國際科技信息

國際科技信息

歐盟智能能源計劃積極促進新能源創新成果轉化

歐盟智能能源計劃由歐委會于2003年正式啟動實施，歐委會能源總司具體運作管理。歐委會公共財政平均每年投資1億歐元的IEE計劃（2007-2013年財政預算7.3億歐元）與成員國財政資金聯合共同資助新能源科技成果的轉化及商業化項目。所選項目主要來自歐盟研發框架計劃或成員國政府科研計劃有關新能源的研發創新成果。IEE計劃旨在提高能效，發展可再生能源，減緩氣候變化影響，保持歐盟未來競爭力。其三大優先目標分別是：1、促進提高能源效率和鼓勵能源合理利用；2、提高新能源和可再生能源的利用率和鼓勵能源多元化；3、推動交通領域的能效提升和可再生能源利用。

IEE計劃資助的優先領域：可再生能源，提高能效，節能建筑，新能源產業化，交通節能減排。IEE計劃資助選擇項目的參照標準（符合愈多標準優先）：吸引金融和社會風險投資，創新成果的先進性及商業潛力，產學研用緊密結合，創新型中小企業積極參與，節能減排新興產業發展，能源可持續及多元化。

IEE計劃資助的項目已經取得明顯的經濟社會效益。例如：推薦的系列新型節能建筑相比傳統建筑至少節能50%；改善和規范了整個歐盟源自可再生能源的電力生產技術支撐平臺的效率；支持歐洲加速發展更清潔、更節能城市等等。

Intelligent Energy – Europe: for a sustainable future

The EU has set itself ambitious targets to achieve clean and secure energy for tomorrow. An optimal use of available tools is necessary to meet these targets. A wide range of technologies and methods exist to improve energy efficiency, turn renewables into viable energy sources and reduce emissions. However, market conditions prevent them from reaching their full potential. This is where the Intelligent Energy –Europe programme comes in.

The Intelligent Energy –Europe (IEE) programme is giving a boost to clean and sustainable solutions. It supports their use and dissemination and the Europe-wide exchange of related knowledge and know-how.

Targeted funding is provided for creative projects putting this idea into practice.

The projects help to further the three main objectives:

· Promoting energy efficiency and encouraging the rational use of energy sources;

· Increasing the use of new and renewable energy sources as well as encouraging energy diversification;

· Stimulating energy efficiency and renewables in the field of transport.

Intelligent Energy – Europe (IEE) offers a helping hand to organisations willing to improve energy sustainability. Launched in 2003 by the European Commission, the programme is part of a broad push to create an energy-intelligent future for us all. It supports EU energy efficiency and renewable energy policies, with a view to reaching the EU 2020 targets (20% cut in greenhouse gas emissions, 20% improvement in energy efficiency and 20% of renewables in EU energy consumption).

Intelligent Energy – Europe creates better conditions for a more sustainable energy future in areas as varied as renewable energy, energy-efficient buildings, industry, consumer products and transport.

The expectation is that by doing this, Europe will also boost its competitiveness, security of energy supply, and innovation standing for the years to come.

Running until 2013, the programme is open to all EU Member States, plus Norway, Iceland, Liechtenstein, Croatia and the Former Yugoslav Republic of Macedonia. A budget of € 730 million is available to fund projects and put into place a range of European portals, facilities and initiatives.

A large part of the programme budget is made available through annual calls for proposals to support projects putting the concept of 'intelligent energy' in practice. Carried out by public, private or non-governmental European organisations, they support three main objectives - more energy efficiency, more renewables, and better transport and mobility. This covers for instance new training schemes, promotion campaigns, or the transfer of good practices between EU countries.

The IEE programme has been up and running since 2003. More than 500 European projects involving 3 500 European organisations have received funding and a lot has been achieved already. The programme and its projects are helping the EU deliver on its 2020 objectives to improve energy efficiency, increase the share of renewables in EU energy consumption and to reduce greenhouse gases.

