Insulating Capping Layers

Organic devices eventually have to meet certain stability requirements to preserve their electrical and/or optical characteristics and to guarantee a longterm functioning. 

A number of recent articles also describe the influence of moisture and ambient gases on device characteristics of organic field-effect transistors (OFETs) 

An encapsulation film for organic devices primarily has to fulfil the following requirements  

We prepared aluminium oxide films by radio frequency (r.f) magnetron sputtering fi om an aluminium oxide target in a dedicated vacuum chamber. To study the growth and structure of these films deposited on silicon oxide and films of DIP we used X-ray reflectivity, cross-sectional transmission electron microscopy (TEM) and atomic force microscopy (AFM) in contact mode. For further details on the preparation of the aluminium oxide films we refer to Refs. [112, 113]. 

2 Growth of Aluminium Oxide Films on Silicon Oxide and Films 

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Dielectric Film Deposition. Dielectric films are found in all VLSI circuits to provide insulation between conducting layers, as diffusion and ion implantation (qv) masks, for diffusion from doped oxides, to cap doped films to prevent outdiffusion, and for passivating devices as a measure of protection against external contamination, moisture, and scratches. Properties that define the nature and function of dielectric films are the dielectric constant, the process temperature, and specific fabrication characteristics such as step coverage, gap-filling capabihties, density stress, contamination, thickness uniformity, deposition rate, and moisture resistance (2). Several processes are used to deposit dielectric films including atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), or plasma-enhanced CVD (PECVD) (see Plasma technology). 

Figure 13.15 Dispersion relation of MIM structure with the insulator region is air and is 0.5Ap thiek and two metal layers are semi-infinitely thick. The fi-equency and the wave vector are normalized with respect to rap and kp where kp=(op/c c is the speed of light in air and top is the plasma frequency. Inset shows the MIM structure, eoo and cap are chosen as 9.6 and 3.76 for Ag, respectively.

The process flow for the fabrication of the microfluidic system includes a single or double metallization layer, a polymer layer for the fluidic system, and a glass sealing cap. There have been some efforts during fabrication to minimize the thermal-dissipation loss. The temperature difference between the two points where the sensors are located is measured with a differential current amplifier, and the flow rate is calibrated. At low flow rates, the temperature difference is a linear function of the flow rate as in Fig. 6. Measurements without heat insulation decrease the sensitivity of the flow sensor and increase the lower limit of flow rate detection. The distance between the heater and the sensors is optimized for the maximum differential temperature. 

The dielectric layer is metallized at one side (e.g., a silver electrode is screened on the mica insulators in mica capacitors), then cut into rectangular pieces. The pieces are stacked with an offset of the alternative layers. The end caps are connected using press fitting and conductive pastes. Then the leads are connected and one of the sealing procedures follows. 

This can again be explained by the inaccessibility of the particle core a second set of core-shell systems where a 50 nm diameter sphere of pure silica was coated with an approximately 5-nm dansyl doped silica shell capped with MPS showed in fact a remarkable sensitivity with only a 30% residual fluorescence. Mancin and coworkers have then designed a last batch of particles to obtain lead ratiometric detection. This was made by a multishell system with a silica core doped with a reference coumarin derivative surrounded by a 7-nm insulating pure silica layer and an outer 3-nm dansyl doped silica shell capped with MPS. The behaviour of this last system was analogous to the previous one but in this case ratiometric detection and calibration were possible thanks to the presence of the reference coumarin emission. 

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