Characterisation of Polycrystalline thin Films of Tellurium

1992 ◽  
Vol 283 ◽  
Author(s):  
A K Ray ◽  
C A Hogarth ◽  
R Swan
Keyword(s):  
High Field ◽  
Room Temperature ◽  
Energy Gap ◽  
High Vacuum ◽  
The Other ◽  
Corning Glass ◽  
A Value ◽  
Polycrystalline Thin Films ◽  
Tellurium Film ◽  
Limited Conduction

ABSTRACTStructural, electrical and optical characterisations were performed on tellurium film deposited under high vacuum conditions on ultrasonically cleaned Corning glass 7059 substrates. SEM and TEM studies reveal the polycrystalline nature of deposited tellurium films. At steady state high field conditions, space charge limited conduction is believed to have occurred due to the existence of a fast decaying density of trapping states in the energy gap. The DC conductivity is believed to exhibit a T-1/ law dependence below room temperature, giving a value of 2×10-l6eV/m3 for conduction states close to the Fermi level. From the power law dependence on frequency of AC conductivity, the barrier for bipolaron hopping is estimated to 0.33eV.Optical absorption in 9nm thick tellurium samples is due to direct transitions both allowed and forbidden producing two edges, the first one at 4eV and the other at about 0.5eV, respectively.

scholarly journals The Effect Of Thickness on The Optical Properties Of ZnS

2007 ◽  
Vol 4 (4) ◽  
pp. 647-652
Author(s):  
Baghdad Science Journal
Keyword(s):  
Band Gap ◽  
Room Temperature ◽  
Near Infrared ◽  
High Vacuum ◽  
Ultra Violet ◽  
Infrared Region ◽  
Complex Dielectric Constant ◽  
Film Properties ◽  
Corning Glass ◽  
Different Thickness

Zinc sulfide(ZnS) thin films of different thickness were deposited on corning glass with the substrate kept at room temperature and high vacuum using thermal evaporation technique.the film properties investigated include their absorbance/transmittance/reflectance spectra,band gap,refractive index,extinction coefficient,complex dielectric constant and thickness.The films were found to exhibt high transmittance(59-98%) ,low absorbance and low reflectance in the visible/near infrared region up to 900 nm..However, the absorbance of the films were found to be high in the ultra violet region with peak around 360 nm.The thickness(using optical interference fringes method) of various films thichness(100,200,300,and 400) nm.The band gap measured was found to be in the range (3.52 -3.78 )eV.

Pulsed Laser Deposition of Poly(Tetrafluoroethylene) Films

1995 ◽  
Vol 397 ◽  
Author(s):  
D.L. Kjendal ◽  
Ashok Kumar ◽  
R.B. Inturi ◽  
J. A. Barnard
Keyword(s):  
Pulsed Laser Deposition ◽  
Room Temperature ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Deposition Technique ◽  
Nano Indentation ◽  
Corning Glass ◽  
Deposition Parameters ◽  
Compositional Properties

ABSTRACTThin films of poly(tetrafluoroethylene) have been deposited on amorphous (7059 Corning Glass) and silicon(l00) substrates at various temperatures by the Pulsed Laser Deposition technique. The deposition was carried out at high vacuum (˜10-6 torr)at temperatures ranging from room temperature to 350°C. The mechanical properties of these films at the varying process temperatures have been evaluated by nano-indentation techniques and compositional properties of the films have been characterized by Fourier Transform Infrared spectroscopy. The deposition parameters have been optimized in order to produce good quality films.

Oscillation and Photoresponse of High-Resistivity n-GaAs Diodes

1972 ◽  
Vol 50 (11) ◽  
pp. 1098-1105 ◽  
Author(s):  
A. B. Torrens ◽  
L. Young
Keyword(s):  
High Field ◽  
Room Temperature ◽  
Ohmic Contacts ◽  
Weak Field ◽  
Photoelectric Effect ◽  
High Resistivity ◽  
Initial Value ◽  
Small Current ◽  
A Value ◽  
Minority Carriers

Diodes of lengths 0.17 mm and 1 mm with ohmic contacts were made from n-type, ~ 16 Ωm-resistivity GaAs. The diode resistance varies with temperature as exp (−Δ*/kT), with Δ** 412 meV. Above a threshold voltage of 50 to 80 V, depending on the diode, a small current oscillation occurs in the short diodes, which can be explained by the periodic propagation of small high-field domains at a velocity of the order of 1 m/s at room temperature. Several features of the transient response of the diodes to pulses are consistent with the occurrence of weak field-enhanced trapping effects which could account for the formation of the high-field domains.The long diodes exhibit a novel photoelectric effect: if a diode is illuminated and is subjected to a high-voltage step, the current assumes initially a value proportional to the voltage. Then, in about 1 μs, it decays by as much as 92% of its initial value. All the characteristics of this effect can be explained in terms of accumulation of minority carriers (holes) at the cathode of the diode (which is blocking for holes).

