View source for Ruthenium

{{distinguish|rutherfordium}}
{{infobox ruthenium}}

'''Ruthenium''' ({{pron-en|ruːˈθiːniəm}} {{respell|r'''oo'''|THEE|nee-əm}}) is the [[chemical element]] with the [[atomic number]] 44, and is represented by the symbol '''Ru'''. It is a rare [[transition metal]] of the [[platinum group]] of the [[periodic table]]; and like the other metals of the platinum group, ruthenium is inert to most other chemicals. The Russian scientist [[Karl Ernst Claus|Karl Klaus]] discovered the element in 1844 and named it after [[Ruthenia]], the Latin word for [[Etymology of Rus and derivatives|Rus']]. Ruthenium is found associated with [[platinum]] ores. Ruthenium is a minor component in these ores and therefore is a relatively rare element. Most ruthenium is used for wear-resistant electrical contacts and the production of thick-film resistors. A minor application of ruthenium is its use in some platinum [[alloy]]s.

==Characteristics==
===Physical properties===
[[File:Ruthenium a half bar.jpg|thumb|left|alt=An irregular bar of lustrous silvery metal. One end is rough, as though broken, while the other, cigar-shaped end is relatively smooth.|A half of a pure, [[Electron beam melting|electron-beam remelted]] ruthenium bar]]

A polyvalent hard white metal, ruthenium is a member of the [[platinum group]] and is in [[group 8 element|group 8]] of the periodic table: 

{| class="wikitable" border="1" cellpadding="3" cellspacing="0"
|-
![[Atomic number|Z]] !! [[Chemical element|Element]] !! [[Electron shell|No. of electrons/shell]] 
|-
| 26 || iron || 2, 8, 14, 2
|- 
| 44 || ruthenium || 2, 8, 18, 15, 1
|- 
| 76 || osmium || 2, 8, 18, 32, 14, 2
|- 
| 108 || hassium || 2, 8, 18, 32, 32, 14, 2
|}

However, it has an atypical configuration in its outermost electron shells: whereas all other group-8 elements have 2 electrons in the outermost shell, in ruthenium, one of those is transferred to a lower shell. (This effect can be observed in the neighborhood of [[niobium]] (41), ruthenium (44), [[rhodium]] (45), and [[palladium]] (46))

Ruthenium has four crystal modifications and does not tarnish at normal temperatures.  Ruthenium dissolves in fused alkalis, is not attacked by acids but is attacked by [[halogen]]s at high temperatures. Small amounts of ruthenium can increase the hardness of [[platinum]] and [[palladium]]. The [[corrosion]] resistance of [[titanium]] is increased markedly by the addition of a small amount of ruthenium.<ref name=crc>Hamond, C.R. "The elements", in {{RubberBible86th}}</ref>

This metal can be plated either by [[electroplating]] or by thermal decomposition methods. A ruthenium-[[molybdenum]] alloy is known to be [[superconductivity|superconductive]] at temperatures below 10.6 [[Kelvin|K]].<ref name=crc/>

===Isotopes===
{{Main|Isotopes of ruthenium}}
Naturally occurring ruthenium is composed of seven stable [[isotope]]s. Additionally, 34 radioactive isotopes have been discovered. Of these [[radioisotope]]s, the most stable are <sup>106</sup>Ru with a [[half-life]] of 373.59 days, <sup>103</sup>Ru with a half-life of 39.26 days and <sup>97</sup>Ru with a half-life of 2.9 days.<ref name=n1/><ref name=n2/>

Fifteen other radioisotopes have been characterized with [[atomic weight]]s ranging from 89.93 [[unified atomic mass unit|u]] (<sup>90</sup>Ru) to 114.928 u (<sup>115</sup>Ru). Most of these have half-lives that are less than five minutes except <sup>95</sup>Ru (half-life: 1.643 hours) and <sup>105</sup>Ru (half-life: 4.44 hours).<ref name=n1/><ref name=n2/>

The primary [[decay mode]] before the most abundant isotope, <sup>102</sup>Ru, is [[electron capture]] and the primary mode after is [[beta emission]]. The primary [[decay product]] before <sup>102</sup>Ru is [[technetium]] and the primary mode after is [[rhodium]].<ref name=n1>{{RubberBible86th}} Section 11, Table of the Isotopes</ref><ref name=n2>{{cite journal|url=http://amdc.in2p3.fr/web/nubase_en.html |doi=10.1016/j.nuclphysa.2003.11.001|title=The Nubase evaluation of nuclear and decay properties|author=Audi, G. ''et al.''|journal=Nuclear Physics A|volume=729|year=2003|pages=3}}</ref>

