The surface attachment properties of the Creutz-Taube ion, i.e., [(NH3)5Ru(pyrazine)Ru(NH3)5]5+, on both hydrophilic and hydrophobic types of surfaces were investigated using X-ray photoelectron spectroscopy (XPS). The results indicated that the Creutz-Taube ions only bound to hydrophilic surfaces, such as SiO2 and –OH terminated organic SAMs on gold substrates. No attachment of the ions on hydrophobic surfaces such as –CH3 terminated organic SAMs and poly(methylmethacrylate) (PMMA) thin films covered gold or SiO2 substrates was observed. Further ellipsometric, atomic force microscopy (AFM) and time-dependent XPS studies suggested that the attached cations could form an inorganic analog of the self-assembled monolayer on SiO2 substrate with a “lying-down” orientation. The strong electrostatic interaction between the highly charged cations and the anionic SiO2 surface was believed to account for these observations. Based on its selective binding property, patterning of wide (~200 nm) and narrow (~35 nm) lines of the Creutz-Taube ions on SiO2 surface were demonstrated through PMMA electron resist masks written by electron beam lithography (EBL).

Utilizing nonequilibrium formation kinetics in porous anodic alumina (PAA) thin films, diamond and hybrid triangle-diamond pore patterns are achieved. During anodization, the self-compensation abilities of PAA allow diamond-shaped pores to form by omitting certain sites in the surface prepatterning process. The effects of tessellation on cell formation in these arrangements yield elongated, regular, and partially compressed hexagonal cell structures leading to diamond, circular, and triangular pores, respectively. The diamond-shaped porous templates provide a low-cost option for the preparation of scalable nanostructures with diamond-shaped cross sections with utility in a range of nanoscale applications, including enhanced sensing and field emission.

The authors report their initial studies of the negative resist behavior of neutral sodium atoms deposited on alkanethiol molecules during neutral atom lithographic processing. Their results show that neutral sodium atoms incident upon octadecanethiol, the longest molecule of the various alkanethiols among alkanethiol self-assembled monolayers (SAMs), formed the most robust negative resist during the patterning process and made high quality patterning profile. In order to interpret the nature of the surface interaction between neutral sodium atoms and SAMs, they examine the surface components using x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and rinse tests. Their results indicate that sodium neutral atoms do not chemically react with or physically damage the SAMs but rather accumulate on and possibly diffuse into the SAMs.

Nanowire field effect transistors have been fabricated using Cd doped InAs nanowires synthesized using a solution-liquid-solid technique. Both n-channel and p-channel characteristics have been observed, which implies that the surface Fermi level is not pinned in the conduction band. The observation of a p channel is attributed to the passivation of surface states by surface ligands introduced during nanowire synthesis and to the effects of heavy acceptor doping. Devices in which the surface ligands are removed by O2 plasma treatment exhibit only n-channel conduction, which would be consistent with surface Fermi level pinning in the conduction band.

The development of assemblies consisting of unencapsulated, sub-10-nm gold particles attached to individual carbon nanotubes (CNTs) with diameters of 2 nm is described. The assemblies are formed on the surface of a porous anodic alumina (PAA) template on which the CNTs (single- or double-walled) are grown by plasma-enhanced chemical vapor deposition. The Au nanoparticles are formed through an indirect evaporation technique using a silicon nitride membrane mask, and diffuse along the PAA surface into the regions containing CNTs. The nanoparticles bind relatively strongly to the CNTs, as indicated by observations of nanoparticles that are suspended over pores or that move along with the CNTs. This approach may provide a new method to functionalize CNTs for chemical or biological sensing and fundamental studies of nanoscale contacts to CNTs.

The existence of large densities of surface states on InAs pins the surface Fermi level above the conduction band and also degrades the electron mobility in thin films and nanowires. Field effect transistors have been fabricated and characterized in the "as fabricated" state and after surface passivation with 1-octadecanethiol (ODT). Electrical characterization of the transistors shows that the subthreshold slope and electron mobility in devices passivated with ODT are superior to the respective values in unpassivated devices. An X-ray photoelectron spectroscopy study of ODT passivated undoped InAs nanowires indicates that sulfur from ODT is bonded to In on the InAs nanowires. Simulations using a two-dimensional device simulator (MEDICI) show that the improvements in device performance after ODT passivation can be quantified in terms of a decrease of interface trap electron donor states, shifts in fixed interfacial charge, and changes in body and surface mobilities.

Colloidal InP quantum wires are grown by the solution-liquid-solid (SLS) method, and passivated with the traditional quantum dots surfactants 1-hexadecylamine and tri-n-octylphosphine oxide. The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to other experimental results for InP quantum dots and wires, and to the predictions of theory. The photoluminescence behavior of the wires is also investigated. Efforts to enhance photoluminescence efficiencies through photochemical etching in the presence of HF result only in photochemical thinning or photooxidation, without a significant influence on quantum-wire photoluminescence. However, photooxidation produces residual dot and rod domains within the wires, which are luminescent. The results establish that the quantum-wire band gaps are weakly influenced by the nature of the surface passivation and that colloidal quantum wires have intrinsically low photoluminescence efficiencies.

