scholarly journals Thin film/substrate systems featuring arbitrary film thickness and misfit strain distributions. Part II: Experimental validation of the non-local stress/curvature relations

2007 ◽  
Vol 44 (6) ◽  
pp. 1755-1767 ◽  
Author(s):  
M.A. Brown ◽  
A.J. Rosakis ◽  
X. Feng ◽  
Y. Huang ◽  
Ersan Üstündag
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Experimental Validation ◽  
Local Stress ◽  
Misfit Strain ◽  
Non Local ◽  
Film Substrate

Elastic Analysis of Twinning in Misfitting Thin Films

1995 ◽  
Vol 389 ◽  
Author(s):  
N. Sridhar ◽  
J.M. Rickman ◽  
D.J. SroIovitz
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Film Thickness ◽  
Misfit Strain ◽  
Elastic Analysis ◽  
Domain Formation ◽  
Linear Elasticity Theory ◽  
Periodic Distribution ◽  
Twin Domain ◽  
Strain Tensors

ABSTRACTWe examine the conditions under which a misfitting thin film on a substrate will twin and the pattern of the twin microstructure that will form. Using linear elasticity theory, we present exact analytical results for the energy released due to the formation of a periodic array of twinned domains as well as that for a single embedded twin domain. While the analysis is applicable to general misfit strain tensors, we specifically analyze the energetics of twinned domain formation for a tetragonal film on a cubic substrate. The analysis shows that for a periodic distribution of twins, the equilibrium width of the domains of the two variants are identical. Our results also show that the equilibrium periodicity of the microstructure scales inversely with film thickness for large film thickness and decays exponentially with increasing film thickness for small film thicknesses.

On the Stoney Formula for a Thin Film/Substrate System With Nonuniform Substrate Thickness

2007 ◽  
Vol 74 (6) ◽  
pp. 1276-1281 ◽  
Author(s):  
X. Feng ◽  
Y. Huang ◽  
A. J. Rosakis
Keyword(s):  
Thin Film ◽  
Misfit Strain ◽  
Film Stress ◽  
Substrate Thickness ◽  
Full Field ◽  
Temperature Changes ◽  
Thin Film Stress ◽  
Curvature Measurements ◽  
Film Substrate ◽  
Stoney Formula

Current methodologies used for the inference of thin film stress through system curvature measurements are strictly restricted to stress and curvature states which are assumed to remain uniform over the entire film/substrate system. Recently Huang, Rosakis, and co-workers [Acta Mech. Sinica, 21, pp. 362–370 (2005); J. Mech. Phys. Solids, 53, 2483–2500 (2005); Thin Solid Films, 515, pp. 2220–2229 (2006); J. Appl. Mech., in press; J. Mech. Mater. Struct., in press] established methods for the film/substrate system subject to nonuniform misfit strain and temperature changes. The film stresses were found to depend nonlocally on system curvatures (i.e., depend on the full-field curvatures). These methods, however, all assume uniform substrate thickness, which is sometimes violated in the thin film/substrate system. Using the perturbation analysis, we extend the methods to nonuniform substrate thickness for the thin film/substrate system subject to nonuniform misfit strain.

Thickness-Dependent Radiative Properties of Y-Ba-Cu-O Thin Films

1992 ◽  
Vol 114 (1) ◽  
pp. 227-233 ◽  
Author(s):  
P. E. Phelan ◽  
G. Chen ◽  
C. L. Tien
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Film Thickness ◽  
Room Temperature ◽  
High Temperature Superconductors ◽  
Normal Incidence ◽  
Radiative Properties ◽  
Continuous Slab ◽  
Optimal Value ◽  
Film Substrate

Some applications of high-temperature superconductors where their radiative behavior is important, such as bolometers, optically triggered switches and gates, and space-cooled electronics, require the superconductor to be in the form of a very thin film whose radiative properties cannot be adequately represented by a semi-infinite analysis. Two properties of particular importance are the film absorptance and the combined film/substrate absorptance, which are crucial to the operation of many devices. Here, calculations of the spectral, normal-incidence absorptance of superconducting-state Y-Ba-Cu-O films on MgO substrates suggest that a decrease in the film thickness often leads to an increase in both the film and the film/substrate absorptance. Furthermore, both can exhibit a maximum at some optimal value of film thickness. Room-temperature experiments verify the qualitative features of the spectral film/substrate absorptance, indicating the assumption that the film is a smooth, continuous slab with a refractive index equal to that of well-aligned bulk Y-Ba-Cu-O is valid, at least in the normal state and for films as thin as 35 nm.