美國發布《美國競爭和創新能力》報告

2012年伊始，美國商務部發布《美國競爭和創新能力》報告，對21世紀以來美國所面臨的挑戰進行了分析，并提出了對策建議。

該報告認為，美國經濟競爭能力下滑，國民收入止步不前，就業增長緩慢，對科技要素的支持力度減弱。

該報告提出，創新是提高競爭能力、增加收入、促進就業、推動經濟長遠發展的關鍵因素，增強創新能力的三項關鍵措施是聯邦政府要加大對基礎研究、教育和基礎設施的支持，特別是增加投入。

為應對挑戰，提高創新和競爭能力，該報告提出了10項具體建議，分別是：1、增加政府對基礎研究的投入，2、加大對企業研發的稅收優惠政策支持力度，3、加速基礎研究成果的商業化應用，4、強化科學、技術、工程和數學（STEM）教育，5、擴大無線通信的頻譜資源，6、加強數據的開放和共享，7、協調聯邦政府對制造業的支持，8、繼續強化區域創新中心建設，9、推動美國產品出口，10、營造企業創新和繁榮的環境。Commerce Department Report Provides Roadmap for Strengthening U.S. Competitiveness

The U.S Department of Commerce today delivered to Congress a comprehensive report on "The Competitiveness and Innovative Capacity of the United States." The report serves as a call to arms, highlighting bipartisan priorities to sustain and promote American innovation and economic competitiveness.

The report makes three important findings:

· Federal investments in research, education and infrastructure were critical building blocks for American economic competitiveness, business expansion and job creation in the last century;

· Failures to properly invest in, and have comprehensive strategies for, those areas have eroded America's competitive position; and,

· In a constrained budgetary environment, prioritizing support for these pillars is imperative for America's economic future and will provide a strong return on investment for the U.S. taxpayer.

Speaking before an event at the Center for American Progress (CAP), Commerce Secretary and former CEO John Bryson highlighted the importance role innovation plays in the nation's economy.

"This is a topic of pivotal importance," Bryson said. "Our ability to innovate as a nation will determine what kind of economy – what kind of country – our children and grandchildren will inherit, and whether it's a country that holds the same promise for them as it did for our parents and grandparents."

The report was mandated as part of the America COMPETES Reauthorization Act of 2010, which was signed into law by President Obama in January last year. The report addresses a diverse range of topics and policy options, including: tax policy; the general business climate in the U.S.; barriers to setting up new firms; trade policy, including export promotion; the effectiveness of federal research and development policy; intellectual property regimes in the U.S. and abroad; the health of the manufacturing sector; and science and technology education.

The full report, as well as additional resources, can be found online at www.commerce.gov/ competes.

Some key findings of the report include:

Basic research. While private citizens and businesses are the top source of new ideas, the government plays a key role in supporting and developing their innovations. Examples of how this federal seed money has helped change our world are can be seen in the development of the Internet, satellite communications and semiconductors, among other job-creating advances. The report recommends federal funding be increased for basic research –universities and research centers, for instance. Consistent with the long-held view of President Obama, the report also recommends a tax credit a tax credit be enhanced and extended for private-sector R&D to give companies appropriate incentives to innovate and improve the way basic research is transferred from the lab into commercial products. The report recognizes that through efforts like the Small Business Jobs Act, the i6 Green Challenge, and a number of other initiatives, including increased funding, the Obama Administration has shown a commitment to spurring innovation through supporting research.

Education. The COMPETES report underscores the importance of education in the science, technology, engineering and mathematics, or STEM, fields. For instance, women with STEM jobs earned 33 percent more than comparable women in non-STEM jobs. As a result, the gender wage gap is smaller in STEM jobs than in non-STEM jobs. Ongoing and new administration initiatives are addressing these challenges by making college more affordable, spurring classroom innovation at all levels and expanding the size and quality of STEM teacher ranks. To succeed in the global economy, government must encourage students and workers to pursue STEM education.

