Insulating behaviour

M = Metal I = Insulator M I = shows a transition from metal to insulator behaviour at a certain temperature. 

In the next experiment, an oxide interlayer was deposited between the Cu(TCNQ) layer and the An top contact (0.5 x 2 mm ). The AI2O3 layer had a thickness of 200 nm and was e-beam evaporated at a rate of 2-3 A/s before deposition of the An pad. In spite of a 200 nm AI2O3 dielectric layer no expeeted insulating behaviour was observed. The rough surface profile (up to 1 pm) of a Cu(TCNQ) layer seemed not to be eompletely covered with insulating AI2O3. 

In a category of materials known as Mott insulators, like MnO, CoO or NiO, with band gaps of 4.8, 3.4, and 1.8 eV, respectively ([2], and references therein), the upper energy band made from 3d states is partially occupied resulting in metallic conduction. The insulating behaviour of these compounds is attributed to a strong intra-atomic Coulomb interaction, which results in the formation of a gap between the filled and empty 3d states [35]. 

Despite the current upsurge of interest about the conduction properties of DNA [105,112], the subject is far from new. Eley and Spivey (1962) were the first to suggest that DNA could act as a conductor [77]. The experimental outcomes about the conductivity of DNA and its mechanisms vary from the wide gap insulating behaviour to the proximity induced superconducting one [95-98, 102,105,113-119]. A clear understanding of the nature of electronic conduction... 

Although polymers are associated with electrically insulating behaviour, the increasing ability to control both the fabrication and the constitution of polymers has led to the development of polymers that show metallic conductivity superior to that of copper (see Section 13.2.8) and to polymers that can conduct ions well enough to serve as polymer electrolytes in batteries and fuel cells (see Sections 9.2.5 and 9.3.7). 

When BaTiOj loses oxygen, the resistivity falls considerably. The reduced materials show semiconducting/insulating behaviour until the composition approaches... 

The majority of polymeric materials do not conduct electricity to any appreciable extent indeed, their frequently excellent insulating behaviour accounts for most of the applications of synthetic organic polymers in the electronics and electrical industries. Nevertheless there are a significant number of polymeric materials which do conduct electricity and these are the focus of our attention here. Other polymeric materials are already of importance in the sensors field and are discussed at various points throughout the book. 

A similar family of polyimides has been described by other workers [38]. The polyamic acid alkylamine salt (23) was used to form a surface monolayer, and this was then deposited into multilayers by the LB technique. By treating the deposited films with acetic acid, a highly stable polyimide multilayer (24) was produced. The major difference between these polyimides and those of structure (22) is the mode of preparation. In this case a chemical method is used, whereas thermal cyclization was used for (22). LB polyimide films of structure (24) have been found to be very stable in various organic solvents and exhibit insulating behaviour (electrical and thermal) comparable to conventional polyimide films. 

The powder conductivities of bridged transition metallomacrocycles in the non-doped state are listed in Table I. All the bridged complexes [MacM(L)]n (L = pyz, tz, dabco), contain cofacially arranged macrocycles, which are separated by approximately the same distance (about 600 pm). While the monomeric complexes PcM(L)2 (L = pyz, dabco, tz M = Fe, Ru, Os) show insulating behaviour, it can be seen (Table I) that the ligand L has a significant effect on the conductivity of the bridged complexes [MacM(L)]. ... 

Volume Res Volume Resistivity (internal resistivity, formerly specific resistance) is used to characterise the insulation behaviour of plastics and elastomers. It is usually given at 0°C or 20°C. Materials with a volume resistivity >10 ohm.cm are classed as insulators (plastics or elastomers). Materials are antistatic in the range 10 to 10 ohm.cm. Conducting polymers are <10 ohm.cm. 

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