The optical and quantum oscillation effects of transfer and the peculiarities of interaction of charge carriers with the CI in bicrystals BiSb
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StatusThe thesis was presented on the 14 September, 2007Approved by NCAA on the 18 October, 2007 Abstract – 0.30 Mb / in romanianThesisCZU 621.315.592
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Summary
The thesis is devoted to a complex research of optical and quantum oscillation effects in bicrystals Bi and alloys Bi1-xSbx (0,06≤x≤0,20) in stationary (up to 18T) and impulse (up to 45T) magnetic fields.
The researched bicrystals consist of two monoblocks and crystallite interface (CI), which width was estimated by the electron microscope and from optical measurements. Bicrystals with the CI of the inclination and twisting types in a wide range of angle disorientation of crystallites have been studied.
The analysis of peculiarities of optical spectrum has revealed the basic channels of modification of power spectrum of charge carriers in area CI in comparison with a spectrum in homogeneous monocrystals with identical parameters. The observable identification is made in spectrum's reflections of peaks.
The research of quantum oscillations of thermomagnetic and galvanomagnetic effects has revealed a number of characteristic peculiarities only for bicrystals: the amplitude and structure of oscillatory spectrums of Hole's resistance strongly depends on the CI type and the angles of disorientation of crystallites. The CI of twisting type with small disorientation angles consist of the central part (70÷90)nm with the high density of states and two adjacent layers (170÷250)nm. The volume of Fermi surface in interfaces grows in comparison with its volume in corresponding monocrystals. The density of electronic state in CI increases practically by three order. The new low-frequency component in a spectrum of Shubnicov-de Haas oscillations is found out at the direction of magnetic field along the CI. The presence of the given frequency is connected to turn of Fermi surface on CI concerning its position in monoblocks.
It was found that in Bi1-xSbx bicrystals of p-type conductivity with the CI of the inclination the Shubnikov-de Haas oscillations represent a superposition of two frequency components. Angular dependencies of their periods are nearly similar in form, but they are out of phase each other by π/2. It is evidenced the Fermi surface rotation on the CI at an angle ≈900.
In bicrystals Bi1-xSbx (0,08≤x≤0,12) the semiconductor-semimetal transition is observed which is connected with the band desplasement in ultra-quantum magnetic fields.
Oficial Reviewers
- Nicolae Sîrbu
doctor habilitat, professor, Technical University of Moldova - Nicolae Popovici
doctor habilitat, professor
Theses
