Making Carbon Nanotube Probes For High Aspect Ratio Scanning Probe Metrology

Carbon nanotubes (CNT) have exceptional mechanical strength at small diameters needed for measuring high aspect ratio features. Manually attached carbon nanotube atomic force microscopy probes have demonstrated considerable longevity. Unfortunately, due to the manual attachment process, and the usually arbitrary diameter and length of the used CNT, such probes are not suitable for high aspect ratio critical dimension metrology (CDM). For reproducible and accurate CDM measurements precisely defined CNT probes are necessary. We are reporting about the progress made growing carbon nanotubes (CNT) directly on top of standard Si probes. The goal is to produce well-defined long lasting probes for CDM measurements in the \u3c100 nm pitch range. Our efforts currently focus on manufacturing aligned CNT having defined locations, diameters and lengths. This is accomplished by using plasma assisted chemical vapor deposition in combination with focused ion beam (FIB) patterning of catalyst films. Our results demonstrate that it is possible to manufacture 1:10 aspect ratio CNT probes at \u3c 100 nm diameters

Photoelectrochemical Processes at n GaAs 100 Aqueous HCl Electrolyte Interface A Synchrotron Photoemission Spectroscopy Study of Emersed Electrodes

High-resolution synchrotron photoemission spectroscopy has been applied to detail the electrochemical and photoelectrochemical corrosion reactions at the liquid junction n‑GaAs(100)/1 M aqueous HCl solution. Under anodic polarization of 1.8 eV, the main process initiated by the presence of holes in the Ga−As bonding states of the valence band is the formation of soluble gallium chloride complexes and insoluble elemental arsenic on the surface. In addition, arsenic hydroxide forms, which reacts further to soluble HAsO2. In toto, the As/Ga atomic ratio increases, which is accompanied by an increase of the work function. The anodic decomposition reaction is enhanced by illumination as more holes reach the n-semiconductor/electrolyte junction. Under cathodic polarization of 1.5 eV, only minor changes are observed in Ga and As core-level spectra, giving no indication of corrosion, but specific adsorption of hydrated HCl molecules and/or Cl −ions considerably modifies valence bandspectra