Andrea Notargiacomo

Nanofabrication by scanning probe microscope lithography: A review

In addition to its well-known capabilities in imaging and spectroscopy, scanning probe microscopy (SPM) has recently shown great potentials for patterning of material structures in nanoscales. It has drawn the attention of not only the scientific community, but also the industry. This article examines various applications of SPM in modification, deposition, removal, and manipulation of materials for nanoscale fabrication. The SPM-based nanofabrication involves two basic technologies: scanning tunneling microscopy and atomic force microscopy. Major techniques related to these two technologies are evaluated with emphasis on their abilities, efficiencies, and reliabilities to make nanostructures. The principle and specific approach underlying each technique are presented; the differences and uniqueness among these techniques are subsequently discussed. Finally, concluding remarks are provided where the strength and weakness of the techniques studied are summarized and the scopes for technology improvement and future research are recommended.

Scratching properties of nickel-iron thin film and silicon using atomic force microscopy

Atomic force microscopy (AFM) is well known for its ability for nanopatterning many different materials. The patterning technique using an AFM tip as a scratch tool, known as scratch nanolithography, is used to study the scratch characteristics of 80% Permalloy thin film and silicon, with the emphasis on establishing their scratchability or the nanoscale machinability. The effects of the scratch parameters, including the applied tip force, scratch speed, and number of scratches, on the size of the scratched geometry were specifically evaluated. The primary factors that measure the scratchability were then identified and the governing material properties for scratchability were evaluated. To demonstrate its versatility, the scratching technique was applied to fabricate a NiFe-based nanoconstriction, which is used for many ferromagnetic devices. All results indicated that NiFe thin film has much better scratchability than that of Si and the scratched groove geometry can be accurately correlated with and pre...

Fabrication and physico-chemical properties of Nafion Langmuir–Schaefer films

The Langmuir monolayer behaviour of Nafion (perfluorinated ionomer) films at the air/water interface for different aqueous subphases was investigated. The pressure–area isotherms and the Brewster angle microscopic study of Langmuir monolayer of Nafion in different electrolytic media allowed us to find the best experimental conditions for the deposition of stable Langmuir–Schaefer (LS) films. The results obtained for Nafion LS films through a combination of physical measurements (UV–vis spectroscopy, atomic force microscopy and nano-gravimetry) indicated a stepwise and uniform growth of films on the substrate. The electrochemical and photoelectrochemical properties of dyes incorporated within Nafion LS films were investigated. This paper reports the first experimental results showing the possibility of obtaining and depositing Nafion LS films.

Preparation, characterization and electrochemical properties of Nafion® doped poly(ortho-anisidine) Langmuir–Schaefer films

Langmuir–Schaefer (LS) films of poly(ortho-anisidine) (POAS) were fabricated by utilizing water and water acidified HCl as subphases, respectively. The uniformity of the films formation and the doping with Nafion were verified by UV–Vis spectroscopy. The morphology and the thickness of the POAS, HCl post-doping POAS and Nafion post-doping POAS LS films were investigated using atomic force microscopy. The electrochemical properties of POAS LS films, HCl post-doping POAS and Nafion post-doping POAS were investigated and compared with our previously published work. The electrochemical switching time of HCl post-doping POAS and Nafion post-doping POAS LS films were also estimated.

Formation of uniform nanoscale oxide layers assembled by overlapping oxide lines using atomic force microscopy

Atomic force microscopy (AFM) has been widely used for creating nanoscale oxide lines on various material surfaces. The assembling technique used for overlapping an array of these oxide lines into a uniform oxide layer is analytically investigated and experimentally verified. The experimental data of the oxide lines induced at different scanning speeds are analytically correlated to provide the basic formula for the assembling technique. The superposition principle is then applied for simulating the assembling process to extract the criteria for assembling a uniform layer. Experiments have been conducted to verify the reliability of the uniformity criteria analytically obtained and the feasibility of the assembling technique developed. Indeed, a uniform oxide layer can be precisely assembled by following the uniformity criteria developed.

Thermal-electric model for piezoelectric ZnO nanowires

The behavior of ZnO nanowires under uniaxial loading is characterized by means of a numerical model that accounts for all coupled mechanical, electrical, and thermal effects. The paper shows that thermal effects in the nanowires may greatly impact the predicted performance of piezoelectric and piezotronic nanodevices. The pyroelectric effect introduces new equivalent volumic charge in the body of the nanowire and surface charges at the boundaries, where Kapitza resistances are located, that act together with the piezoelectric charges to improve the predicted performance. It is shown that the proposed model is able to reproduce several effects experimentally observed by other research groups, and is a promising tool for the design of ultra-high efficient nanodevices.

Impact of Non-Linear Piezoelectricity on the Piezotronic Effect of ZnO Nanowires

ZnO is receiving a considerable attention for the development of novel cost-effective nanostructures with outstanding functional properties for applications in electronics and energy. In this paper, we investigate the effects of the nonlinear piezoelectricity, that has been recently observed in ZnO nanostructures, on the piezotronic effect of ZnO nanowires (NWs). We insert a physically-based model of the nonlinear direct piezoelectric effect into a fully-coupled thermo-mechanical-electric scheme to study the current-voltage characteristic of ZnO NWs under a purely vertical compressive/tensile strain. Our results show for the first time that the nonlinear piezoelectricity deeply affects the current transport processes inside the NW and the behavior of devices for piezoelectric-piezotronic applications and provides remarkable insights into the underlying physics.

Profile Uniformity of Overlapped Oxide Dots Induced by Atomic Force Microscopy: (Journal of Nanoscience and Nanotechnology, Vol. 10, pp. 4390–4399 (2010))

The technique for assembling a uniform oxide line by overlapping a series of nanosized oxide dots induced by atomic force microscopy is analytically and experimentally investigated. In addition to the normal continuous (static) pulses, the oxide growth rates under various discontinuous (modulated) pluses are studied to quantify the overlapping effect under multiple pulses used by the assembling technique. In the analysis of the assembling technique, the superposition principle is used to predict the assembled profiles and to define the uniformity criteria. Experiments have been performed to demonstrate the analytical prediction, including the threshold or minimum pitch for forming uniform lines, and the onset pitch for the overlapping effect to be considered. Indeed, by following the uniformity criteria developed, uniform and reliable oxide lines can be obtained by overlapping oxide dots.