Russian specialists in space materials technology have elaborated a fundamental research program for the period up to 2010. Research into the Synthesis of Transistor Multi-Layer Epitaxial Structures in Space Vacuum behind a Molecular Screen is a new subject at the top of the list. The Institute of Transistor Physics of the RAS Siberian Branch has been assigned as the head institution responsible for its implementation. The department for growth and structure of transistor crystals and films, led by Oleg Pchelyakov, Dr. Sc. (Phys. & Math.), will be engaged directly in the development of methods and equipment for the implementation of this space technology called EKRAN (Screen). He spoke about the project in his interview granted to the newspaper Nauka v Sibiri.

The researcher stressed that as a result of the development of transistor materiology in the past 25 years, high-precision and science-intensive technologies have been developed with the use of high and pure vacuum, with molecular-beam epitaxy (MBE) primarily among them. The process is associated with the growth of monocrystalline thin films and multi-layer structures consisting of varied chemical compounds and solid solutions with transistor, metal or insulating properties.

The process consists in the application of these films with the help of molecular and atomic beams in superhigh vacuum to the surface of a transistor plate with strict control over the chemical composition, structure and thickness of each of its layers. Such systems are used as the initial material for building micro- and optical electronic circuits and devices. Moreover, the MBE technology in combination with modern lithography methods for formation of the pattern of microcircuits (by analogy with nanocircuits) has made it possible to switch over from micron layers and linear dimensions of individual elements to nano-metric ones. Three orders of magnitude for each of the three dimensions in the electronic device space have been discarded. At the same time we have a qualitative breakthrough of nano-electronics to the ultra-high frequency band of operation for transmitting and receiving devices and to superminiature high-density electronic memory circuits.

However, there are obstacles in the way of reducing the size and increasing the number of elements in integral circuits. In the course of the technological process we find alien particles that are larger than the elements in the space surrounding the plate with nano-circuits, while on the circuit surface they suddenly act as the circuit's killers. As the process goes on or as next layers are applied, these "killers" close the electrodes giving rise to irreparable defects. That is why the respective modern production lines are placed in special shops, with their cleanliness group determined by the quantity of specks of dust per sq inch per hour. And the workers operating there have to wear special uniforms looking much like spacesuits for dust not to be produced by them. What with the trend for the further development of completely integrated electronic production units, forecasts are made for possible uses in outer space of high vacuum technologies in the future.

Research of this kind has so far been carried out solely by specialists in the USA (since 1989) and in Russia (since 1996). Incidentally, the idea of a molecular screen to be used for ultra-high vacuum to be produced in outer space at low orbits was put forward by American researchers. They proved by calculations that if a screen-a polished stainless steel disc-orbited the earth at an altitude of 200 - 400 km (where orbital stations usually

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operate) at orbital velocity, a cone trace practically devoid of any matter will be formed in its wake. Such a high degree of rarefaction may be obtained with the help of a disc that it will take you a million years to see the appearance of one oxygen atom on a platform of 1 sq decimeter (O₂ is the basic component of a gaseous medium at the altitude of the orbital flight of space stations). All pressure behind the screen will be determined by helium and hydrogen atoms, produced by the Sun, and also by the matter evaporating from the screen surface. To compare: ground superhigh-vacuum technological installations with cryogen pumps produce thousands of times less maximum rarefaction than that obtained in the first American space experiments with a molecular screen.

After the American experiments Russian researchers launched their own research in this sphere. The best results were attained by the group of specialists from Zelenograd, Moscow Region, led by Yevgeny Markov, Dr. Sc. (Phys. & Math.). The Russian project, described as EKRAN, was later implemented by them jointly with members of the Russian Space Corporation Energiya named after S. R Korolev (Korolev, Moscow Region), researchers of Tomsk State University, of Moscow State Technical University named after N. E. Bauman, the RAS Crystallography Institute named after A. V. Shubnikov (Moscow) and of its branch in Kaluga.

As to priorities in the elaboration of this problem, the fact is that long ago Aristotle (384 - 322 B. C.) formulated it approximately in this way: "vacancy (vacuum) is space formed in the trace of the stone thrown from a sling. True, it vanishes in no time, for particles from the surrounding space rush into it..." The great Greek thinker had only to conclude: "and if we make the stone develop a speed comparable to that of all particles in the surrounding space, then absolutely vacant space will always exist behind it in its flight." Then we would have been able to regard him as the author of the latest method to obtain high vacuum!

And I should add the following: it would take millions of dollars to design and operate modern super-vacuum installations. After the implementation of the domestic EKRAN project, it is planned to build an orbital mini factory for the manufacture of an alternative substratum material in order to obtain complex transistor compounds and multi-layer heterostructures on the surface of large-diameter silicon plates for the further development of integral opto-, micro- and nano-electronics.

G. Shpak, "Vacuum Technologies in Open Space", Nauka v Sibiri (Science in Siberia), Nos 20 - 21, 2007

Prepared by Yaroslav RENKAS