===Occurrence===
{{See also|category:Ruthenium minerals}}
Ruthenium is exceedingly rare and is the 74th [[Abundance of elements in Earth's crust|most abundant metal on Earth]].<ref name="Emsley">{{cite book|title = Nature's Building Blocks: An A-Z Guide to the Elements|last = Emsley|first=J.|publisher = Oxford University Press|year = 2003|location = Oxford, England, UK|isbn = 0198503407|chapter = Ruthenium|pages=368–370}}</ref> This element is generally found in ores with the other platinum group metals in the [[Ural Mountains]] and in North and South America. Small but commercially important quantities are also found in [[pentlandite]] extracted from [[Greater Sudbury|Sudbury]], [[Ontario]], [[Canada]], and in [[pyroxenite]] deposits in [[South Africa]]. The native ruthenium is very rare mineral (Ir replaces part of Ru in its structure).<ref name="USGS-YB-2006">{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2006-plati.pdf |publisher = United States Geological Survey USGS|accessdate = 2008-09-16|title = 2006 Minerals Yearbook: Platinum-Group Metals| first = Micheal W.|last = George}}</ref><ref name="USGS-CS-2008">{{cite web|url = http://minerals.usgs.gov/minerals/pubs/commodity/platinum/mcs-2008-plati.pdf |publisher = United States Geological Survey USGS|accessdate = 2008-09-16|title = Commodity Report: Platinum-Group Metals}}</ref>

==Production==
===Mining===
Roughly 12 tonnes of Ru is mined each year with world reserves estimated as 5,000 tonnes.<ref name="Emsley"/> The composition of the mined platinum group metal (PGM) mixtures varies in a wide range depending on the geochemical formation. For example, the PGMs mined in South Africa contain on average 11% ruthenium while the PGMs mined in the USSR contain only 2% based on research dating from 1992.<ref>{{cite book|url = http://books.google.com/?id=Wm6QMRaX9C4C&pg=PA69|page =69|isbn = 9780873351003|editor = Hartman, H. L.; Britton, S. G.|year = 1992|publisher = Society for Mining, Metallurgy, and Exploration|location = Littleton, Colo.|title = SME mining engineering handbook}}</ref><ref>{{cite journal|url = http://canmin.geoscienceworld.org/cgi/content/abstract/12/2/104|journal = The Canadian Mineralogist|year = 1973| volume = 12|issue = 2|pages = 104–112|title = The nomenclature of the natural alloys of osmium, iridium and ruthenium based on new compositional data of alloys from world-wide occurrences| first = Donald C.|last = Harris|coauthors =Cabri, L. J.}}</ref>

Ruthenium, like the other platinum group metals, is obtained commercially as a by-product from [[nickel]] and [[copper]] mining and processing as well as by the processing of platinum group metal ores. During [[Copper extraction techniques#Electrorefining|electrorefining of copper]] and nickel, noble metals such as silver, gold and the platinum group metals including [[selenium]] and [[tellurium]] settle to the bottom of the cell as ''anode mud'', which forms the starting point for their extraction.<ref name="USGS-YB-2006"/><ref name="USGS-CS-2008"/> In order to separate the metals, they must first be brought into solution. Several methods are available depending on the separation process and the composition of the mixture; two representative methods are fusion with [[sodium peroxide]] followed by dissolution in [[aqua regia]], and dissolution in a mixture of [[chlorine]] with [[hydrochloric acid]].<ref name="ullmann-pt">{{cite book |author=Renner, H.; Schlamp, G.; Kleinwächter, I.; Drost, E.; Lüschow, H. M.; Tews, P.; Panster, P.; Diehl, M.; Lang, J.; Kreuzer, T.; Knödler, A.; Starz, K. A.; Dermann, K.; Rothaut, J.; Drieselman, R. |chapter=Platinum group metals and compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |publisher=Wiley |year=2002 |doi=10.1002/14356007.a21_075}}</ref><ref name="kirk-pt">{{cite book |title=Kirk Othmer Encyclopedia of Chemical Technology |first =R. J.|last = Seymour|coauthors = O'Farrelly, J. I. |chapter=Platinum-group metals |doi=10.1002/0471238961.1612012019052513.a01.pub2 |year=2001 |publisher=Wiley}}</ref> Osmium, ruthenium, rhodium and iridium can be separated from platinum and gold and base metals by their insolubility in aqua regia, leaving a solid residue. Rhodium can be separated from the residue by treatment with molten sodium bisulfate. The insoluble residue, containing Ru, Os and Ir is treated with sodium oxide, in which Ir is insoluble, producing water-soluble Ru and Os salts. After oxidation to the volatile oxides, {{chem|RuO|4}} is separated from {{chem|OsO|4}} by precipitation of (NH<sub>4</sub>)<sub>3</sub>RuCl<sub>6</sub> with ammonium chloride or by distillation or extraction with organic solvents of the volatile osmium tetroxide.<ref>{{cite journal|title = The Platinum Metals.|first = Raleigh|last = Gilchrist|journal = Chemical Reviews|year = 1943|volume = 32|issue = 3|pages = 277–372|doi = 10.1021/cr60103a002}}</ref> [[Hydrogen]] is used to reduce [[ammonium]] ruthenium chloride yielding a powder.<ref name=cotton>{{cite book|last = Cotton|first = Simon|title = Chemistry of Precious Metals| pages = 1–20|publisher = Springer-Verlag New York, LLC|year = 1997|isbn-13 = 9780751404135|url = http://books.google.com/?id=6VKAs6iLmwcC&pg=PA2|isbn = 0751404136}}</ref> The first method to precipitate the ruthenium with ammonium chloride is similar to the procedure that [[Smithson Tennant]] and [[William Hyde Wollaston]] used for their separation. Several methods are suitable for industrial scale production. In either case, the product is reduced using hydrogen, yielding the metal as a powder or sponge that can be treated using [[powder metallurgy]] techniques or by [[argon]]-[[arc welding]].<ref name="Hunt 1969 126–138">{{cite journal |first = L. B. |last = Hunt|coauthors = Lever, F. M. |journal = Platinum Metals Review|volume = 13 |issue = 4|year = 1969 |pages = 126–138|title = Platinum Metals: A Survey of Productive Resources to industrial Uses|url = http://www.platinummetalsreview.com/pdf/pmr-v13-i4-126-138.pdf}}</ref>

