Many of the excellent techniques that provide atomic resolution are not best suited to study the features the forefront of integrated circuit technology, where interest now lies in the 0.1 micron regime. Most scanning techniques are also limited to surface structures, whereas in most solid-state devices the interesting properties depend upon details at buried interfaces. And because the electron interacts so strongly with matter, electron microscopy and other excitation techniques can be also limited to surfaces or sectioned, thinned and stained specimens. The aperture of a solid-state detector is shown at right. Absorption can be used to determine local atomic environments and valance.
Diffraction provides a means to understand or disorder, and micro-crystalline state.
And fluorescence excitation spectra, unique to each atom, can be used to determine atomic spatial distributions In this article we will describe an experiment using fluorescence excitation to determine the spatial distribution of a germanium atoms selectively doped into a communications grade optical fiber. Communications fibers are doped in an attempt to create a perfect optical channel, having no attenuation or loss over hundreds of kilometers distance. Since the final dopant concentration profiles determine the performance of the fiber, a diagnostic tool is needed to characterize those profiles during the manufacturing process. They were fabricated starting with a hollow, cylindrical borosilicate glass form. Ultra-high purity silica is deposited from vapor on inner surface, followed by a multiple deposition cycle of pure germania.