Patterned monolayers

The most prominent technique among these is based on soft lithography [97]. This set of methods allows the generation of micropattemed polymer surfaces or microparticles of different shapes. Each method has certain limits such as scale and aspect ratio (cf. Table 3.5) that will be discussed in detail. Initially, two methods from soft lithography micropatterning and micromolding will be described, originally developed by Whitesides and coworkers. The technique relies on an elastomeric soft material that is either used as a stamp or as a mold in order to pattern surfaces 2D with a monolayer or 3D with a microstmcture (Fig. 3.65). In the first case, one can obtain a fine monolayer pattern (-lOOnrn) but no aspect ratio can be obtained. Nevertheless, by... 

Zhou, E, et al. 2004. Manipulation of the ultimate pattern of polypyrrole film on self-assembled monolayer patterned substrate by negative or positive electrodeposition. Surf Sci 561 1. 

In the presence of concentrated acid (e.g., 5 Af H2SO4) or at sufficiently anodic potentials (Eu > 1.65 V in 1M H2SO4), the highly capacitive oxide layer is dissolved and the original monolayer pattern of potentiodynamic curve is restored. 

Monolayer patterns of different alkanethiolates (dode-canethiol, hexadecanethiol (HDT), HUT, DSU) were prepared according the microcontact printing ... 

Dulcey CS, Georger JH Jr, Krauthamer V, Stenger DA, Fare TL, and Calvert JM (1991) Deep UV photochemistry of chemisorbed monolayers patterned coplanar molecular assembhes. Science 252 551-554... 

Mino N, Ozaki S, Ogawa K, Hatada M (1994) Fabrication of self-assembled monolayer patterns by selective electron beam irradiation and a chemical adsorption technique. Thin Sohd Films 243 374-377... 

Husemann, M., Mecerreyes, D., Hawker, C.J., Hedrick, J.L., Shah, R., and Abbott, N.L. 1999. Surface-initiated polymerization for amplification of self-assembled monolayers patterned by microcontact printing. 

S. T. Liu, R. Maoz, G. Schmid, and). Sagiv, Template guided self-assembly of [Auss] clusters on nanolithographically defined monolayer patterns. Nano Lett, 2,1055-1060 (2002). 

Dulcey,C.S., J. H. Georger, Jr. etal. 1991. Deep UV photochemistry ofchemisorbed monolayers Patterned coplanar molecular assemblies. Science 252(5005) 551-554. 

Saito, N., Hayashi, K., Sugimura, H., Takai, O., and Nakagiri, N. (2002) Surface potential images of self-assembled monolayers patterned by organosilanes ab initio molecular orbital calculations. Surf. Interface Anal, 34, 601-605. 

Fig. VIII-10. (a) Intensity versus energy of scattered electron (inset shows LEED pattern) for a Rh(lll) surface covered with a monolayer of ethylidyne (CCH3), the structure of chemisorbed ethylene, (b) Auger electron spectrum, (c) High-resolution electron energy loss spectrum. [Reprinted with permission from G. A. Somoijai and B. E. Bent, Prog. Colloid Polym. ScL, 70, 38 (1985) (Ref. 6). Copyright 1985, Pergamon Press.]...

Fig. XV-9. Fluorescence micrograph of the stripe patterns observed in a monolayer from a mixture of PA and SP-Bi-25 (20% by weight peptide) on a buffered saline subphase at 16 C and zero surface pressure. (From Ref. 55.)...

Kumar A, Biebuyok FI A and Whitesides G M 1994 Patterning self-assembled monolayers—applioations in materials soienoe Langmuir 10 1498-511... 

Patterns of ordered molecular islands surrounded by disordered molecules are common in Langmuir layers, where even in zero surface pressure molecules self-organize at the air—water interface. The difference between the two systems is that in SAMs of trichlorosilanes the island is comprised of polymerized surfactants, and therefore the mobihty of individual molecules is restricted. This lack of mobihty is probably the principal reason why SAMs of alkyltrichlorosilanes are less ordered than, for example, fatty acids on AgO, or thiols on gold. The coupling of polymerization and surface anchoring is a primary source of the reproducibihty problems. Small differences in water content and in surface Si—OH group concentration may result in a significant difference in monolayer quahty. Alkyl silanes remain, however, ideal materials for surface modification and functionalization apphcations, eg, as adhesion promoters (166—168) and boundary lubricants (169—171). 

When a ledge is formed on an atomically smooth monolayer during tire formation of a thin film the intensity of the diffraction pattern is reduced due to the reduction in the beatrr intensity by inelastic scattering of electrons at the ledge-monolayer junction. The diffraction intensity catr thus be used during deposition of several monolayers to indicate the completion of a monolayer through the relative increase in intensity at tlris time. Observation of this effect of intensity oscillation is used in practice to count the number of monolayers which are laid down during a deposition process. 

Figure 4 (a) Photograph of a RHEED pattern for 4 monolayers of In deposited on... 

Element mapping with non-resonant laser- SNM S can be used to investigate the structure of electronic devices and to locate defects and microcontaminants [3.114]. Typical SNMS maps for a GaAs test pattern are shown in Fig. 3.43. In the subscript of each map the maximum number of counts obtained in one pixel is given. The images were acquired by use of a 25-keV Ga" liquid metal ion source with a spot size of approximately 150-200 nm. For the given images only 1.5 % of a monolayer was consumed -"static SNMS". 

H. Ohtani, C.-T. Kao, M.A.V. Hove, and G. Somorjai, A tabulation and classification of the stmctures of clean solid surfaces and of adsorbed atomic and molecular monolayes as determined from low energy electron diffraction patterns, Progress in Surface Science 23(2,3), 155-316 (1986) and reference therein. 

Fig. 4. Schematic representation of the smectic layering along with their characteristic diffraction patterns for the monolayer (Ai), the partially bilayer (Aj), the bilayer (A2) and the two-dimensional (A) phases. The arrows indicate permanent dipoles, the solid points are Bragg reflections...

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