===From used nuclear fuels===
{{Main|Synthesis of precious metals}}
Ruthenium is a fission product of [[uranium-235]], therefore each kilo of fission products contains significant amounts of the lighter platinum group metals and therefore also ruthenium. [[Used nuclear fuel]] might be a possible source for ruthenium. The complicated extraction is expensive and the also present radioactive isotopes of ruthenium would make a storage for several half-lives of the decaying isotopes necessary. This makes this source of ruthenium unattractive and no large-scale extraction has been started.<ref>{{cite journal|doi = 10.1595/147106705X35263|url = http://www.platinummetalsreview.com/pdf/79-90-pmr-apr05.pdf|title = Potential Applications of Fission Platinoids in Industry|year = 2005| last1 = Kolarik|first1 = Zdenek|last2 = Renard|first2 = Edouard V.|journal = Platinum Metals Review|volume = 49|pages = 79}}</ref><ref>{{cite journal|title = Recovery of Value Fission Platinoids from Spent Nuclear Fuel. Part I PART I: General Considerations and Basic Chemistry|url =http://www.platinummetalsreview.com/pdf/pmr-v47-i2-074-087.pdf| first1 =Zdenek|last1 =Kolarik|first2 =Edouard V.|last2 =Renard| journal = Platinum Metals Review|volume = 47|issue = 2|year = 2003|pages = 74–87}}</ref><ref>{{cite journal|title = Recovery of Value Fission Platinoids from Spent Nuclear Fuel. Part II: Separation Process| url =http://www.platinummetalsreview.com/pdf/pmr-v47-i2-074-087.pdf|first1 =Zdenek|last1 =Kolarik|first2 =Edouard V.|last2 =Renard| journal = Platinum Metals Review|volume = 47|issue = 2|year = 2003|pages = 123–131}}</ref>

==Chemical compounds==
{{See also|Category:Ruthenium compounds}}
The [[oxidation state]]s of ruthenium range from 0 to +8, and −2. The properties of ruthenium and osmium [[Chemical compound|compound]]s are often similar.  The +2, +3, and +4 states are the most common. The most prevalent precursor is [[ruthenium trichloride]], a red solid that is poorly defined chemically but versatile synthetically.<ref name=cotton/>

===Oxides===
Ru can [[oxidation|oxidize]] to [[ruthenium tetroxide]], RuO<sub>4</sub>, a strong oxidizing agent with structure analogous to [[osmium tetroxide]]. Other examples are [[ruthenium(IV) oxide]] (RuO<sub>2</sub>, oxidation state +4), dipotassium '''ruthenate''' (K<sub>2</sub>RuO<sub>4</sub>, +6), and potassium '''perruthenate''' (K<sub></sub>RuO<sub>4</sub>, +7).<ref>Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.</ref>

===Coordination complexes===
[[File:Tris(bipyridine)ruthenium(II)-chloride-powder.jpg|thumb|left|Tris(bipyridine)ruthenium(II) chloride.]]
Ruthenium forms a variety of coordination complexes.  Examples are the many pentammine derivatives [Ru(NH<sub>3</sub>)<sub>5</sub>L]<sup>n+</sup> which often exist in both Ru(II) and Ru(III).  Derivatives of bipyridine and terpyridine are numerous, best known being the luminiscent [[tris(bipyridine)ruthenium(II) chloride]].

====Organometallic compounds====
{{Main|Organoruthenium chemistry}}
Ruthenium form a wide range compounds with carbon-ruthenium bonds.  [[Ruthenocene]] is analogous to ferrocene structurally, but exhibits distinctive redox properties.  A large number of complexes of carbon monoxide are known, the parent being [[triruthenium dodecacarbonyl]].  The analogue of [[iron pentacarbonyl]], ruthenium pentacarbonyl is unstable at ambient conditions.  Ruthenium trichloride [[carbonylation|carbonylates]] (reacts with carbon monoxide) to give mono- and diruthenium(II) carbonyls from which many derivatives have been prepared such as RuHCl(CO)(PPh<sub>3</sub>)<sub>3</sub> and Ru(CO)<sub>2</sub>(PPh<sub>3</sub>)<sub>3</sub> ([[Roper's complex]]). Heating solutions of ruthenium trichloride in alcohols with [[triphenylphosphine]] gives [[tris(triphenylphosphine)ruthenium dichloride]] (RuCl<sub>2</sub>(PPh<sub>3</sub>)<sub>3</sub>), which converts to the hydride complex chlorohydridotris(triphenylphosphine)ruthenium(II) (RuHCl(PPh<sub>3</sub>)<sub>3</sub>).<ref name=cotton/>  
 
In the area of fine chemical synthesis, [[Grubbs' catalyst]] is used for alkene metathesis.<ref>Hartwig, J. F. Organotransition Metal Chemistry, from Bonding to Catalysis; University Science Books: New York, 2010. ISBN 189138953X</ref>