THE EFFECT OF INCIDENT ATOMIC VELOCITY ON THE STRUCTURE OF EVAPORATED SILVER FILMS

1956 ◽  
Vol 34 (8) ◽  
pp. 731-736 ◽  
Author(s):  
R. A. Aziz ◽  
G. D. Scott
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
High Vacuum ◽  
The Other ◽  
Qualitative Explanation ◽  
Nitrogen Gas ◽  
Silver Films ◽  
Resistivity Measurements

The influence of the incident atomic velocity on the structure of evaporated films has been studied for silver films in the thickness range from 50 to 500 Å. The thermal velocities of the evaporated atoms were reduced (i) by "reflection" from a teflon surface at room temperature, and (ii) by "diffusion" through nitrogen gas at 3.0 μ. Films formed by these two methods are compared with "normal" high vacuum films for the same rates of deposition, which were relatively slow (0.4 to 4 Å of thickness per second). The results of both resistivity measurements and electron microscopy show that "diffusion" films are less aggregated, i.e. more continuous, than "normal" high vacuum films. "Reflected" films have a structure intermediate between the other two. A qualitative explanation of the observed effects is given in terms of the formation of nuclei and the growth of aggregates.

Thermoelectric properties of thin-film germanium-based layers

2015 ◽  
Vol 32 (3) ◽  
pp. 115-121 ◽  
Author(s):  
Piotr Markowski ◽  
Eugeniusz Prociów ◽  
Łukasz Urbaniak
Keyword(s):  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Power Factor ◽  
Room Temperature ◽  
Nitrogen Atmosphere ◽  
Thin Layers ◽  
Activation Process ◽  
Content Type ◽  
Corning Glass ◽  
A Value

Purpose – The purpose of this paper is to determine the thermoelectric properties of the germanium-based thin films and selecting the most suitable ones for fabrication of micrognerators. Design/methodology/approach – The germanium layers were deposited by low pressure magnetron sputtering method, in the pressure of 10−3/104 mbar range. The amount of dopants (germanium or vanadium) was changed in a limited extent. The influence of such changes on the layers output properties was studied. Post-processing heat treatment at temperature below 823 K was applied to activate the layers. It leads to improve the electrical and thermoelectrical performance. Findings – The special attention was paid to the power factor (PF = S2/ρ) of the layers. To estimate power factor (PF) electrical resistivity (ρ) and Seebeck coefficient (S) were determined. The achieved Seebeck coefficient value was 185 Volt/Kelvin (μV/K) for germanium doped with vanadium (Ge:V1.15) and 225 μV/K for germanium doped with gold(Ge:Au3.13) layers at room temperature. After activation process, the PF reached a value of 2.5 × 10−4 W/m · K2 for the Ge:Au3.13 and 1.1 × 10−4 W/m · K2 for the Ge:V1.15 layers. Originality/value – The fabricated thermoelectric layers can be thermally annealed in temperature up to 823 K in the air and in 1,023 K under a nitrogen atmosphere. This enables integration of thin layers with thick-film technology. Corning glass or low temperature cofired ceramic was used as a substrate.

(111) Monocrystalline Nickel Films

1972 ◽  
Vol 30 ◽  
pp. 512-513
Author(s):  
T.E. Pratt ◽  
R.W. Vook
Keyword(s):  
Film Thickness ◽  
Deposition Rate ◽  
Room Temperature ◽  
Narrow Range ◽  
High Vacuum ◽  
Residual Pressure ◽  
Temperature Dependent ◽  
Deposition Parameters ◽  
Transmission Electron ◽  
Substrate Temperatures

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

TEM sample preparation of wear-tested room-temperature pulsed-laser-deposited thin films of MoS2 by ultramicrotomy

1993 ◽  
Vol 51 ◽  
pp. 1118-1119
Author(s):  
Pamela F. Lloyd ◽  
Scott D. Walck
Keyword(s):  
Thin Films ◽  
Sample Preparation ◽  
Room Temperature ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Ultra High Vacuum ◽  
Wear Testing ◽  
Preparation Technique ◽  
Cross Sectional ◽  
Aerospace Applications

