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| {{Technical|section=|date=July 2009}}
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| [[Image:LO Matrix.PNG|thumb|Local oxidation procedure: 3D representation 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.]]
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| '''Local oxidation nanolithography''' (LON) is a [[scanning probe lithography|tip-based]] [[nanofabrication]] method. It is based on the spatial confinement on an [[Redox|oxidation]] reaction under the sharp tip of an [[atomic force microscope]].
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| The first materials on which LON was demonstrated were [[Silicon|Si]](111) and polycrystalline [[tantalum]]. Subsequently, the technique has been extended to [[Boron group|III]]–[[Nitrogen group|V]] [[semiconductor]]s, [[silicon carbide]], [[metal]]s such as [[titanium]], tantalum, [[aluminium]], [[molybdenum]], [[nickel]] and [[niobium]]; thin films of [[manganite]] in the [[perovskite]] form; [[dielectric]]s like [[silicon nitride]], [[organosilicon#Organosilanes|organosilane]] [[self-assembled monolayer]]s, [[Dendrite (crystal)|dendritic]] macromolecules and [[carbon]]aceous films.<ref name=Garcia2005>{{Cite journal|last=Garcia |first=R |coauthors= Martinez, RV; Martinez, J|year=2005 |title=Nano-chemistry and scanning probe nanolithographies |journal=[[Chemical Society Reviews|Chem. Soc. Rev.]] |volume=35 |pages=29–38 |doi=10.1039/b501599p |pmid=16365640 |issue=1}}</ref>
| | If an existing Word - Press code is found vulnerable, Word - Press will immediately issue an update for that. Also, you may want to opt for a more professioanl theme if you are planning on showing your site off to a high volume of potential customers each day. * A community forum for debate of the product together with some other customers in the comments spot. Keep reading for some great Word - Press ideas you can start using today. You can customize the appearance with PSD to Word - Press conversion ''. <br><br>The Internet is a vast open market where businesses and consumers congregate. Some of the Wordpress development services offered by us are:. Some plugins ask users to match pictures or add numbers, and although effective, they appear unprofessional and unnecessary. If you liked this post and you would like to acquire much more info relating to [http://ammi.me/wordpress_backup_plugin_482591 wordpress backup plugin] kindly check out our web page. So, if you are looking for some option to build a giant e-commerce website, then e-shopping preferable CMS tools will be helpful for you. Akismet is really a sophisticated junk e-mail blocker and it's also very useful thinking about I recieve many junk e-mail comments day-to-day across my various web-sites. <br><br>Minor and medium sized corporations also have a lot to obtain by shelling out in a very good website. Browse through the popular Wordpress theme clubs like the Elegant Themes, Studio Press, Woo - Themes, Rocket Theme, Simple Themes and many more. I've applied numerous Search engine optimization-ready Word - Press themes and I can say from knowledge that I consider the Genesis Search engine marketing panel one particular of the simplest to use. In crux the developer must have a detailed knowledge not only about the marketing tool but also about the ways in which it can be applied profitably. Premium vs Customised Word - Press Themes - Premium themes are a lot like customised themes but without the customised price and without the wait. <br><br>If all else fails, please leave a comment on this post with the issue(s) you're having and help will be on the way. As an example, if you are promoting a product that cures hair-loss, you most likely would not wish to target your adverts to teens. The templates are designed to be stand alone pages that have a different look and feel from the rest of your website. The company gains commission from the customers' payment. This includes enriching the content with proper key words, tactfully defining the tags and URL. <br><br>Under Settings —> Reading, determine if posts or a static page will be your home page, and if your home page is a static page, what page will contain blog posts. Here's a list of some exciting Word - Press features that have created waves in the web development industry:. Word - Press can also be quickly extended however improvement API is not as potent as Joomla's. with posts or testimonials updated as they are uploaded to a particular section of the website. Verify whether your company has a team of developers or programmers having hands-on experience and knowledge about all Word - Press concepts. |
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| ==History==
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| The local oxidation of a surface by means of a [[scanning probe microscope|scanning probe]] technique was first observed by Dagata and co-workers in 1990 who locally modified a [[hydrogen-terminated silicon surface]] into [[silicon dioxide]] by applying a bias voltage between the tip of a [[scanning tunneling microscope]] and the surface itself.<ref name=Dagata1990>{{Cite journal|last=Dagata |first=JA |coauthors= Schneir, J; Harary, HH; Evans, CJ; Postek, MT; Bennett, J|year=1990 |title=Modification of hydrogen-passivated silicon by a scanning tunneling microscope operating in air |journal=[[Applied Physics Letters|Appl. Phys. Lett.]] |volume=56 |pages=2001 |doi=10.1063/1.102999|bibcode = 1990ApPhL..56.2001D|issue=20 }}</ref> 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.<ref name=Day1993>{{Cite journal|last=Day |first=HC |coauthors= Allee, DR|year=1993 |title=Selective area oxidation of silicon with a scanning force microscope |journal=[[Applied Physics Letters|Appl. Phys. Lett.]] |volume=62 |pages=2691 |doi=10.1063/1.109259|bibcode = 1993ApPhL..62.2691D|issue=21 }}</ref>
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| ==Basic principle==
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| [[Image:LO steps.PNG|thumb|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.]]