==History==
Though naturally occurring platinum, containing all six [[platinum group metal]]s, was used for a long time by [[pre-Columbian]] Americans and known as a material to European chemists from the mid-16th century, it took until the mid-18th century for platinum to be identified as a pure element. The discovery that natural platinum contained palladium, rhodium, osmium and iridium took place in the first decade of the 19th century.<ref name="Weeks8">{{cite journal|doi = 10.1021/ed009p1017|title = The discovery of the elements. VIII. The platinum metals|year = 1932|last1 = Weeks|first1 = Mary Elvira|journal = Journal of Chemical Education|volume = 9|pages = 1017}}</ref> Platinum in [[alluvium|alluvial sands]] of Russian rivers gave access to raw material for use in plates and medals and for the minting of [[ruble]] [[coins]], starting in 1828.<ref name="Roubles">{{cite journal|url = http://www.platinummetalsreview.com/dynamic/article/view/48-2-066-069|volume = 48 |issue = 2|year = 2004| pages = 66–69|title = The Minting of Platinum Roubles. Part I: History and Current Investigations|first = Christoph J.|last = Raub}}</ref> Residues of platinum production for minting were available in the Russian Empire, and therefore most of the research on them was done in Eastern Europe. 

It is possible that the [[Poland|Polish]] chemist [[Jędrzej Śniadecki]] isolated element 44 (which he called "vestium") from platinum ores in 1807. His work was never confirmed, however, and he later withdrew his claim of discovery.<ref name="Emsley"/> [[Jöns Berzelius]] and [[Gottfried Osann]] nearly discovered ruthenium in 1827.<ref>{{cite journal|url = http://books.google.com/?id=x57C3yhRPUAC&pg=PA391|pages = 391–392|title = New Metals in the Uralian Platina|volume = 2|year = 1827| journal = The Philosophical Magazine}}</ref> They examined residues that were left after dissolving crude platinum from the [[Ural Mountains]] in [[aqua regia]]. Berzelius did not find any unusual metals, but Osann thought he found three new metals, pluranium, ruthenium and polinium. This discrepancy led to a long-standing controversy between Berzelius and Osann about the composition of the residues.<ref name="DiscoRu">{{cite journal|title = The Discovery of Ruthenium| first = V. N.|last = Pitchkov|journal = Platinum Metals Review|volume = 40|issue = 4|year = 1996|pages =181–188|url = http://www.platinummetalsreview.com/dynamic/article/view/pmr-v40-i4-181-188}}</ref> 

In 1844, the Russian scientist [[Karl Ernst Claus|Karl Klaus]] showed that the compounds prepared by Gottfried Osann contained small amounts of ruthenium, which Klaus had [[discovery of the chemical elements|discovered]] the same year.<ref name="Weeks8"/> Klaus isolated ruthenium from the platinum residues of the rouble production while he was working in [[Kazan University]], [[Kazan]].<ref name="DiscoRu"/> Klaus showed that ruthenium oxide contained a new metal and obtained 6&nbsp;grams of ruthenium from the part of crude platinum that is insoluble in [[aqua regia]].<ref name="DiscoRu"/>

The name derives from [[Ruthenia]], the Latin word for [[Etymology of Rus and derivatives|Rus']], a historical area which includes present-day western [[Russia]], [[Ukraine]], [[Belarus]], and parts of [[Slovakia]] and [[Poland]]. Karl Klaus used the name proposed by [[Gottfried Osann]] in 1828. He chose the element's name in honor of his birthland, as he was born in [[Tartu]], [[Estonia]], which was at the time a part of the [[Russian Empire]].<ref name="Weeks8"/><ref>{{cite book|year = 1964|title = History of Chemistry|volume = 4|page = 499|first = James Riddick|last = Partington|authorlink = James Riddick Partington|location=London |publisher = Macmillan & Co}}</ref>

==Applications==
Because of its ability to harden platinum and palladium, ruthenium is used in platinum and palladium alloys to make wear-resistant [[Switch#Contacts|electrical contacts]]. In this application, only thin plated films are used to achieve the necessary wear-resistance. Because of its lower cost and similar properties compared to rhodium,<ref name="Hunt 1969 126–138"/> the use as plating material for electric contacts is one of the major applications.<ref name="USGS-YB-2006"/><ref>{{cite journal|doi = 10.1016/j.ccr.2004.08.015|title = Chemical and electrochemical depositions of platinum group metals and their applications|year = 2005|author = Rao, C|journal = Coordination Chemistry Reviews|volume = 249|pages = 613|last2 = Trivedi|first2 = D}}</ref> The thin coatings are either put on by electroplating<ref>{{cite journal|doi = 10.1016/S0026-0576(00)83089-5|title = Ruthenium plating|year = 1999|author = Weisberg, A|journal = Metal Finishing|volume = 97|pages = 297}}</ref> or sputtering.<ref>{{cite book|isbn = 9780871702852| url = http://books.google.com/?id=EkStW7v8VPkC&pg=RA3-PA550|page = 184|author = prepared under the direction of the ASM International Handbook Committee ; Merrill L. Minges, technical chairman.|year = 1989|publisher = ASM International|location = Materials Park, OH|title = Electronic materials handbook}}</ref> 

