Lithographic methods

It is well known that resists likely to be used in any of these lithographic methods are classified into two groups according to their behavior under irradiation ... 

Fuel cells incorporating lithographic methods and masking/deposition/etching protocols have been fabricated on Si wafers and thereby satisfy two critical needs in a standard fuel cell collection of electrons (current collectors) and controlling the flow field of fuel and oxidant. Kelley et al. produced a miniature direct methanol fuel cell (DMFC) with a current— voltage and fuel utilization performance that matched standard-sized DMFCs prepared in-lab.A working volume for the miniature DMFC of 12 mm was reported, with an operational performance of 822 W h kg at 70 °C. ... 

Deposit Si3N4 on the wafer, to form the shape of the eantilever using a lithographic method. 

The technologies for making nm-scale structures by current lithographic methods are largely restricted to planar or quasi-planar geometries. (An array of trenches carved into... 

The micro mixer was fabricated by UV lithography of SU-8 [54], Two lithography masks were employed, one for the inlet and outlet channels and sidewalls and the other for making the array of micro nozzles. A non-conventional tilted lithographic method was used. A thick layer of SU-8 was exposed at 45° and -45° as well as other angles. A special resist development technique for the small and deep nozzle structures also had to be explored. 

Each of these stamps can then be used many times for printing. In a common approach for the high-resolution techniques that are the focus of this chapter, an established lithographic method, such as one of those developed for the microelectronics industry, defines the master. Figure 10.10 schematically illustrates two possible routes to stamps. Both use photolithography to define a pattern of resist on a silicon wafer. 

Contact lithography can offer a high resolution and is in principle less expensive than the optical lithographic methods. It uses a method similar as in optical disk fabrication. It has been demonstrated that imprint technology... 

Using lithography in contact mode the surface is modified by increasing the apphed normal load during the scan. The tip indents the sample and scratches the surface. This lithographic method is called also static plowing. 

Rankin, S.E., Malanoski, A.P. and Van Swol, F., Materials Research Society Symposium Proceedings 636 (Nonlithographic and Lithographic Methods of Nanofabrication From Ultralarge-Scale Integration to Photonics to Molecular Electronics) D1.2/1-D1.2/6, Boston, 2001. 

The first functional protein and peptide arrays were micropat-terned using lithographic methods in 1992 (66). Several years later, MacBeath and Schreiber (13) reported spotted functional protein microarrays capable of detecting protein-protein interactions, protein-ligand interactions, and biochemical activities. 

Lithographic methods are able to generate very uniform nanoparticle arrays and can be used to monitor the preparation process. In combination with additional techniques, even various three-dimensionally shaped structures can be formed (see, e.g., [16]). However, lithographic methods suffer from the limitation that the small interparticle spacings required for huge electromagnetic enhancement are not technically feasible. 

Oligonucleotides may be deposited onto solid surfaces in defined patterns, and this has been utilised to use oligonucleotide conjugates for a variety of applications. A widely used application is lithography that takes advantage of the fact that DNA interacts with various metals, and various new lithographic methods have been reported.A method for templated replication of DNA nanoscaffolds has also been developed. 

Zhao XM, Xia YN, Whitesides GM. Soft lithographic methods for nanofabrication. J Mater Chem 1997 7 1069-74. 

We consider below recent progress in EBL and colloidal lithography (CL) to make well-defined planar model catalysts. The former method has been used for almost a decade in various model studies in catalysis mainly by us and Somorjai and coworkers at Berkeley [66-71], and must be considered as an old lithographic method, at least in comparison with the many other methods discussed above. Colloidal lithography, however, represents a new method that brings together ideas from surface chemistry of self-assembly and lithographic methods in terms of process versatility and cleanliness. These two methods represent slow serial (EBL) and fast parallel (CL) fabrication of model nanocatalysts. 

Transmission electron microscopy (TEM) is probably the most powerful technique for obtaining structural information of supported nanoparticles [115-118], Complementary methods are STM, AFM, and SEM. Both the latter and TEM analysis provide more or less detailed size, shape, and morphology information, i.e., imaging in real space. TEM has the great additional advantage to provide information in Fourier transform space, i.e., diffraction information, which can be transformed to crystal structure information. From a practical point of view, considering the kinds of planar model catalysts discussed above, STM, AFM, and SEM are more easily applied for analysis than TEM, since the former three can be applied without additional sample preparation, once the model catalyst is made. In contrast, TEM usually requires one or more additional preparation steps. In this section, we concentrate on recent developments of microfabrication methods to prepare flat TEM membrane supports, or windows, by lithographic methods, which eliminate the requirement of postfabrication preparation of model catalysts for TEM analysis. For a more comprehensive treatment of other, more conventional, procedures to make flat TEM supports, and also similar microfabrication procedures as described here, we refer to previous reviews [118-120]. 

The results presented here demonstrate that well-defined model catalysts with particle sizes in the 10-100-nm regime can be efficiently processed with lithographic methods. These model catalysts possess most of the desirable characteristics that are required in fundamental heterogeneous catalysis research. There are considerable advantages, compared to model catalysts prepared by, e.g., incipient wetness impregnation methods, which are enumerated ... 

Yoshimura, M., and Gallage, R. 2008. Direct patterning of nanostructured ceramics from solution-differences from conventional printing and lithographic methods. Journal of Solid State Electrochemistry. 12, 775-782. 

Precisely this latter situation arises if the confining solid surface is endowed with a chemical pattern that is both nanoscopic in size and hnite in extent. Such chemical patterns may be created by lithographic methods [179]. Atomic beams have been employed to produce hexagonal nemostruc-tures [180]. Other methods capable of creating cliemically nanostnictured substrate surfaces involve microphase separation in diblock copolymer films [181] or the use of forc( microscopy to locally oxidize silicon surfaces [182]. 

It should be pointed out that for the ELD method in partieular, there exists a similarity to the photographie proeess, where initially formed Ag nanopartieles (the latent pieture ) are used for the eatalytie amplifieation in the development step. In our case, micro-contact printing (pCP) was used for the localised deposition of the seeds. This well-established, soft-lithographic method was originally developed by Whitesides and coworkers for the printing of al-kanethiols [20-22] but was later extended inter alia to nanopartieles [23]. Such printed nanopartieles have already been used to seed the deposition of other metals, e.g. copper or silver [23, 24], but the quality of the metal layers obtained in this way was not satisfactory for application in micro-electronic devices. In addition, the problem of hetero-metallic contacts arose, as will be discussed later. 

Although the resolution of this lithographic method by current standards is somewhat low, this method nevertheless demonstrates that metal-metal bond-containing polymers may be useful in applications where reversible imaging is needed and where the image can be made permanent if need be. Because this example is the only example of reversible lithography using polymers of this type, further study would seem to be called for. 

---