Shelest T. Influence of selenium vacancies on electrophysical properties of quasi-low-dimensional systems NbSe2 and NbSe3

The object of study: processes of defect formation in quasi-low-dimensional systems. The aim of investigation: setting of processes of selenium vacancies formation in quasi-low-dimensional systems NbSe2 and NbSe3 and clearing up of influence of vacancies on the physical properties of these systems. The methods of investigations: measurements of temperature and temperature-time resistivity dependencies, thermal expansion, x-ray investigation, theoretical analysis of influence of vacancies on temperature resistivity dependence. Results, novelty: considerable deviation of temperature dependence of resistivity from a linearity above 400 К it was revealed for quasi-low-dimensional monocrystals NbSe2 and NbSe3. It is caused by selenium vacancies formation. The dependencies of effective energy of selenium vacancies formation from time exposure for monocrystals NbSe2 was established. It is caused by redistribution of charge carriers with the increase of vacancies concentration. An anomalous large value (~150 %) of temperature dependent part of vacancies contribution to electric resistivity for monocrystals NbSe2 and NbSe3 was firstly discovered. A theoretical model for explanation of a great value of temperature-depended part of vacancies contribution to electric resistivity in NbSe3 was proposed. It is based on a different character of the scattering on lattice defects and phonons for electrons localized on different structural chains of the quasi-one-dimensional metal. Field of application: solid state physics, physics of low-dimensional systems