Wednesday, June 15, 2011

The fine art of etching

They see more than the naked eye and could make traffic safer: miniaturized thermal imaging sensors. But they are difficult to manufacture on a commercial scale. Researchers have now developed a new system. On it, special micro-electromechanical systems can be produced – with the correct etching technique.

A winding country road. It is dark, and a thick ground fog has settled in. The driver of a car cautiously enters the next curve, when suddenly a caution lamp flashes – a fallen motorcycle rider lies on the street. Thanks to the intelligent assistant, the driver has been warned and is able to brake in time. Infrared cameras see more than the naked eye and could make traffic safer. Indeed, cameras are already used in certain applications – in the construction industry and the military, for example. Such infrared cameras, however, are hardly available in the mobile area, for example in automotive safety systems. The reason: long-range infrared microsensors are currently difficult to produce commercially.

Researchers of the Fraunhofer Institute for Microelectronic Circuits and Systems IMS in Duisburg, Germany, are now offering a solution. On June 22, they will be opening a new facility in which the production of such micro-system technology, or MST for short, is possible. MST involves minute , valves or other mechanical components that are integrated into semiconductor chips. For instance, in airbags they serve as motion sensors, and they are no thicker than a human hair. If MST is to be applied on semiconductors and integrated, one has to master the art of etching – which is where the researchers at IMS come in.

To apply MST to a semiconductor, one essentially puts three layers on top of each other. The bottom layer is the substrate, namely the silicon wafer; in the center there is a sacrificial layer that serves as a spacer, and this is topped by the  function layer. The sacrificial layer is later etched away, leaving only the desired sensor structure behind. The problem: “Traditional etching methods allow us only to etch vertically into the layers,“ explains Dr. Marco Russ, project manager at IMS. “However, unsupported structures are decisive for the mechanical functions of many items of MST.“ In other words: the etching must work not only vertically but evenly in all directions. Experts call this process “isotropic etching.“ This ensures that the etching substance not only eats vertically to the substrate but also digs itself under the function layer, like a tunnel. What remains is an unsupported structure of the function layer that is only one hundred nanometers thin and connected to the substrate only at certain suspension points.

“A conventional technique is etching with liquids“, says Russ. However, capillary forces can occur when the etching fluid dries. The result: the filigree membranes are glued to the substrate or are even destroyed. In addition, most etching liquids do not permit the choice of just any combination of materials for the function and sacrificial layers. “We bypass these problems with our new facility,“ says Russ. The highlight: “We can use two different gases in the processing chambers of the machine instead of fluids.“ They are highly selective: hydrogen fluoride (HF) has strong properties on silicon dioxide but does not affect silicon. The exact reverse is the case with xenon difluoride gas (XeF2).

“This way, we can select which material is better suited to be the function layer,“ says Russ. The new facility could revolutionize MST production, since the process works in a highly precise manner on an industrial scale. And: whether thermal detectors, acceleration sensors and pressure sensors or micro machines – a multitude of MST structures can be produced in this way.

Provided by Fraunhofer-Gesellschaft (news : web)

Unique Polish detector can observe rare decays of nickel nuclei

 Conducting research on the phenomenon of radioactivity is the only way of gaining insight into the properties of some atomic nuclei. Polish scientists from the Faculty of Physics, University of Warsaw have built a unique detector that has made it possible to observe atypical decays of one of the isotopes of nickel, during which two protons were emitted simultaneously.

An article on the subject will appear in the journal Physical Review C.

Isotopes are varieties of a chemical element that share the same number of protons in the nucleus but differ in the number of neutrons. The mass number is the total number of neutrons and protons. Nickel has 28 protons in the nucleus and at least 30 isotopes, including five stable ones, for example nickel-58. Isotopes of nickel in which the equilibrium between the number of protons and neutrons is disturbed the most are hard to obtain and even harder to study -- they are unstable and decay quickly, transforming into nuclei of other elements. Scientists from the Nuclear Spectroscopy Division at the Institute of Experimental Physics (IFD) of the Faculty of Physics, University of Warsaw (FUW) have undertaken research into nickel-48, a highly peculiar isotope. It has 28 protons and only 20 neutrons in its nucleus. It is the most neutron deficient nucleus ever studied. Such an isotope "lives" only 2 thousandths of a second and then decays. The research by the Polish scientists from FUW has shown that the most frequent decay mode of nickel-48 is two-proton emission.

