bluuebunny/crossref_metadata_2025 huggingface dataset:
Leonard Rotherham CBE. 31 August 1913 – 23 March 2001
Authors: Quayle J. Rodney , Greenwood Geoffrey W.
Published: December 2006

Leonard Rotherham was born in Sutton-in-Ashfield, near Nottingham, on 31 August 1913 and his early life went through difficult times. His father, Bernard Rotherham, who left school at the age of 13, first became a coalminer, and later started a small haulage business with two lorries and a bus with solid tyres. The business prospered for a while but was sold up during the recession and his father returned to coal mining at the Welbeck colliery. Leonard's mother, Jane Rotherham, died when he was 10 years old; his father felt unable to look after his son and sent him to live with an aunt, Mrs Rhoda Page, who also had four sons of her own. By all accounts, Mrs Page was an inspirational woman, although the family lived on a poor farm with very little money. However, Leonard went to the Crich Church of England primary school, where he attracted the interest and support of the headmaster, a Mr Haywood; this marked a turning point for him. From this school Leonard won a scholarship to The Herbert Strutt School in Belper, Derbyshire. This school was founded in the name of a famous family, for Jedediah Strutt was once a partner of Richard Arkwright's; together they established the first cotton mill in Nottingham. At this school he met Nora Mary Thompson, whom he would marry in 1937. From here he won a scholarship from the Nottingham branch of the newly formed Mineworkers Union, a Derby County Major Scholarship, as well as a State Scholarship. With this combined support, he gained a place at University College London, where, in 1934, he obtained a first-class honours degree in physics with subsidiary mathematics. A year later he received an MSc from the same institution for research on the viscosity of liquids performed under the supervision of Professor E.N. da C. Andrade (FRS 1935). Following his decision to undertake research in industry, Rotherham joined the large steelmaking company Firth–Brown in Sheffield in 1935. He was appointed as a physicist in the research department under the direction of Dr William H. Hatfield (FRS 1935), who was Head of the Brown–Firth Research Laboratories. Their name was peculiarly reversed from that of the company, although they were totally integrated within it.
Dame Sheila Patricia Violet Sherlock. 31 March 1918 – 30 December 2001 Elected FRS 2001
Authors: Pepys Mark
Published: December 2006

Dame Sheila Patricia Violet Beckett Sherlock was the world's leading female physicianscientist of the twentieth century. Her brilliant, wide-ranging, original contributions to the investigation, diagnosis, classification, epidemiology, pathogenesis and management of liver disease played a leading role in the establishment of hepatology as a medical specialty. Her rigorous, highly focused, studies combined experimental and laboratory investigations with meticulous clinical observation, encompassed most aspects of liver function, disease and treatment, and led directly to enormous benefit for millions of patients. Her remarkable individual personality also had a profound influence not only on her medical and scientific specialty but also on several generations of physicians throughout the world. She was the first female professor of medicine and head of a department of medicine in the UK, and the pioneer of women in modern medicine. The importance of her contributions to knowledge and her massive influence on training in and the practice of medicine related to liver disease were recognized by a glittering array of honours and awards from professional societies and academic institutions throughout the world, including 19 honorary degrees, and, very belatedly, election to Fellowship of The Royal Society in the last year of her life.
Thomas Stevens Stevens. 8 October 1900 – 13 November 2000
Authors: Haslam Edwin , Morris David G.
Published: December 2006

Born at Renfrew on 8 October 1900, Thomas Stevens Stevens (‘TSS’) was the only child of John and Jane Stevens. His father, a draughtsman and engineer, was production director of William Simons and Company Ltd of Renfrew, shipbuilders specializing in dredger construction. Before her marriage in 1898, his mother Jane (née Irving) was a schoolteacher. His upbringing was typically middle-class, and both parents gave every encouragement for their son to study. However, as a delicate asthmatic youngster Tom's early education was given, until the age of eight, at home by his mother—a fact held by many to be responsible for the seeds that brought forth his great love of language and his sensitive and wide-ranging intellect. Thereafter he attended Paisley Grammar School (1909–15) and the Glasgow Academy (1915–17). At Paisley Grammar School his attention was drawn by Joseph Towers, a teacher of English, and at the Glasgow Academy he delighted in the sardonic humour of G.L. Moffatt, who taught mathematics. Physics and chemistry had nevertheless captured his imagination and in the Academy he enjoyed the extensive opportunities that were provided for practical chemistry. It was a love and a boyish enthusiasm that he retained and continued to practise throughout his professional career. In a popular lecture that he gave in the 1950s, ‘The anatomy of the chemist’, Tommy includes the account given by the famous American teacher, Ira Remsen, of the most impressive experiment he had ever performed: ‘nitric acid acts upon copper’. The story ends, ‘… I drew my fingers across my trousers and another fact was discovered. Nitric acid acts on trousers…’. With its smells, fizzes and bangs it is surely a portrait of the young Stevens himself.
Rosa Susan Penelope Beddington. 23 March 1956 – 18 May 2001
Authors: Rastan Sohaila , Robertson Elizabeth
Published: December 2006

