Line-focus acoustic microscopy measurements of Nb/sub 2/O/sub 5//MgO and BaTiO/sub 3//LaAlO/sub 3/ thin-film/substrate configurations

1995 ◽  
Vol 42 (3) ◽  
pp. 376-380 ◽  
Author(s):  
Y.-C. Lee ◽  
J.D. Achenbach ◽  
M.J. Nystrom ◽  
S.R. Gilbert ◽  
B.A. Block ◽  
...  
Keyword(s):  
Thin Film ◽  
Acoustic Microscopy ◽  
Film Substrate ◽  
Line Focus

Effective Elastic Constants of Superlattice Films Measured by Line-Focus Acoustic Microscopy

1995 ◽  
Vol 117 (4) ◽  
pp. 395-401 ◽  
Author(s):  
Jin O. Kim ◽  
Jan D. Achenbach ◽  
Meenam Shinn ◽  
Scott A. Barnett
Keyword(s):  
Elastic Constants ◽  
Calculation Method ◽  
Measurement Method ◽  
Acoustic Microscopy ◽  
Effective Elastic Constants ◽  
Dispersion Data ◽  
Rough Interfaces ◽  
Film Substrate ◽  
Sharp Interfaces ◽  
Line Focus

The effective elastic constants of single-crystal nitride superlattice films have been determined by calculation and by measurement methods. The calculation method uses formulas to calculate the effective elastic constants of superlattices from the measured elastic constants of the constituent layers. The calculated effective elastic constants are tested by comparing the corresponding surface acoustic wave (SAW) velocities calculated for thin-film/substrate systems with the corresponding SAW velocities measured by line-focus acoustic microscopy (LFAM). The measurement method determines the effective elastic constants of the superlattices directly from the SAW velocity dispersion data measured by LFAM. Two kinds of superlattice films are considered: one has relatively flat and sharp interfaces between layers, and the other has rough interfaces with interdiffusion. The calculation method has yielded very good results for the superlattices with flat and sharp interfaces but not for the superlattices with rough interfaces. The measurement method yields results for both kinds, with the restriction that the constituent layers have similar crystal symmetries.

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.

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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