44 research outputs found
Dinâmicas do fluxo das águas subterrâneas no complexo sistema aquĂfero da Bacia do Rio Gidabo (Vale do Rift EtĂope): uma abordagem de multi-indicadores
Nanoscale changes in chromatin organization represent the initial steps of tumorigenesis: a transmission electron microscopy study
Ion projection surface structuring with noble gas ions at 75 keV
Compared to focused ion beam writing, ion projection lithography is a parallel structuring process which transfers the pattern of an open stencil mask with electrostatic demagnification optics onto the target surface. The parallel structuring process combined with the unique energy deposition characteristics (small forward scattering, small penetration depth) makes ion projection a very efficient structuring process. Using the different penetration depths of ions from a plasma source, fabrication of 3D-structures in resist, like free standing grids or T-gate structures, is possible. The ion induced intermixing of magnetic multilayers has been investigated for the creation of nano dots for data storage. The intermixing efficiency is greatly increased by using heavy ions (Ar+, Xe+). The creation of ion induced nucleation centers on p-Si allows for subsequent selective electroplating of nano structures. These nucleation centers can also start metal deposition on non-conducting surfaces (glass, polymers) by electrode less deposition in super saturated metal salt solutions. The expensive and time consuming production of open stencil masks may in future be avoided by an aperture plate with individually switchable openings. This is the aim of a European project: CHARPAN (Charged Particle Nanotech)
Characterization of measurement effects in an MST based nano probe
\u3cp\u3eA tactile probe has been designed at the Eindhoven University of Technology to measure a translation of its tip with a 3D uncertainty of 20 nm or better. The suspension of this probe and the electrical connections are manufactured in a series of etching and deposition steps and can be considered to be a Micro Electro-Mechanical System (MEMS). It will be shown that hysteresis effects can have a dominant influence on the probe measurement uncertainty. Several sources of hysteresis within the probe system are investigated experimentally.\u3c/p\u3
Multibody interactions of actuated magnetic particles used as fluid drivers in microchannels
The forced motion of superparamagnetic particles and their multibody interactions are studied in view of the application as integrated fluid drivers in microchannel systems. Previous studies on particle manipulation in open fluid volumes serve as our starting point for the analysis of particle dynamics and interplay effects in confined fluid volumes. An experimental setup is designed that offers a constant force field on all individual particles dispersed in a microchannel. Distinguishable multi-particle configurations are observed and analyzed on the basis of magnetic and hydrodynamic particle interaction mechanisms. The fluid driving performance and the efficiency of the particles are evaluated on system level by means of numerical simulation models
Nanoscale Magnetostrictive Response in a Thin Film Owing to a Local magnetic Field
Scanning probe microscope experiments are presented in which thin magnetostrictive films deposited on top of micrometer-sized magnetic write heads as used in magnetic hard disk drives, are used to visualize their emanating magnetic field. The magnetostrictive expansion owing to magnetic writing fields is discussed, together with the transduction mechanisms that lead to the vertical and lateral contrast observed. Experimental results verify that the techniques described have a lateral resolution in the realm of 100 n
Closed-loop control of laser assisted chemical vapor deposition growth of carbon nanotubes
Laser-assisted chemical vapor deposition growth is an attractive mask-less process for growing locally aligned nanotubes in selected places on temperature sensitive substrates. An essential parameter for a successful and reproducible synthesis of nanotubes is the temperature during growth. Here, we demonstrate a temperature feedback control mechanism based on the dynamic, in situ monitoring of the infrared radiation coupled with reflectivity information. With the information provided by these sensors, an infrared laser, focused on a silicon substrate covered with aluminum-oxide and iron catalyst layers, can be controlled. The growth takes place in a gaseous mixture of argon (carrier gas), hydrogen (process gas), and ethylene (carbon-containing gas). Scanning electron microscopy and Raman spectroscopy analysis demonstrate the excellent reproducibility of the closed-loop control process over multiple experiments. Furthermore, we developed a unique method to identify the onset for catalyst formation and activation by monitoring the fluctuation of the reflected laser beam