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We present a technique for fabricating nanoelectrode extensions to microcantilevers for multiprobe electrical characterization. For electrical measurements of fragile samples, such as thin films and nanostructures, it is advantageous to combine a small contact force with a small contact area, which can be done by reducing the dimensions of the electrodes to nanoscale dimensions. Here we report a fabrication method of a nanoscale four-point probe utilizing silicon nanowires as templates for metal electrodes. Using nanomanipulation, we attach 200–300 nm wide silicon nanowires to microfabricated cantilevers. By subsequently covering these nanowires with a metallic coating, they are made conducting and at the same time fixed to the cantilevers. These silicon nanowire four-point probes were tested on 7 and 35 nm thick Au films as well as poorly adhering 16 nm thin Au nanowires deposited on a silicon surface through a nanofabricated shadow mask. It was found that the nanowire extensions dramatically reduce the damage of the studied samples, while nearly reproducing the resistivity measurements of the unmodified, but more destructive micro four-point probes. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present a complementary metal-oxide-semiconductor compatible, nanoscale 12-point-probe based on TiW electrodes placed on a SiO2 monocantilever. Probes are mass fabricated on Si wafers by a combination of electron beam and UV lithography, realizing TiW electrode tips with a width down to 250 nm and a probe pitch of 500 nm. In-air four-point measurements have been performed on indium tin oxide, ruthenium, and titanium-tungsten, showing good agreement with values obtained by other four-point probes. In-vacuum four-point resistance measurements have been performed on clean Bi(111) using different probe spacings. The results show the expected behavior for bulk Bi, indicating that the contribution of electronic surface states to the transport properties is very small. [ABSTRACT FROM AUTHOR]

A method for fabricating microscopic four-point probes is presented. The method uses silicon-based microfabrication technology involving only two patterning steps. The last step in the fabrication process is an unmasked deposition of the conducting probe material, and it is thus possible to select the conducting material either for a silicon wafer or a single probe unit. Using shadow masking photolithography an electrode spacing (pitch) down to 1.1 μm was obtained, with cantilever separation down to 200 nm. Characterisation measurements have shown the microscopic probes to be mechanically very flexible and robust. Repeated conductivity measurements on polythiophene films in the same surface area are reproduced within an accuracy of 3%. Automated nanoresolution position control allows scanning across millimetre sized areas, in order to create high spatial resolution maps of the in-plane conductivity. [Copyright &y& Elsevier]

Abstract: We present here a proof of concept for a novel fabrication method of vertically aligned carbon nanotube forests, utilizing black silicon nanograss (a forest of silicon nanometer-sized spikes created with reactive ion etching) coated with titanium tungsten diffusion barrier as a template. The method allows maskless definition of carbon nanotube forests with control of their density, nanotube diameter and height. Four nanograss reactive ion etching recipes are investigated and their wafer-to-wafer repeatability, wafer uniformity, and density control is discussed. Evaluation of carbon nanotube forests grown on the nanograss substrates is presented with discussion of their morphology, diameter distribution, and catalyst thickness influence. [Copyright &y& Elsevier]

Abstract: High resolution 100kV electron beam lithography in thin layers of the negative resist SU-8 is demonstrated. Sub-30nm lines with a pitch down to 300nm are written in 100nm thick SU-8. Two reactive ion etch processes are developed in order to transfer the SU-8 structures into a silicon substrate, a soft O2-plasma process to remove SU-8 residues on the silicon surface after development and a highly anisotropic SF6/O2/CHF3 based process to transfer the pattern into a silicon substrate, with selectivity between silicon and SU-8 of approximately 2. 30nm lines patterned in SU-8 are successfully transferred into a silicon substrate, which is used as a stamp in a nanoimprint lithography process to fabricate a nanochannel device for DNA stretching experiments. [Copyright &y& Elsevier]

Abstract: Individual multi-walled carbon nanotubes were positioned on silicon oxide microcantilevers using nanomanipulation tools. A silicon nanowire with a diameter of 200nm is positioned across the nanotube, and serves as shadow mask during deposition of conducting electrode material, leading to a 200 nm gap in the cantilever electrode only connected by the nanotube. By deflecting the cantilever, tensile strain of the nanotube up to 0.6% can be applied, with negligible transverse deformation or bending. Measurements of the conductance as a function of strain on different samples showed large variations in the response. Using a simple resistor model we estimate the expected conductance-strain response for a multi-walled carbon nanotube, and compare to our results on multi-walled carbon nanotubes as well as measurements by others on single-walled carbon nanotubes. Integration of nanotubes or nanowires with microcantilevers could lead to highly compact force feedback sensors for characterization and manipulation of nanostructures. [Copyright &y& Elsevier]

Applying protective or barrier layers to isolate a target item from the environment is a common approach to prevent or delay its degradation. The impermeability of two-dimensional materials such as graphene and hexagonal boron nitride (hBN) has generated a great deal of interest in corrosion and material science. Owing to their different electronic properties (graphene is a semimetal, whereas hBN is a wide-bandgap insulator), their protection behaviour is distinctly different. Here we investigate the performance of graphene and hBN as barrier coatings applied on copper substrates through a real-time study in two different oxidative conditions. Our findings show that the evolution of the copper oxidation is remarkably different for the two coating materials. [ABSTRACT FROM AUTHOR]