Anisotropy of the hopping conductivity in TlGaSe2 single crystals

Abstract

The temperature dependences of the conductivities parallel and perpendicular to the layers in layered TlGaSe2 single crystals are investigated in the temperature range from 10 K to 293 K. It is shown that hopping conduction with a variable hopping length among localized states near the Fermi level takes place in TlGaSe2 single crystals in the low-temperature range, both along and across the layers. Hopping conduction along the layers begins to prevail over conduction in an allowed band only at very low temperatures (10–30 K), whereas hopping conduction across the layers is observed at fairly high temperatures (T⩽210 K) and spans a broader temperature range. The density of states near the Fermi level is determined, NF=1.3×1019eV·cm3)−1, along with the energy scatter of these states J=0.011 eV and the hopping lengths at various temperatures. The hopping length R along the layers of TlGaSe2 single crystals increases from 130 A to 170 A as the temperature is lowered from 30 K to 10 K. The temperature dependence of the degree of anisotropy of the conductivity of TlGaSe2 single crystals is investigated.