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| Currently, local oxidation experiments are performed with an [[atomic force microscope]] operated in [[Atomic force microscope#Imaging modes|contact or noncontact mode]] with additional circuits to apply [[voltage]] pulses between tip and sample. The local oxidation process is mediated by the formation of a water [[meniscus]].<ref name=Garcia1999>{{Cite journal|last=Garcia |first=R |coauthors= Calleja, M; [[Heinrich Rohrer|Rohrer, H]]|year=1999 |title=Patterning of silicon surfaces with noncontact atomic force microscopy: Field-induced formation of nanometer-size water bridges |journal=[[Journal of Applied Physics|J. Appl. Phys.]] |volume=86 |pages=1898 |doi=10.1063/1.370985 |bibcode = 1999JAP....86.1898G|issue=4 }}</ref>
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| In order to perform Local Oxidation Nanolithography, the [[relative humidity]] in the AFM chamber is kept between 30% and 60%. A voltage pulse is applied between a conductive AFM tip and the sample. The applied voltage induces the formation of a water bridge between tip and sample whenever the amplitude of the voltage pulse is above a certain threshold voltage. When the liquid [[meniscus]] is created the applied voltage pulse causes an [[Electrolytic cell|oxidation]] reaction by breaking the [[covalent bond]]s in the [[water (molecule)|water]] [[molecule]]s. The liquid bridge provides the [[oxyanion]]s ([[Hydroxyl|OH<sup>-</sup>]],O<sup>-</sup>) needed to form the oxide and confines the lateral extension of the region to be oxidized.
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| The chemical reactions that govern the Local Oxidation in a [[metal]]lic substrate (M) are the following:<ref name=Bhushan>{{Cite book| last=Tello | first=Marta | last2=García |first2=Fernando |last3=García| first3=Ricardo| editor=Bhushan, Bharat; Fuchs, Harald | title=Applied Scanning Probe Methods IV - Industrial Applications | year=2004 | publisher=Springer | location=Berlin | isbn=3-540-26912-6 | pages=137–158}}</ref>
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| <math>M+nH_{2}O\rightarrow MO_{n}+2nH^{+}+2ne^{-}</math>
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| <math>M^{n}+2nH_{2}O+2ne^{-}\rightarrow nH_{2}+2nOH^{-}+M</math>
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| while [[hydrogen]] gas is liberated at the AFM tip through the reduction reaction:
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| <math>2H^+ + 2e^- \rightarrow H_2</math>
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| 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. Finally the AFM continues to scan the sample thus allowing to image MO<sub>n</sub> nanostructure fabricated during the Local Oxidation process with the very same tip used for its fabrication.
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| The method to form liquid bridges is so precise that water meniscus diameters of 20 nm or below are easily obtained. This has led to the reproducible fabrication of sub-10 nm structures in silicon and other metallic surfaces.
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| ==Experimental setup==
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| Local oxidation experiments can be performed with almost any kind of [[atomic force microscope]]. The key requirement is the possibility to apply [[voltage]] pulses between the tip and the sample. It is recommendable to enclose the microscope in a chamber where the atmosphere is controlled. In the simplest case, the [[Oxidizing agent|oxidant]] is [[water vapor]], which is naturally present in the [[air]]. Controlling the [[relative humidity]] generally helps to obtain more reproducible results. 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.