Protons ejected from a nucleus carry information about its internal structure. In order to gain insight into the structure, the correlations between the emitted particles are studied by observing their tracks. An appropriate device is therefore necessary. "The detectors used earlier recorded electronic signals in which all the information about the correlation between the two protons was lost," says Prof. Marek Pfützner from the Nuclear Spectroscopy Division IFD FUW, head coordinator of the research. In the detection method developed by Polish scientists images are recorded by a camera, making the results easy to interpret -- one can simply see what happened. The cutting-edge detector was built in Warsaw according to the design of Prof. Wojciech Dominik from the Particles and Fundamental Interactions Division IFD FUW. The pioneering device not only makes it possible to gather information about the tracks of charged particles moving inside a chamber but also generates their striking visual image. The experiment using the Polish detector was conducted in the U.S. at the National Superconducting Cyclotron Laboratory in Michigan with the collaboration of the University of Tennessee and the Oak Ridge National Laboratory.

The process of the production of unstable nickel has several stages. Atoms of the stable isotope nickel-58 are accelerated in a cyclotron and subsequently directed towards a revolving nickel target containing a natural mixture of stable isotopes of the element. The collisions cause nuclear reactions and a beam of various isotopes of different elements is created. It falls into a magnetic separator, which makes a selection on the basis of mass number. The selected beam falls into a detector filled with a mixture of gases -- helium, argon and nitrogen. There, as a result of the stopping power of the gaseous medium, the energy is dissipated and the atoms come to a halt. The radioactive decay of their nuclei takes place. The whole event is recorded by a camera. The probability of the formation of a nickel-48 nucleus is very small. Which is why during 156 hours of measurements, when 1017 (ten with seventeen zeros!) projectiles hit the target , only six atoms of this rare isotope were observed. The nuclei of four of them decayed by two-proton emission. The rest underwent a different transformation.

"The simultaneous two-proton emission is a very rare phenomenon -- so far it has only been observed in three other atomic nuclei: magnesium-19, zinc-54 and iron-45," says Zenon Janas, PhD, co-author of the experiment. It was also the physicists from Warsaw that observed the two-proton decay of iron. "The possibility of studying such rare decays, providing rich insight into the internal structure of nuclei, has a great learning value," adds Prof. Pfützner. "It can make it possible to verify hypotheses and models describing this still elusive area of matter that makes up the world around us and ourselves."

"Research in physics of nuclei has a long tradition at the University of Warsaw -- first works in the field date back as early as the 1930s," says Prof. Teresa Rząca-Urban, Dean of FUW, a nuclear physics herself. Before the war, such scientists as Leonard Sosnowski and Andrzej Sołtan, who put the first Polish accelerator into operation in 1934, were at the core of nuclear physics at the University of Warsaw. After the war, Jerzy Pniewski and Marian Danysz gained renown for the discovery of hypernuclei -- atomic nuclei containing unstable particles of matter different from the one that surrounds us. Today, nuclear physicists from Warsaw participate in large international experiments, and the successes of Prof. Pfützner's group show that they can also put forward and carry out their own interesting projects and build the equipment necessary for their realization. The University of Warsaw also has its own large research device -- a heavy ion cyclotron used for research in nuclear and atomic physics and for medical applications.

Nuclear physicists do not limit themselves to fundamental research but also try to meet the current economic needs. Already in November the University of Warsaw introduces new "Nuclear power engineering and nuclear chemistry" interdisciplinary studies, a joint effort of the Faculties of Physics and Chemistry. The introduction of the new interdisciplinary studies focused on nuclear power engineering is related to the expected construction of the first Polish nuclear power plant and the need to train an adequate number of specialists prepared to tackle various aspects of its operation. The curriculum of the studies focuses, among others, on issues related to the production, storage and recycling of reactor fuel. "Students will also gain knowledge of physical phenomena, chemical processes as well as legal and administrative aspects related to the functioning of a nuclear power plant," explains Przemysław Olbratowski, PhD, coordinator of the new interdisciplinary studies.

This year also sees the centenary of the awarding of the Nobel Prize in chemistry to Maria Skłodowska-Curie and the centenary of the discovery of the atomic nucleus. In order to celebrate the anniversaries, Prof. Marek Pfützner organizes "The legacy of Maria Skłodowska-Curie -- 100 years after the discovery of the atomic nucleus" conference. It takes place between 11th and 18th September 2011 in Piaski, Mazury. The great-grandson of our Noble Laureate -- French astrophysicist Yves Langevin has confirmed his presence at the event. The opening lecture will be delivered by Prof. Andrzej Kajetan Wróblewski -- eminent physicist, popularizer and scholar of the history of science.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Faculty of Physics Warsaw, via AlphaGalileo.

Süd-Chemie AG´s Managing Board and Supervisory Board recommend acceptance of takeover bid from Clariant

The Managing Board and the Supervisory Board of Süd-Chemie AG, Munich, published their joint statement on the takeover offer made to Süd-Chemie AG shareholders by Clariant Verwaltungsgesellschaft mbH, Frankfurt am Main and on the offer document published on 17 May 2011.

Applying various valuation methods, the Managing Board and the Supervisory Board of Süd-Chemie AG have evaluated the compensation amounting to 126.38 euros per Süd-Chemie AG share offered by the bidder, giving due consideration to both corporate and market aspects. The Managing Board and Supervisory Board were advised by the WestLB AG bank in Düsseldorf which submitted a fairness opinion on the bid.

