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Charge writing with an atomic force microscope tip and electrostatic attachment of colloidal particles to the charge patterns
| Content Provider | Semantic Scholar |
|---|---|
| Author | Mesquida, Patrick |
| Copyright Year | 2002 |
| Abstract | In addition to established lithographic methods, nanotechnological processes taking place in liquid – as in nature – will increase in importance. A key element thereof is the specific, geometrical functionalisation of surfaces for the targeted fixing of molecules or microscopic particles. In addition to chemical or topographical structuring, electrostatic structuring can be used to achieve this because particles which are dispersed in liquids can be moved and specifically positioned using electric fields. In this work a new method for generating charge patterns on thin, dielectric films is presented for fixing oppositely charged, colloidal particles to defined locations. To achieve this, positive or negative voltage pulses are applied to a conductive atomic force microscope tip, which is laterally scanned in tapping mode over the sample surface under ambient conditions. Subsequently the sample is immersed in a suspension of nanoparticles for developing the latent, electric pattern. A resolution of ca. 100 nm (as determined by Kelvin probe microscopy) could be achieved for the electric charge patterns on a thin, teflon-like fluorocarbon film on silicon substrates. The charge decay times were of the order of several hours also at high humidity. The transferred charge quantities were of the order of some 100 up to several 1000 elementary charges per voltage pulse depending on pulse height (20 V – 100 V) and film thickness (20 nm – 200 nm). For a pulse length larger than the oscillation period of the cantilever the charge amounts were independent of the pulse length. As the charges are neutralised very rapidly on contact with water electrically highly insulating fluorocarbon liquids were used for the particle suspensions. Ultrasonically dispersed gold particles of 20 nm diameter and silica particles of 50 nm diameter could be positioned with a resolution of 500 nm and 1 μm, respectively. The solid particles were thereby trapped within small water droplets resulting from the preparation method. These droplets were triboelectrically charged according to Coehn’s rule with positive sign and were attracted by Coulomb force to the negative surface charge patterns. The resolution and the used materials of the method presented here are not restricted by any principle, so that various applications are conceivable ranging |
| File Format | PDF HTM / HTML |
| DOI | 10.3929/ethz-a-004494822 |
| Alternate Webpage(s) | https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/147256/eth-26253-02.pdf?isAllowed=y&sequence=2 |
| Alternate Webpage(s) | https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/147256/eth-26253-01.pdf?isAllowed=y&sequence=1 |
| Alternate Webpage(s) | https://doi.org/10.3929/ethz-a-004494822 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