InAs nanowire field effect transistors have been fabricated using solution-synthesized wires, with average diameters of 20 nm. Wires using either Zn and Cd dopants, both acceptors and both incorporated at relatively high doping densities, have been studied. The Zn-doped wires showed n-channel transistor characteristics, and were unipolar with relatively large on/off ratios. The Cd-doped wires were ambipolar, with on/off ratios below 10 at room temperature. This study expand the possible applications of InAs nanowire devices in high speed electronic circuits in contrast to the existing reports of only n type conductivity behavior of InAs nanowire devices.

A nanocapacitor with ultra high capacitance (718 ± 0.2 pF) has been fabricated using electro-deposited Au nanowires manipulated between two Au microelectrodes by the dielectrophoresis technique. A high dc resistance value (∼100 MΩ) and nonlinear current–voltage characteristics indicate the formation of a dielectric interface between the nanowires. From frequency dependent conductivity, it is seen that the interface exhibits a giant dielectric permittivity (ε∼1.8 × 107), which shows no frequency dispersion over the range from 30 Hz to 1 MHz. The enhancement of this permittivity value is attributed to the formation of a disordered interface containing gold atoms disrupted from the surface of the Au nanowires.

Electron beam lithography patterning of polymethylmethacrylate (PMMA) is a versatile tool for defining molecular structures on the sub-10 nm scale. We demonstrate lithographic resolution to about 5 nm using a cold development technique. Narrow trenches are used to pattern Creutz-Taube molecules with resolution to about 15 nm. In addition, DNA rafts are patterned with high fidelity at linewidths of about 100 nm. This technique can be applied to molecular patterning in general, and quantum-dot cellular automata (QCA) in particular.

As nanotechnology approaches molecular scales, issues of surface contamination by unremoved resists will play an important role in device fabrication. Electron beam lithography of polymethylmethacrylate (PMMA) resist is still among the most widely used nanofabrication techniques, so it is relevant to study its residual contamination on both exposed and unexposed surfaces using a variety of resist removers. We systematically characterized the effectiveness of several different strippers. Our experiments show that 1,2-dichloroethane is an efficient PMMA remover, and can produce almost the same surface roughness as the original SiO2 surface (i.e., no contamination), whereas the popular PMMA remover, acetone, cannot. Estimates of the polymer–solvent Flory–Huggins interaction parameters and surface–solvent interfacial energy (from contact angle measurements) satisfactorily predict the effectiveness of the solvents. This method should also be applicable to any PMMA-like films on any substrate to find a good surface cleaner.

Toward the development of a practical molecular computing scheme, certain molecules are thought to be able to perform quantum state switching at room temperature (for example, digital bit 1 to 0). For the implementation of logic functions, these molecules must be arranged on surfaces in a controlled manner. The Creutz–Taube molecule [(NH3)5Ru(pyrazine)Ru(NH3)5](o-toluenesulphonate)5 (CT5) can be viewed as a two-dot molecule for the purposes of molecular computing. We report here nanopatterning of CT5 molecules through the use of electron-beam lithography (EBL) and poly(methylmethacrylate) (PMMA) electron resist. After development of electron-beam modified PMMA films on SiO2, trenches with exposed surfaces were formed. These wafers were then soaked in CT5 aqueous solution. Atomic force microscopy and x-ray photoelectron spectroscopy were used to investigate the surface characteristics of wafers after dissolution of the PMMA and to confirm the binding of a monolayer of CT5 molecules on the wafer within the areas delimited by the PMMA trenches. CT5 molecules were deposited as a monolayer with two Ru atoms lying on the SiO2 surface. 35-nm-wide lines of a monolayer of CT5 molecules on a SiO2 surface were demonstrated.

For quantum-dot cellular automata molecular electronic devices, one of the fundamental tasks is to arrange the molecules on a surface in a controlled manner. In this report, we discuss a molecular lift off technique to form nanopatterns toward the development of molecular circuits. In our molecular lift off technique, we use electron beam lithography to form nano-trenches on a polymethylmethacrylate (PMMA) film on a SiO2 wafer. This wafer is soaked in a Creutz-Taube ion [(NH3)5Ru(pyrazine)Ru(NH3)5](o-toluenesulfonate)5 (CT5) aqueous solution. After residual PMMA removal, atomic force microscopy is used to investigate the resulting surface. Thirty-five nanometer CT5 lines are demonstrated on a SiO2 surface. Compared with other molecular nanopatterning techniques, ours is both economical and capable of high-resolution.

Electron beam lithography was used to make nanometer trenches in thin polymethylmethacrylate (PMMA). After development, the wafers were dipped in an aqueous solution of the Creutz–Taube ion [(NH3)5Ru(pyrazine)Ru(NH3)5](o-toluenesulphonate)5 (CT5), and the PMMA was removed with acetone or dichloromethane. Atomic force microscopy and x-ray photoelectron spectroscopy were used to investigate the surface characteristics of wafers after dissolution of the PMMA and to confirm the binding of a monolayer of CT5 molecules on the wafer within the areas delimited by the PMMA trenches. This masking technique has so far been demonstrated to pattern 35 nm lines of a monolayer of CT5 molecules on silicon dioxide.

介绍一维硅纳米线的合成及控制硅纳米线直径的方法、生长机制和不同硅纳米线形态的生成机理以及硅纳米线的量子限制效应.