RESUMEN
Local oxidation of metal, semiconductor, and polymer surfaces has provided a common basis from which to explore fundamental principles of nanolithography and prototype functional nanostructures for many years now. This article summarizes an investigation of local oxidation for iron and Group IV metal thin films using both scanning probe microscopy and high-voltage nanoimprinting methods. We illustrate how the underlying kinetics of metal oxidation in the presence of nitrogen, which is incorporated into the metal film during the growth process, is dramatically enhanced compared with that of single-crystal silicon. We then go on to demonstrate subsequent selective etching of latent features and a potential magnetic application.
RESUMEN
Intact liposome-based targeted nanoparticle delivery systems (NDS) are immobilized by non-selective binding and characterized by scanning probe microscopy (SPM) in a fluid imaging environment. The size, size distribution, functionality, and stability of an NDS with a payload consisting of a super-paramagnetic iron oxide contrast agent for magnetic resonance imaging are determined. SPM results are combined with information obtained by more familiar techniques such as superconducting quantum interference device (SQUID) magnetometry, dynamic light scattering, and electron microscopy. By integrating the methods presented in this work into the NDS formulation and manufacturing process, size-dependent statistical properties of the complex can be obtained and the structure-function relationship of individual, multi-component nanoscale entities can be assessed in a reliable and reproducible manner.
RESUMEN
Carbon nanotube (CNT) probes enhance the stability of the nano-oxidation process under dynamic-mode operation. In this paper we investigate how the hydrophobic nature of the CNT allows oxide nanostructures to be fabricated with constant aspect ratio over a wide range of relative humidity values. In particular, we characterize oxide growth by measuring both the integrated ionic current and volume expansion. Behaviour of different CNT probes was compared to assess individual stability and performance under identical voltage and humidity conditions. While much remains to be established about the relationship between exposure conditions and dynamic-mode parameters on nanoscale oxide fabrication, hydrophobicity is a key factor in the improved reliability of CNT probes over conventional ones.
RESUMEN
Part I demonstrated that nano-oxidation in the dynamic-force mode was enhanced by the use of conductive carbon nanotube (CNT) probes. Fabrication of oxide nanostructures using CNT probes benefited not only from the smaller tip apex compared to conventional probes but from improved operational stability over a wide range of exposure conditions primarily due to the hydrophobic nature of the CNT. Here we investigate the bending response of CNT probes to electrostatic and meniscus forces during nano-oxidation. We conclude that bending of the CNT introduces an additional cushion in the combined cantilever-probe deflection system, thus improving overall stability of the tip-sample junction during nano-oxidation.
RESUMEN
Scanning probe microscope (SPM) oxidation was used to form zirconium oxide features on 200 nm thick ZrN films. The features exhibit rapid yet controlled growth kinetics, even in contact mode with 70 V dc applied between the probe tip and substrate. The features grown for times longer than 10 s are higher than 200 nm, and reach more than 1000 nm in height after 300 s. Long-time oxidation experiments and selective etching of the oxides and nitrides lead us to propose that as the oxidation reaches the silicon substrate, delamination occurs with the simultaneous formation of a thin layer of new material at the ZrN/Si interface. High-voltage oxide growth on ZrN is fast and sustainable, and the robust oxide features are promising candidates for multiscale (nanometre-to-micrometre) applications.