Papers by Niklas Olofsson
Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanoengineering and Nanosystems, 2008
ABSTRACT Arrays of carbon nanotubes were reversibly actuated by applying a bias voltage. The actu... more ABSTRACT Arrays of carbon nanotubes were reversibly actuated by applying a bias voltage. The actuation results in a variable capacitance between the arrays, which can be used to build a varactor. The capacitances were evaluated by simulating the scattering parameters in an equivalent electrical circuit while using the capacitance between the arrays as a fitting parameter. These simulations were compared with radio-frequency (RF) measurements on devices. A very good agreement between measurement and model was obtained. The capacitance could be varied by more than 20 per cent before the arrays were pulled into contact.
Nanotechnology, 2009
The feasibility of using carbon nanotube (CNT) bundles as the fillers of through silicon vias (TS... more The feasibility of using carbon nanotube (CNT) bundles as the fillers of through silicon vias (TSVs) has been demonstrated. CNT bundles are synthesized directly inside TSVs by thermal chemical vapor deposition (TCVD). The growth of CNTs in vias is found to be highly dependent on the geometric dimensions and arrangement patterns of the vias at atmospheric pressure. The CNT-Si structure is planarized by a combined lapping and polishing process to achieve both a high removal rate and a fine surface finish. Electrical tests of the CNT TSVs have been performed and their electrical resistance was found to be in the few hundred ohms range. The reasons for the high electrical resistance have been discussed and possible methods to decrease the electrical resistance have been proposed.
Nanotechnology, 2009
The electromechanical properties of arrays of vertically aligned multiwalled carbon nanotubes wer... more The electromechanical properties of arrays of vertically aligned multiwalled carbon nanotubes were studied in a parallel plate capacitor geometry. The electrostatic actuation was visualized using both optical microscopy and scanning electron microscopy, and highly reproducible behaviour was achieved for actuation voltages below the pull-in voltage. The walls of vertically aligned carbon nanotubes behave as solid cohesive units. The effective Young's modulus for the carbon nanotube arrays was determined by comparing the actuation results with the results of electrostatic simulations and was found to be exceptionally low, of the order of 1-10 MPa. The capacitance change and Q-factor were determined by measuring the frequency dependence of the radio-frequency transmission. Capacitance changes of over 20% and Q-factors in the range 100-10 were achieved for a frequency range of 0.2-1.5 GHz.
Carbon, 2009
We report the effect of catalyst pattern geometry on the growth behaviour of carbon nanotube (CNT... more We report the effect of catalyst pattern geometry on the growth behaviour of carbon nanotube (CNT) vertical arrays. Larger patterns are seen to produce longer CNT arrays. We show that this is predominantly related to the pattern size dependence of the number of walls and relate this to the local availability of carbon feedstock species. In addition, the vertical alignment of CNT pillar arrays is seen to depend on the pattern design, in particular the relationship between the pillar dimension and the inter-pillar spacing. (E.E.B. Campbell). C A R B O N 4 7 ( 2 0 0 9 ) 6 9 6 -7 0 4 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w. e l s e v i e r . c o m/ l o c a t e / c a r b o n C A R B O N 4 7 ( 2 0 0 9 ) 6 9 6 -7 0 4
International Journal of High Speed Electronics and Systems, 2011
ABSTRACT Carbon-based nanoelectromechanical devices are approaching applications in electronics. ... more ABSTRACT Carbon-based nanoelectromechanical devices are approaching applications in electronics. Switches based on individual carbon nanotubes deliver record low off-state leakage currents. Arrays of vertically aligned carbon nanotubes or nanofibers can be fabricated to constitute varactors. Very porous, low density arrays of quasi-vertically aligned arrays of carbon nanotubes behave mechanically as a single unit with very unusual material properties.
Uploads
Papers by Niklas Olofsson