Site: L'viv State University
Department of Physics
Department of Chemistry
290602, L'viv, vul. Universytetska 1.
Ukraine

Date Visited: October 28, 1993

Report Author: O.D. Lavrentovich

ATTENDEES

WTEC:

M.J. DeHaemer
O.D. Lavrentovich

HOSTS:

Professor Yosyp M. Stakhira

Head, Semiconductors Department

Professor Orest V. Vlokh

Director, Institute of Physical Optics and
Head, Department of Nonlinear Optics

Professor P.G. Stakhiv
Professor M.S. Pidzyrailo,
Professor M.M. Soltys

Dept. of Physical and Colloidal Chemistry

Professor Olena I. Aksimentyeva

Dept. of Chemistry
Fax: 7 (0322) 72 7054

Professor V.T. Avtym

BACKGROUND

L'viv State University (LSU) is one of the oldest universities in Europe. The Physics and Chemistry departments perform investigations in a variety of fields, including display-related research and development.

RESEARCH AND DEVELOPMENT ACTIVITIES

Research in the field of liquid crystals is performed in the Department of Nonlinear Optics (Professor O.V. Vlokh, Head; Prof. Yu. A. Nastishin, PI). This includes basic investigations of the lyotropic smectic and twist-grain boundary (or chiral smectic A) phases. Another field of interest is a phenomenon of electrogyration and incommensurate phases in crystals {N(CH3)4}2ZnCl4 (Kapustianik 1992) (Prof. V. Kapustianik, PI) and CS2CdBr4 (Kityk 1993) (Prof. A.V. Kityk, PI).

Professor M.S. Pidzyrailo and M.M. Soltys (Dept. of Physical and Colloidal Chemistry) told about research and development on cathodoluminescent screens based on phosphor powders of three kinds (425, 450, and 540 nm) (Dutsyak 1993). The following materials with small (1-4 microns) crystal grains are typically used: ZnS:Ag, Y3Al5O12-Ce, and Y2SiO5-Ce. Collaboration with Erotron L'viv has resulted in technology of high informative displays with a line width of 60 microns. The screen operates in two color modes (red and green); the threshold of the color switching is 5-10 kV.

Prof. Vyacheslav D. Bondar (Laboratory of Physical Electronics) performs R&D on luminescent screens. The screen is composed of two luminescent films possessing different colors (e.g., Y2O2S:Eu with red color). The electron irradiation causes luminescence with color that depends on the intensity of the electron beam. The physical reason for the color changes is that the beam intensity defines its penetration depth. If the intensity is weak, then only the upper film is excited. The more intense beam penetrates into the lower film and thus changes the color of the luminescence.

Professors Olena I. Aksimentyeva and V.T. Artym synthesize conducting polymeric materials based on compounds such as polyaniline, polyparaphenilene, polyaminophenole, and their derivatives. The polyaniline and polyaminophenole films that can be used as electrochromic coatings were demonstrated. The film thickness is 0.2 microns; voltage changes in the range 0-0.4 V lead to changes in the film color. These electrochromic materials can be obtained as powders. The contrast is lower than for the LCD. Similar work is performed at Penn State University.

Professor Yo. M. Stakhira investigates the effect of electron beams on semiconductor films (e.g., GaSe). The electron beam creates a junction between different layers of the structure and causes the 2-D to 3-D structural transition. The structural transition results in changes of the optical parameters of the film (refractive indices). The effect can be used, for example, in large screen production.

SUMMARY

L'viv State University performs interesting R&D that might be used in display technologies. Successful collaboration with industry (Erotron L'viv) resulted in excellent EL-type devices. Less attention has been paid to the LCDs.

REFERENCES

Dutsyak, I.S., T.M. Duzhiy, V.P. Martynova, O.G. Mykolajchuk, V.V. Pigrukh, M.S. Pidzirajlo, and M. M. Soltys. 1993. Nucl. Tracks Radiat. Meas. 21:125.

Kapustianik, V.P., I.I. Polovinko, S.A. Sveleba, O.G. Vlokh, and V.S. Zhmurko. 1992. Europhys. Lett. 19:429.

Kityk, A.V., O.M. Mokry, V.P. Soprunyuk, and O.G. Vlokh. 1993. J. Phys. Condens. Matter. 5:5189.


Published: December 1994; WTEC Hyper-Librarian