Ruthenium dioxide, lead and bismuth<ref>{{cite journal|doi =10.1007/s10854-006-0036-x|title =Microstructure development and electrical properties of RuO2-based lead-free thick film resistors|year =2006|author =Busana, M. G.|journal =Journal of Materials Science Materials in Electronics|volume =17|pages =951|last2 =Prudenziati|first2 =M.|last3 =Hormadaly|first3 =J.}}</ref> ruthenates, the latter with [[Perovskite (structure)|perovskite crystal structure]],<ref>{{cite journal|doi = 10.1016/j.matlet.2006.05.015|title = Environment friendly perovskite ruthenate based thick film resistors|year = 2007|author = Rane, Sunit|journal = Materials Letters|volume = 61|pages = 595|last2 = Prudenziati|first2 = Maria|last3 = Morten|first3 = Bruno}}</ref> are used in thick film chip resistors.<ref>{{cite book|isbn = 9780824719340| url = http://books.google.com/?id=c2YxCCaM9RIC&pg=PA184|page = 550|editor = Slade, Paul G.|year = 1999|publisher = Dekker|location = New York, NY|title = Electrical contacts : principles and applications}}</ref><!--http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=N8113268AH--> The first two applications account for 50% of the ruthenium consumption.<ref name="Emsley"/>

There are only a few alloys used other than with elements of the platinum group metals. Ruthenium is always used in small quantities in those alloys to improve certain properties of the alloys. One example is the use of small amounts of ruthenium to increase the stability of gold in [[jewelry]]. The beneficial effect on the corrosion resistance of [[titanium]] alloys led to the development of a special alloy containing 0.1% ruthenium .<ref>{{cite journal|url = http://www.platinummetalsreview.com/pdf/pmr-v40-i2-054-061.pdf|title = Ruthenium Enhanced Titanium Alloys|first = R. W.|last = Schutz|journal = Platinum Metals Review|volume = 40|issue = 2|year = 1996|pages = 54–61}}</ref> Ruthenium is also used in some advanced high-temperature single-crystal [[superalloys]], with applications including the turbine blades in [[jet engines]]. Several nickel based superalloy compositions are described in the literature. Among them are EPM-102 (with 3&nbsp;% Ru) and TMS-162 (with 6&nbsp;% Ru), both containing 6&nbsp;% [[rhenium]],<ref>{{cite journal|doi = 10.1007/s11041-006-0099-6|title = Effect of high-gradient directed crystallization on the structure and properties of rhenium-bearing single-crystal alloy|year = 2006|author = Bondarenko, Yu. A.|journal = Metal Science and Heat Treatment|volume = 48|pages = 360|last2 = Kablov|first2 = E. N.|last3 = Surova|first3 = V. A.|last4 = Echin|first4 = A. B.}}</ref> as well as TMS-138<ref>{{cite news| title=Fourth generation nickel base single crystal superalloy|url=http://sakimori.nims.go.jp/catalog/TMS-138-A.pdf}}</ref> and TMS-174.<ref>{{cite journal|author=Koizumi, Yutaka ''et al.''|title= Development of a Next-Generation Ni-base Single Crystal Superalloy|url=http://nippon.zaidan.info/seikabutsu/2003/00916/pdf/igtc2003tokyo_ts119.pdf|work=Proceedings of the International Gas Turbine Congress, Tokyo November 2–7, 2003}}</ref><ref>{{cite news| title=Joint Development of a Fourth Generation Single Crystal Superalloy|author=Walston, S.; Cetel, A.; MacKay, R.; O'Hara, K.; Duhl, D.; Dreshfield, R.|url=http://gltrs.grc.nasa.gov/reports/2004/TM-2004-213062.pdf}}</ref> [[Fountain pen]] nibs are frequently tipped with alloys containing ruthenium. From 1944 onward, the famous [[Parker 51]] fountain pen was fitted with the "RU" nib, a 14K gold nib tipped with 96.2% ruthenium and 3.8% [[iridium]].<ref>{{cite journal|url=http://www.nibs.com/ArticleIndex.html|journal=The PENnant|volume=XIII|issue=2|year=1999|title=Notes from the Nib Works—Where's the Iridium?|author=Mottishaw, J.}}</ref>

