Impurity Conduction in Silicon Carbide

2007 ◽  
Vol 556-557 ◽  
pp. 367-370 ◽  
Author(s):  
Michael Krieger ◽  
Kurt Semmelroth ◽  
Heiko B. Weber ◽  
Gerhard Pensl ◽  
Martin Rambach ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Low Temperatures ◽  
Nearest Neighbor ◽  
Arrhenius Plot ◽  
Schottky Contacts ◽  
Steep Slope ◽  
Admittance Spectroscopy ◽  
Resistivity Measurements ◽  
Impurity Conduction

We report on admittance spectroscopy (AS) investigations taken on aluminum (Al)- doped 6H-SiC crystals at low temperatures. Admittance spectra taken on Schottky contacts of highly doped samples (NA ≥ 7.2×1017 cm-3) reveal two series of conductance peaks, which cause two different slopes of the Arrhenius plot. The steep slope is attributed to the Al acceptor, while the flatter one - obtained from the low temperature peaks - is attributed to the activation energy ε3 of nearest neighbor hopping. We propose a model, which explains the unexpected sharpness of the low temperature conductance peaks and the disappearance of these peaks for low acceptor concentrations. The model is verified by simulation, and the AS results are compared with corresponding results obtained from resistivity measurements taken on 4H- and the identical 6HSiC samples.

Low temperature photoconductivity in a-ZnSe

1977 ◽  
Vol 55 (24) ◽  
pp. 2142-2144 ◽  
Author(s):  
D. E. Brodie ◽  
P. K. Lim ◽  
R. T. S. Shiah
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Low Temperatures

At lower temperatures, the photoconductivity of near stoichiometric or slightly selenium-rich a-ZnSe increases with an activation energy of 0.04 eV as the temperature decreases. Slightly Zn-rich samples do not exhibit this behaviour. This paper presents a model and a possible mechanism for this effect, which involves intimate valence alternation pairs as the controlling recombination centres at low temperatures. A similar effect has been observed in tellurium-rich a-CdTe.

Direct observation of dienols produced by photochemical enolisation of α,β-unsaturated ketones: rates and activation parameters for dienol reketonisation via a 1,5-hydrogen shift

1987 ◽  
Vol 65 (8) ◽  
pp. 1867-1872 ◽  
Author(s):  
Randy M. Duhaime ◽  
Alan C. Weedon
Keyword(s):  
Activation Energy ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Arrhenius Plot ◽  
Activation Parameters ◽  
Activation Entropy ◽  
Hydrogen Shift ◽  
Unsaturated Ketones ◽  
Ultraviolet Light Irradiation ◽  
Stable Solutions

The production of stable solutions of Z-dienols by ultraviolet light irradiation of α,β-unsaturated ketones at low temperatures (ca. −76 °C) in d4-methanol is reported. The rates of reketonisation of the dienols via a 1,5-sigmatropic hydrogen shift were determined at various temperatures between −43 °C and + 2 °C by monitoring the proton nmr spectra of the dienols. From the data the activation parameters for the reaction were calculated. For the dienol Z-2-hydroxy-4-methyl-2,4-pentadiene, 2, derived from photoenolisation of 4-methyl-3-penten-2-one, 1, the activation energy from the Arrhenius plot is 62 ± 4 kJ/mol, and the activation entropy and enthalpy from the Eyring plot are −87 ± 15 J/mol K and 60 ± 4 kJ/mol, respectively. For the dienol Z-4-tert-butyl-2-hydroxy-2,4-pentadiene, 4, obtained from photoenolisation of 4,5,5-trimethyl-3-hexen-2-one, 3, the activation energy, entropy, and enthalpy were found to be 47 ± 5 kJ/mol, −135 ± 19 J/mol K, and 45 ± 5 kJ/mol, respectively.

