Imprimir Republish

Electronic Microscopy

Spy hole sees the position of the atom

A laboratory in Campinas using very high resolution microscopes is consolidates and winning international praise

In 15 months of operation, the Electronic Microscope Laboratory (LME) of Campinas, has become a valuable resource for 80 researchers in 55 groups throughout the country: studies undertaken there have already resulted in the publication of 36 articles and around 80 presentations at conferences. A part of the structure open to multiple users of the National Light Synchrotron Laboratory (LNLS) of the Ministry of Science and Technology, the LME was recently appraised by an international scientific committee at the request of FAPESP. The committee judged its productivity exceptional and described the work done there as “of the maximum scientific quality”.

One of these works was awarded the best Doctoral Thesis Prize by the Brazilian Physics Society (SBF). It was that of Daniela Zanchet, a chemical engineering graduate from the Federal University of Paraná and with a doctorate from the State University of Campinas (Unicamp), who built and characterized new type of gold crystal. Daniela, 28, went to do her postdoctorate at the Chemistry Department of the University of California, Berkeley, United States.

First rank
To equip the laboratory’s five rooms, FAPESP invested US$ 1.9 million in equipment. The most important is the electron microscope, whose resolution is up to 0.17 nanometers – a nanometer is a millionth of a millimeter – or less than the distance between two neighboring atoms in most materials.

The only of its kind in Latin America, the powerful instrument expands images up to 1.5 million times. With it, accurate images of the position of atoms, allowing users to see how they are arranged, can be achieved. In the room housing the equipment, the temperature is kept under strict control and the walls are covered with soundproof material.

Another two rooms house scanning microscopes: with resolutions of 1.5 or 3.0 nanometers, amplify images up to 300,000 times, enough identify the morphology of grains or parts of a material.

In the room where the sample preparation laboratory is housed a basic part of research takes place: for microscopic analysis, the material is submitted to specific techniques according to the study intended.

This advanced infrastructure has brought a great benefit: state-of-the-art scientific work on materials can now be undertaken without the need of going abroad. This used to make much research difficult or even impossible.

“At present, much of the research depends on microscopic analyses of this sort. To understand the physical and chemical properties of the materials, we need to be able to see their structures down to the level of atoms”, says the LME’s coordinator, Daniel Ugarte. With the laboratory’s tools, we can monitor, on an equal footing with the most advanced centers in the world, the general trend toward miniaturization produced by microelectronics, which seems to expand to all materials science.

Set up in less than a year, “a record time for a complex of this sort”, according to Ugarte, the LME operates as a support center open to academic or business research. Only a quarter of the work already published is by the MLE team itself.

Free of charge for academic research, the use of the laboratory involves no great formalities – the project just has to be submitted to the LME’s coordinating committee – but it requires beginners to go through a training period, a week long for the electronic scanning microscope and two months for the an electron microscope.

Training center
The LME, however, was not set up to provide services, as other laboratories do: “We offer the tools, and we train people how to use them, but everything else is up to the researcher”. This philosophy that Ugarte introduced allows the laboratory to work with a minimal team – only four hired employees, plus a doctoral and a postdoctoral student – but its main objective is to train professionals qualified in electronic microscopy. Besides the training, Ugarte gives talks all over the country and lectures at Unicamp – the LME has already trained, for example, 40 postgraduate students.

Juan Carlos Gonzalez Pérez, of the Minas Gerais Institute of Exact Sciences (UFMG), spent a month and a half at the LME to obtain the images necessary for his doctoral thesis on multi-layers of quantum points self-constructed with indium and gallium arsenite. “The support of the people at the LME was essential”, says Wagner Nunes Rodrigues, Pérez’s thesis tutor, whose objective is to produce systems of objects called “quantum points” measuring a few tenths of a nanometer across. These objects that behave like “giant atoms” or atoms made up of atoms, can be used to build lasers that are more stable at ambient temperatures, as well as serving as memories.

Relying on the LME to prepare samples was essential for completing the research, emphasizes Rodrigues: “Preparing this type of sample for microscopy is not easy, since it requires special equipment, not always available in other microscopy laboratories in Brazil”. The images obtained help in understanding better the system of producing quantum points and gave support for the continuation of the studies, which also involved the use of the synchrotron light available at the LNLS.

Alloy Magnetism
Another regular user of the LNLS is Marcelo Knobel, of the Unicamp Physics Institute. Since 1990, he has been studying magnetism in nano-crystals, particles of crystal measuring 5 to 50 nanometers. Recently, he has been using the LME’s electron microscope to characterize the atomic structure of an iron, zirconium, copper, and boron alloy known as Nanoperm. This alloy, which was discovered by Japanese researchers, has magnetic properties vastly superior to those of common materials available in the market”, explains Knobel. Because it is readily magnetized and demagnetized, it can be used in the nucleuses of transformers, magnetic recording heads, magnetic field sensors, transducers, and magnetic shielding.

The study of the structure of the nano-particles in the alloy allow us to learn more about the mechanisms responsible for their magnetic properties, as these properties are related to the heating to which the alloy was submitted in the manufacturing process, it has been possible to test other methods of thermal treatment.

The novelty in the research was the use of an electric current to treat the material, allowing higher rates of heating that those obtained in conventional furnaces. Consequently, there was greater control over the formation of nano-structures, making possible the optimization of the material’s magnetic properties.

The LME’s own team undertook an important piece of research in the physics of nano-structured materials: Ugarte is investigating the structure and electric properties of nano-lines (lines so small that they can be made up of a mere file of atoms) for application in tiny electronic systems.

He points out that properties such as conductivity and insulation from electricity can be substantially altered when a material is reduced to the size or thickness of a just a few atoms. A material like silicon oxide (similar to conventional glass), for  example, is a good electricity insulator, but it may not have the same insulating properties when used in very thin films (1.5 nanometers or 4 or 5 atomic layers). This fact sets a even lower limit to the miniaturization of electronic circuits compared to the current technology based on silicon.

Besides research in physics, the majority, there are many works in chemistry, engineering, geology, and odontology at the LME. Ugarte envisions growth in the number and complexity of items of research when the laboratory gets another microscope, known as the FEG-TEM (electronic transmission microscope equipped with a field force electron gun), specifically for chemical and spectroscopic analysis in regions of around one nanometer or less in size. This equipment, which is part of the LME’s expansion project to be submitted this year, will require investment of around US$ 2 million.

The installation of the FEG-TEM microscope, which was part of the LME’s initial project, was one of the main recommendations of the international committee, which judged it necessary and timely to expand the laboratory. Indeed, the LME is operating at the limit of its capacity, with the equipment working 12 hours a day and a waiting list of two months to get a working session on the electronic transmission microscope. Although the cost is high, the committee considers it essential to keeping up the high standards achieved there.

The Project
High Resolution Electronic Microscopy Center (nº 96/04241-5); Type
Infrastructure program 3; Coordinator Daniel Mário Ugarte – National Synchrotron Light Laboratory; Investment R$ 38,300 and US$ 1,811,000