Microtomy of spherical Al2O3 powders

1983 ◽  
Vol 41 ◽  
pp. 74-75
Author(s):  
E.J. Jenkins ◽  
D.S. Tucker ◽  
J.J. Hren
Keyword(s):  
Thin Film ◽  
Size Range ◽  
Particle Aggregation ◽  
Ion Milling ◽  
Thin Sections ◽  
Α Phase ◽  
Convenient Means ◽  
Van Der Waals Attraction ◽  
Negative Feature ◽  
Film Substrate

The size range of mineral and ceramic particles of one to a few microns is awkward to prepare for examination by TEM. Electrons can be transmitted through smaller particles directly and larger particles can be thinned by crushing and dispersion onto a substrate or by embedding in a film followed by ion milling. Attempts at dispersion onto a thin film substrate often result in particle aggregation by van der Waals attraction. In the present work we studied 1-10 μm diameter Al2O3 spheres which were transformed from the amprphous state to the stable α phase.After the appropriate heat treatment, the spherical powders were embedded in as high a density as practicable in a hard EPON, and then microtomed into thin sections. There are several advantages to this method. Obviously, this is a rapid and convenient means to study the microstructure of serial slices. EDS, ELS, and diffraction studies are also considerably more informative. Furthermore, confidence in sampling reliability is considerably enhanced. The major negative feature is some distortion of the microstructure inherent to the microtoming operation; however, this appears to have been surprisingly small. The details of the method and some typical results follow.

Structural and electronic properties of defects in semiconductors

1995 ◽  
Vol 53 ◽  
pp. 4-5
Author(s):  
J.L. Batstone
Keyword(s):  
Semiconductor Device ◽  
Chemical Vapor ◽  
Misfit Strain ◽  
Organic Chemical ◽  
Extended Defects ◽  
Transmission Electron ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Metal Organic ◽  
Film Substrate

The development of growth techniques such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy during the last fifteen years has resulted in the growth of high quality epitaxial semiconductor thin films for the semiconductor device industry. The III-V and II-VI semiconductors exhibit a wide range of fundamental band gap energies, enabling the fabrication of sophisticated optoelectronic devices such as lasers and electroluminescent displays. However, the radiative efficiency of such devices is strongly affected by the presence of optically and electrically active defects within the epitaxial layer; thus an understanding of factors influencing the defect densities is required.Extended defects such as dislocations, twins, stacking faults and grain boundaries can occur during epitaxial growth to relieve the misfit strain that builds up. Such defects can nucleate either at surfaces or thin film/substrate interfaces and the growth and nucleation events can be determined by in situ transmission electron microscopy (TEM).

Microstructural investigation of surface roughness in MBE-grown AlAs

1995 ◽  
Vol 53 ◽  
pp. 454-455
Author(s):  
R. Rajesh ◽  
R. Droopad ◽  
C. H. Kuo ◽  
R. W. Carpenter ◽  
G. N. Maracas
Keyword(s):  
Thin Film ◽  
Real Time ◽  
Growth Control ◽  
Native Oxide ◽  
Effusion Cell ◽  
Surface Oxide Layer ◽  
Microstructural Investigation ◽  
Mbe Growth ◽  
Film Substrate ◽  
And Control

Knowledge of material pseudodielectric functions at MBE growth temperatures is essential for achieving in-situ, real time growth control. This allows us to accurately monitor and control thicknesses of the layers during growth. Undesired effusion cell temperature fluctuations during growth can thus be compensated for in real-time by spectroscopic ellipsometry. The accuracy in determining pseudodielectric functions is increased if one does not require applying a structure model to correct for the presence of an unknown surface layer such as a native oxide. Performing these measurements in an MBE reactor on as-grown material gives us this advantage. Thus, a simple three phase model (vacuum/thin film/substrate) can be used to obtain thin film data without uncertainties arising from a surface oxide layer of unknown composition and temperature dependence.In this study, we obtain the pseudodielectric functions of MBE-grown AlAs from growth temperature (650°C) to room temperature (30°C). The profile of the wavelength-dependent function from the ellipsometry data indicated a rough surface after growth of 0.5 μm of AlAs at a substrate temperature of 600°C, which is typical for MBE-growth of GaAs.

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