Electrophysical properties of the (SnSe)1−x–(SmSe)x solid solutions at high and low temperature

2019 ◽  
Vol 34 (01) ◽  
pp. 2050008
Author(s):  
V. A. Abdurahmanova ◽  
N. M. Abdullaev ◽  
Sh. S. Ismayilov
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Low Temperature ◽  
Solid Solutions ◽  
Low Temperatures ◽  
Electrophysical Properties ◽  
Type Specimens ◽  
Text Type ◽  
Donor Type ◽  
Text Density

The temperature range of [Formula: see text] = 77–770 K in the system alloys: Holl coefficient [Formula: see text], thermo-emf [Formula: see text], electric conductivity [Formula: see text], measured [Formula: see text]-density of components and analyzed. It has been established that samarium additive atoms contain donor-type properties and the effectiveness increases with the temperature increase: up to 40% proportional to [Formula: see text] K in [Formula: see text]-type specimens, whereas in [Formula: see text]-type samples this increase is higher and covers the contents of pH varying from [Formula: see text] to [Formula: see text]. An electrical conductivity of compounds increased due to the carrier activation with further increase of temperature. The activation energy of carriers at low temperatures ([Formula: see text] K) is [Formula: see text] eV for [Formula: see text] mol.% and [Formula: see text] mol.% compounds at [Formula: see text] = 77–320 K and for [Formula: see text] mol.% and [Formula: see text] mol.% compounds are [Formula: see text] eV. [Formula: see text] const at [Formula: see text]–400 K for [Formula: see text] mol.% and [Formula: see text] mol.% compounds, and passing with minimum increases at [Formula: see text] = 400–500 K.

Tracer Impurity Diffusion in Liquid Metals: Au in Ga

1974 ◽  
Vol 29 (6) ◽  
pp. 959-960 ◽  
Author(s):  
P.-E. Eriksson ◽  
S. J. Larsson
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Low Temperatures ◽  
Arrhenius Plot ◽  
Liquid Metals ◽  
Impurity Diffusion ◽  
Straight Line ◽  
Linear Plot

The diffusion coefficient of 198Au in liquid Ga has been measured between 35 and 460 °C. The results can be represented by a linear plot of D vs T or by an Arrhenius plot. The latter yields the parameters D0 = 4.9·10-4 cm2/s and Q = 2.65 kcal/mol. However, some distinct departures from the straight line characteristics, showing a considerably higher “activation energy” at the low temperatures, suggest the possibility that clusters composed of two or several atoms may partake in diffusion.

scholarly journals Low-Temperature Sintering of Apatite-Type Lanthanum Silicate with Fluoride Additives

2010 ◽  
Vol 62 ◽  
pp. 235-240
Author(s):  
Junichi Takahashi ◽  
Hidetoshi Honda ◽  
Takaya Akashi ◽  
Kazutomo Abe ◽  
Hidenobu Itoh ◽  
...  
Keyword(s):  
Activation Energy ◽  
Liquid Phase ◽  
Low Temperature ◽  
Bulk Density ◽  
Grain Growth ◽  
Low Temperatures ◽  
Abnormal Grain Growth ◽  
Low Temperature Sintering ◽  
Lanthanum Silicate ◽  
Apatite Type

Various fluorides (3 - 8 wt%) were added to a La9.33Si6O26 (LSO) powder synthesized by calcining the corresponding oxides mixture at 1100°C for 4 h. The addition of BaF2, AlF3 or Ba3Al2F12 caused an appreciable and substantial increase in bulk density after sintering at 1400º and 1450°C, respectively. These fluorides melt below 1400°C to form liquid phase which could assist the densification at low temperatures. Abnormal grain growth was observed for LSO samples with the addition of AlF3 and Ba3Al2F12, but it was effectively suppressed by stepwise sintering at 1400º and 1450°C. The BaF2 addition brought about the simultaneous promotion of densification and moderate grain growth, leading to the production of a densified LSO sample showing a conductivity of 1.5 x 10–2 Scm–1 at 800°C with an activation energy of 1.23 eV.

