Local oxidation nanolithography

Subsequently, the technique has been extended to III–V semiconductors, silicon carbide, metals such as titanium, tantalum, aluminium, molybdenum, nickel and niobium; thin films of manganite in the perovskite form; dielectrics like silicon nitride, organosilane self-assembled monolayers, dendritic macromolecules and carbonaceous films.

[2] In 1993 Day and Allee demonstrated the possibility of performing local oxidation experiments with an atomic force microscope, which opened the way to applying the technique to a large variety of materials.

[3] Currently, local oxidation experiments are performed with an atomic force microscope operated in contact or noncontact mode with additional circuits to apply voltage pulses between tip and sample.

When the liquid meniscus is created the applied voltage pulse causes an oxidation reaction by breaking the covalent bonds in the water molecules.

The chemical reactions that govern the local oxidation in a metallic substrate (M) are the following:[5] while hydrogen gas is liberated at the AFM tip through the reduction reaction: When the voltage pulse is off the AFM feedback forces the cantilever to recover its original oscillation amplitude withdrawing the tip from the sample and breaking the liquid meniscus.

The method to form liquid bridges is so precise that water meniscus diameters of 20 nm or below are easily obtained.

The size of the fabricated features depends on a number of parameters, such as the distance between the sample and the tip, the amplitude and the duration of the voltage pulse, and the relative humidity of the atmosphere.

Local Oxidation Nanolithography allows to create a large variety of motives like dots, lines and letters with nanometer accuracy.

Potential applications of single-molecule magnets (SMMs) such as Mn12 as bits for information storage or qubits for quantum computation require methods for nanoscale-controlled positioning and/or manipulation of those molecules.

Local oxidation procedure: 3D representation of the Local Oxidation Nanolithography process. A voltage pulse applied between the AFM tip and the scanned surface yields to the formation of a liquid meniscus that confines a nanometric oxidation reaction.
Steps of the local oxidation process in noncontact mode. I: The tip is scanning the sample in noncontact mode oscillating at a constant amplitude. II:When the voltage pulse is applied a liquid meniscus between tip and sample is induced by the electrical field. This liquid meniscus acts like a nanometer-size electrochemical cell where an oxidation reaction is held. III:When the voltage pulse is off, the AFM feedbacks withdraw the tip from the sample stretching the liquid meniscus. IV: After the meniscus is broken the tip recovers its original oscillation amplitude and continues the scanning.
First paragraph of Cervantes' Don Quixote written on a silicon chip.
π number with twenty decimals: 3,1415926535 8979323846 written in binary code by Local Oxidation on a silicon surface.
Using specific functionalizations it is possible to deposit molecules and nanoparticles only in very small domains over a substrate surface. LON is a powerful technique to fabricate this kind of domains for the preferential growth.
Two SiO 2 stripes were fabricated by LON over a substrate functionalized with APTES. After the deposition of a 0.1mM solution of Mn 12 the single-molecule magnets are deposited only over the regions defined by the AFM.
In order to fabricate SiNW using the Top-Down approach of the nanotechnology a nanomask is fabricated by LON over a Silicon On Insulator substrate. After the SOI etching a SiNW is defined under the nanomask. Then the nanomask is removed with a HF etching and finally the SiNW is connected to the whole circuit using Electron Beam lithography.
SiNW nanotransistor fabricated with the term 'NANO'. This pattern exhibits a good electrical response based on in the SiNW properties only.
Typical atomic force microscopy set-up
Typical atomic force microscopy set-up