A summary of the life of the developmental biologist Rosa Susan Penelope Beddington reads: born in Hurstbourne Tarrant, Hampshire, 23 March 1956; Research Fellow, Lister Institute for Preventive Medicine, Oxford, 1983–88; research scientist, ICRF, Oxford, 1988–91; Senior Research Fellow, Centre for Genome Research, Edinburgh, 1991–93; Head, Division of Mammalian Development, MRC National Institute for Medical Research, 1993–2001; married Rev. Robin Denniston 1987; died in Great Tew, Oxfordshire, 18 May 2001.
Rupert Everett Billingham. 15 October 1921 – 16 November 2002
Authors: Brent Leslie Baruch
Published: December 2006

Rupert Billingham, known as Bill by his family, friends and professional colleagues, was a biologist whose outstanding experimental flair was sharply focused on the fields of transplantation immunology and the mysteriously intimate relationship between the mammalian mother and her foetus. Having entered these fields of study at a time when they were poorly understood, he made numerous fundamental contributions to our modern knowledge of the mechanisms of graft rejection and how to prevent it, and he analysed some of the mechanisms responsible for the survival of the mammalian foetus in an immunologically hostile environment. He was without doubt one of the true pioneers.
Bertram Neville Brockhouse. 15 July 1918 – 13 October 2003
Authors: Cowley Roger
Published: December 2006

Bertram Neville Brockhouse was born on 15 July 1918 in Lethbridge, Alberta, Canada. His grandfather was a miner who emigrated to North America from England. He became active in a strike to unionize the mines and to protest against the poor working conditions; as a result he had to leave mining. He then, with his son, Israel Bertram Brockhouse, went homesteading in Southern Alberta with a small farm and domestic animals, where his son married Mabel Emily Brockhouse (née Neville), who had grown up in Illinois and belonged to a family of English Americans. They had a family of four, the eldest of whom was Bertram Neville, known to his friends and family as Bert. He had a sister, Alice, and two younger brothers, Robert, who died in infancy, and Gordon, who became a civil engineer for the railroad. The homestead was on the Milk River close to the Canada–USA border and the local school was a one–room elementary school a couple of miles from the farm. Bert was a nominal attendee at this school but did not remember learning to read or to do simple arithmetic there.
Geoffrey Bertram Robert Feilden CBE. 20 February 1917 – 1 May 2004
Authors: Bray Kelvin , Moulton Alexander
Published: December 2006

Bob Feilden will be remembered by scientists and engineers around the world for his innovative work on industrial gas turbines which became, in the Ruston Type TAgas turbine, a prime mover of choice for all those who wanted high reliability and automatic or remote operation.
Gordon Lowe. 31 May 1933 – 6 August 2003
Authors: Stirling C. J. M.
Published: December 2006

Gordon Lowe made major contributions to the understanding of the mechanisms of enzyme action, pioneering the use in particular of novel isotopically chiral phosphate and sulphate esters. In the latter part of his scientific work he discovered new peptide nucleic acids, probed the interaction of platinum complexes with enzymes, leading to potential new antimalarial drugs, and discovered, by combinatorial methods, effective active–site enzyme inhibitors.
Walter Thomas James Morgan CBE. 5 October 1900 – 10 February 2003
Authors: Watkins Winifred M. , Bagshawe Kenneth D.
Published: December 2006

Walter Morgan's long and distinguished career followed modest beginnings in Islington, where he was born the second child of Walter Morgan and Anne Edith Morgan (
née
James). To his children he recalled the street gas lamp lighters and the ‘knockers–up’ who tapped on workers’ bedroom windows with a long pole before alarm clocks were generally used. In some autobiographical notes he recalled his paternal grandfather who was a ‘Tipstaff’ for the Royal Courts of Justice and whose job was to take into custody nobility and persons ‘illustrious by rank’ when ordered to do so by a Judge of the High Court. On his maternal side an uncle became a chemist specializing in oils and fats who eventually spent most of his life in Borneo, where he discovered a vegetable poison that resulted in the development of the insecticide pyrethrum.
Henton Morrogh CBE FRS FREng. 29 September 1917 – 20 September 2003
Authors: Evans E. Raymond
Published: December 2006

Henton Morrogh devoted the whole of his working life to the study of cast iron, its structure, properties, applications and aspects of its production. He was particularly responsible for the development of techniques for preparing microspecimens to a state of perfection, which enabled him to study the morphology of the graphite phase, and he played a major role in the development of the revolutionary as–cast spheroidal graphite irons.He progressed from apprenticeship with British Cast Iron Research Association (BCIRA) to becoming its Director and was primarily responsible for the success of this Association and in establishing its worldwide reputation. He was a modest man, generous in the encouragement of his staff to perform research and to apply the results to the benefit of the iron founding industry. In short, it could be said that Henton Morrogh was the BCIRA and the BCIRA was Henton Morrogh–such was his unique character.
John Robert Philip. 18 January 1927 – 26 June 1999
Authors: Smiles David
Published: December 2006

John Philip was struck by a car and killed on Saturday 26 June 1999 in Amsterdam, where he was visiting the Centre for Mathematics and Information Science. He was a Fellow of the Royal Society, a Fellow of the Australian Academy of Science, a Fellow of the American Geophysical Union, a Foreign Member of the All–Union (later Russian) Academy of Agricultural Sciences, and only the second Australian Foreign Associate of the US National Academy of Engineering. He was the first non–American recipient of the Robert E. Horton Medal, the highest award for hydrology of the American Geophysical Union. In 1998 he was made an Officer of the Order of Australia for ‘service to the science of hydrology, to scientific communication in promoting the interests of science for the community, and to Australian culture through architecture and literature’.This memoir discusses John Philip's character and his work as Australia's most distinguished environmental physicist. It also explores his management of science as well as his poetry and his fascination with architecture.
David Shoenberg. 4 January 1911 — 10 March 2004
Authors: Pippard Sir Brian
Published: December 2006