Ruthenium is a component of [[mixed-metal oxide]] (MMO) anodes used for cathodic protection of underground and submerged structures, and for electrolytic cells for chemical processes such as [[Chlorine production|generating chlorine]] from salt water.<ref>{{cite book|title =Materials Handbook: A Concise Desktop Reference|url = http://books.google.com/?id=ArsfQZig_9AC&pg=PT612|pages = 581–582| first1 = François|last1 = Cardarelli|chapter = Dimensionally Stable Anodes (DSA®) for Chlorine Evolution|isbn = 9781846286681|year =2008|publisher =Springer|location =London}}</ref> The [[fluorescence]] of some ruthenium complexes is quenched by oxygen, which has led to their use as [[optode]] sensors for oxygen.<ref>{{cite book|title = Chemical sensors in oceanography|chapter = Oxygen Microoptode|pages = 150|first1 = Mark S.|last1 = Varney|year = 2000|isbn = 9789056992552|publisher = Gordon & Breach|location = Amsterdam}}</ref> [[Ruthenium red]], [(NH<sub>3</sub>)<sub>5</sub>Ru-O-Ru(NH<sub>3</sub>)<sub>4</sub>-O-Ru(NH<sub>3</sub>)<sub>5</sub>]<sup>6+</sup>, is a [[biological stain]] used to stain [[polyanion]]ic molecules such as [[pectin]] and [[nucleic acids]] for [[light microscopy]] and [[electron microscopy]].<ref>{{cite book|title = Stains and cytochemical methods|chapter = Ruthenium red|first1 = M. A.|last1 = Hayat|url = http://books.google.com/?id=oGj7MLioFlQC&pg=PA305|pages = 305–310|isbn = 9780306442940|year = 1993|publisher = Plenum Press|location = New York, NY}}</ref> The beta-decaying isotope 106 of ruthenium is used in radiotherapy of eye tumors, mainly [[malignant melanoma]]s of the [[uvea]].<ref>{{cite book|url = http://books.google.com/?id=Aa83RoXCNk0C&pg=PA97|title = Radiotherapy of ocular disease, Ausgabe 13020|first1 = T.|last1 = Wiegel|isbn = 9783805563925|year = 1997|publisher = Karger|location = Basel ;Freiburg}}</ref> Ruthenium-centered complexes are being researched for possible anticancer properties.<ref>{{cite journal |last = Richards|first = A.D.|coauthor = Rodger, A.|year = 2007|url = http://www.rsc.org/publishing/journals/CS/article.asp?doi=b609495c|title = Synthetic metallomolecules as agents for the control of DNA structure|journal = Chem. Soc. Rev.|volume = 36|pages = 471–483|doi = 10.1039/b609495c |pmid = 17325786 |last1 = Richards |first1 = AD |last2 = Rodger |first2 = A |issue = 3}}</ref> Ruthenium, unlike traditional platinum complexes, shows greater resistance to hydrolysis and more selective action on tumors. NAMI-A and KP1019 are two drugs undergoing clinical evaluation against metastatic tumors and colon cancers.

==Laboratory uses==
Ruthenium is also a versatile catalyst. [[Hydrogen sulfide]] can be split by light by using an aqueous suspension of [[Cadmium sulfide|CdS]] particles loaded with ruthenium dioxide. This may be useful in the removal of [[hydrogen|H]]<sub>2</sub>S from [[oil refinery|oil refineries]] and from other industrial processes.<ref>{{cite book|title = Innovations in Mineral and Coal Processing|first1 = Suna|last1 = Atak|first2 = Mehmet Sabri|last2 = C̦elik|url = http://books.google.com/?id=fI8Yo0bX7BwC&pg=PA498|year = 1998|isbn = 9789058090133|publisher = Taylor & Francis|page = 498}}</ref> [[Organometallic]] ruthenium [[carbene]] and [[allenylidene]] complexes have recently been found as highly efficient catalysts for [[olefin metathesis]] with important applications in organic and pharmaceutical chemistry.<ref>{{cite journal|doi = 10.1002/1521-3773(20000901)39:17<3012::AID-ANIE3012>3.0.CO;2-G|title=Olefin Metathesis and Beyond|author=Fürstner, Alois|journal=Angewandte Chemie International Edition|volume=39|year=2000|pages=3012}}</ref> Some ruthenium complexes [[Absorption (electromagnetic radiation)|absorb light]] throughout the visible spectrum and are being actively researched in various, potential, [[solar energy]] technologies. Ruthenium-based compounds have been used for light absorption in [[dye-sensitized solar cell]]s, a promising new [[low-cost solar cell]] system.<ref>{{cite journal|doi =10.1021/ja058540p|title =High Molar Extinction Coefficient Heteroleptic Ruthenium Complexes for Thin Film Dye-Sensitized Solar Cells|year =2006|last1 =Kuang|first1 =Daibin|last2 =Ito|first2 =Seigo|last3 =Wenger|first3 =Bernard|last4 =Klein|first4 =Cedric|last5 =Moser|first5 =Jacques-E|last6 =Humphry-Baker|first6 =Robin|last7 =Zakeeruddin|first7 =Shaik M.|last8 =Grätzel|first8 =Michael|journal =Journal of the American Chemical Society|volume =128|pages =4146|pmid =16551124|issue =12}}</ref> [[Ruthenium chemical vapor deposition]] (CVD) is used as a method to produce thin films of pure ruthenium on substrates. These films show promising properties for the use in microchips and for the [[giant magnetoresistive]] read element for hard disk drives.<ref>{{cite book|url = http://books.google.com/?id=5YYIlaownVMC&pg=PA569|page = 569|title = Physics and Technology of High-k Gate Dielectrics 5, Ausgabe 4|first = Samares|last = Kar|publisher = The Electrochemical Society|isbn = 20079781566775700|date = 2007-09}}</ref> Ruthenium was also suggested as a possible material for microelectronics because its use is compatible with semiconductor processing techniques.<ref>{{cite journal|chapter = Etching Byproducts of Ruthenium Wafers Using Various Etching Chemistries| first1 = A. H.-B. |last1=Cheng| first2 = M.|last2=Daniels| first3 = J. D. |last3= Luttmer|title = Environmental issues in the electronics/semiconductor industries and: Electrochemical/photochemical methods for pollution|publisher = The Electrochemical Society|year = 1998| isbn = 9781566771993|pages = 10–14}}</ref>
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===Applications of ruthenium thin films in microelectronics===
Relatively recently, ruthenium has been suggested as a material that could beneficially replace other metals and [[silicide]]s in microelectronics components. Ruthenium tetroxide (RuO<sub>4</sub>) is highly volatile, as is ruthenium trioxide (RuO<sub>3</sub>).<ref>{{cite journal|last =Wei|first = P.|coauthor = Desu, S. B.|title = Reactive ion etching of RuO<sub>2</sub> films: the role of additive gases in O<sub>2</sub> discharge|journal = Physica Status Solidi A |year = 1997 |volume = 161|issue = 1|pages = 201–215|doi =10.1002/1521-396X(199705)161:1<201::AID-PSSA201>3.0.CO;2-U}}</ref> By oxidizing ruthenium (for example with an oxygen plasma) into the volatile oxides, ruthenium can be easily patterned.<ref>{{cite journal
|last = Lesaicherre|first = P. Y.|coauthor = Yamamichi, S.; Takemura, K.; Yamaguchi, H.; Tokashiki, K.; Miyasaka, Y.; Yoshida, M.; Ono, H.|title = A Gbit-scale DRAM stacked capacitor with ECR MOCVD SrTiO<sub>3</sub> over RIE patterned RuO<sub>2</sub>/TiN storage nodes|journal = Integrated Ferroelectrics |year = 1995|volume = 11|issue = 1–4 |pages = 81–100|doi = 10.1109/IEDM.1994.383296}}</ref><ref>{{cite journal|last = Pan|first = W.|coauthor = Desu, S. B.|title = Reactive Ion Etching of RuO<sub>2</sub>, Thin-Films Using the Gas-Mixture O<sub>2</sub> CF<sub>3</sub>CFH<sub>2</sub>|journal = Journal of Vacuum Science & Technology B |year = 1994 |volume = 12|issue = 6 |pages = 3208–3213|doi = 10.1116/1.587501}}</ref><ref>{{cite journal|last = Vijay|first = D. P.|coauthor = Desu, S. B.; Pan, W.,|title = Reactive Ion Etching of Lead-Zirconate-Titanate (PZT) Thin-Film Capacitors|journal = Journal of the Electrochemical Society |year = 1993 |volume = 140 |issue = 9|pages = 2635–2639|doi = 10.1149/1.2220876}}</ref><ref>{{cite journal|last = Saito|first = S. |coauthor =Kuramasu, K.|title = Plasma etching of RuO<sub>2</sub> thin films|journal = Japanese Journal of Applied Physics |year = 1992 |volume = 31|issue = 1|pages = 135–138|doi = 10.1143/JJAP.31.135}}</ref> The properties of the common ruthenium oxides make ruthenium a metal compatible with the semiconductor processing techniques needed to manufacture microelectronics.