Infrastructure. The report highlights the importance of federal government investment in an expansive modern electrical grid that provides robust broadband Internet access in both urban and rural communities. Presently, 68 percent of American households have adopted broadband, an almost eight-fold increase since 2001. Small and medium-sized enterprises (SMEs) have benefited hugely from the Internet and created more than twice the number of jobs as firms not on the Web, creating 2.6 jobs for each one eliminated. The report also highlights Obama Administration efforts to build a 21st century infrastructure, including the NextGen Air Traffic Control System, opening spectrum for wireless communication, creating smart grid standards and providing unprecedented funding for road, rail and bridge projects across the country.

Supporting Manufacturing. The report also examines manufacturing, recognizing that a flourishing U.S. manufacturing sector is crucial to competitive strength, economic growth and job creation, as well as to sustaining a strong middle class. In 2009, manufacturing comprised 11.2 percent of GDP and 9.1 percent of total U.S. employment, directly employing over 11 million workers. Manufacturing is also the biggest source of innovation in our economy. Sixty-seven percent of all the business R&D in America is done by manufacturing companies. The report outlines a series of steps the Obama administration has taken to support American manufacturing, including rescuing the U.S. auto industry, creating the White House Office of Manufacturing Policy and forming the Advanced Manufacturing Partnership (AMP), as well as initiatives such as the Materials Genome Initiative and the National Digital Engineering and Manufacturing Consortium.

The report also touches on a number of other areas, including the benefits of regional clusters, the Administration's Startup America Initiative, the National Export Initiative, corporate tax reform, as well as the importance of intellectual property protection.

歐盟美國加強針對微生物抗體的共同研究

2012年1月5日，歐委會科技合作委員會（COST）組織的由歐盟生物醫學和分子生物學高層專家和科研人員組成的生物醫學特別顧問委員會會議在布魯塞爾舉行，研究和確定歐盟同美國開展針對微生物抗體合作研究計劃的優先領域和共同研究課題。歐美針對微生物抗體的共同合作研究機制由雙方2009年領導人峰會確立，合作研究計劃分別由歐盟流行病控制中心（ECDC）和美國疾病預防控制中心具體負責執行。

世界抗生素的濫用以及人員的相互流動和商品交換，以食品或其它各種方式造成人類和動物病原體耐藥性抗體在全球范圍內持續快速地傳播，引起世界衛生組織（WHO）和各國政府及醫藥界的高度關注，其后果已成為人類和動物健康的新威脅。特別是已有多種細菌種類耐多藥性單抗體（Multidrug Resistant Isolate）的出現和人類在該領域知識的相對匱乏，更加重了這種趨勢，為人類提出了新挑戰。

專家顧問委員會經過討論和篩選，確定了歐美雙方需要加強合作研究的三大關鍵領域：1）研究衛生醫療和動物健康領域抗生素藥物的合理療法及合理使用；2）研究微生物抗體相關聯的公眾擔憂和對人畜健康的不良影響及預防措施；3）研究新型抗生素藥物的改進辦法和新藥物研究。圍繞上述三大關鍵領域，歐盟推薦了17項需要歐美雙方加強共同研究的科研課題。Debating bacterial adaptation to selection following antibiotic treatment

COST Actions in the f eld of Biomedicine and Molecular Biosciences collaborate to investigate bacterial adaptation and resistance.

he continuous and rapid emergence of resistant pathogens of human and animal importance is a worrying health problem worldwide, recognised as a public health challenge by governments as well as international institutions such as the European Union, United States Government, European Centre for Disease Control (ECDC), Centres for Disease Control & Prevention (CDC) in Atlanta and the World Health Organization (WHO).

This problem is exacerbated by the rapid dissemination of multidrug resistant isolates of various bacterial species involved in both human and animal diseases through i.e. international travel and global trade in food and other commodities.

A recent report issued by the Transatlantic Taskforce on Antimicrobial Resistance

T Recommendations for future collaboration between the U.S. and EU argues that “the societal and financial costs of treating antimicrobial-resistant infections place a significant human and economic burden on society, as individuals infected with drugresistant organisms are more likely to remain in the hospital for a longer period of time and to have a poor prognosis”.