David Shoenberg was the last surviving pioneer of British low-temperature physics, having outlived Nicholas Kurti FRS, who died at the age of 90 in 1988, and J. S. (Jack) Allen, who was nearly 93 when he died in 2001. At the time they began work, before World War II, liquid helium was a rare commodity. In England it was made first in Oxford (1933), with Cambridge following a year later; L. C. Jackson in Bristol could liquefy hydrogen, which was used occasionally to prime a small helium liquefier. Before the outbreak of war halted academic research, all three centres had made significant discoveries in magnetism, superconductivity and superfluidity. P. L. Kapitza's expansion engine regularly supplied liquid helium for Cambridge and, on a few occasions, the other two; it was the forerunner of S. C. Collins's design of commercial liquefier, which, with generous postwar government support for research, made the USA the most prolific performer in low-temperature physics. But the English laboratories built on their prewar distinction and were soon active once more after 1945, with Shoenberg a leading figure. The work he initiated, particularly on the de Haas–van Alphen effect, has continued to spread across the world and into realms of thought he never contemplated in his active years.
Marthe Louise Vogt. 8 September 1903 — 9 September 2003
Authors: Cuthbert Alan W.
Published: December 2006

Marthe Vogt was one of the leading neuroscientists of the twentieth century, with her research career spanning more than 50 years. Marthe's legacy cannot be judged only by what she was able to accomplish herself but by the impetus she gave to all those who followed to revolutionize the treatment of mental illness.
Basil Charles Leicester Weedon. 18 July 1923 — 10 October 2003
Authors: Pattenden Gerald
Published: December 2006

Basil Charles Leicester Weedon, ‘Prof’ to his chemistry colleagues but ‘Jimmy’ to his friends and family, died on 10 October 2003. He had two distinct careers, the first as Professor of Organic Chemistry at Queen Mary College, London, over the period 1960–76, and the second as Vice-Chancellor of Nottingham University from 1976 to 1988.
Sir Michael Francis Addison Woodruff. 3 April 1911 – 10 March 2001
Authors: Morris Peter
Published: December 2006

Michael Woodruff, one of the pioneers in transplantation, performed the first successful kidney transplant in the UK in 1960. But in addition he was a true surgeon scientist, who made many major contributions to transplantation biology. These included studies of the immunosuppressive activities and mechanisms of action of antilymphocyte sera, tolerance induction and mechanisms of tissue allograft rejection. He was a lateral thinker, a trait he displayed from his earliest days, and not least during his three and a half years as a prisoner of war in the notorious Japanese prisoner–of–war camp at Changi.
Darwin's illness: a final diagnosis
Authors: Orrego Fernando , Quintana Carlos
Published: December 2006

We have re-examined many of the abundant publications on the illness that afflicted Charles Darwin during most of his life, including some of the 416 health-related letters in his correspondence, as well as his autobiographical writings. We have concluded that he suffered from Crohn's disease, located mainly in his upper small intestine. This explains his upper abdominal pain, his flatulence and vomiting, as well as his articular and neurological symptoms, his ‘extreme fatigue’, low fever and especially the chronic, relapsing course of his illness that evolved in bouts, did not affect his life expectancy and decreased with old age, and also the time of life at which it started. It apparently does not explain, however, many of his cutaneous symptoms. We do not support other diagnoses such as Chagas' disease, lactose intolerance or the many psychiatric conditions that have been postulated.
Stochastic Spatial Models: A User's Guide to Ecological Applications
Authors: Durrett Richard , Levin Simon A.
Published: December 2006

Spatial pattern, how it arises and how it is maintained, are central foci for ecological theory. In recent years, some attention has shifted from continuum models to spatially discrete analogues, which allow easy treatment of local stochastic effects and of non-local spatial influences. Many of these fall within the area of mathematics known as `interacting particle systems', which provides a body of results that facilitate the interpretation of the suite of simulation models that have been considered, and point towards future analyses. In this paper we review the basic mathematical literature. Three influential examples from the ecological literature are considered and placed within the general framework, which is shown to be a powerful one for the study of spatial ecological interactions.
Micromechanical resonators and filters for microelectromechanical system applications
Authors: Motiee Mehrnaz , Mansour Raafat R. , Khajepour Amir
Published: December 2006

Microelectromechanical system (MEMS) based mechanical resonators and filters have shown promising characteristics in achieving high Q values and good stability. In this article, new designs for integrated circuit–compatible microelectromechanical intermediate frequency (IF) filters are introduced. These filters have been fabricated and tested, and experimental results are included in this work. One of the novel filters is composed of two-cantilever beam resonators coupled by a soft flexural-mode beam. Different configurations of these filters and their (RF) simulation and experimental responses are presented. One of the advantages of these filters is that the coupling elements can be added from more than one side in order to have elliptical responses. The authors also introduce a novel V-shape coupling element that is used to mechanically couple two clamped-clamped MEMS resonators laterally. The stiffness of the proposed V-shape coupling element is adjustable via changing the length of the V sidelines and/or the V conjunction angle to flatten the filter passband. A two-pole bandpass filter operating in the IF range is constructed using these coupling elements. A lumped modeling approach is presented for a fast and accurate filter design and optimization. Using finite element analysis, the validity and accuracy of the lumped model are investigated. The fabricated filters have center frequencies varying from 700kHzto1.7MHz, with quality factors of 300–1500 when tested at ambient pressure. The experimental results are presented and compared with lumped and finite element simulation results.
On the use of alloying elements for Cu interconnect applications
Authors: Barmak K. , Cabral C. , Rodbell K. P. , Harper J. M. E.
Published: December 2006

