In Situ Electron Microscope Investigations of the Growth and Structure of Thin Films

1968 ◽  
Vol 26 ◽  
pp. 376-377
Author(s):  
Thos. E. Hutchinson
Keyword(s):  
Thin Films ◽  
Electron Microscope ◽  
Nucleation And Growth ◽  
Time Sequence ◽  
Experimental Chamber ◽  
Growth Mechanisms ◽  
Sequence Of Events ◽  
Atom Clusters ◽  
Film Nucleation

Few areas of investigation have benefited more from the use of the electron microscope than thin films. This is most strikingly demonstrated by the state of knowledge of the structure and growth mechanisms prior to and subsequent to electron microscope investigations.The use of the electron microscope as an experimental chamber in which both growth and observation take place simultaneously, has been responsible primarily for the broad quasi-quantitative view of the process of formation of thin films we now hold. The great advantage of the in situ experimental arrangement lies in its ability to examine in detail the time sequence of events occuring during thin film nucleation and growth. Each stage in the process of formation of thin films has been examined, and although questions still remain as to the exact mechanisms involved, the general features are well characterized. These are nucleation of ad-atom clusters on the substrate, growth of the atom clusters both laterally and perpendicular to the substrate, coalescence of the nuclei into larger sub-units and finally, elimination of channels between the extended islands.

A TEM study of the microstructure of avian eggshells

1992 ◽  
Vol 50 (2) ◽  
pp. 1102-1103
Author(s):  
S. Q. Xiao ◽  
S. Baden ◽  
A. H. Heuer
Keyword(s):  
Electron Microscope ◽  
Calcium Carbonate ◽  
Nucleation And Growth ◽  
Growth Mechanisms ◽  
Shell Surface ◽  
Thin Sections ◽  
Polycrystalline Metals ◽  
Transmission Electron ◽  
Nucleation And Growth Mechanisms

The avian eggshell is one of the most rapidly mineralizing biological systems known. In situ, 5g of calcium carbonate are crystallized in less than 20 hrs to fabricate the shell. Although there have been much work about the formation of eggshells, controversy about the nucleation and growth mechanisms of the calcite crystals, and their texture in the eggshell, still remain unclear. In this report the microstructure and microchemistry of avian eggshells have been analyzed using transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS).Fresh white and dry brown eggshells were broken and fixed in Karnosky's fixative (kaltitanden) for 2 hrs, then rinsed in distilled H2O. Small speckles of the eggshells were embedded in Spurr medium and thin sections were made ultramicrotome.The crystalline part of eggshells are composed of many small plate-like calcite grains, whose plate normals are approximately parallel to the shell surface. The sizes of the grains are about 0.3×0.3×1 μm3 (Fig.l). These grains are not as closely packed as man-made polycrystalline metals and ceramics, and small gaps between adjacent grains are visible indicating the absence of conventional grain boundaries.

Thin Film Nucleation and Growth Under Controlled Conditions

1968 ◽  
Vol 26 ◽  
pp. 378-379
Author(s):  
Helmut Poppa
Keyword(s):  
Electron Microscope ◽  
Image Intensifier ◽  
Nucleation And Growth ◽  
Nucleation Kinetics ◽  
Extraction Replica ◽  
In Situ Deposition ◽  
Theoretical Predictions ◽  
Experimental Approaches ◽  
Film Nucleation

Results of controlled in-situ nucleation experiments inside the electron microscope were reported recently. The experimental technique employed permitted detailed quantitative studies of the nucleation kinetics which led to a comparison of test results with nucleation theoretical predictions. However, the background pressures were still of the order of 10-7 to 5x10-8 torr and the experimental arrangement did not provide for producing and maintaining clean single-crystal substrates. It was therefore necessary to limit the choice of substrate-overgrowth material combinations, delete epitaxial studies completely, and defer meaningful investigations of the effect of residual gases on nucleation and growth processes. In addition, the influence on the experimental results of the high-intensity imaging electron beam could only be assessed in a qualitative manner.A research program involving two methodically different experimental approaches has since been initiated that promises to eliminate most of the previous test restrictions. The two approaches entail the use of a modified low-energy electron diffraction (LEED) system in conjunction with extraction replica electron microscopy, and a newly designed ultrahigh-vacuum (UHV) electron-microscope specimen chamber in combination with a microscope image intensifier system for in-situ deposition studies.

Thermally Activated Nucleation and Faceting in Immiscible Cu-Cr thin Films

1970 ◽  
Vol 28 ◽  
pp. 518-519
Author(s):  
K. P. Staudhammer ◽  
L. E. Murr
Keyword(s):  
Thin Films ◽  
Phase Separation ◽  
Average Particle Size ◽  
Three Dimensional ◽  
Nucleation And Growth ◽  
Experimental Chamber ◽  
Average Particle ◽  
Component Structure ◽  
Motion Picture Film ◽  
Sequence Of Events

The use of the electron microscope as an experimental chamber in which nucleation and growth observations can take place simultaneously has allowed in-situ studies to be performed on Cu-Cr thin films. Detailed investigations of the time-temperature sequence of events occurring during phase separation of two immiscible materials have been recorded on motion picture film. Each stage in the process of thermally induced phase separation of these thin films has been examined and characterized.Co-evaporation and deposition of Cu-Cr at ambient temperatures on freshly cleaved (100) NaCI substrates results in a polycrystalline two-component structure such as shown in Fig. I(a) where the average particle size was less than 100A. Microprobe data showed the composition of the co-evaporated film to be 59.4 Cu - 40.6 Cr. The advantage of working with unsupported nucle-ation of films of immiscible materials as compared to other techniques of substrate supported nucleation studies lies in the inherent nature of immiscible materials. Because surface diffusion is a controlling mechanism, nucleation, faceting and subsequent growth are more rapid. Exsolved parti-cles once nucleated are three dimensional with minimal constraints, and are on the surface of the thin film as compared to platelet geometries obtained from nucleation and growth on most substrate-type investigations.

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