In order to continue miniaturization of microelectronics, new materials are needed as dimensions change. There are three main applications for thin ruthenium films in microelectronics. The first is using thin films of ruthenium as electrodes on both sides of tantalum pentoxide (Ta<sub>2</sub>O<sub>5</sub>) or barium strontium titanate ((Ba, Sr)TiO<sub>3</sub>, also known as BST) in the next generation of three-dimensional [[Dynamic random access memory|dynamic random access memories]] (DRAMs).<ref>{{cite journal|title=Ruthenium films prepared by liquid source chemical vapor deposition using bis-(ethylcyclopentadienyl)ruthenium|journal= Japanese Journal of Applied Physics |year=1999|volume=38|pages=1134–6|doi=10.1143/JJAP.38.L1134|author1=Aoyama, T|author2=Eguchi, K}}</ref><ref>{{cite journal|title=(Ba,Sr)TiO<sub>3</sub> thin film capacitors with Ru electrodes for application to ULSI processes|journal=NEC Research and Development|year=2001|volume=42|pages=64–9|author1=Iizuka, T|author2=Arita, K|author3=Yamamoto, I|author4=Yamamichi, S}}</ref><ref>{{cite journal|title=A stacked capacitor technology with ECR plasma MOCVD (Ba,Sr)TiO<sub>3</sub> and RuO<sub>2</sub>/Ru/TiN/TiSi<sub>x</sub> storage nodes for Gb-scale DRAM's. IEEE Transactions on Electron Devices |year=1997|volume=44|pages=1076–1083|author=Yamamichi, S ''et al.''}}</ref> Ruthenium thin film electrodes could also be deposited on top of lead zirconate titanate (Pb(Zr<sub>x</sub>Ti<sub>1-x</sub>)O<sub>3</sub>, also known as PZT) in another kind of [[Random-access memory|RAM]], [[Ferroelectric RAM|ferroelectric random access memory]] (FRAM).<ref>{{cite journal|title=Simple Ru electrode scheme for ferroelectric (Pb,La)(Zr,Ti)O<sub>3</sub> capacitors directly on silicon|journal=Journal of Applied Physics|year=1998|volume=84|issue=2|pages=1121–1125|doi=10.1063/1.368112|author1=Bandaru, J|author2=Sands, T|author3=Tsakalakos, L}}</ref><ref>{{cite journal|title=Preparation and properties of Ru and RuO<sub>2</sub> thin film electrodes for ferroelectric thin films. Jpn. J. Appl. Phys. |year=1994|volume=33|pages=5223–6|author1=Maiwa, H|author2=Ichinose, N|author3=Okazaki, K}}</ref> Platinum has been used as the electrodes in RAMs in laboratory settings, but it is difficult to pattern. Ruthenium is chemically similar to platinum, preserving the function of the RAMs, but in contrast to Pt patterns easily. The second is using thin ruthenium films as metal gates in p-doped metal-oxide-semiconductor field effect transistors (p-MOSFETs).<ref>{{cite journal|title=Issues in high-kappa gate stack interfaces. MRS Bulletin|year=2002|volume=27|pages=212–216|author1=Misra, V|author2=Lucovsky, G|author3=Parsons, G}}</ref> When replacing [[silicide]] gates with metal gates in [[MOSFET]]s, a key property of the metal is its [[work function]]. The work function needs to match the surrounding materials. For p-MOSFETs, the ruthenium work function is the best materials property match with surrounding materials such as HfO<sub>2</sub>, HfSiO<sub>x</sub>, HfNO<sub>x</sub>, and HfSiNO<sub>x</sub>, to achieve the desired electrical properties. The third large-scale application for ruthenium films is as a combination adhesion promoter and electroplating seed layer between TaN and Cu in the copper dual damascene process.<ref>{{cite journal|title=Diffusion Studies of Copper on Ruthenium Thin Film. Electrochemical and Solid-State Letters|year=2004|volume=7|pages=G154–G157|author1=Chan, R|author2=Arunagiri, T. N|author3=Zhang, Y|author4=Chyan, O|author5=Wallace, R. M|author6=Kim, M. J|author7=Hurd, T. Q}}</ref><ref>{{cite journal|title=Damascene Cu electrodeposition on metal organic chemical vapor deposition-grown Ru thin film barrier|journal=Journal of Vacuum Science and Technology B|year=2004|volume=22|pages=2649–2653|doi=10.1116/1.1819911|author1=Cho, S. K|author2=Kim, S.-K|author3=Kim, J. J|author4=Oh, S. M|last5=Oh|first5=Seung Mo}}</ref><ref>{{cite journal|title=Electrodeposition of Copper Thin Film on Ruthenium|journal= Journal of the Electrochemical Society|year=2003|volume=150|pages=C347–C350|doi=10.1149/1.1565138|author1=Chyan, O|author2=Arunagiri, T. N|author3=Ponnuswamy, T}}</ref><ref>{{cite journal|title=PEALD of a Ruthenium Adhesion Layer for Copper Interconnects|journal=Journal of the Electrochemical Society|year=2004|volume=151|pages=C753–C756|doi=10.1149/1.1809576|author1=Kwon, O.-K|author2=Kwon, S.-H|author3=Park, H.-S|author4=Kang, S.-W}}</ref><ref>{{cite journal|title=Atomic Layer Deposition of Ruthenium Thin Films for Copper Glue Layer|journal=Journal of the Electrochemical Society|year=2004|volume=151|pages=G109–G112|doi=10.1149/1.1640633|author1=Kwon, O.-K|author2=Kim, J.-H|author3=Park, H.-S|author4=Kang, S.-W}}</ref> Copper can be directly electroplated onto ruthenium<ref>{{cite journal|title=Electrodeposition of Cu on Ru Barrier Layers for Damascene Processing|journal=Journal of the Electrochemical Society|year=2006|volume=153|pages=C37–C50|doi=10.1149/1.2131826|author=Moffat, T. P ''et al.''}}</ref>, in contrast to tantalum nitride. Copper also adheres poorly to TaN, but well to Ru. By depositing a layer of ruthenium on the TaN barrier layer, copper adhesion would be improved and deposition of a copper seed layer would not be necessary.

