Surface modification and patterning at the nanoscale is a frontier in science with significant possible applications in biomedical technology and nanoelectronics. Here we show that an atomic force microscope (AFM) can be employed to simultaneously pattern and functionalize hydrogen-terminated silicon (111) surfaces. The AFM probe was used to break Si–H and Si–Si bonds in the presence of reactive molecules, which covalently bonded to the scribed Si surface. Functionalized patches and patterned lines of molecules were produced. Linewidths down to 30 nm were made by varying the force at the tip.

We have previously demonstrated a facile, chemomechanical method of simultaneously functionalizing and patterning silicon with single organic monolayers by scribing it while it is wet with 1-alkenes, [1] 1-alkynes, [1] and 1-haloalkanes. [2] Here we show that this method can be extended to create individual surfaces that have different monolayer coatings in distinct and precisely controlled regions (Figure 1). Like microcontact [*] Dr.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed on monolayers prepared by scribing silicon under a homologous series of 1-alkenes, 1-alkynes, and 1-haloalkanes:  CH2CH(CH2) n CH3 (n = 2, 5, 9), HC⋮C(CH2) n CH3 (n = 2, 5, 9), Cl(CH2) n CH3 (n = 4, 7, 9), Br(CH2) n CH3 (n = 4, 7, 11), I(CH2) n CH3 (n = 0, 1, 2, 4, 7, 11), and I13CH3. Numerous SiC x H y + and C x H y + fragments and adduct ions were observed. The results support a proposed binding model that 1-haloalkanes bind to the silicon surface through one C−Si bond and that 1-alkenes and 1-alkynes generally bind through two C−Si bonds. For instance, silicon surfaces scribed under 1-haloalkanes show less carbon by X-ray photoelectron spectroscopy (XPS) than silicon scribed under 1-alkenes and 1-alkynes with the same number of carbon atoms, but they show more intense SiC x H y + fragments by ToF-SIMS. Above a certain chain length, the relative intensities of the fragment and adduct ions for a homologous series generally increase with increasing alkyl chain length, which is in agreement with carbon surface coverages measured by XPS and the proposed binding models. Anomalously strong SiCH3 + and SiC2H5 + fragments observed in silicon scribed under CH3I and CH3CH2I suggest formation of methyl- and ethyl-terminated silicon, respectively. An isotopic study of silicon scribed under 13CH3I and CH3I provides additional evidence for formation of methyl-terminated silicon and suggests sputter-induced decomposition of the near-surface region by ToF-SIMS. Ab initio calculations of a few SiC x H y + type fragments are shown to verify assignments of structure. We also note an alternative explanation for some of the results based on the density of alkyl chains on the surfaces.

Cation attachment during matrix-assisted laser desorption/ionization (MALDI) of various synthetic polymers was investigated. The ions were created in a field-free source and extracted by a pulsed electric field applied at a known and variable time delay after the laser pulse. This is shown to increase the magnitude of the cationized polymer signal obtained, and also allows higher laser intensities to be used to induce fragmentation in the polymer. Additional structural information is thus provided about the monomers and end groups that is not available from measurements solely of the mass distribution of the intact cationized polymer. Delayed extraction can also provide important information about the timescale of the cation attachment processes occurring during MALDI.

The ability to interconnect different nanostructures is crucial to nanocircuit fabrication efforts. A simple and versatile direct-write nanolithography technique for the fabrication of interconnects is presented. Decomposition of a metalorganic precursor gas by a focused electron beam resulted in the deposition of conductive platinum nanowires. The combination of in situ secondary electron imaging with deposition allows for the simultaneous identification and interconnection of nanoscale components. However, the deposition was not entirely localized to the electron beam raster area, as shown by secondary ion mass spectrometry measurements. The electrical impact of the metallic spread was quantified by measuring the leakage current between closely spaced wires. The origins of the spread and strategies for minimizing it are discussed. These results indicate that, while this direct-write methodology is a convenient one for rapid prototyping of nanocircuits, caution must be used to avoid unwanted decoration of nanostructures by metallic species.