To address the future use of alloying elements for Cu interconnect applications in integrated circuits, first, available bulk experimental data such as residual resistivity per at. % solute and binary phase diagrams are used to arrive at a set of 24 potential elements. Next, experimental results in thin films and lines allow the authors to arrive at a smaller set that includes ten elements, namely, Pd, Au, Al, Ag, Nb, Cr, B, Ti, In, and Mn, with higher priority and six, namely, Zn, V, C, Mg, P, and Sn with lower priority for further studies. These additional studies are needed before a strong case for or against alloying additions to Cu can be made. The available thin film and line data are summarized in a series of tables that should prove useful for the readers. In particular, the thin film data allow the authors to obtain an effective average residual resistivity (EARR) per at. % solute that combines the effects of impurity scattering, second phase precipitates, and grain size refinement resulting from solute additions.
Metal-insulator-metal capacitors using atomic-layer-deposited Al2O3∕HfO2∕Al2O3 sandwiched dielectrics for wireless communications
Authors: Ding Shi-Jin , Huang Yu-Jian , Li Yanbo , Zhang D. W. , Zhu C. , Li M.-F.
Published: December 2006

High density metal-insulator-metal (MIM) capacitors are required for radio frequency and analog/mixed-signal integration circuit applications. In this article, high permittivity Al2O3∕HfO2∕Al2O3 (AHA) dielectrics have been evaluated in comparison with HfO2 using atomic layer deposition technique for MIM capacitor applications. The results indicate that the AHA dielectrics exhibit electrical performance superior to the HfO2 dielectric while retaining similar capacitance density. With respect to 2nm individual Al2O3 barriers, the MIM capacitor can offer a capacitance density of 2.6fF∕μm2, voltage coefficients of capacitance of 71ppm∕V2 and 9ppm∕V, a leakage current as low as 3×10−9A∕cm2 at 1MV∕cm and 125°C, an operating voltage of around 3V for a ten-year lifetime at 125°C in terms of 50% failure.
Mechanical characteristics and applications of diamondlike-carbon cantilevers fabricated by focused-ion-beam chemical vapor deposition
Authors: Igaki Jun-ya , Nakamatsu Ken-ichiro , Kometani Reo , Kanda Kazuhiro , Haruyama Yuichi , Kaito Takashi , Matsui Shinji
Published: December 2006

Diamondlike-carbon (DLC) cantilevers were fabricated with a commercially available focused-ion-beam chemical-vapor-deposition (FIB-CVD) system using a beam of 30keV Ga+ ions, and the mechanical characteristics of the cantilevers were measured. Vibration frequency of the cantilevers was passively measured using scanning electron microscopy. Resonant frequency of DLC cantilevers fabricated at 0.1–0.5pA beam current was found to be constant. The equivalent spring constant of the cantilevers was identified by squeezing the tip of a Si3N4 cantilever and a DLC cantilever together. Using the measured displacement, the spring constant of the DLC cantilever was calculated as (1.1±0.2)×10−2N∕m. Furthermore, Young’s modulus and the density of the DLC cantilevers were measured to be 187±32GPa and (3.8±0.7)×103kg∕m3, respectively. The DLC cantilevers were used as mass sensors in an ultrasensitive sensing application. A small amount of DLC was deposited on the tip of a DLC cantilever as a mass adhesion by FIB-CVD at 0.5pA beam current. As a result, the authors were able to measure a small amount of mass shift in the femtogram range using a DLC cantilever.
Characterization and operation of a mechanically actuated silicon microgripper
Authors: Blideran Marius M. , Fleischer Monika , Henschel Wolfgang , Kern Dieter P. , Sterr Jochen , Schock Klaus , Kleindiek Stephan , Langer Matthias G. , Löffler Karsten , Grauvogel Francois
Published: December 2006

Since the manipulation of biological objects is usually performed in a life-sustaining environment, electrical fields or thermal gradients through the liquid may cause perturbations. The authors present a microgripper fabricated in silicon by a combination of bulk and surface micromachining processes that exhibits several advantages compared to previous reports. In order to avoid any possible perturbation caused by electrical fields, their microgripper is mechanically actuated. The complete system including the microgripper, a piezoactuator, and a nanomanipulator is described in detail together with manipulation of micrometer sized glass spheres.
Process optimization and proximity effect correction for gray scale e-beam lithography
Authors: Murali Raghunath , Brown Devin K. , Martin Kevin P. , Meindl James D.
Published: December 2006

Three-dimensional microstructures find applications in diffractive optical elements, photonic elements, etc., and can be efficiently fabricated by e-beam lithography. Good process control and efficient proximity effect correction are important for achieving the desired structures. With polymethylmethacrylate as the resist, a process optimization of different develop conditions is carried out to identify a process that is most conductive to gray scale features. A novel proximity effect correction scheme called effective dose-depth (EDD) method is proposed. Using the EDD method for grating design and the optimized process, blazed gratings have been fabricated with excellent uniformity and low surface roughness.
Direct die-to-database electron beam inspection of fused silica imprint templates
Authors: Resnick D. J. , Myron L. J. , Thompson E. , Hasebe T. , Tokumoto T. , Yan C. , Yamamoto M. , Wakamori H. , Inoue M. , Ainley Eric , Nordquist Kevin J. , Dauksher William J.
Published: December 2006

