Investigation of Size Effect on the Emissivity of Thin Films

2012 ◽  
Author(s):  
Sheila Edalatpour ◽  
Mathieu Francoeur
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Size Effect ◽  
Critical Thickness ◽  
Model Simulation ◽  
Direct Method ◽  
Approximate Expression ◽  
Multiple Reflections ◽  
The Mathematical Model ◽  
Kirchhoff's Law

The size effect on the emissivity of thin films is analyzed via a direct method based on Maxwell’s equations combined with fluctuational electrodynamics. Traditional indirect approaches involve computation of absorption, and the emissivity is then predicted by invoking Kirchhoff’s law. The direct method employed in this work does not require Kirchhoff’s law. Instead, Kirchhoff’s law emerges naturally from the mathematical model. Simulation results reveal that the emissivity of metal films increase above bulk values as the film thickness decreases. This counterintuitive behavior is due to the extraneous contributions of waves experiencing multiple reflections within the thin layer, which are usually internally absorbed for metallic bulks. Conversely, for dielectrics, the emissivity of films decreases as the film thickness decreases due to a loss of source volume. The critical thickness above which no size effect is observed for metals is about a hundred of nanometers, while it is as large as a few centimeters for dielectrics. Finally, a simple approximate expression is suggested for evaluating the critical thickness; this expression can be used as a quick reference to determine if the size effect on the emissivity of thin films should be considered.

FINITE SIZE EFFECT ON YBCO/PBCAO AND YBCO/PBCGO NANOMETER MULTILAYERS

2013 ◽  
Vol 27 (15) ◽  
pp. 1362009
Author(s):  
TAR-PIN CHEN ◽  
KE WU ◽  
S. Z. WANG ◽  
QI LI ◽  
BENJAMIN CHEN ◽  
...  
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Size Effect ◽  
Ybco Film ◽  
Finite Size ◽  
Finite Size Effect ◽  
Ybco Films ◽  
Electrical Resistivities ◽  
Superconducting Onset Temperature ◽  
2D To 3D

We have fabricated (110) epitaxy YBa 2 Cu 3 O 7-δ (YBCO), PrBa 2 Cu 0.8 Al 0.2 O 7 (PBCAO), PrBa 2 Cu 0.8 Ga 0.2 O 7-δ (PBCGO) nanometer-thin films and YBCO/PBCAO, YBCO/PBCGO multilayers of a variety of film thicknesses. Electrical resistivities measured from these systems were plotted against temperatures and film thicknesses and are presented in this paper. Superconducting onset temperature Tc of the YBCO films was estimated and plotted against YBCO film thickness. Superconducting coupling length was deduced. Finite size effect and 2D to 3D transition are also discussed.

Specular Scattering in Electrical Transport in the Thin Tilm System CoSi2/Si

1984 ◽  
Vol 37 ◽  
Author(s):  
J. C. Hensel ◽  
R. T. Tung ◽  
J. M. Poate ◽  
F. C. Unterwald
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Size Effect ◽  
Electrical Transport ◽  
Low Temperatures ◽  
Boundary Scattering ◽  
Specular Scattering ◽  
Bulk Scattering ◽  
Scattering Lengths ◽  
High Degree

AbstractWe have investigated electrical transport in thin films of CoSi2 at low temperatures as a function of film thickness and observe in conductivity a size effect much smaller than seen heretofore indicative of a high degree of specularity in the boundary scattering. This in large part owes to the unique characteristics of these films, i.e., they are single crystal and continuous down to ∼60Å thickness with long bulk scattering lengths (≈1000Å) in transport at liquid He temperatures and have nearly atomically perfect interfaces.

Measuring the critical thickness of thin metalorganic precursor films

1999 ◽  
Vol 14 (6) ◽  
pp. 2364-2368 ◽  
Author(s):  
Ryan K. Roeder ◽  
Elliott B. Slamovich
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Critical Thickness ◽  
Sol Gel ◽  
Optical Microscope ◽  
Precursor Film ◽  
Ceramic Thin Films ◽  
Color Fringe ◽  
Metalorganic Decomposition ◽  
Critical Film Thickness

Successful application of sol-gel, metalorganic decomposition, or hydrothermal routes to ceramic thin films depends on the mechanical integrity of the precursor film. Above a critical thickness, a precursor film will crack or decohere from the substrate during drying. The cracking and thickness of thin metalorganic precursor films were simultaneously observed during drying using a standard optical microscope. Isochromatic color fringes produced by interference of reflected white light were used to monitor film thickness. The critical film thickness was determined by the color fringe corresponding to the thickness at which propagating cracks terminated. As a demonstration of the technique, the critical thickness of titanium di(isopropoxide) bis(ethyl acetoacetate) films was measured, showing increased critical thickness with the addition of small amounts of an elastomeric polymer.

