Common Dopants

3 DOPANTS, AND ALTERNATIVE DOPING TECHNIQUES 5.3.1 Common Dopants 

TABLE S-3 Common dopants studied in prior work with CPs. When relevant, the typical CP or class of CPs to which the dopant is applicable is given in italics this is by no means an exclusive list. (References cited only where appropriate). 

Ptaromatic amines). P(bi/diioohenes) as dopant electrolyte, chemical/electrochemical prepn.  

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It is often necessary to iatroduce dopant atoms iato the epitaxial (epi) layers. Typically, the dopant sources are hydrides (qv) of the impurity atoms. Common dopants are boron hydride, ie, diborane(6) [19287-45-7] 2 6 p-ty e dopiag, and arsiae [7784-42-17, AsH, and phosphoms hydrides for n-ty e dopiag (11). For example ... 

Theoretical studies of diffusion aim to predict the distribution profile of an exposed substrate given the known process parameters of concentration, temperature, crystal orientation, dopant properties, etc. On an atomic level, diffusion of a dopant in a siUcon crystal is caused by the movement of the introduced element that is allowed by the available vacancies or defects in the crystal. Both host atoms and impurity atoms can enter vacancies. Movement of a host atom from one lattice site to a vacancy is called self-diffusion. The same movement by a dopant is called impurity diffusion. If an atom does not form a covalent bond with siUcon, the atom can occupy in interstitial site and then subsequently displace a lattice-site atom. This latter movement is beheved to be the dominant mechanism for diffusion of the common dopant atoms, P, B, As, and Sb (26). 

The oxidation of methacrolein to methacrylic acid is most often performed over a phosphomolybdic acid-based catalyst, usually with copper, vanadium, and a heavy alkaU metal added. Arsenic and antimony are other common dopants. Conversions of methacrolein range from 85—95%, with selectivities to methacrylic acid of 85—95%. Although numerous catalyst improvements have been reported since the 1980s (120—123), the highest claimed yield of methacryhc acid (86%) is still that described in a 1981 patent to Air Products (124). 

Lanthanum chromite is a p-type conductor so divalent ions, which act as electron acceptors on the trivalent (La3+ or Cr3+) sites, are used to increase the conductivity. As discussed above, the most common dopants are calcium and strontium on the lanthanum site. Although there is considerable scatter in the conductivities reported by different researchers due to differences in microstrucure and morpohology, the increase in conductivity with calcium doping is typically higher than that with strontium doping [4], The increase in conductivity at 700°C in air with calcium additions is shown in Figure 4.1 [1, 2, 28-44], One of the advantages of the perovskite structure is that it... 

Donor dopants, i.e. those of higher charge than that of the ions they replace, are compensated by cation vacancies acceptors, i.e. dopants of lower charge than that of the replaced ions, are compensated by oxygen vacancies. Each dopant type tends to suppress the vacancy type that the other promotes. The common dopants in perovskite-type ceramics are listed in Table 6.1. The effects of aliovalent substituents are discussed in Section 2.6.2. 

A similar polymer to poly(aniline) is poly(o-toluidine). The polymer can be synthesized electrochemically, and it is typically doped for modifying its electrical properties. Common dopants are salicylidine-aniline and salicylidine-o-aminophenol. Reports on thermal stability of this polymer are available in literature [4]. 

SIMS is used for quantitative depth profile determinations of trace elements in solids. These traces can be impurities or deliberately added elements, such as dopants in semiconductors. Accurate depth prohles require uniform bombardment of the analyzed area and the sputter rate in the material must be determined. The sputter rate is usually determined by physical measurement of the crater depth for multilayered materials, each layer may have a unique sputter rate that must be determined. Depth prohle standards are required. Government standards agencies like NIST have such standard reference materials available for a limited number of applications. For example, SRM depth profile standards of phosphorus in silicon, boron in silicon, and arsenic in silicon are available from NIST for calibration of SIMS instmments. P, As, and B are common dopants in the semiconductor industry and their accurate determination is critical to semiconductor manufacture and quality control. 

Figure 2 shows the reference coordinates and nomenclature of this geometry. Theoretical calculations of the projected range and straggle for various dopants and substrates have been calculated and shown in graphical form (4, 21-26). Some common dopant ions for silicon and gallium arsenide are shown in Figures 3, 4, 5, and 6. 

Yamashiro and co-workers have estimated the dopant-chain interaction and its role in interchain transfer [82]. They showed that the dopants mediate the largest interchain transfer of about 0.3-0.1 eV with five to seven carbon atoms in another chain that is in contact with a common dopant column. The interchain transfer via dopants has little effect on interchain states but yields a modification of the orbital energy spectrum. 

One of the most common dopants is Nd ", which substitutes for yttrium in the crystal lattice. Commercial Nd-doped YAG is regularly produced with Nd concentrations ranging between 0 and 1.5 substitutional percent (sub%) of yttrium sites from the chemical formula Y3 c(Ndx)Al50i2, the substitutional percent Nd is given by x/3. For instance, 1.02 sub% Nd = 0.153 at% Nd. Few crystals beyond 1.5 sub% Nd are available commercially. 

The physical, chemical, and electrical properties of PPy can be easily modified by various doping agents and preparation conditions. There are many available dopant ions for the generation of good quality deposited polymer films [63-64]. Two of the most common dopants that are codeposited with PPy are polystyrene-sulfonate (PSS) and sodium dodecylbenzenesulfonate (NaDBS). PPy/PSS and PPy/NaDBS polymers have been used in many applications ranging from actuators and neural scaffolds to neural electrode coatings [22, 53, 61, 65]. It is reported that electrode materials, electrolyte solution, deposition methods (current-or potential-controlled deposition), deposition time, and solution temperature during electrochemical polymerization affect both the structure and electroactivity of PPy films [66]. 

One of the most common dopants for indium oxide is tin such dopant ions increase the n-type character of cubic lu203 by providing additional electrons in the valence band. Thanks to its increased conductivity, ITO coatings are widely used as transparent electrodes in displays, solar cells, LEDs, and other optoelectronic devices. The synthetic approaches to prepare ITO films or... 

Enumerate the most common dopants for one member of each of the polymer classes listed in problem 1 above and briefly outline the doping method. 

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