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| ==Applications==
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| [[File:QuijoteFinal.JPG|thumb|First paragraph of [[Miguel de Cervantes|Cervantes']] ''[[Don Quixote]]'' written on a [[silicon]] chip. The local oxidation technique would allow to write all the book (more than 1,000 pages) on a surface as big as the tip of one human [[hair]].]]
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| The development of nanometer-scale [[nanolithography|lithographies]] is the focus of an intense research activity because progress on [[nanotechnology]] depends on the capability to fabricate, position and interconnect nanometer-scale structures.
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| ===Patterning===
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| Local Oxidation Nanolithography allows to create a large variety of motives like dots, lines and letters with nanometer accuracy. In 2005, researchers at the [[Spanish National Research Council]] in [[Madrid]] wrote the first ten lines of [[Miguel de Cervantes|Cervantes']] ''[[Don Quixote]]'' on a few square micrometres of silicon.<ref name=Garcia2005/> This pattern versatility can be used for [[Data storage device|information storage]] or to design etch-resistant [[Photomask|nanomasks]] in order to fabricate [[Nanocircuitry|nanodevices]] as well as many other applications.
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| ===Data storage===
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| [[File:PI-number-LON.png|thumb|left|[[Pi|π]] number with twenty decimals: 3,1415926535 8979323846 written in binary code by Local Oxidation on a silicon surface.]]
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| It is possible to store information using dot-like nanostructures created by the local oxidation of a surface. This storage uses the [[binary code]] considering the presence of a nanostructure as a 1 and its lack as a 0. In this way information can be stored in a small surface with a single [[Silicon dioxide|SiO<sub>2</sub>]] dot constituting a [[bit]]. In 1999 Cooper ''et al.'' demonstrated that this methods allows to obtain an [[Memory storage density|information density]] of 1.6 [[terabit|Tbit]]/in<sup>2</sup>.<ref name=Cooper1999>{{Cite journal|last=Cooper |first=EB |coauthors= Manalis, SR; Fang, H; [[Hongjie Dai|Dai, H]]; Matsumoto, K|year=1999 |title=Terabit-per-square-inch data storage with the atomic force microscope |journal=[[Applied Physics Letters|Appl. Phys. Lett.]] |volume=75 |pages=3566 |doi=10.1063/1.125390|bibcode = 1999ApPhL..75.3566C|issue=22 }}</ref> However, only [[read-only memory|read-only memories]] can be fabricated with this technique.
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| ===Molecular template growth and preferential deposition===
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| [[File:Mn12 Deposition Procedure.png|thumb|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.]]
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| [[File:Mn12 before and after.png|thumb|Two SiO<sub>2</sub> stripes were fabricated by LON over a substrate functionalized with APTES. After the deposition of a 0.1mM solution of Mn<sub>12</sub> the single molecule magnets are deposited only over the regions defined by the AFM.]]
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| Local oxidation of silicon surfaces by noncontact atomic-force microscopy is an emerging and promising method for patterning surfaces at the nanometer scale due to its very precise control of the feature size. The features created with this technique can be used for the template growth and preferential deposition of different [[molecule]]s like [[Magnet#Single-molecule magnets (SMMs) and single-chain magnets (SCMs)|single molecule magnets]], [[biomolecule]]s and [[Conjugated system|conjugated organic molecules]].
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| This method of nanopositioning is an important tool for the fabrication of new nanodevices based on the novel properties exhibited by some [[nanoparticle]]s and molecules. Potential applications of single-molecule magnets (SMMs) such as [[Mn12]] as bits for information storage or [[qubit]]s for [[Quantum computer|quantum computation]] require methods for nanoscale-controlled positioning and/or manipulation of those molecules.<ref name=Coronado2009>{{Cite journal|last=Coronado |first=E |coauthors= Epstein, AJ|year=2009 |title=Molecular spintronics and quantum computing |journal=[[Journal of Materials Chemistry|J. Mater. Chem.]] |volume=19 |pages=1670–1671 |doi=10.1039/b901955n|issue=12}}</ref> The patterning of the Mn<sub>12</sub> molecules on a silicon surface is achieved by first derivatizing this surface with a [[self-assembled monolayer]] of [[APTES]], which leaves it terminated by [[amine|amino]] groups (-NH<sub>2</sub>). Such termination electrostatically repels the Mn12 molecules. Subsequently, a pattern of silicon dioxide is defined by LON. The SMM molecules are predominantly deposited on the oxide motives because of electrostatic attraction. <!-- Figure "Preferential deposition steps" shows the process followed in order to achieve the preferential growth of Mn<sub>12</sub> molecules over a silicon substrate. This process uses the electrostatic repulsion of the Mn12 molecules with [[amine|amino]] groups (-NH<sub>2</sub>) of a [[self-assembled monolayer]] of [[APTES]]. --> The electrostatic attraction between the silicon oxide fabricated by LON and the Mn<sub>12</sub> molecules achieves the preferential deposition of this molecules with a nanoscale accuracy.