Impurity Conduction in n-Type 4H-SIC

1996 ◽  
Vol 423 ◽  
Author(s):  
A. O. Evwaraye ◽  
S. R. Smith ◽  
W. C. Mitchel ◽  
M. D. Roth
Keyword(s):  
Activation Energies ◽  
Hopping Conduction ◽  
Admittance Spectroscopy ◽  
Temperature Dependent ◽  
Resistivity Measurements ◽  
Nitrogen Levels ◽  
Impurity Conduction ◽  
Measured Activation ◽  
Temperature Dependent Resistivity ◽  
Type Sample

AbstractImpurity conduction (or hopping conduction) has been observed in the more heavily n-type 4H-SiC samples by both temperature dependent resistivity measurements and thermal admittance spectroscopy. The measured activation energies ɛ 3 for hopping were 4–5 meV and 2.3–3.0 meV respectively. No evidence of hopping conduction was seen by either method in the sample where ND-NA < 1018 cm-3. The thermal admittance spectrum of the lightly n-type sample showed the two nitrogen levels at 53 and 100 meV.

THE PHOTOLYSIS OF BIACETYL

1955 ◽  
Vol 33 (1) ◽  
pp. 39-46 ◽  
Author(s):  
P. Ausloos ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Excellent Agreement ◽  
Low Temperatures ◽  
Arrhenius Plot ◽  
Disproportionation Reaction ◽  
Methyl Radicals

The photolysis of biacetyl has been reinvestigated. The results are, in general, in excellent agreement with those of Blacet and Bell. Curvature occurs at low temperatures in the Arrhenius plot of [Formula: see text][Biacetyl], and this is attributed to wall reactions, and to the disproportionation reaction[Formula: see text]Azomethane–biacetyl mixtures have been photolyzed to give further information on these points. An activation energy of 8.5 kcal. has been found for the reaction of methyl radicals with biacetyl.

Persistent Conductivity in n-Type 3C-SiC Observed at Low Temperatures

2014 ◽  
Vol 778-780 ◽  
pp. 265-268 ◽  
Author(s):  
Svetlana Beljakowa ◽  
Martin Hauck ◽  
Michel Bockstedte ◽  
Felix Fromm ◽  
Martin Hundhausen ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Low Temperature ◽  
Hall Effect ◽  
Electron Density ◽  
Wide Temperature Range ◽  
Low Temperatures ◽  
Admittance Spectroscopy ◽  
Temperature Range ◽  
Low Temperature Photoluminescence

Persistent conductivity in n-type 3C-SiC is investigated in a wide temperature range down to 3 K by Hall effect, admittance spectroscopy, low temperature photoluminescence (LTPL) and Raman spectroscopy. We propose a model, which clearly explains the persistent behavior of the electron density n below 50 K. It is experimentally verified that the persistent conductivity results from doped SF bunches, which can be considered as nanopolytype inclusions in 3C-SiC.

THERMOELECTRICITY AND ELECTRICAL RESISTIVITY OF DILUTE COPPER ALLOYS OF CHROMIUM, MANGANESE, IRON, AND COBALT AT LOW TEMPERATURES

1962 ◽  
Vol 40 (1) ◽  
pp. 98-112 ◽  
Author(s):  
A. Kjekshus ◽  
W. B. Pearson
Keyword(s):  
Electrical Resistivity ◽  
Low Temperature ◽  
Thermoelectric Power ◽  
Low Temperatures ◽  
Copper Alloys ◽  
Pure Copper ◽  
Gold Alloys ◽  
Resistivity Measurements ◽  
First Time

Low-temperature thermoelectric and electrical resistivity measurements on dilute copper alloys with Cr, Mn, Fe, or Co are reported and discussed, particularly in relation to similar measurements on gold alloys. Both thermoelectric and resistivity measurements have been made for the first time on the same alloys. This paper is a sequel to an earlier paper where the thermoelectric power of "pure" copper was analyzed.

Sign in / Sign up

Export Citation Format

Share Document