There are also other suggested uses. In 1990, [[IBM]] scientists discovered that a thin layer of ruthenium atoms created a strong anti-parallel coupling between adjacent [[ferromagnetic]] layers, stronger than any other nonmagnetic spacer-layer element. Such a ruthenium layer was used in the first [[Giant magnetoresistance|giant magnetoresistive]] read element for [[hard disk drive]]s. In 2001, IBM announced a three-atom-thick layer of the element ruthenium, informally referred to as "pixie dust", which would allow a quadrupling of the data density of current hard disk drive media.<ref>{{cite journal|author=Hayes, Brian |title=Terabyte Territory|journal=American Scientist|volume= 90|issue=3|year=2002|page=212|url=http://www.americanscientist.org/issues/pub/terabyte-territory}}</ref>
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==References==
{{Reflist|2}}

==External links==
{{Commons|Ruthenium}}
{{Wiktionary|ruthenium}}
*[http://www.brightsurf.com/news/headlines/32014/Nano-layer_of_ruthenium_stabilizes_magnetic_sensors.html Nano-layer of ruthenium stabilizes magnetic sensors]
*[http://www.webelements.com/webelements/elements/text/Ru/index.html WebElements.com – Ruthenium]

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{{compact periodic table}}

[[Category:Chemical elements]]
[[Category:Transition metals]]
[[Category:Metals]]
[[Category:Precious metals]]
[[Category:Ruthenium|*]]
[[Category:Noble metals]]
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