Multilayers layer thickness determination

Fig. 21. Film thickness, determined by ellipsometry, vs layer number, measured on eight different multilayer samples [194]...

Here, Df is the fractal dimension, which differs for the monolayer and multilayer situations, implying that Df is determined not only by lateral movement (virtually independent of layer thickness) but also by a cascade effect from overlying layers. By quantifying Df as a function of the molecule/surface coupling, as well as the number of monolayers, Dj can be used as a fingerprint to analyze lubricant/surface pairs, and possibly become a critical parameter for the selection of optimal lubricants. 

Fig. 2.19. (upper figure) Differential scanning calorimetry scans of various Nr/Zr multilayer diffusion couples heated at a constant rate of 20 C/s. The heat flow rate, k, has been normalized by the total Ni/Zr interfacial area in the diffusion couple. The dotted line corresponds to an individual Ni layer thickness of 30 nm and an individual Zr layer thickness of 45 nm, the dashed line to 50nm/8nm, and the solid line to lOOnm/lOOnm, respectively. (lower figure) a plot of In (X%) (note that H is proportional to A"-the proportionality constant is determined by direct measurement of Hm and I, the final thickness of the amorphous layers) vs. (1/7 ) for the third sample in the upper figure. See text for further explanation. The slope of the curve gives the activation energy for interdiffusion of Ni and Zr in the amorphous layer [2.69]... 

The first of our preliminary results we demonstrate here is mass sensitivity. To do this we use a polyelectrolyte multilayer layer-by-layer deposition technique. Briefly, multilayers of polyethyleneimine and polyacrylic acid were deposited on the glutaraldehyde functionalized NOSA device, and on similarly functionalized silicon wafers in parallel. After deposition of each layer, output spectra were recorded to quantify shift in resonant wavelengths and polyelectrolyte multilayer film thickness was determined on silicon wafers using ellipsometry. Output spectra were compared to the initial baseline spectra to determine resonance shift (AA, in mn), and were plotted against film thickness as shown in Fig. 2. 

The thickness of the deposited layer is determined by the height of the doctor blade above the polymer sheet. Multilayer films are possible using the approach illustrated in Figure 27.2. The special feature of the doctor blade is that it produces a very uniform thickness. A typical doctor blade assembly is shown in Figure 27.3. The cast tape is dried, peeled from the polymer sheet, and reeled up to wait for further processing. At this stage of the process the tape is flexible because it still contains a... 

In this section we give a brief review of the experimental results including the layered or compositionally modulated structure for R/T multilayers, the layer thickness and temperature dependencies of magnetic properties for Dy/Fe, Dy/Co and Tb/Fe multilayers. We will not provide a comprehensive review of all recent work in this field. Rather, our aim is to focus on discussing die above fimdamental properties, and only limited references which are closely related to this discussion are dted. The role that the interfacial magnetism plays in determining magnetic properties will be emphasized. 

The shape configuration of the mechanical actuator is important because it determines the ampUtude and the direction of the movement. Conventional shapes (like planar, tube or roll) are not able to induce linear contraction as can be found in muscles. One of the possibilities is to use a stack-like configuration inspired by piezoelectric technology. It consists of a multilayer stmcture of a planar actuator. When high voltage is applied, the entire device contraction is the sum of each layer thickness compression (Carpi et al., 2005). 

The r-plot is involved in most of the methods for the reason that on a relatively flat surface in the absence of pores, adsorption occurs and the adsorbed film becomes several molecular layers thick before the vapor pressure reaches p/p l.O for the bulk liquid. Obviously, in the multilayer film the properties of the nitrogen are not the same as in the bulk. As already pointed out, determination of pore size requires not only the Kelvin equation to calculate the size of pores that fill with bulk liquid- nitrogen but also the thickness of the adsorbed film on the inner surface of pores that are not filled. 

The melting point can also be determined in a penetration-mode measurement, which is important in the characterization of multilayer polymer hlms and coatings. Multilayer thin films are used primarily as packaging materials in order to control the end-use properties, such as selective atmosphere permeability or toughness. TMA in the penetration mode can characterize multilayer films in terms of layer thickness as shown in Fig. 4.11. Here, a multilayer film coated on a foil substrate was characterized in a penetration-mode experiment. Two distinct changes due to the penetration of the probe are clear at 103 °C and 258 °C, suggesting that two layers of film were coated onto the metal substrate.The thicknesses of the layers were measured as 93 pm (polymer 1) and 15 pm (polymer 2). These temperatures are close to the melting points... 

With regards to stratified systems, it is noticeable that the layer thickness can, in principle, be determined by using the ellipsometric method. However, this does not hold for ultrathin films (monolayers and multilayers) because the infiuence of anisotropy, molecular density, and thickness cannot be discriminated in this case [68]. 

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