Electrical properties of some low-dimensional compounds
Schaffman, Mark Jonathan
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https://hdl.handle.net/2142/25635
Description
Title
Electrical properties of some low-dimensional compounds
Author(s)
Schaffman, Mark Jonathan
Issue Date
1977
Doctoral Committee Chair(s)
Salamon, Myron B.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
electrical properties
low-dimensional compounds
conducting-insulating transitions
pseudo-one-dimensional compounds
Language
en
Abstract
Three low-dimensional compounds exhibiting conducting-insulating transitions have been studied. The first of these is the pseudo-one-dimensional compound [C(NH2)3]2Pt(CN)4Bro.23 HLO (GCP) , a material similar to KCP, with the potassium replaced with a large, asymmetric organic cation. Diffuse x-ray scattering shows evidence of a Peierls distortion in GCP at room temperature. Data from heat capacity, infrared, and magnetic susceptibility experiments provide confirmation that the effective Peierls transition temperature is higher than that of KCP and is greater than room temperature. The electrical conductivity of GCP was extensively studied, and its temperature-dependence suggests that the conductivity results from solitary-wave excitations in a charge-densitywave state. Further~evidence for this interpretation is provided by the observation of non-ohmic behavior below 160 K at high field strengths. A calculation is given to show that the non-ohmic behavior is due to the conductivity mechanism and can not be ascribed to sample heating. The differences in transition temperature and in conductivity between KCP and GCP are discussed in terms of the, structural differences between the two materials.
The remaining compounds studied in this work are ethylated TTF-TCNQ, another pseudo-one-dimensional compound, . and IT-Til+x Se2, a two-dimensional compound. Electrical conductivity and heat capacity measurements on TTF-DETCNQ reveal a metal-insulator transition at III ± 1 K, a temperature higher than the transition temperature of TTF-TCNQ. This difference is explained in terms of the difference in charge transfer, using a single band model. An electrical conductivity transition in the two-dimensional compound Til + se2 also has been observed, and the transition temperature has been determined by measuring directly the temperature
derivative of the resistivity.
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