Imprint lithography has been included on the ITRS Lithography Roadmap at the 32 and 22nm nodes. Step and flash imprint lithography (S-FIL™) is a unique method for printing sub-100-nm geometries. Relative to other imprinting processes S-FIL has the advantage that the template is transparent, thereby facilitating conventional overlay techniques. Further, S-FIL provides sub-100-nm feature resolution without the significant expense of multielement, high quality projection optics or advanced illumination sources. However, since the technology is 1X, it is critical to address the infrastructure associated with the fabrication of templates. With respect to inspection, although defects as small as 70nm have been detected using optical techniques, it is clear that it will be necessary to take advantage of the resolution capabilities of electron beam inspection techniques. This article reports the first systematic study of die-to-database electron beam inspection of patterns that were imprinted using an Imprio 250 system. The die-to-database inspection of the wafers was performed on an NGR2100 inspection system. Metal 1 and logic patterns with dimensions as small as 70nm were inspected. Using a pixel address of 3nm and a defect threshold of 20nm, problem areas in the design of the pattern layout were clearly identified. Ultimately, the most desirable solution is to directly inspect the fused silica template. This article also reports the results on the first experiments of direct inspection fused silica substrates at data rates of 200MHz.
Impact of stray light depending on image quality: An approximation using total integrated scatter
Authors: Kim Young-Chang , De Bisschop Peter , Vandenberghe Geert , Van Den Hove Luc , Cho Hanku , Moon Jootae
Published: December 2006

Stray light (or flare) in optical microlithography causes critical dimension (CD) variation depending on local mask transmission. This CD change can be approximately estimated using image quality and total integrated scatter (TIS) which is defined as the integral of stray-light characteristic function, power spectral density. This TIS approximation is experimentally verified for various features on ArF lithographic processes and is particularly useful for determination of tool specification for a given application.
Electron beam lithography for magnetic recording heads: Characterization and optimization of critical components
Authors: Yang XiaoMin , Zhou Jianyun , Xiao Shuaigang , Mountfield Keith
Published: December 2006

Electron beam lithography has been implemented with a chemically amplified negative tone NEB-31 resist to fabricate the write top pole and read sensors for magnetic recording. To better understand the proximity effect and optimize these two critical components in electron beam patterning, Monte Carlo simulation with SELID software has been employed to characterize the energy distribution of the write top pole structure and simulate the resist profile in the break point (BP) region. To obtain a sharp BP angle and a pole area that has a uniform and narrow pole width, the authors have optimized the computer-aided design and the yoke/pole dose ratios based on their simulation results. The authors have also experimentally verified these results with NEB-31 resist. In addition, the electron backscattering effect from the relevant metallic underlayers, such as NiFe and Ta of varying thickness on the top pole critical dimension as a function of BP angle was simulated and analyzed. Experiments were conducted to verify the simulation results, and both are in good agreement.
Helium ion microscope: A new tool for nanoscale microscopy and metrology
Authors: Ward B. W. , Notte John A. , Economou N. P.
Published: December 2006

ALIS Corporation has developed a new helium ion microscope which has many advantages over both traditional scanning electron microscopes (SEMs) and focused ion beams (FIBs). This new technology is expected to produce an ultimate focused spot size of 0.25nm. This high resolution is attributed to the high source brightness (B>4×109A∕cm2sr), low energy spread (ΔE∕E∼2×10−5), and small diffraction effects (λ∼80fm). The interaction of helium ions with matter offers several valuable contrast mechanisms and a surface interaction volume which is much smaller than a SEM or conventional FIB.
Chemically responsive molecular transistors fabricated by self-aligned lithography and chemical self-assembly
Authors: Tang J. , Wang Y. , Nuckolls C. , Wind S. J.
Published: December 2006

The authors present the fabrication and characterization of molecular transistors comprising at most a small number of molecules, which display a distinct chemical function. The fabrication involves a self-aligned technique capable of patterning metal electrodes with interelectrode separations of ∼2nm with very high yield. The electrodes are bridged by molecules with a metal-ion core which can be inserted by in situ designed chemical reaction. The presence or absence of the ion modulates the electrical conductance of the device.
Epoxy-containing ArF resists with narrow molecular weight distribution
Authors: Shirai Masamitsu , Manabe Makoto , Tsuji Shou , Itani Toshiro
Published: December 2006

Terpolymers consisting of γ-butyrolactone-2-yl methacrylate, 2-methyl-2-adamantyl methacrylate, and 1-methyl-1-(6-methyl-7-oxabicyclo[4,1,0]hept-3-yl)ethyl methacrylate were prepared by the reversible addition-fragmentation chain transfer polymerization technique. The molecular weight distribution of the polymers was 1.29–1.39. Although the polymers have epoxy units and cross-linking of the polymer occurred during prebake treatment, they worked as a highly sensitive positive-tone resist. The cross-linking efficiency of the resist was dependent on the type of amines used as a quencher. The line edge roughness values were dependent on the prebake temperature.
Focused ion beam fabrication of two dimensional photonic crystals in silicon-on-insulator
Authors: Balasubramanian K. , Heard P. J. , Cryan M. J.
Published: December 2006