COST Action BM0701 on‘Antibiotic Transport and Efflux: New Strategies to combat bacterial resistance (ATENS)’ and COST Action BM1003 on ‘Microbial cell surface determinants of virulence as targets for new therapeutics in Cystic Fibrosis’ have teamed up to focus their research efforts on the emerging threat of antimicrobial resistance and bacterial respiratory diseases.

At a recent meeting held in Brussels, scientists and researchers discussed the role of bacterial adaptation to selection following antibiotic treatment, with a particular focus on the lifethreatening respiratory disease cystic fibrosis. Participation of the European Commission’s Directorate General for Health and Consumers (SANCO) ensured that discussions included the current policy position being developed to combat antimicrobial resistance at EU level.

This initiative also involves COST Action CM0804 on ‘Chemical Biology with Natural Products’, from the COST Domain for Chemistry and Molecular Sciences and Technologies (CMST), testifying the interdisciplinary nature of COST Actions and the benefits of networking in the field of science and technology at pan-European level.

美研制出增強薄膜太陽能電池吸光技術薄層厚度等于或小于可見光波長時的吸光能力不再取決于厚度

據英國《自然》雜志網站近日報道，盡管薄膜太陽能電池應用廣泛，但其也有“先天不足”：薄膜越薄，制造成本越低，但當其變得更薄時，會失去捕光能力。美國科學家表示，當薄層厚度等于或小于可見光的波長時，其捕光能力會變得很強。科學家們可據此研制出厚度僅為現在商用薄膜太陽能電池厚度的1%、但捕光能力卻大有改善的薄膜太陽能電池。

科學家們用射線—光極值這一理論最大捕光值來標識一種材料最多能捕獲多少光線，但是，只有當材料具有一定的厚度時，才能達到這一峰值。目前，科學家們已經制造出了吸光層的厚度僅為0.1納米的薄膜太陽能電池，但這樣纖細的薄膜會漏掉很多光。

然而，現在，加州理工學院應用物理和材料科學教授哈里·阿特沃特和同事在最新一期《納米快報》雜志上指出，他們找到了一種巧妙的方法，使薄層能幫助太陽能電池超越射線—光極值。他們發現，當薄層的厚度小于可見光的波長（400到700納米）時，薄層會同這些可見光的波特性相互作用而不是將可見光看成一條直直的射線。阿特沃特說：“當我們制造出的薄層厚度等于或小于可見光的波長時，一切規則都改變了。”這樣，一種材料的吸光能力不再取決于厚度，而取決于光線和吸收材料之間的波作用。

通過計算和計算機模擬，阿特沃特團隊證明，讓一種材料對光更有“胃口”的技巧在于，制造出更多“光態”讓光來占領，這些“光態”就像狹縫一樣，能吸收特定波長的光。一種材料的“光態”數量部分取決于該材料的折射率，折射率越高，其能支持的“光態”就越多。

其實，早在2010年，斯坦福大學的教授范汕洄（音譯）和同事就將“光態”數確定為一種材料能吸入多少光線的主要因素。他們用一種折射率較高的材料將一種折射率低的材料包圍，結果發現，高折射率材料的出現能有效提高低折射率材料的折射率，增強其捕光能力。

阿特沃特團隊對上述結論進行了延伸，最新研究表明，薄膜吸光器內擠滿 “光態”會大大增強其捕光能力。而且，可通過幾種方式（比如，用金屬或晶體結構包住吸光層或將吸光器嵌入一個更復雜的三維陣列中）來提高吸收器的有效折射率。范汕洄表示：“最新研究表明，我們可以采用多種不同的方法有效地突破射線—光極值?！?/p>

美國托萊多大學的羅伯特·柯林斯表示，阿特沃特團隊的研究是“非常關鍵的第一步”。但他也認為，這項技術還面臨著諸多挑戰，比如，需要額外的工業過程來制造這些超薄的薄膜，這會導致成本增加。

Engineering slimmer solar cells A recipe to increase a thin film’s appetite for light

Thin-film solar cells are plagued by diminishing returns: thinner panels are cheaper to make, but as the semiconductor layer gets thinner it loses its lighttrapping ability. Researchers at the California Institute of Technology in Pasadena now report the secret to making thin layers more absorbent— making it possible to use layers up to 100 times thinner than those in the commercial devices available today.

