Using of laser irradiation for the diagnosis of polar state in dielectrics Текст научной статьи по специальности «Физика»

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Using of laser irradiation for the diagnosis of polar state in dielectrics

O. Sergeeva1, A. Solnyshkin1,I. Pronin2, S. Sharofidinov3, S. Kukushkin4 1Tver State University, Department of Condensed Matter Physics, Tver, Russian Federation 2Ioffe Institute, Department of Dielectrics and Semiconductors, Saint-Petersburg, Russian Federation

3Ioffe Institute, Center of Nanoheterosrtuctures, Saint-Petersburg, Russian Federation 4Institute of Problems of Mechanical Engineering RAS, Laboratory of Phase Transitions, Saint-Petersburg, Russian Federation

Coherent monochromatic laser radiation has a small divergence of beam and constant power. Therefore, a laser is a convenient source of thermal radiation to characterize the polar state in pyroelectric materials. In this paper, the study results of the dynamic pyroelectric effect in thin films of linear pyroelectric of aluminum nitride (AlN) are presented. The AlN thin films epitaxially grown on silicon substrates oriented in the directions <111>, < 110> and <100>. Buffer nanolayer of silicon carbide (SiC) is between the silicon substrate and the AlN film [1]. Pyroelectric properties were studied by the dynamic method of non-destructive testing of a polarized state using laser radiation modulated by rectangular shape pulses. The laser light belongs to the near-IR region (X = 980 nm). The bipolar shape of the electrical response, as well as its frequency dependence, may indicate a pyroelectric nature and, therefore, the existence of a polarized state (Fig. 1).

Fig. 1. The forms of the modulated heat flow (curve 2) and electrical response (curve 1) (a) and its frequency dependence (b) of AlN films epitaxial expressed on 111-oriented SiC / Si substrates.

The calculation showed that the values of pyroelectric coefficient p and figure of merit p/s (s is dielectric permittivity, for AlN ~ 9) were the highest for the films grown on substrates oriented in the <111>-direction (Table.1).

Table 1.

Films of aluminum nitride p, 10-9 C/cm2K p/s, 10-9 C/cm2K AlN/SiC/Si(100) 0,9 0,01

AlN/SiC/Si(110) 0,9 0,01

AlN/SiC/Si(111) 2,0 0,22

AlN/SiC/Si(111) films with wide temperature range of the polar state existence and the high value of the figure of merit are promising structures for electronic devices based on the pyroelectric effect.

References

[1] Kukushkin S.A. and Osipov A.V. J Appl Phys. 113, 4909 (2013).