This article presents results for the optical characterization of two-dimensional photonic crystals (PhCs) in silicon-on-insulator fabricated using focused ion beam (FIB) etching. A detailed description of fabrication techniques is given and the use of gas assisted etching for large area etches is outlined. The optical characterization shows PhC band edges at the expected wavelengths but with reduced depth. Three dimensional finite difference time domain modeling is used to investigate this discrepancy and this suggests that reduced sidewall verticality is not critical in this strong vertical guiding regime. Other possible explanations for reduced band edge depth are discussed including gallium implantation and FIB induced optical damage.
Direct correlation of negative magnetoresistance with concentrations of localized holes in Be delta-doped GaAs structures
Authors: Noh J. P. , Iwasaki S. , Jung D. W. , Touhidul Islam A. Z. M. , Otsuka N.
Published: December 2006

The origin of negative magnetoresistance of GaAs structures with a pair of Be and Si delta-doped layers is investigated with samples in which Be and Si doping concentrations are selectively varied. Magnitudes of negative magnetoresistance are directly correlated to concentrations of localized holes in these samples, suggesting that the negative magnetoresistance results from scattering of carriers by spins associated with these localized holes. The temperature dependence of magnetoresistance curves of the samples which exhibit large negative magnetoresistance is described by the Brillouin function with the Landé g factor and total angular momentum J whose values are expected for a localized hole in GaAs.
In
As
∕
Al
Sb
high-electron-mobility transistors by molecular-beam epitaxy for low-power applications
Authors: Lange M. D. , Tsai R. S. , Deal W. R. , Nam P. S. , Lee L. J. , Sandhu R. S. , Hsing R. , Poust B. D. , Kraus J. L. , Gutierrez-Aitken A. L. , Bennett B. R. , Boos J. B. , Noori A. M. , Hayashi S. L. , Goorsky M. S.
Published: December 2006

In As ∕ Al Sb high-electron-mobility transistor technology has transitioned from research to development stages in recent years. Development efforts at Northrop Grumman Space Technology, in collaboration with the Naval Research Laboratory and the University of California, Los Angeles, have focused on X-band and W-band low-noise amplifier monolithic millimeter-wave integrated circuits fabricated for applications requiring ultralow-power dissipation. The materials for the circuits discussed in this article were grown at Northrop Grumman Space Technology on 3-in.-diameter semi-insulating GaAs substrates by molecular-beam epitaxy. Atomic-force microscopy of the as-grown surface on each wafer showed that the rms roughness for all of the wafers ranged between 0.5 and 3.5nm, and this range of roughness was fully compatible with the fabrication process. The high electron mobility that InAs can provide was achieved reproducibly in these materials. It was maintained almost always above 25000cm2V−1s−1, and in several cases even exceeded 30000cm2V−1s−1. The associated electron sheet concentration ranged between 1.2×1012 and 1.8×1012cm−2. These combined mobilities and sheet concentrations gave corresponding sheet resistances in the range of 170±40Ω∕sq, with nonuniformity below 6% over these 3-in.-diameter wafers. These materials characteristics enabled successful fabrication of several recently published X-band and W-band low-noise amplifier circuits, and figures of merit for the circuits that were made specifically from these materials are referenced in this article.
Epitaxial growth and strain relaxation of MgO thin films on Si grown by molecular beam epitaxy
Authors: Niu F. , Meier A. L. , Wessels B. W.
Published: December 2006

High quality epitaxial MgO thin films have been grown on Si (001) wafers by molecular beam epitaxy using SrTiO3 (STO) as a buffer layer. The STO buffer layer reduces both the large lattice mismatch of 23% and the large thermal mismatch of 520% between MgO and Si. X-ray diffraction (XRD) measurements indicate that the MgO film grown on the STO buffered Si is epitaxial with MgO (002)‖Si (004) and MgO [110]‖Si [002]. The full width at half maximum (FWHM) of MgO (002) rocking curve width Δω is 0.30° (out-of-plane), and the FWHM of MgO (202) ϕ angle scan width Δϕ is 0.34° (in-plane) for a 155nm thick film. Strain relaxation and growth mechanisms of the MgO film on Si were studied by in situ reflection high-energy electron diffraction (RHEED) analysis in combination with XRD and atomic force microscopy. The results indicate that the MgO first forms a pseudomorphic wetting layer and subsequently undergoes a Stranski-Krastanov transition to form three-dimensional coherent islands to relieve misfit strain. A decrease in the width of the RHEED spots with increasing MgO thickness is observed that is attributed to reduction of coherency strain. A smooth surface redevelops once MgO growth continues, which is attributed to island coalescence.
Mobility and charge density tuning in double δ-doped pseudomorphic high-electron-mobility transistors grown by metal organic chemical vapor deposition
Authors: Lee Chong-Yi , Shiao Hung-Pin , Kuo Kuan-Chu , Wu Hsin-Yen , Lin Wen-Hsiang
Published: December 2006