A theoretical light-trapping limit, called the ray-optic limit, sets out the maximum amount of light that a material can trap, but reaching that pinnacle requires the material to be thick. Researchers have made thin-film solar cells with absorbing layers just tens of nanometers thick, but such a fine film can allow much of the light to pass through before it has a chance to be absorbed.

However, Harry Atwater and his colleagues argue in Nano Letters that cleverly made thin layers could help solar cells to overcome the rayoptic limit. When the layers have thicknesses below the wavelength of visible light — 400~700 nanometres — they interact with its wave properties rather than treating it as a straight ray. “In this regime, where the structures we make are at or below the scale of the wavelength of light, suddenly all the rules change,” says Atwater. In this case, rather than depending on thickness, a material’s ability to absorb light depends on the wave interactions between the light and the absorber.

Through calculations and computer simulations, Atwater’s team demonstrated that the trick to upping a material’s thirst for light is to create more ‘optical states’ for the light to occupy — which are like slots that can accept light with a certain wavelength, similar to the energy levels of electrons in atoms. The number of optical states in a material depends, in part, on its refractive index, which determines how much the material shortens the wavelength of light passing through it. The higher the refractive index, the more compressed the light, and the more optical states the material can support.

In 2010, Shanhui Fan of Stanford University in California and his colleagues identified the number of optical states as a major factor in how much light a material could absorb. They studied a material with a low refractive index bordered by a layer with a highrefractive index. Near the interface, they found that the presence of the higher-index material effectively raised the refractive index of the low-index material, allowing it to absorb more light.

Atwater’s team has

generalized this idea to show that cramming in more optical states can make many thin-film light absorbers take up more light than usual. The study also demonstrates that this can be accomplished in many ways — by coating the absorbing layer with metal or with a crystal structure that contains patterns on the scale of the wavelength of light, by embedding the absorber in a more complex three-dimensional array. Through different mechanisms, each of these strategies raises the effective refractive index of the absorber.

“Their work provides a comprehensive study of a variety of different designs that can potentially go beyond the ray-optic limit,” says Fan.

Robert Collins of the University of Toledo, Ohio, who works with the thin-film photovoltaic start-up company Xunlight, says the team’s concept is a “fundamental first step”. But he anticipates technological challenges ahead, such as a requirement for extra processing steps to create and control films on a submicrometre scale in an industrial setting, the added cost of which must be balanced by the savings in materials.

科學家確認存在“長壽基因”

2011年7月，《科學》（Science）雜志發表聲明稱應作者要求，撤銷了來自美國波士頓大學公共健康學院、意大利生物技術學院等處研究人員聯合發表的關于百歲老人遺傳學特征研究成果的論文。近日，這一研究團隊就該問題進行了重申，他們重新在更嚴格的質控條件下進行了獨立實驗，最新的研究論文以與Science雜志原論文相同的題目“Genetic Signatures of Exceptional Longevity in Humans”發表在1月18日的《公共科學圖書館—綜合》（PloS ONE）期刊上。

健康

長壽是每一個人的夢想，但至今科學家們還并不清楚長壽的奧秘。2010年該研究團隊稱他們通過檢測超過1000名的百歲或百歲以上的老人以及相同數目的作為對照的人的基因組，發現了一系列與一般人群相比特別常見的遺傳學特征，并將研究數據發表在了當年7月的Sceince雜志上。