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| <!-- Figure "Preferential deposition results" shows a pair of SiO<sub>2</sub> motives fabricated by LON before and after the deposition of a 0.1mM solution of Mn<sub>12</sub> molecules for 1 min. All the molecules were deposited over the SiO<sub>2</sub> pattern showing a great preferentiality. -->
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| ===Fabrication of nanodevices===
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| [[File:SiNW Fabrication.png|thumb|left|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.]]
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| [[File:Silicon nanowire transistor in the shape of the word NANO.jpg|thumb|SiNW nanotransistor fabricated with the term 'NANO'. This pattern exhibits a good electrical response based on in the SiNW properties only.]]
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| By using local oxidation nanolithography as tool for the fabrication of etch-resistant nanomasks, it is possible to fabricate nanoscale electronic devices, such as [[field effect transistor]]s, [[single electron transistor]]s, [[Josephson junction]]s, [[quantum ring]]s or [[SQUID]]s.<ref name=Bhushan/> LON also allows to fabricate [[silicon]] [[nanowire]]s (SiNWs) in a top-down fashion starting from [[silicon on insulator]] (SOI) [[Wafer (electronics)|wafers]].<ref name=Martinez2008>{{Cite journal|last=Martinez |first=J |coauthors= Martínez, RV; Garcia, R|year=2008 |title=Silicon Nanowire Transistors with a Channel Width of 4 nm Fabricated by Atomic Force Microscope Nanolithography |journal=[[Nano Letters|Nano Lett.]] |volume=8 |pages=3636–3639 |doi=10.1021/nl801599k |pmid=18826289 |issue=11|bibcode = 2008NanoL...8.3636M }}</ref> Local oxidation nanolithography contributes to the nanometric precision of the device fabrication. This [[Top-down and bottom-up design|top-down]] fabrication technique allows the fabrication of a large variety of SiNWs with different shapes, from angular to circular. It also allows the precise positioning of the silicon nanowires in ant desired position, making easier its [[Integrated circuit|integration]]; indeed, this technique is compatible with the standard silicon [[CMOS]] processing technology. Single crystalline silicon nanowires have already shown a great potential as ultrasensitive [[biosensor|sensors]] by detecting changes in the nanowire conductivity when a specific analyte is present.<ref name=Cui2001>{{Cite journal|last=Cui |first=Y |coauthors= Wei, Q; Park, H; [[Charles Lieber|Lieber, CM]]|year=1999 |title=Nanowire Nanosensors for Highly Sensitive and Selective Detection of Biological and Chemical Species |journal=[[Science (journal)|Science]] |volume=293 |pages=1289–92 |doi=10.1126/science.1062711 |pmid=11509722 |issue=5533|bibcode = 2001Sci...293.1289C }}</ref> Local oxidation nanolithography, therefore, is a promising technique to allow the realisation of array of biosensors.
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| {{-}}
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| ==References==
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| {{Reflist}}
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| ==External links==
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| *[http://www.imm.cnm.csic.es/spm/index.html Local oxidation nanolithography page in García's research group at CSIC]
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| *[http://www.phy.bris.ac.uk/groups/nanophysics/research/struct_nanofab.html Miles' research group at the University of Bristol]
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| *[http://www.stanford.edu/group/quate_group/Litho/LithoPages/OxidationofSilicon/OxidationofSiliconFrame.html Quate's group at Stanford University]
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| {{Scanning probe microscopy}}
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| {{Nanolithography}}
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| {{DEFAULTSORT:Local Oxidation Nanolithography}}
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| [[Category:Scanning probe microscopy]]
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| [[Category:Lithography (microfabrication)]]
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