Scanning Electron Microscopy of Nanoscale Chemical Patterns

Abstract

A series of nanoscale chemical patterning methods based on soft and hybrid nanolithographies have been characterized using scanning electron microscopy with corroborating evidence from scanning tunneling microscopy and lateral force microscopy. We demonstrate and discuss the unique advantages of the scanning electron microscope as an analytical tool to image chemical patterns of molecules highly diluted within a host self-assembled monolayer and to distinguish regions of differential mass coverage in patterned self-assembled monolayers. We show that the relative contrast of self-assembled monolayer patterns in scanning electron micrographs depends on the operating primary electron beam voltage, monolayer composition, and monolayer order, suggesting that secondary electron emission and scattering can be used to elucidate chemical patterns.

Molecular Flux Dependence of Chemical Patterning by Microcontact Printing

“…We have previously shown that the SEM is sensitive to exposed chemical functionality and chemical patterns. 47 ■ RESULTS AND DISCUSSION Infrared Spectroscopy of Printed Films. Infrared reflectance adsorption spectroscopy (IRRAS) is an ensemble technique used to determine SAM structural and compositional details.…”

Hybrid approaches to nanometer-scale patterning: Exploiting tailored intermolecular interactions

“…Functionalization of chemically patterned surfaces adds new degrees of utility by enabling surface reactivity to be patterned at the nanometer scale. This has led to nanoscale films being used as biocompatible/bioactive scaffolds, molecular-sized electronic components, selective molecular resists, and other types of surfaces where both patterned structure and molecular interactions are necessary (Chen et al 1997;Xia and Whitesides 1998a;Smith et al 2004;Srinivasan et al 2007). As processes are developed for creating such chemical patterns, metrology tools and methods must be developed in lockstep in order to follow the patterning steps and to optimize the quality of the surfaces obtained.…”

“…As processes are developed for creating such chemical patterns, metrology tools and methods must be developed in lockstep in order to follow the patterning steps and to optimize the quality of the surfaces obtained. These metrology methods remain in their infancy (Allara and Nuzzo 1985;Porter et al 1987;Nuzzo et al 1990;Lopez et al 1993;Pertsin and Grunze 1994;Lahiri et al 1999a;Srinivasan et al 2007;Mrksich 2008).…”

“…One technique to fabricate chemically patterned surfaces is lithography-assisted chemical patterning (LACP), where conventional lithography is employed in conjunction with SAMs to create chemical patterns with high fidelity (Anderson et al 2006;Srinivasan et al 2007). This is accomplished by exploiting a commercially available lift-off resist that can withstand the selfassembly process without disrupting the underlying SAM.…”

“…One approach has been the development of hybrid patterning strategies for a wide range of applications. These utilize self-and directed assembly in conjunction with existing nanofabrication infrastructure (Xia et al 1999;Lewis et al 2001a;Smith et al 2004;Srinivasan et al 2007). …”