen Concentration ◽  
Hydrogen Content ◽  
Linear Dependence ◽  
Optical Bandgap ◽  
Silicon Films ◽  
Concentration Region

AbstractThe dependence of the optical bandgap on the hydrogen concentration is measured for amorphous silicon films prepared under different glow-discharge conditions. A deviation from the usually accepted linear dependence is found for hydrogen concentrations above 12 at.‰ We find that in this concentration region an increase of hydrogen incorporated as SiH2 is responsible for this behaviour.

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.

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.

Comparative Study of Structure and Hydrogen Incorporation in Glow Discharge a-Si:C:H and a-Si:N:H Alloys

1987 ◽  
Vol 95 ◽  
Author(s):  
W. Beyer ◽  
H. Wagner ◽  
H. Mell
Keyword(s):  
Glow Discharge ◽  
Comparative Study ◽  
Substrate Temperature ◽  
Nitrogen Content ◽  
Hydrogen Evolution ◽  
Hydrogen Concentration ◽  
Infrared Absorption ◽  
Hydrogen Incorporation ◽  
Nitrogen Incorporation ◽  
Void Structure

AbstractPlasma-deposited a-Si:C:H and a-Si:N:H alloys both show a rapidly rising hydrogen incorporation with increasing carbon or nitrogen content. For hydrogen concentrations exceeding ∼ 20 at.%, the host material starts to lose its connectiveness leading to the formation of a void structure as evidenced by hydrogen evolution and infrared absorption. Raising the substrate temperature leads to a reduction of the hydrogen concentration, to an increase of the Si-C and Si-N bond concentration and to a more compact naterial. However, for a-Si:C:H films it leads also to graphitic carbon bonds. The widening of the optical bandgap of a-Si:C:H films up to about 50 at.% of carbon is almost entirely due to the increased hydrogen incorporation whereas for a-Si:N:H films both hydrogen and nitrogen incorporation plays a role.

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.

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