Giant Anisotropy of Conductivity in Hydrogenated Nanocrystalline Silicon Thin Films

1998 ◽  
Vol 536 ◽  
Author(s):  
A. B. Pevtsov ◽  
N. A. Feoktistov ◽  
V. G. Golubev
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Percolation Theory ◽  
Nanocrystalline Silicon ◽  
Spatial Light Modulators ◽  
Light Emitting ◽  
Light Modulators ◽  
Silicon Thin Films ◽  
Longitudinal Conductivity ◽  
Transverse Conductivity

AbstractThin (<1000 Å) hydrogenated nanocrystalline silicon films are widely used in solar cells, light emitting diodes, and spatial light modulators. In this work the conductivity of doped and undoped amorphous-nanocrystalline silicon thin films is studied as a function of film thickness: a giant anisotropy of conductivity is established. The longitudinal conductivity decreases dramatically (by a factor of 109 − 1010) as the layer thickness is reduced from 1500 Å to 200 Å, while the transverse conductivity remains close to that of a doped a- Si:H. The data obtained are interpreted in terms of the percolation theory.

scholarly journals Optical Constant and Conformality Analysis of SiO2 Thin Films Deposited on Linear Array Microstructure Substrate by PECVD

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 510
Author(s):  
Yongqiang Pan ◽  
Huan Liu ◽  
Zhuoman Wang ◽  
Jinmei Jia ◽  
Jijie Zhao
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Deposition Rate ◽  
Optical Constant ◽  
Photoelectron Spectroscopy ◽  
Linear Array ◽  
Chemical Vapor ◽  
Rf Plasma ◽  
X Ray ◽  
Sio2 Thin Film

SiO2 thin films are deposited by radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) technique using SiH4 and N2O as precursor gases. The stoichiometry of SiO2 thin films is determined by the X-ray photoelectron spectroscopy (XPS), and the optical constant n and k are obtained by using variable angle spectroscopic ellipsometer (VASE) in the spectral range 380–1600 nm. The refractive index and extinction coefficient of the deposited SiO2 thin films at 500 nm are 1.464 and 0.0069, respectively. The deposition rate of SiO2 thin films is controlled by changing the reaction pressure. The effects of deposition rate, film thickness, and microstructure size on the conformality of SiO2 thin films are studied. The conformality of SiO2 thin films increases from 0.68 to 0.91, with the increase of deposition rate of the SiO2 thin film from 20.84 to 41.92 nm/min. The conformality of SiO2 thin films decreases with the increase of film thickness, and the higher the step height, the smaller the conformality of SiO2 thin films.

scholarly journals Emergence and Evolution of Crystallization in TiO2 Thin Films: A Structural and Morphological Study

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1409
Author(s):  
Ofelia Durante ◽  
Cinzia Di Giorgio ◽  
Veronica Granata ◽  
Joshua Neilson ◽  
Rosalba Fittipaldi ◽  
...  
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Transition Metal Oxides ◽  
Annealing Temperature ◽  
Morphological Properties ◽  
Degree Of Crystallinity ◽  
Tio2 Thin Films ◽  
Force Microscopy ◽  
Heat Treated ◽  
Complementary Techniques

Among all transition metal oxides, titanium dioxide (TiO2) is one of the most intensively investigated materials due to its large range of applications, both in the amorphous and crystalline forms. We have produced amorphous TiO2 thin films by means of room temperature ion-plasma assisted e-beam deposition, and we have heat-treated the samples to study the onset of crystallization. Herein, we have detailed the earliest stage and the evolution of crystallization, as a function of both the annealing temperature, in the range 250–1000 °C, and the TiO2 thickness, varying between 5 and 200 nm. We have explored the structural and morphological properties of the as grown and heat-treated samples with Atomic Force Microscopy, Scanning Electron Microscopy, X-ray Diffractometry, and Raman spectroscopy. We have observed an increasing crystallization onset temperature as the film thickness is reduced, as well as remarkable differences in the crystallization evolution, depending on the film thickness. Moreover, we have shown a strong cross-talking among the complementary techniques used displaying that also surface imaging can provide distinctive information on material crystallization. Finally, we have also explored the phonon lifetime as a function of the TiO2 thickness and annealing temperature, both ultimately affecting the degree of crystallinity.

