Calorimetric Investigation of Relaxation Processes in Disordered Semiconductors

1996 ◽  
Vol 420 ◽  
Author(s):  
B. G. Budaguan ◽  
A. A. Aivazov ◽  
A. Yu. Sazonov
Keyword(s):  
Porous Silicon ◽  
Low Temperature ◽  
Electrochemical Etching ◽  
Structural Rearrangement ◽  
Endothermic Effect ◽  
Relaxation Processes ◽  
Exothermic Effect ◽  
Scanning Calorimetry ◽  
Si Substrates ◽  
Dsc Measurements

AbstractThe comparative study of relaxation processes in amorphous hydrogenated (a- Si:H) and porous silicon (PS) by use of differential scanning calorimetry (DSC) measurements is presented. Films of a-Si:H were deposited by RF glow discharge of two gas mixtures (10% SiH4+ 90% H2) and (5% SiH4 + 95% He). PS films have been prepared by electrochemical etching of 1Ω-cm (p- PS) and of 0.01Ω-cm (p+ PS) ptype Si substrates. The DSC traces were recorded during the heating of samples at a constant rate of 10°C/min from 20 to 5700C in an Ar atmosphere. All investigated samples present a low temperature exothermic effect with a maxima within 120-2800C. At higher temperatures (T>3000C) a second exothermic effect is observed for a-Si:H films prepared from both hydrogen and helium diluted silane mixtures while two endothermic effects are observed for PS samples. Analysis of the low temperature exothermic effects has been performed, and focussed on the relaxation of weak Si-Si bonds which are the features of both amorphous hydrogenated and porous silicon. It was shown that the endothermic effect connected with hydrogen effusion from PS at higher temperatures is compensated by exothermic structural rearrangement in the case of a-Si:H.

Optical Properties of Free-Standing Ultrahigh Porosity Silicon Films Prepared by Supercritical Drying

1996 ◽  
Vol 452 ◽  
Author(s):  
J. Von Behren ◽  
P. M. Fauchet ◽  
E. H. Chimowitz ◽  
C. T. Lira
Keyword(s):  
Porous Silicon ◽  
Electrochemical Etching ◽  
Supercritical Drying ◽  
Silicon Films ◽  
Index Of Refraction ◽  
Free Standing ◽  
Crystal Silicon ◽  
Si Substrates ◽  
Type C ◽  
P Type

AbstractHighly luminescent free-standing porous silicon thin films of excellent optical quality have been manufactured by using electrochemical etching and lift-off steps combined with supercritical drying. One to 50 μm thick free-standing layers made from highly (p+) and moderately (p) Boron doped single crystal silicon (c-Si) substrates have been produced with porosities (P) up to 95 %. The Fabry-Pérot fringes observed in the transmission and photoluminescence (PL) spectra are used to determine the refractive index. At the highest P the index of refraction is below 1.2 from the IR to 2 eV. The absorption coefficients follow a nearly exponential behavior in the energy range from 1.2 eV and 4 eV. The porosity corrected absorption spectra of free-standing films made from p type c-Si substrates are blue shifted with respect to those prepared from p+ substrates. For P > 70 % a blue shift is also observed in PL. At equal porosities the luminescence intensities of porous silicon films made from p+ and p type c-Si are different by one order of magnitude.

scholarly journals Room-Temperature H2 Gas Sensing Characterization of Graphene-Doped Porous Silicon via a Facile Solution Dropping Method

2017 ◽  
Author(s):  
Nu Si A Eom ◽  
Hong-Baek Cho ◽  
Yoseb Song ◽  
Woojin Lee ◽  
Tohru Sekino ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Gas Sensor ◽  
Room Temperature ◽  
Gas Sensing ◽  
Electrochemical Etching ◽  
Sensor Material ◽  
Sensing Mechanism ◽  
Si Substrates ◽  
H2 Sensor ◽  
P Type

In this study, a graphene-doped porous silicon (G-doped/p-Si) substrate for low ppm H2 gas detection by an inexpensive synthesis route was proposed as a potential noble graphene-based gas sensor material and to understand the sensing mechanism. The G-doped/p-Si gas sensor was synthesized by a simple capillary force-assisted solution dropping method on p-Si substrates, whose porosity was generated through an electrochemical etching process. G-doped/p-Si was fabricated with various graphene concentrations and exploited as a H2 sensor operated at room temperature. The sensing mechanism of the sensor with/without graphene decoration on p-Si was proposed to elucidate the synergetic gas sensing effect generated from the interface between the graphene and p-type silicon.