原文章中，研究人員對超過1000名的百歲或百歲以上的老人以及相同數目的作為對照的人的基因組進行了檢測。他們找到了在百歲或以上的老人與隨機選擇的個人之間有著最大差異的多個基因標志。因為人要活到非常老的年齡一定會有多個基因的參與，之后研究人員根據150個基因標志研發出了一個可計算一個人達到異常高壽概率的模型。應用這一模型，研究人員可以預測某人是否可以活到百歲或以上，而且精確性達77%。研究人員還在90%的研究對象身上發現總共19個不同的“格外長壽”基因標簽。他們發現，研究對象中最長壽人群，即年齡不低于110歲的老人中，45%老人所含基因標簽顯示他們“擁有最高比例的長壽相關基因變異體”。

但是該論文一經發表，就被質疑存在缺陷而引起了多方的關注和爭議，同年11月12日《科學》主編Bruce Alberts發表聲明表示對此事高度關注。2011年7月，在該論文發表1周年之際，Science宣布應作者要求，以實驗所用芯片出現一些“技術性錯誤”，以及不充分的質量控制方法從而導致結果出現錯誤為由，正式撤銷這篇論文。

在《PLoS綜合》新文章中，研究人員重新在更嚴格的質控條件下進行了獨立實驗，去除了模糊不明的SNPs結果，在獨立平臺上再分析基因型數據，利用原文章中的方法再次分析了刪減后的數據。研究人員收集了801名百歲或百歲以上的老人（平均年齡為104歲）和914名健康對照人群的基因數據進行了對比分析，發現了281個與人類壽命有關的基因標記。

這些基因大部分被證實與老年人的常見疾病有關聯，譬如老年性癡呆癥、心血管疾病、糖尿病等。研究發現，這些長壽老人往往到90歲以后才出現老年病癥狀，似乎他們的一些基因能推遲或避免老年疾病的發生。

研究學者表示，雖然環境在很大程度上影響著人類的壽命，但基因卻決定了90歲以后的身體狀況。不過他們同時忠告人們，即使基因對壽命有一定的影響，還是建議人們遵循健康的生活方式。

Like most complex phenotypes, exceptional longevity is thought to reflect a combined influence of environmental (e.g., lifestyle choices, where we live) and genetic factors. To explore the genetic contribution, we undertook a genome-wide association study of exceptional longevity in 801 centenarians (median age at death 104 years) and 914 genetically matched healthy controls. Using these data, we built a genetic model that includes 281 single nucleotide polymorphisms (SNPs) and discriminated between cases and controls of the discovery set with 89% sensitivity and specificity,

and with 58% specificity and 60% sensitivity in an independent cohort of 341 controls and 253 genetically matched nonagenarians and centenarians (median age 100 years). Consistent with the hypothesis that the genetic contribution is largest with the oldest ages, the sensitivity of the model increased in the independent cohort with older and older ages (71% to classify subjects with an age at death>102 and 85% to classify subjects with an age at death>105). For further validation, we applied the model to an additional, unmatched 60 centenarians (median age 107 years) resulting in 78% sensitivity, and 2863 unmatched controls with 61% specificity. The 281 SNPs include the SNP rs2075650 in TOMM40/APOE that reached irrefutable genome wide significance (posterior probability of association = 1) and replicated in the independent cohort. Removal of this SNP from the model reduced the accuracy by only 1%. Further insilico analysis suggests that 90% of centenarians can be grouped into clusters characterized by different“genetic signatures” of varying predictive values for exceptional longevity. The correlation between 3 signatures and 3 different life spans was replicated in the combined replication sets. The different signatures may help dissect this complex phenotype into sub-phenotypes of exceptional longevity.

Introduction

The average human lifespan in developed countries now ranges from about 80 to 85 years. Environmental factors such as lifestyle choices and where we choose to live as well as genetic factors all contribute to healthy aging. Supporting the importance of environmental factors in survival to old age is the 88 year average life expectancy of Seventh-Day Adventists, who by virtue of their religion have health related behaviors conducive to healthy aging.