In this article, the authors present mobility and charge density tuning for metal organic chemical vapor deposition (MOCVD)-grown double δ-doped pseudomorphic high-electron-mobility transistors (PHEMTs). Good epitaxial wafers were obtained by MOCVD as indicated by uniform and abrupt interfaces seen in measurements taken using a transmission electron microscope and two pronounced Si-δ-doped peaks in the secondary ion mass spectrometry analysis. The 1-μm-gate-length PHEMT device exhibited good dc performance with a threshold voltage of −1.34V, a maximum drain current of 570mA∕mm, and a maximum transconductance of 279mS∕mm. From the dependences of mobility and charge density between the δ-doping level and spacer layer thickness, most PHEMT design requirements in the ranges between 5750 and 7500cm2∕Vs (for mobility) and 2.4×1012 and 3.6×1012cm−2 (for charge density) can be satisfied.
Replication of diffractive-optical arrays via photocurable nanoimprint lithography
Authors: Galus Matthias D. , Moon Euclid , Smith Henry I. , Menon Rajesh
Published: December 2006

Photocurable nanoimprint lithography was used to replicate an array of Fresnel zone plates onto a SiO2 substrate. This array was transferred into the substrate and used for zone-plate-array lithography (ZPAL). The experimentally determined point-spread function showed good agreement with simulation. The authors also demonstrate the use of ZPAL as a tool for patterning and replicating diffractive optics.
Using laser-cooled atoms as a focused ion beam source
Authors: Hanssen J. L. , Dakin E. A. , McClelland J. J. , Jacka M.
Published: December 2006

The authors describe a new method for creating a high quality focused ion beam using laser-cooled neutral atoms in a magneto-optical trap as an ion source. They show that this new technique can provide spot resolutions and brightness values that are better than the state of the art in focused ion beams. The source can be used with a range of different ionic species and can be combined with laser cooling techniques to exert unprecedented control over the ion emission, for example, producing single ions “on demand.” The beam quality is a result of a high brightness and a narrow energy distribution, both of which stem from the cold temperature (≈100μK) of the atoms. The ions are produced by subjecting the cold neutral atoms to a photoionization laser, after which they become a compact source of nearly monoenergetic ions. With the application of a potential gradient, the ions form a beam that can be focused via standard ion optical techniques. They discuss estimations based on the initial size of the ion cloud and the energy distribution and show that the resulting beam has a low emittance.
Ultrafast patterning of nanoparticles by electrostatic lithography
Authors: Joo Jaebum , Moon SangJun , Jacobson Joseph M.
Published: December 2006

Electron beam lithography is one of the best tools for patterning nanostructures, but its usage is limited due to slow processing. To enhance the patterning speed, the authors used a low dose electron beam to generate a “latent” charge pattern image and then create a real pattern by attaching positively charged particles by electrospray. Hard baked 2.3μm thick polymethylmethacrylate substrates were irradiated with a 2keV electron beam with a dose of 50nC∕cm2. Positively charged silver nanoparticles were generated by an electrospray technique in which a nanoparticle solution mixed with hexane was sprayed through a 15μm diameter capillary tip with an applied potential of 4.5kV. Charged nanoparticles were deposited to the charge patterned sites by electrostatic attraction with a resolution of 0.7μm. This patterning approach, which we call “electrostatic lithography,” represents a speed increase of ∼20 times over standard fast electron beam resists that require typical doses of 1μC∕cm2. This approach may lead to a general capability for ultrafast patterning of nanomaterial building blocks including nanoparticles and nanotubes without requiring additional etching or other processing steps.
Pattern reconstruction of scanning electron microscope images using long-range content complexity analysis of the edge ridge signal
Authors: Feng Hanying , Ye Jun , Pease R. Fabian
Published: December 2006

Based on the observation that human visual system connects broken edge segments according to long-range pattern contents, the authors here describe a general methodology for pattern reconstruction from scanning electron microscope (SEM) based on intuitive conjectures of human intelligence. In particular, we formulate the problem of pattern reconstruction as a problem of minimizing an objective function, which includes the information of pattern complexity and template matching. This approach of objective function minimization is also consistent with the famous “Occam’s razor” principle. They then describe a potential objective function formulation, introduce implementations with acceptable computation complexity, and demonstrate reconstruction results on edge ridge signals extracted from real SEM images. This methodology can greatly improve the robustness of SEM image processing and has the potential to be applied to many other fields, such as computer vision and robust human voice detection as well as inspection of nanoscale structures in the SEM.
Deposition and patterning of diamondlike carbon as antiwear nanoimprint templates
Authors: Ramachandran S. , Tao L. , Lee T. H. , Sant S. , Overzet L. J. , Goeckner M. J. , Kim M. J. , Lee G. S. , Hu W.
Published: December 2006

In this work, antiwear nanoimprint templates were made by depositing and patterning diamondlike carbon (DLC) films on Si and quartz. A capacitively coupled plasma enhanced chemical vapor deposition (PECVD) system was configured to deposit 100nm–1μm thick DLC films on Si and quartz substrates. These films were characterized with Raman spectroscopy, electron energy loss spectroscopy, atomic force microscopy, nanoindentation, contact angle measurements, and optical transmission measurements. The rf power and pressure of the PECVD process were varied to obtain uniform coating of DLC films with smooth surface (∼0.2nm rms), low surface energy (∼40mJ∕m2), and high hardness (∼22GPa). The resulting films’ wear resistance is more than three times better than quartz. The DLC films were patterned by nanoimprint lithography using polymethylmethacrylate (PMMA) followed by CF4 plasma etch. Thermal nanoimprint tests with DLC templates were performed in PMMA. Atomic force microscopy measurements indicated excellent pattern-transfer fidelity and template-polymer separation.
Photoelectron emission studies in CsBr at 257nm
Authors: Maldonado Juan R. , Liu Zhi , Sun Yun , Pianetta Piero A. , Pease Fabian W.
Published: December 2006

