A reversible electronic switching effect has been observed in plasma polymer films with embedded silver nanoparticles. The electrical and nanostructural properties of the films have been investigated, and three different structure types were observed: metallic, percolation, and dielectric. While for the metallic and dielectric types, respectively, metallic conduction and thermally activated tunneling can be identified as the dominant electronic conduction mechanisms, switching appears only in percolation structures. These drastic, abrupt changes of up to six orders of magnitude in the current-voltage behavior are highly reversible for these nanocomposite materials, and are defined as threshold switching
Titanium nitride is a hard and inert conducting material that has yet not been widely used as electrode material for electroanalytical applications although there are highly developed protocols available to produce well adherent micro and nanostructured electrodes. In this paper the possibilities of using titanium nitride thin films for electroanalytical applications is investigated. Scanning electrochemical microscope (SECM) was used for analysis of the redox kinetics of a selected fast redox couple at thin films of titanium nitride (TiN) in different thicknesses. The investigation was carried out by approaching an amperometric ultramicroelectrode (UME) to the TiN film while the soluble redox couple (ferrocenemethanol/ferrociniummethanol) served as mediator in a SECM configuration. The substrate was biased at a potential so that it rereduces the species being produced at the UME, thus controlling the feedback effect. Normalized current -distance curves were fitted to the theoretical model in order to find the apparent heterogeneous standard rate constant (k8) at the sample. The data are further supported by structural investigation of the TiN films using scanning force microscopy and X-ray photoelectron spectroscopy. It was found that the kinetics are little influenced by prolonged storage in air. The heterogeneous standard rate constants in 2 mM ferrocenemethanol were (0.73 AE 0.05) Â 10 À3 cm s À1 for 20 nm TiN thin layer, (1.5 AE 0.2) Â 10 À3 cm s À1 for 100 nm TiN thin layer and (1.3 AE 0.2) Â 10 À3 cm s À1 for 300 nm TiN thin layer after prolonged storage in air. Oxidative surface treatment (in order to remove organic adsorbates) decreased the kinetics in agreement with a thicker oxide layer on the material. The results suggest that their direct use for amperometric detection of reversible redox systems in particular at miniaturized configurations may be advantageous.
Short chains of Au55(PPh3)12Cl6 clusters were generated between tungsten tips on an SiO2 surface, and their electrical behavior was studied.
The clusters were deposited from solution by applying a voltage of 2 V between tips of 30 nm in distance. Current−voltage (I−V) measurements
of the nanowires showed Coulomb blockades at room temperature in the region between −0.5 to +0.5 V, demonstrating quantum dot character
and single electron transistor (SET) behavior, respectively.
The interaction between oxygen vacancies and La atoms in the La doped HfO(2) dielectric were studied using first principles total energy calculations. La dopants in the vicinity of a neutral oxygen vacancy (V(O)) show lower formation energy compared to the La defects far from V(O) centres. La doping in HfO(2) leads to the shift of the defect states of oxygen vacancies towards the conduction band edge. A statistical average of this shift over several possible configurations of La atoms and V(O) shows that the incorporation of La effectively passivates the V(O) induced defect states leading to the reduction of the gate leakage current and improvement of the device reliability.
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