scholarly journals Experimental Study on the Thickness-Dependent Hardness of SiO2 Thin Films Using Nanoindentation

Coatings ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 23
Author(s):  
Weiguang Zhang ◽  
Jijun Li ◽  
Yongming Xing ◽  
Xiaomeng Nie ◽  
Fengchao Lang ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Grain Size ◽  
Integrated Circuits ◽  
Film Thickness ◽  
Depth Range ◽  
Micro Electro Mechanical Systems ◽  
Si Substrates ◽  
Sio2 Thin Film ◽  
Average Grain Size

SiO2 thin films are widely used in micro-electro-mechanical systems, integrated circuits and optical thin film devices. Tremendous efforts have been devoted to studying the preparation technology and optical properties of SiO2 thin films, but little attention has been paid to their mechanical properties. Herein, the surface morphology of the 500-nm-thick, 1000-nm-thick and 2000-nm-thick SiO2 thin films on the Si substrates was observed by atomic force microscopy. The hardnesses of the three SiO2 thin films with different thicknesses were investigated by nanoindentation technique, and the dependence of the hardness of the SiO2 thin film with its thickness was analyzed. The results showed that the average grain size of SiO2 thin film increased with increasing film thickness. For the three SiO2 thin films with different thicknesses, the same relative penetration depth range of ~0.4–0.5 existed, above which the intrinsic hardness without substrate influence can be determined. The average intrinsic hardness of the SiO2 thin film decreased with the increasing film thickness and average grain size, which showed the similar trend with the Hall-Petch type relationship.

scholarly journals Precise control of Jeff=12 magnetic properties in Sr2IrO4 epitaxial thin films by variation of strain and thin film thickness

2020 ◽  
Vol 102 (21) ◽  
Author(s):  
Stephan Geprägs ◽  
Björn Erik Skovdal ◽  
Monika Scheufele ◽  
Matthias Opel ◽  
Didier Wermeille ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Magnetic Properties ◽  
Film Thickness ◽  
Epitaxial Thin Films ◽  
Thin Film Thickness ◽  
Precise Control

scholarly journals Robust force and displacement control of an active landing gear for vibration reduction at touchdown and during taxiing

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Mehran Pirooz ◽  
Seyed Hossein Mirmahdi ◽  
Ahmad Reza Khoogar
Keyword(s):  
Control System ◽  
Force Control ◽  
Direct Method ◽  
Landing Gear ◽  
Gear System ◽  
Displacement Control ◽  
Robust Nonlinear Control ◽  
Control Loops ◽  
Tire Force ◽  
The Mathematical Model

AbstractIn this paper, a new approach is proposed to control the dynamic response of a landing gear system subjected to runway force, both on heavy landing conditions and at the taxiing process. The mathematical model of the system is used in a way that covers nonlinear dynamics characteristics of landing gear and nonlinear/nonaffine property of the external actuator. The operation of the landing gear system and its components are described briefly. The desired control system includes two different interior loops for displacement and force control. The inner loop determines the actuator force and the outer loop performs the displacement control. A lumped uncertainty is considered in both displacement and force control loops that represent uncertainties including parametric errors, measurement noises, unmodeled dynamics, disturbance due to runway excitation, and other disturbances. The direct method of Lyapunov is utilized for asymptotic stability analysis of the robust nonlinear control system (RNCS). This system is simulated in MATLAB software and the performance of the proposed controller is analyzed exactly. Besides, the results are compared with a passive system and conventional PID control. The comparison indicates that RNCS works better and more precisely. This method can reduce vibrations at touchdown and taxiing and effectively overcome uncertainty and provide well aircraft handling by decreasing the changes in tire force.

scholarly journals Correlation of film thickness to optical band gap of Sol-gel derived Ba0.9Gd0.1TiO3 thin films for optoelectronic applications

2017 ◽  
Vol 162 ◽  
pp. 01042
Author(s):  
Yen Chin Teh ◽  
Ala’eddin A. Saif ◽  
Zul Azhar Zahid Jamal ◽  
Prabakaran Poopalan
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Band Gap ◽  
Optical Band Gap ◽  
Sol Gel ◽  
Optoelectronic Applications
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