N-type conductor

Extrinsic Semiconductors. Impurity levels can be either donor levels near the empty zone (normal or n-type), or acceptor levels near the filled band (abnormal or p-type). Conductivity in n-type conductors will be due to electrons in the empty band donated by the impurity levels, and in p-type conductors, to positive holes in the previously filled band, arising from the transition of electrons to the impurity acceptor levels. 

Figure 40 presents the conductivity of a-phase of PrO oxides, which varies as a linear function of the oxygen partial pressure. This indicates that the lanthanide higher oxides with disordered oxygen vacancies are n-type conductors. 

Both techniques in principle bear the potential to distinguish between p- and n-type conductors and—if applicable to ion conductors—to distinguish between interstitial and vacancy contribution provided the nature of the mobile ion is known. 

A few works have also been published reporting unusual valence states of metal ions in lattices of such oxide semiconductors as ln203, ZnO, Sn02 [44, 55-68]. These compounds attract researchers attention because they are very perspective materials like thin films and ceramics for constructing new chemical sensors [55], as well as highly conductive thermo- and chemically stable n-type conductors (ln203). 

Figure 6. Three experimental examples of Kroger-Vink diagrams in a pure oxide MO with ideal defect chemistry SnOj as n-type conductor, PbO as mixed conductor and La2Cu04 as p-type conductor.45 (Reprinted from J. Maier, Ionic and Mixed Conductors for Electrochemical Devices, Radiat. Eff. Defects Solids, 158, 1-10. Copyright 2003 with permission from Taylor Francis.)...

Solid state detectors consist of three layers, a layer of pure silicon sandwiched between a p-type and an n-type conductor. We recall that an example of an n-type conductor is germanium to which is added P or As, an impurity. The extra electron in the phosphorus or arsenic atoms is thought of as being in an energy level close to the conduction band. These electrons are readily thermally excited into the conduction band increasing the conductivity. A p-type semiconductor may be silicon to which a trivalent element such as boron or aluminum is added as an impurity. This creates holes close to the valence band. Electrons are readily promoted to these holes leaving positive holes in the valence band that provide for a conduction pathway. 

The p- and n-type conductors are necessary in the solid state detector because silicon crystals are very difficult to obtain pure. Usually they contain impurities such as boron, which would make it a p-type semiconductor. This situation would allow thermal electrons to cross the silicon energy gap to the low lying hole state. However, we want only electrons that are excited by X-ray photons to act as conductors. Interference of thermal electrons is avoided by a process called drifting in which a small amount of lithium is added, usually by thermal diffusion, to one side of the Si crystal and a larger amount to the opposite side. The lithium ionizes within the silicon... 

In addition, the following results were described thermoelectromotoric force (n-type conductors) influence of different metal atoms on o of polyMPc - a... 

The R-based mixed oxides with p-type electronic conductivity as well as the superconducting oxides were found to be inactive for the OCM reaction, and only total combustion of methane was observed. The only exception was Lao Sro MnOj 5, which is probably an n-type conductor under the experimental conditions used. This solid is likely to be n-type under reducing atmosphere due to the stability of the Mn2+ ion. LaftsSro.2Mn03and LaFeo.sNdo.2O3 5, both considered n-type conductors, had low selectivity to C2, whereas La-Sr-Y-O systems, either ionic conductors or insulators, presented a good selectivity to those compounds (table 8). 

The compound Mg2Ti04 is an inverse spinel, which can be written as (Mg)[Mg Ti]04, where the round brackets indicate cations in tetrahedral sites and the square brackets indicate cations in octahedral sites. The compound MgTi204 is a normal spinel, (Mg)[Ti2]04. (see Section 5.3.10). Both compounds are insulators. What are the charges on the ions A small amount of MgTi204 is doped into Mg2Ti04 to form Mg2- cTii+ c04. What are the charges on the ions and how are they distributed in the spinel structure Will the material be a p-type or an n-type conductor ... 

Yim et al. (1972) have studied ScP and ScAs single-crystal epitaxial layers. Each compound has a fee lattice (a = 5.31 A and a = 5.46 A, respectively). They are n-type conductors, totally miscible in all proportions, and form a continuous series of solid-solution alloys. The optical absorption shows a minimum. The band gaps are 1.1 eV for ScP and 0.76 eV for ScAs. 

The reduction of PtATi02 with hydrogen removes lattice oxygen from leaving defects and Ti " ions. This process increases the conductivity of pellets by making n-type conductor. The authors reported that strong metal support interaction has no influence on the WGS activity. However, the addition of 3.5 wt% NaOH increases the WGS rate by 16 times. 

Relatively little is known about the non-stoichiometry, disorder, and transport properties of hematite Fe203 (a-corundum structure). However, it can be said with certainty that Fc203 exhibits a small excess of cations, and that this excess is dependent upon the oxygen partial pressure. Furthermore, Fc203 is a n-type conductor over a wide range of oxygen partial pressures, and the diffusion coefficients of oxygen ions and of iron ions are of the same order cm /sec at r 1200 °C) [40]. 

Electronic Transport, General Description. Gallium Nitride (GaN). Undoped GaN is normally an n-type conductor. Carrier concentrations in undoped films can vary from 5 x 10 cm to 5 x 10 cm because of unintentional incorporation of extrinsic impurities, mainly silicon and oxygen. In the purest a-GaN material (w = 10 cm ), conductivities of the order of... 

Group I polymers are singularly important for applications wh,ere the reversibility of the doping process is a key feature, as in secondary batteries, visual displays, and variable transmission shields. These polymers are generally characterized by a broad valence band and low ionization energy for formation of p-type conductors and a broad conduction band and high electron affinity for formation of n-type conductors. 

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