Showing papers on "Local oxidation nanolithography published in 2008"

Atomic force microscope local oxidation nanolithography of graphene

Abstract: We demonstrate the local oxidation nanopatterning of graphene films by an atomic force microscope. The technique provides a method to form insulating trenches in graphene flakes and to fabricate nanodevices with sub-nanometer precision. We demonstrate fabrication of a 25-nm-wide nanoribbon and submicron size nanoring from a graphene flake. We also found that we can write either trenches or bumps on the graphene surface depending on the lithography conditions. We attribute the bumps to partial oxidation of the surface and incorporation of oxygen into the graphene lattice.

AFM local oxidation nanolithography of graphene

Abstract: We demonstrate the local oxidation nanopatterning of graphene films by an atomic force microscope. The technique provides a method to form insulating trenches in graphene flakes and to fabricate nanodevices with sub-nm precision. We demonstrate fabrication of a 25-nm-wide nanoribbon and sub-micron size nanoring from a graphene flake. We also found that we can write either trenches or bumps on the graphene surface depending on the lithography conditions. We attribute the bumps to partial oxidation of the surface and incorporation of oxygen into the graphene lattice.

Fabrication of graphene nanoribbon by local anodic oxidation lithography using atomic force microscope

Abstract: We conducted local anodic oxidation (LAO) lithography in single-layer, bilayer, and multilayer graphene using tapping-mode atomic force microscope. The width of insulating oxidized area depends systematically on the number of graphene layers. An 800-nm-wide bar-shaped device fabricated in single-layer graphene exhibits the half-integer quantum Hall effect. We also fabricated a 55-nm-wide graphene nanoribbon (GNR). The conductance of the GNR at the charge neutrality point was suppressed at low temperature, which suggests the opening of an energy gap due to lateral confinement of charge carriers. These results show that LAO lithography is an effective technique for the fabrication of graphene nanodevices.

Electronic contribution to friction on GaAs: An atomic force microscope study

Abstract: The electronic contribution to friction at semiconductor surfaces was investigated by using a Pt-coated tip with 50 nm radius in an atomic force microscope sliding against an $n$-type GaAs(100) substrate. The GaAs surface was covered by an approximately 1 nm thick oxide layer. Charge accumulation or depletion was induced by the application of forward or reverse bias voltages. We observed a substantial increase in friction force in accumulation (forward bias) with respect to depletion (reverse bias). We propose a model based on the force exerted by the trapped charges that quantitatively explains the experimental observations of excess friction.

Cantilevers with integrated sensor for time-resolved force measurement in tapping-mode atomic force microscopy

Abstract: We present a micromachined cantilever with an integrated high-bandwidth resonator for direct measurement of tip-sample interaction forces in tapping-mode atomic force microscopy. Force measurements are achieved by a diffraction grating that serves as a differential displacement sensor for the tip motion relative to the cantilever body. Time-resolved tip-sample interaction force measurement is demonstrated on a silicon sample following calibration of the probe structure. By using lock-in detection, the harmonics of periodic tip-sample interaction have been utilized to obtain high-contrast, material specific images. The harmonic images of patterned silicon/silicon nitride control samples and triblock copolymers are presented.

Sub-50 nm positioning of organic compounds onto silicon oxide patterns fabricated by local oxidation nanolithography

Abstract: We present a process to fabricate molecule-based nanostructures by merging a bottom-up interaction and a top-down nanolithography. Direct nanoscale positioning arises from the attractive electrostatic interactions between the molecules and silicon dioxide nanopatterns. Local oxidation nanolithography is used to fabricate silicon oxide domains with variable gap separations ranging from 40 nm to several microns in length. We demonstrate that an ionic tetrathiafulvalene (TTF) semiconductor can be directed from a macroscopic liquid solution (1 µM) and selectively deposited onto predefined nanoscale regions of a 1 cm(2) silicon chip with an accuracy of 40 nm.

Nanoscale lithography with frequency-modulation atomic force microscopy.

Abstract: A lithographic method to draw nanoscale structures by repetitive depositions of the tip material by field evaporation has been developed based on frequency-modulation atomic force microscopy (FM-AFM). Because of high stiffness of quartz tuning forks, a force sensor in the AFM, unwanted mechanical contact of the AFM tip with the substrate was prevented. Precise control of the tip-substrate gap distance with FM-AFM and a gold tip sharpened with focused ion beam enable us to deposit gold dots as small as approximately 20 nm in size and construct nanoscale patterns.

Tapping mode SPM local oxidation nanolithography with sub-10 nm resolution

Abstract: Tapping mode SPM local oxidation nanolithography with sub-10 nm resolution is investigated by optimizing the applied bias voltage (V), scanning speed (S) and the oscillation amplitude of the cantilever (A) We fabricated Si oxide wires with an average width of 98 nm (V = 175 V, S = 250 nm/s, A = 292 nm) In SPM local oxidation with tapping mode operation, it is possible to decrease the size of the water meniscus by enhancing the oscillation amplitude of cantilever Hence, it seems that the water meniscus with sub-10 nm dimensions could be formed by precisely optimizing the oxidation conditions Moreover, we quantitatively explain the size (width and height) of Si oxide wires with a model based on the oxidation ratio, which is defined as the oxidation time divided by the period of the cantilever oscillation The model allows us to understand the mechanism of local oxidation in tapping mode operation with amplitude modulation The results imply that the sub-10 nm resolution could be achieved using tapping mode SPM local oxidation technique with the optimization of the cantilever dynamics

Fabrication of Silicon-Oxide Nanostructures on Low-Energy Ar-Ion-Bombarded Silicon via Atomic Force Microscope Nanolithography

Abstract: We report the electrochemical oxidation of Ar-ion bombarded Si(100) by using atomic force microscope (AFM) nanolithography. The changes in the properties of Ar-ion-bombarded Si substrates are investigated with a contact angle goniometer and an AFM surface analyzing tool. The Ar-ionbombarded substrates reveal not only changes in surface morphology and electrical properties but also an enhancement in the AFM lithographic performance. Our result that the height of the oxide features reaches ca. 10 nm is very promising for fabricating devices with nanometer-scale feature by using AFM lithography.

Measurement of Reaction Current during Atomic Force Microscope Local Oxidation of Conductive Surfaces Capped with Insulating Layers

Abstract: A local oxidation technique using an atomic force microscope (AFM) was studied. The reaction current passing through the AFM tip was measured in order to evaluate its dependence on the resistivity and surface condition of the samples. The current efficiency actually contributing the oxidation reaction was about 0.5 for a Si substrate. The ratio was constant regardless of the tip scan speed. As for NiFe thin films, the current was higher and the current efficiency was lower than those of the Si substrate. The Al2O3 capped layer on the NiFe thin films reduced the excess current, which did not contribute to the oxidation.

Magnetization switching of magnetic submicron structure fabricated by atomic force microscope

Abstract: Magnetization switching of a CoFe submicron structure was studied. A patterned stripe-shaped film consisting of CoFe/Cu/Co multilayer was prepared. By fabricating two oxide nanowires on the top CoFe layer by a nano-oxidation technique using an atomic force microscope (AFM), a rectangular isolated region of CoFe was obtained. The magnetization of the CoFe rectangle was successfully switched by applying a pulsed current of 100 mA with 1-ms duration through this stripe film. This switching was reproducible and observed with a threshold current of around 90 mA.  2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.