Nanometer-scale patterning, application

The possibilities afforded by SAM-controlled electrochemical metal deposition were already demonstrated some time ago by Sondag-Huethorst et al. [36] who used patterned SAMs as templates to deposit metal structures with line widths below 100 nm. While this initial work illustrated the potential of SAM-controlled deposition on the nanometer scale further activities towards technological exploitation have been surprisingly moderate and mostly concerned with basic studies on metal deposition on uniform, alkane thiol-based SAMs [37-40] that have been extended in more recent years to aromatic thiols [41-43]. A major reason for the slow development of this area is that electrochemical metal deposition with, in principle, the advantage of better control via the electrochemical potential compared to none-lectrochemical methods such as electroless metal deposition or evaporation, is quite critical in conjunction with SAMs. Relying on their ability to act as barriers for charge transfer and particle diffusion, the minimization of defects in and control of the structural quality of SAMs are key to their performance and set the limits for their nanotechnological applications. 

For direct patterning on the nanometer scale, scanning probe microscopy (SPM) based techniques such as dip-pen-nanolithography (DPN), [112-114] nanograftingf, nanoshaving or scanning tunneling microscopy (STM) based techniques such as electron induced diffusion or evaporation have recently been developed (Fig. 9.14) [115, 116]. The SPM based methods, allows the deposition of as-sembhes into restricted areas with 15 nm linewidths and 5 nm spatial resolution. Current capabihties and future applications of DPN are discussed in Ref. [117]. 

Another important outcome of these CVD experiments is the possibility to synthesize meta-stable phases as transparent films, like HAIO. The subsequent local treatment with different energy beams allows the structural patterning of the meta-stable layers to create chemical landscapes, which have the characteristics to consist of physically and chemically different regions of the surface (A1 AI2O3 parts in a HAIO matrix). These patterns can in principal be reduced to nanometer scales, opening a large field of applications. 

The precise positioning capabilities, which make high spatial resolution possible, give the SECM an important edge over other electrochemical techniques employing UMEs [20]. For example, the SECM can pattern the substrate surface, visualize its topography, and probe chemical reactivity on the micrometer or nanometer scale. Here, we briefly survey the fundamentals of various modes of the SECM operation and then focus on more recent advances in SECM theory and applications. 

SNR L/CVD Carbon Resist System. We have proposed another approach to improve the nanometer-scale resolution of the SNR 2-layer resist system, viz., the application of carbon films as the bottom layer material. (5) Carbon films prepard by plasma CVD are hard and thermally stable. Figure 5 shows about 40 nm-wide SNR/carbon patterns with a 150 nm pitch on a Si substrate. The narrow lines are well resolved with a steep profile, and the lines at both edges of the pattern have not bent or fallen down. This excellent stability of nanometer-scale carbon patterns facilitates the evaluation of the resolution limit SNR in 2-layer resist application. 

Scanning-probe-based lithographic techniques have been successfully used for patterning and delivering material on nanometer scales in many different applications. These versatile techniques have also been applied to patterning and grafting CP nanostmctures. In this section, we will review important studies and progresses in this area. 

An illustration of such a function is shown in Figure 7.18. The peaks in this figure correspond to the broad bands seen in the diffraction pattern. The corresponding plot for the crystalline material is also shown. The function is equally applicable for a crystal, but the peaks are then delta functions. What is less clear is whether a particular (or any) glass is truly amorphous or if crystallites at the nanometer scale are present. 

Atomic force microscope tips can also be used to deposit matter on a surface at nanometer scale. The reference example is dip-pen nanolithography where molecules deposited on the tip diffuse to the surface when in contact and define patterns with dimensions as small as 15 nm. An extension is the so-called NADIS technique, for which a nanochannel drilled at the tip apex is used to deposit liquid from a reservoir defined on the top of the cantilever (for a review of these methods refer to chapter 12). Besides its applications for nanopatterning, the NADIS method is a unique method to study liquids at submicron scale and, more particularly, liquid meniscus with controlled dimensions. The capillary force curve experienced by the tip during the deposition and measured with AFM is a good way to assess calculation methods and finally to get more insight into the liquid transfer mechanism from the reservoir to the surface. ... 

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