Cs Br ∕ Cr photocathodes were found [J. R. Maldonado et al., J. Vac. Sci. Technol. B 22, 3025 (2004); J. R. Maldonado et al., Proc. SPIE 5520, 46 (2003)] to meet the requirements of a multielectron beam lithography system operating with a light energy of 4.8eV (257nm). The fact that photoemission was observed with a light energy below the reported 7.3eV band gap for CsBr was not understood. This article presents experimental results on the presence of intra-band-gap absorption sites (IBASs) in CsBr thin film photoelectron emitters, and presents a model based on IBAS to explain the observed photoelectron emission behavior at energies below band gap. A fluorescence band centered at 330nm with a full width at half maximum of about 0.34eV was observed in CsBr∕Cr samples under 257nm laser illumination, which can be attributed to IBAS and agrees well with previously obtained synchrotron photoelectron spectra [J. R. Maldonado et al., J. Vac. Sci. Technol. B 22, 3025 (2004)] from the valence band of CsBr films.
Electrical properties of fluorine-doped silicon-oxycarbide dielectric barrier for copper interconnect
Authors: Huang Chun-Chieh , Huang Jow-Lay , Wang Ying-Lang , Chang Juin-Jie
Published: December 2006

A fluorine-doped amorphous silicon-oxycarbide (SiCOF) dielectric barrier deposited by chemical vapor deposition system is used to replace nitrogen doped silicon carbide (SiCN) and silicon oxycarbide (SiCO) in the 45nm Cu-interconnect structure due to its low leakage current and dielectric constant. In this article, the low leakage current and dielectric constant of SiCOF mechanism are reported for the first time. The low leakage current of the SiCOF films is due to less trapped sites of electron transportation via Pool-Frenkel model than SiCO. The dangling and weak bonds such as Si–H and –CHx are eliminated by fluorine to form Si–F, and less charge will be trapped in the SiCOF film. A dielectric polarization model is proposed to explain the low dielectric constant of SiCOF. The elimination of molecule dipole is attributed to the incorporated fluorine atoms, which destroy the Si–O–Si tetrahedral network structures. A carrier injection model combined with the polarization is proposed to explain the flatband voltage (Vfb) shift of the C-V curves. The polarization is further verified by using thermal oxide under carbide films to reject the carrier injection from the silicon. At a high electrical field of 2MV∕cm, undoped SiCO has an obvious C-V hysteresis loop, but SiCOF does not. Both at low 1MV∕cm and high 2MV∕cm electric fields SiCOF had a lower C-V hysteresis loop and flatband voltage shift than undoped SiCO. The root causes of this phenomena are the unsaturated bonds in the film and the interface trap sites of SiCO(SiCOF)/silicon elimination. SiCOF is therefore a good candidate as a dielectric barrier for processes with a back end line requirement under 45nm.
Fabrication and characterization of high breakdown voltage AlGaN∕GaN heterojunction field effect transistors on sapphire substrates
Authors: Choi Y. C. , Pophristic M. , Peres B. , Spencer M. G. , Eastman L. F.
Published: December 2006

High-quality C-doped GaN buffers with a very low doping concentration were grown on 2in. c-plane sapphire substrates, and high-power AlGaN∕GaN heterojunction field effect transistors (HFETs) on sapphire substrates for high-power switching applications were fabricated using a self-align process. The fabricated devices with gate-drain spacing (Lgd) of 16μm exhibited a high breakdown voltage (BV) over 1100V and low specific on resistance (ARDS(on)) of 4.2mΩcm2, with no additional photolithography process for a field plate design. This result approaches the SiC theoretical limit and is a record achievement for GaN-based HFETs on sapphire substrates, to the best of our knowledge. Based on the investigation of the influence of Lgd on device characteristics, it was shown that Lgd had a strong effect on ARDS(on) and BV while no noticeable change in maximum transconductance (gm,max) and maximum drain current (IDS,max) was observed when Lgd was varied. The ARDS(on) of a device [1.5μm gate length (Lg)] with Lgd>7μm was mainly determined by the gate-drain channel resistance. For a device (1.5μmLg)with Lgd<7μm, on the other hand, the ARDS(on) should be optimized by considering other important resistance components. The measured BVs increased with Lgd, suggesting that the actual device breakdown was determined by the gate-drain breakdown. The trend of the BV-ARDS(on) performance showed a clearly linear relation, suggesting that the device performance is very predictable with the variation of Lgd. As a result, with improvements in the material quality of a GaN buffer on sapphire substrate, the off-state BV and ARDS(on) were all enhanced to the point that high-power AlGaN∕GaN HFETs on sapphire substrates are now strong competitors for high-power switching applications.
Electron cyclotron plasma etching damage investigated by InGaAs∕GaAs quantum well photoluminescence
Authors: Mestanza S. N. M. , Frateschi N. C.
Published: December 2006

Photoluminescence (PL) was used to study the damage of (100) GaAs surfaces exposed to BCl3∕Ar plasma generated by an electron cyclotron resonance system. With PL measurement of strained InGaAs∕GaAs quantum wells within the etched top GaAs layer, our analysis shows that this technique assesses damages to the structure not detected by atomic force microscopy and photoreflectance. A transport model is used to show a 100 times reduction in the Debye length for a 100nm layer underneath the etching surface.