The Stability Improvement of a-Si:H Films for Photovoltaic Applications

1996 ◽  
Vol 420 ◽  
Author(s):  
B. G. Budaguan ◽  
A. A. Aivazov ◽  
M. N. Meytin
Keyword(s):  
Elevated Temperatures ◽  
Exothermic Peak ◽  
Joint Analysis ◽  
Relaxation Processes ◽  
Scanning Calorimetry ◽  
Defect Generation ◽  
Dsc Measurements ◽  
Microstructure Parameters ◽  
Staebler Wronski Effect ◽  
Kinetics Of

AbstractThe origin of metastability in a-SiH films deposited at different deposition conditions has been investigated by joint analysis of light-induced defect generation kinetics (Staebler-Wronski Effect) and differential scanning calorimetry (DSC) measurements. Light-induced defect generation kinetics were measured at elevated temperatures of 80-150°C_ DSC measurements were performed in a temperature range of 20°C - 570°C. The films microstructure were studied by IR spectroscopy analysis.The simulation of DSC curves has been used to deduce the kinetics of the low-temperature exothermic peak (LTEP) observed at 80-150° C. It was found that kinetic parameters of LTEP and SW effects has the same dependence on microstructure parameters, γ, which suggests their common nature. The analysis of a-SiH stability improvement concerning the influence of films microstructure on the kinetics of relaxation processes is presented.

A low-temperature technique for measuring enthalpies of formation

1996 ◽  
Vol 11 (6) ◽  
pp. 1403-1409 ◽  
Author(s):  
T. P. Weihs ◽  
T. W. Barbee ◽  
M. A. Wall
Keyword(s):  
Low Temperature ◽  
Enthalpy Of Formation ◽  
Enthalpies Of Formation ◽  
Scanning Calorimetry ◽  
Free Standing ◽  
Metal Compounds ◽  
Si Substrates ◽  
Multilayer Foils ◽  
Formation Enthalpies ◽  
The Enthalpy Of Formation

A technique to accurately measure the formation enthalpies of transition metal compounds at relatively low temperatures using thick multilayer foils and differential scanning calorimetry is demonstrated. The enthalpy of formation of Cu51Zr14 was measured using 25 μm thick, free-standing Cu–Zr multilayer foils. The multilayers were deposited onto Si substrates using a planetary, magnetron source sputtering system. They were removed from their substrates, cut into 6 mm diameter specimens, and scanned in temperature from 50 °C to 725 °C in a differential scanning calorimeter. Three distinct exothermic reactions were systematically observed. The heats from the first two reactions were summed and then analyzed using a simple model that accounts for interfacial reactions and heat losses during deposition. The enthalpy of formation for Cu51Zr14 was measured to be 14.3 ± 0.3 kJ/mol. This quantity agrees with the single value of ΔHf = 14.07 ± 1.07 kJ/mol reported in the literature for this Cu–Zr compound. The advantages of measuring formation enthalpies using thick multilayer foils and low temperature calorimetry are discussed.

scholarly journals Photo and electroluminescence of porous silicon layers

BIBECHANA ◽  
2012 ◽  
Vol 8 ◽  
pp. 46-52
Author(s):  
E Haji-Ali
Keyword(s):  
Porous Silicon ◽  
Light Emission ◽  
Electrochemical Cell ◽  
Electrochemical Etching ◽  
Light Illumination ◽  
Porous Layers ◽  
Si Substrates ◽  
Orange Yellow ◽  
Intense Light ◽  
P Type

Porous silicon layers were prepared by both chemical and electrochemical methods on n- and ptype Si substrates. In the former technique, light emission was obtained from p-type and n-type samples. It was found that intense light illumination during the preparation process was essential for PSi formation on n-type substrates.An efficient electrochemical cell with some useful features was designed for electrochemical etching of silicon. Various preparation parameters were studied and photoluminescence emissions ranging from dark red to light blue were obtained from PSi samples prepared on p-type substrates. N-type samples produced emissions ranging from dark red to orange-yellow. Electroluminescence of porous silicon samples showed that the color of the emission was the same as the photoluminescence color of the sample, and its intensity and duration depended on the current density passed through the sample. The effects of exposure of samples to air, storage in vacuum, and heat-treatment in air on luminescence intensity of the samples and preparation of patterned porous layers were also studied.Keywords: Porous silicon layers; photoluminescence; electroluminescenceDOI: http://dx.doi.org/10.3126/bibechana.v8i0.4897  BIBECHANA 8 (2012) 46-52

The Stability Improvement of a-Si:H Films for Photovoltaic Applications

1996 ◽  
Vol 426 ◽  
Author(s):  
B. G. Budaguan ◽  
A. A. Aivazov ◽  
M. N. Meytin
Keyword(s):  
Elevated Temperatures ◽  
Exothermic Peak ◽  
Joint Analysis ◽  
Relaxation Processes ◽  
Scanning Calorimetry ◽  
Defect Generation ◽  
Dsc Measurements ◽  
Microstructure Parameters ◽  
Staebler Wronski Effect ◽  
Kinetics Of

