Controlling Multiple-Layer Growth

The control of the film thickness and in particular the adjustment of the number of assembled layers may have critical influence for many applications since it influences directly the structural optical or electrical properties of the According to Eq. 15.1, the 

Considering a given solid content and a given temperature (i.e., a given evaporation rate Je), the withdrawal speed of the substrate can be used to switch from a single layer to multiple layers. 

The number of layers, N, can be associated to color changes that can be observed through optical microscopy (Fig. 15.8b). Indeed, a modification in the layer thickness induces an abrupt color change due to interference phenomena occurring between the light reflected from the top and bottom interfaces. 

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With the advent of sophisticated techniques such as molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MCXTVD), synthesis of heterostructure such as multiple quantum wells or superlattices with precise interface layer down to one monolayer have been routinely possible. This not only allows modulation of electronic properties such as carrier confinement and concentration profile, but also optical confinement and wave guiding properties with appropriate choice of refractive indices of the materials. Such precise controls over the growth and material properties have opened the field of band gap engineering . 

Prior to each experiment, foraminifers were incubated in calcein (Bernhard et al. 2004). Calcein staining prior to culture chamber inoculation provided a way to distinguish pre-experimental individuals (and pre-experimental chambers within an individual) from individuals or chambers that calcified under controlled conditions during the experiments. At the start of each culturing experiment 80-100 calcein-stained specimens (multiple species from a single site, > 90 p,m in diameter) were added to cell tissue culture cups (8 mL volume, 8 p,m nonunal pore diameter) housed in acrylic culture chambers. There were nine culture chambers in the 2001 experiment and twelve in the 2002 experiment. Each culture cup contained a l-2mm-thick layer of silt-sized silicon dioxide to provide the physical substrate required for foraminiferal growth the culture chamber design and use of an artificial substrate minimize formation of sedimentary microhabitats within the culture cups (Wilson-Finelli et al. 1998 Havach et al. 2001 Hintz et al. 2004). 

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