Probe current-voltage characteristics

Figure 31. Current-voltage characteristics of an electric probe. The ion and electron current are f and 1, and the floating and plasma potentials are Vf and Vp, respectively.

An STM probe has been used to isolate individual MS (M = Cd, Pb) particles and to measure electronic phenomena (55,56,81). The MS films were prepared either by exposure of metal ion/fatty acid films to H2S (55,56) or by transfer of a compressed DDAB-complexed CdS monolayer (81). All the films were transferred onto highly oriented pyrolytic graphite (HOPG) for the STM measurements. A junction was created at an individual CdS particle with the STM tip as one electrode and the graphite as the other, and the current/voltage characteristics of the panicles were measured. For the particle prepared in the fatty acid films the I/V curves exhibit step-like features characteristic of monoelectron phenomena. In the case of the DDAB-coated CdS particles the I/V measurements demonstrated n-type semiconductor behavior. The absence of steps in this system is probably a reflection of the larger size of the particles in the DDAB films (8 nm by AFM) compared to the 2-nm particle size typically found for MS particles formed in fatty acid films. 

Effects of Plasma-Polymerized Film on the Current-Voltage Characteristics of Single Probe... 

The films and devices were characterized by inductive-coupled plasma spectrometry (ICP), Auger electron spectroscopy (AES), X-ray diffraction, electron-probe microanalysis (EPMA), current-voltage characteristics, and spectral response. 

Figure 4 shows the current-voltage characteristics of the 121 filament-Al-stabilized wire. The shape of the voltage takeoff curves indicates that the NbTi filaments were well stabilized. The distance between the current terminals was 50 mm, with 10 mm between the voltage probes. The superconductor critical current density in the NbTi at 5 T was 1630 A/mm, comparable with NbTi processed in a Cu matrix. However, the overall conductor current density (472 A/mm at 5 T, for a similar normal state resistivity) was higher than that of copper matrix wire (333 A/mm at 5 T). 

Theoretical work fnnction on electrical transport (tunneling) in metal-mole-cule-metal jnnctions indicates that junction impedance is significantly affected by the properties of the metal-molecule contacts. Specifically, the presence of barriers to electron (or hole) injection leads to drops in electrostatic potential at the metal-molecule interface, resulting in contact impedances. Various methods are currently available for probing the electrical conductance of discrete molecules or clusters of molecules bridged between metal or semiconductor electrodes to understand how the structure and electroiuc properties of molecules and their associated contacts affect the current-voltage (I V) characteristics observed for the junction [133,136,146-161]. 

The general current voltage relation characteristic of a small spherical probe with large counterelectrodes immersed in a neutral plasma is shown in Fig. 3.12. 

Current probe - to measure the third harmonic component of/p It is then converted to actual I, from the ZnO characteristic data provided by the arrester manufacturer, /r versus /jr, corrected to the site operating temperature and voltage. The value of is then used to assess the condition of the arrester. 

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