AbstractThe origin of metastability in a-Si:H films deposited at different deposition conditions has been investigated by joint analysis of light-induced defect generation kinetics (Staebler-Wronski Effect) and differential scanning calorimetry (DSC) measurements. Light-induced defect generation kinetics were measured at elevated temperatures of 80–150 °C. DSC measurements were performed in a temperature range of 20 °C – 570°C. The films microstructure were studied by IR spectroscopy analysis.The simulation of DSC curves has been used to deduce the kinetics of the low-temperature exothermic peak (LTEP) observed at 80–150°C. It was found that kinetic parameters of LTEP and SW effects has the same dependence on microstructure parameters, γ, which suggests their common nature. The analysis of a-Si:H stability improvement concerning the influence of films microstructure on the kinetics of relaxation processes is presented.

Low-temperature structure of V6O13

2003 ◽  
Vol 59 (6) ◽  
pp. 747-752 ◽  
Author(s):  
Jonas Höwing ◽  
Torbjörn Gustafsson ◽  
John O. Thomas
Keyword(s):  
Low Temperature ◽  
Mirror Plane ◽  
Temperature Phase ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Acta Cryst ◽  
Lithium Polymer Batteries ◽  
Space Group ◽  
Dsc Measurements

The structure of the transition metal oxide V6O13, a potential cathode material in lithium-polymer batteries, has been studied at 95 K using single-crystal X-ray diffraction (XRD). A phase transition has been determined by differential scanning calorimetry (DSC) measurements to occur at 153 K, with a heat of transition of −1.98 kJ mol−1. In this low-temperature phase, the V and O atoms move by up to 0.21 Å out of the mirror plane they occupy in the room-temperature structure. It is concluded that the earlier reported space group P21/a [Kawada et al. (1978). Acta Cryst. B34, 1037–1039] is incorrect and that a more appropriate choice of space group is Pc.

scholarly journals Polypropylene/Lignin/POSS Nanocomposites: Thermal and Wettability Properties, Application in Water Remediation

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3950
Author(s):  
Abeer Alassod ◽  
Syed Rashedul Islam ◽  
Mina Shahriari Khalaji ◽  
Rogers Tusiime ◽  
Wanzhen Huang ◽  
...  
Keyword(s):  
Organic Liquid ◽  
Contact Angles ◽  
Water Remediation ◽  
Scanning Calorimetry ◽  
Water Contact ◽  
Thermally Induced ◽  
Dsc Measurements ◽  
Infrared Measurement ◽  
Oligomeric Silsesquioxane ◽  
Tga And Dsc

Compositing is an interesting strategy that has always been employed to introduce or enhance desired functionalities in material systems. In this paper, sponges containing polypropylene, lignin, and octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) were successfully prepared via an easy and elegant strategy called thermally induced phase separation (TIPS). To fully explore the behaviour of different components of prepared sponges, properties were characterized by a thermogravimetric analyser (TGA), differential scanning calorimetry (DSC), Fourier transform infrared measurement (FTIR), and scanning electron microscopy (SEM). Furthermore, wettability properties toward an organic liquid and oil were investigated. The FTIR analysis confirmed the chemical modification of the components. TGA and DSC measurements revealed thermal stability was much better with an increase in OV-POSS content. OV-POSS modified sponges exhibited ultra-hydrophobicity and high oleophilicity with water contact angles of more than 125°. The SEM revealed that POSS molecules acted as a support for reduced surface roughness. Moreover, OV-POSS-based blend sponges showed higher sorption capacities compared with other blend sponges without OV-POSS. The new blend sponges demonstrated a potential for use as sorbent engineering materials in water remediation.

scholarly journals Combined thermal analysis of plant oils

2021 ◽  
Author(s):  
Kinga Tamási ◽  
Kálmán Marossy
Keyword(s):  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Low Temperature ◽  
Glassy State ◽  
Mechanical Analysis ◽  
Plant Oils ◽  
Scanning Calorimetry ◽  
Natural Plant ◽  
The Moment ◽  
Current Reversal

AbstractThe paper deals with the study of seven selected natural plant oils. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermally stimulated discharge (TSD) methods were used. It has been found that most of the oils tested are in a glassy state at low temperature and have multiple transitions in the low temperature range. DSC shows complex melting-like processes or glass transition. For both DMA and TSD, the scaffold supportive method was used and found as a suitable one. DMA and TSD proved more sensitive than DSC and revealed at least two transitions between − 120 and − 40 °C. In the case of three oils (argan, avocado and sunflower), current reversal was observed by TSD; this symptom cannot be fully explained at the moment.

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