The electrical conductivity of TlBiSe 2 narrow gap semiconductors prepared by the Bridgman-Stockbarger method was investigated. The temperature dependence of the electrical conductivity was measured to establish the dominant conductivity mechanism in a temperature range between 293 K and 373 K. The conduction activation energy has a single value indicating the existence of one type of conduction mechanism in the investigated temperature range. The electrical conductivity of the sample is controlled by a thermally activated mechanism. It was also found that these samples exhibit a current-controlled negative resistance and threshold switching. The value of the threshold voltage decreases exponentially with increasing temperature. The calculated ratio of the threshold energy to the activation energy is one half, and is derived from the electro-thermal model for the switching process. Therefore, the electrical switching in the investigated samples can be explained in terms of the electro-thermal model. A possible conduction mechanism in the pre-switching state of the sample associated with the space charge limited current is described.
A comprehensive analysis of the electrical conductivity of TlSbSe 2 layered compounds prepared using the Bridgman-Stockbarger technique is presented. The temperature dependence of the electrical conductivity of TlSbSe 2 and its anisotropy (as measured parallel and perpendicular to the layers) was studied for temperatures between 233 and 353 K. We show that the anisotropy of the electrical conductivity is temperature dependent. The ratio a of the conductivities parallel and perpendicular to the layers obeys an exponential law, with a barrier height of about 37 meV. The dielectric constant and dielectric loss of TlSbSe 2 were determined using ohmic Au electrodes in the frequency range 10 Hz-100 kHz and within the temperature interval 233-373 K. The dielectric constant and the dielectric loss are found to decrease with increasing frequency and increase with increasing temperature. These behaviors are due to the polarization mechanisms in the samples. Lastly the activation energy values were derived from dielectric measurements.
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