Pulsed laser deposition (PLD) is a novel technique for the deposition of tribological thin films. MoS2 is the archetypical solid lubricant material for aerospace applications. It provides a low coefficient of friction from cryogenic temperatures to about 350°C and can be used in ultra high vacuum environments. The TEM is ideally suited for studying the microstructural and tribo-chemical changes that occur during wear. The normal cross sectional TEM sample preparation method does not work well because the material’s lubricity causes the sandwich to separate. Walck et al. deposited MoS2 through a mesh mask which gave suitable results for as-deposited films, but the discontinuous nature of the film is unsuitable for wear-testing. To investigate wear-tested, room temperature (RT) PLD MoS2 films, the sample preparation technique of Heuer and Howitt was adapted.Two 300 run thick films were deposited on single crystal NaCl substrates. One was wear-tested on a ball-on-disk tribometer using a 30 gm load at 150 rpm for one minute, and subsequently coated with a heavy layer of evaporated gold.

Electron microscope studies of the plastic deformation of ternary alloys based on GaAs

1990 ◽  
Vol 48 (4) ◽  
pp. 1120-1120
Author(s):  
R. Haswell ◽  
U. Bangert ◽  
P. Charsley
Keyword(s):  
Plastic Deformation ◽  
Electron Microscope ◽  
Room Temperature ◽  
Stacking Faults ◽  
The Other ◽  
Ternary Alloys ◽  
Dislocation Mobility ◽  
Semiconducting Materials ◽  
Micro Indentation

A knowledge of the behaviour of dislocations in semiconducting materials is essential to the understanding of devices which use them . This work is concerned with dislocations in alloys related to the semiconductor GaAs . Previous work on GaAs has shown that microtwinning occurs on one of the <110> rosette arms after indentation in preference to the other . We have shown that the effect of replacing some of the Ga atoms by Al results in microtwinning in both of the rosette arms.In the work to be reported dislocations in specimens of different compositions of Gax Al(1-x) As and Gax In(1-x) As have been studied by using micro indentation on a (001) face at room temperature . A range of electron microscope techniques have been used to investigate the type of dislocations and stacking faults/microtwins in the rosette arms , which are parallel to the [110] and [10] , as a function of composition for both alloys . Under certain conditions microtwinning occurs in both directions . This will be discussed in terms of the dislocation mobility.

HAYNES STELLITE ALLOY No. 98M2

Alloy Digest ◽  
1960 ◽  
Vol 9 (7) ◽  
Keyword(s):  
Fracture Toughness ◽  
Compressive Strength ◽  
Physical Properties ◽  
Room Temperature ◽  
Base Alloy ◽  
Heat Treating ◽  
The Other ◽  
Stellite Alloy ◽  
Cobalt Base Alloy ◽  
Cobalt Base

Abstract HAYNES STELLITE 98M2 Alloy is a cobalt-base alloy having higher compressive strength and higher hardness than all the other cobalt-base alloys at room temperature and in the red heat range. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and compressive strength as well as fracture toughness. It also includes information on heat treating, machining, and joining. Filing Code: Co-22. Producer or source: Haynes Stellite Company.

The Reactivity of Different Active Forms of Sodium Carbonate with Respect to Sulfur Dioxide

1992 ◽  
Vol 57 (11) ◽  
pp. 2302-2308
Author(s):  
Karel Mocek ◽  
Erich Lippert ◽  
Emerich Erdös
Keyword(s):  
Thermal Decomposition ◽  
Liquid Phase ◽  
Sulfur Dioxide ◽  
Specific Surface ◽  
Surface Area ◽  
Sodium Carbonate ◽  
Room Temperature ◽  
Active Form ◽  
The Other ◽  
Kinetics Of

The kinetics of the reaction of solid sodium carbonate with sulfur dioxide depends on the microstructure of the solid, which in turn is affected by the way and conditions of its preparation. The active form, analogous to that obtained by thermal decomposition of NaHCO3, emerges from the dehydration of Na2CO3 . 10 H2O in a vacuum or its weathering in air at room temperature. The two active forms are porous and have approximately the same specific surface area. Partial hydration of the active Na2CO3 in air at room temperature followed by thermal dehydration does not bring about a significant decrease in reactivity. On the other hand, if the preparation of anhydrous Na2CO3 involves, partly or completely, the liquid phase, the reactivity of the product is substantially lower.

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