Human twin studies suggest that only 20～30% of the variation in survival to about 85 years is determined by genetic variation. However, the existence of rare families demonstrating remarkable clustering for extreme ages, the increased relative risks of survival amongst siblings of nonagenarians and of centenarians, the fact that children of centenarians experience a marked delay in agerelated diseases, and the similarity of centenarians' lifestyles to the general population, all argue that genetic factors play a much stronger role in living 25～35 years beyond the mid-eighties. Impressively, siblings of centenarians born in 1900 have a relative risk of living nearly 100 years that is 8 (females) to 17 times (males) greater than that for the average of their birth cohort. The rarity of the trait —only 1 centenarian amongst approximately 5,000 people in the US and only 1 supercentenarian (age 110+ years) amongst seven million people— places exceptional longevity in a very different category from both average life expectancy and common complex traits associated with aging.

Based upon the hypothesis that exceptionally old individuals are carriers of multiple genetic variants that influence human lifespan, we conducted a genomewide association study (GWAS) of centenarians. We began with a traditional one SNP at a time analysis to identify SNPs that are individually associated with exceptional longevity. We then used a novel approach to build a family of genetic risk models based on Bayes rule which, while taking into account the simultaneous influence of many genetic variants, can accurately discriminate between subjects with average versus exceptional longevity. Next, we used this family of models to construct subject-specific genetic risk profiles that, by cluster analysis, can be used to discover sub-phenotypes of exceptional longevity that are characterized by different genetic signatures.

據美國物理學家組織網2月2日（北京時間）報道，來自IBM、蘇黎世理工學院和美國普渡大學的工程師近日表示，他們構建出了首個10納米以下的碳納米管（CNT）晶體管，而這種尺寸正是未來十年計算技術所需的。這種微型晶體管能有效控制電流，在極低的工作電壓下，仍能保持出眾的電流密度，甚至可超過同尺寸性能最好的硅晶體管的表現。相關研究報告發表在最新一期的《納米快報》雜志上。

很多科研小組都致力研

首個10納米以下碳納米管晶體管問世

發小尺寸的晶體管，以切合未來計算技術對于更小、更密集的集成電路的需要。但現有的硅基晶體管一旦尺寸縮小，就會失去有效控制電流的能力，即產生所謂的“短溝道效應”。

在新研究中，科研人員舍棄硅改用單壁碳納米管進行實驗。碳納米管具有出色的電氣性能和僅為直徑1納米至2納米的超薄“身軀”，這使其在極短的通道長度內也能保持對電流的閘門控制，避免“短溝道效應”的生成。而IBM團隊研制的10納米以下碳納米管晶體管首次證明了這些優勢。

科學家表示，理論曾預測超薄的碳納米管將失去對于電流的閘門控制，或減少輸出時的漏極電流飽和，而這都會導致性能的降低。此次研究的最大意義在于，證明了10納米以下的碳納米管晶體管也能表現良好，且優于同等長度性能最佳的硅基晶體管，這標志著碳納米管可成為規?；a晶體管的可行備選。

工程師在同一個納米管上制造出若干個獨立的晶體管，其中最小一個的通道長度僅為9納米，而這個晶體管也表現出了極好的轉換行為和漏極電流飽和，打破了理論的預言。當與性能最佳，但設計和直徑不同的10納米以下硅基晶體管進行對比時，9納米的碳納米管晶體管具有的直徑歸一化（漏）電流密度，可達到硅晶體管的4倍以上。而且其所處的工作電壓僅為0.5伏，這對于降低能耗十分重要。此外，超薄碳納米管晶體管的極高效能也顯示出了其在未來計算技術中大規模使用的潛力。

Engineers build first sub-10-nm carbon nanotube transistor

Engineers have built the first carbon nanotube (CNT) transistor with a channel length below 10 nm, a size that is considered a requirement for computing technology in the next decade. Not only can the tiny transistor sufficiently control current, it does so significantly better than predicted by theory. It even outperforms the best competing silicon transistors at this scale, demonstrating a superior current density at a very low operating voltage.