Based on the analyses carried out, both the Managing Board and the Supervisory Board reach the conclusion in their joint statement that from a financial point of view, the amount of 126.38 euros per share offered by the bidder, represents reasonable compensation. Furthermore, they are of the opinion that in view of the additional promising development potential for Süd-Chemie´s business activities, the company´s integration into the Clariant Group is in the best interests of both Süd-Chemie and its stakeholders. In particular, the Managing Board and Supervisory Board support the intention of the bidder not to change Süd-Chemie´s business activities and to retain its areas of operation. The Managing Board and the Supervisory Board recommend that Süd-Chemie AG shareholders accept the takeover offer.

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ECHA: The Member State Committee identifies seven new Substances of Very High Concern

Seven Substances of Very High Concern (SVHCs) will soon be added to the Candidate List. During its 18th meeting, the Member State Committee also unanimously agreed on four draft decisions based on ECHA’s testing proposal examination and on five draft decisions based on compliance checks.

The seven new substances identified as SVHCs are: 2-ethoxyethylacetate, strontium chromate, 1,2-Benzenedicarboxylic acid, di-C7-11 branched and linear alkyl esters (DHNUP), hydrazine, 1-methyl-2-pyrrolidone, 1,2,3-trichloropropane, 1,2-benzenedicarboxylic acid and di-C6-8-branched alkyl esters, C7-rich (DIHP). These substances are either carcinogenic, mutagenic or reprotoxic (CMR) substances. DHNUP and DIHP will complement the Candidate List with two additional phthalates.

In addition, as a result of the procedure for identification as SVHC a new identification basis (toxic for reproduction) will be added for cobalt(II)chloride that is already on the Candidate List because of its carcinogenic hazards. No comments challenging the new identification basis were received during public consultation and thus no formal agreement of MSC was needed for this case.

The Candidate List will be updated soon as the seven new substances and the “toxic for reproduction” will be added as the basis for identification as an SVHC for cobalt (II)chloride .

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Chemists devise better way to prepare workhorse molecules

 In chemistry, so-called aromatic molecules compose a large and versatile family of chemical compounds that are the stuff of pharmaceuticals, electronic materials and consumer products ranging from sunscreen to plastic soda bottles.

Writing in the current online issue (June 9) of the journal Science, a team led by University of Wisconsin-Madison chemistry Professor Shannon Stahl reports a new, environmentally friendly way to make substituted aromatic molecules that can be customized for different industrial needs.

As college chemistry students know, aromatic molecules have a special stability conferred by a ring of six carbon atoms with alternating single and double bonds. "The ultimate utility of these molecules depends on the chemical groups attached at the corners of this hexagonal platform," explains Stahl. "Interest in preparing substituted aromatic molecules traces back to the dawn of organic chemistry."

In fact, the 2010 Nobel Prize in Chemistry was awarded for catalytic chemical reactions that allow the introduction of specific groups to the periphery of aromatic molecules. These methods, and older traditional methods, rely on modifying an existing aromatic molecule, Stahl explains. But the stability of aromatic molecules can make such approaches difficult, and existing methods also have many limitations in the types and patterns of chemical groups that can be installed.

The method devised by Stahl and Wisconsin colleagues Yusuke Izawa and Doris Pun owes its success to the discovery of a new palladium catalyst. The catalyst gives chemists a way to peel off hydrogen from cyclic molecules to form aromatic products with the desired substitution patterns already in place. The hydrogen removed by the palladium catalyst is combined with oxygen, and water is formed as the only byproduct.

The Wisconsin team demonstrated the utility and efficiency of the new process on phenols, aromatic compounds that are produced on a large scale as precursors to many kinds of industrial materials and pharmaceutical agents. While the new catalytic method can be used to make a broad spectrum of aromatic molecules of interest to science and industry, the new work will be of most immediate practical use to drug companies, according to Stahl. For example, an anticancer agent that was difficult to make using previously known methods was efficiently produced using the strategy devised by the team.

Stahl notes that the work published June 9 in Science will require more development before it is suitable for large-scale industrial production, but he emphasizes that concepts introduced by the new work will have broad utility. "Many new catalysts, reaction conditions and target molecules can be envisioned. Overall, this route to substituted aromatic molecules has a lot of potential," he says.

The new study was supported by grants from the U.S. National Institutes of Health, the Mitsubishi Chemical Corp. and the U.S. National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Wisconsin-Madison.

Journal Reference:

Yusuke Izawa, Doris Pun and Shannon S. Stahl. Palladium-Catalyzed Aerobic Dehydrogenation of Substituted Cyclohexanones to Phenols. Science, 9 June 2011 DOI: 10.1126/science.1204183