The engineers, from the IBM T.J. Watson Research Center in Yorktown Heights, New York; ETH Zurich in Zurich, Switzerland; and Purdue University in West Lafayette, Indiana, have published their study on the first sub-10-nm CNT transistor in a recent issue of Nano Letters.

Many research groups are working on reducing the size of transistors in order to meet the requirements of future computing technology for smaller, denser integrated circuits. When today’s transistors (silicon metal-oxidesemiconductor field-effect transistors, or Si MOS-FETs) are shrunk, they lose their ability to effectively control electric current, a problem called short-channel effects. For this reason, researchers have been modifying the Si MOSFET design in an attempt to make the transistor perform better at sub-10-nm gate lengths, but these devices still face performance challenges.

In the new study, the engineers have discarded silicon altogether and turned to singlewalled CNTs. Due to their superior electrical properties and ultrathin (1～2-nm diameter) bodies, CNTs have been proposed as a replacement for silicon for several years. Their ultrathin bodies should allow CNTs to maintain gate control of the current in a transistor even at short channel lengths, potentially enabling them to avoid shortchannel effects. The IBM team’s sub-10-nm CNT transistor is the first to demonstrate these advantages.

“The greatest significance of this work is in the demonstration that carbon nanotube transistors can not only perform well at sub-10-nm lengths, but that their performance is better than the best-reported Si-based transistors at similar lengths,” IBM researcher Aaron Franklin told PhysOrg.com.“For years it has been known that scaling bulk silicon devices would be extremely challenging, if not impossible, when lengths close in on 10～15 nm….The superb low voltage performance of this scaled carbon nanotube transistor is a sign post showing that there is a demonstrable alternative for extremely scaled transistors.”

Until the engineers built the sub-10-nm CNT transistor, no one knew that they would perform this well. Theories predicted that CNTs with ultrathin channels would experience a loss of gate control as well as a loss of drain current saturation in the output, both of which would degrade performance.

“The reason that theory projected a loss of gate control for nanotube transistors below 15 nm or so (despite their being extremely thin) is related to other unique transport physics for nanotube devices,” Franklin said. “Namely, the carrier effective masses (mass of electrons) are very small for nanotubes compared to other semiconductors, meaning they can tunnel or leak in the device more easily. This is one of the reasons that theories had suggested a loss of gate control, because these 'light' carriers would begin tunneling uncontrollably when the lengths became too small. In the paper, we show that the reason for this discrepancy is largely due to insufficient physics models for transport at the nanotube-metal contacts – previous models mostly ignore what could be happening with electrons getting through the metal-nanotube junction.”

When the engineers fabricated several individual transistors on the same nanotube, the smallest having a channel length of just 9 nm, they observed that the tiniest transistor exhibited superb switching behavior and drain current saturation, defying predictions. When compared to the best-performing sub-10-nm Si transistors of varying designs and diameters, the 9-nm CNT transistor had a diameter-normalized current density of more than four times that of the best silicon transistor. And it exhibited this impressive current density at a low operating voltage (0.5 volts), which is important for reducing power consumption.

The researchers predict that theoretical models can be improved by focusing more on the transport between the metal contacts and CNT. They also think that the highperforming 9-nm CNT transistors demonstrate the potential for using CNT transistors in tomorrow’s computing technology.

“The chief implication is that carbon nanotubes are still worth consideration for a future scaled transistor technology,” Franklin said.“What is often not realized by those outside the field is that carbon nanotube transistors are essentially the only non-silicon devices that have experimentally been shown to have promise in extremely scaled transistors. There are many devices promoted by theory, or demonstrated in larger device structures, but none have been able to show the level of research bench-top performance that nanotubes have. Now, that said, it should be noted that there are challenges ahead before anyone will see an integrated transistor solution from nanotubes. But, to date, nothing related to nanotube transistors has been shown to be fundamentally impossible to solve, from placement of nanotubes in precise locations to the complete separation of metallic and semiconducting nanotubes.”

Genetic Signatures of Exceptional Longevity in Humans