Doping processes

These conjugated polymers can be chemically and electrochemically reduced and reoxidized in a reversible manner. In all cases the charges on the polymer backbone must be compensated by ions from the reaction medium which are then incorporated into the polymer lattice. The rate of the doping process is dependent on the mobiHty of these charge compensating ions into and out of the polymer matrix. 

This restriction, however, could be circumvented by the doped CNT with either Lewis acid or base [32-36], since such doping, even to semiconductive CNT could enhance the density of states at the Fermi level as well as bring about the metallic property. Appearance of metallic conductivity in helical CNT by such doping process would be of interest in that it could make molecular solenoid of nanometer size [37]. 

Scheme 17) [35,36]. Polymers (61) were amenable to p- and n-doping processes with good reversibility. Absorption spectra of the de-doped polymers showed that the values of A nset considerably red-shifted compared with those ob-... 

Implantation dose or fluence it controls the amount of dopant (i.e., its local concentration) introduced in the target per unit surface area. It is measured in ions/cm and it is the integral over the depth of the concentration profile. Typical values in the nanocluster synthesis are lO -lO ions/cm. For a comparison, the t5 pical fluence values for semiconductor doping processes are 10 -10 ions/cm. ... 

Bellosta von Colbe, J.M., B. Bogdanovic, M. Felderhoff, A. Pommerin, and F. Schuth, Recording of hydrogen evolution—a way for controlling the doping process of sodium alanate by ball milling, /. Alloys Compd., 370, 104-109, 2004. 

The doping process may be controlled by changing the integrated flux of neutrons, making possible the approximate prediction of the resistivity of thermistors as a function of temperature. 

Parent (unsubstituted) PF was first synthesized electrochemically by anodic oxidation of fluorene in 1985 [266] and electrochemical polymerization of various 9-substituted fluorenes was studied in detail later [220,267]. Cyclic voltammogram of fluorene ( r1ed= 1.33 V, Eox = 1.75 V vs. Ag/Ag+ in acetonitrile [267]) with repetitive scanning between 0 and 1.35 V showed the growth of electroactive PF film on the electrode with an onset of the p-doping process at 0.5 V (vs. Ag/Ag+). The unsubstituted PF was an insoluble and infusible material and was only studied as a possible material for modification of electrochemical electrodes. For this reason, it is of little interest for electronic or optical applications, limiting the discussion below to the chemically prepared 9-substituted PFs. 

Very recently, an exciting approach to control the chiral ordering in optically active polythiophenes by a doping process has been reported [130]. It was found that the addition of Fe(C104)3, NaS03CF3, or AgS03CF3 to chiral polythiophenes had a dramatic effect on the chiral arrangement of the polymer chains. No detailed description of the nature of the helical... 

Diazonium salts are also useful as a photosensitive material in a photobleachable two-layer resist system based on a doping process (10). High-resolution resist patterns were obtained using this two-layer resist scheme and an i-line reduction projection aligner. 

Application to the two-layer resist system. Photobleachable resist systems that have a strong absorption before exposure and that bleach completely upon UV exposure alleviate the light reflection from the substrate. A photobleachable resist system formed by means of the doping process liras reported in our previous paper (9). This resist system consists of two layers in which a diazonium salt is distributed in both the top and bottom layers. When exposed to i-line, the diazonium salt in... 

The exposure curve of the two-layer resist based on the doping process is shown in Figure 8. The two-layer resist system has a high contrast and high resolution capability. Submicron line-and-space patterns are obtained using this two-layer resist system (Figure 9). 

A central point of research is still the analysis of the electrochemical reaction occurring during charging, which are also known under the term doping process . Even in the earhest stage of research it was clear that these processes were not comparable with the classic doping of typical semiconductors. Rather, they correspond to oxidation in the case of /7-doping or... 

Similarly, we can describe the n-doping process due to exposure to a reducing agent, say M, as the formation of a negatively charged polymer complex ... 

A second major event in the saga of polymer conductors was the discovery that the doping processes of polyacetylene could be promoted and driven electrochemically in a reversible fashion by polarising the polymer film electrode in a suitable electrochemical cell (MacDiarmid and Maxfield, 1987). Typically, a three-electrode cell, containing the (CH) film as the working electrode, a suitable electrolyte (e.g. a non-aqueous solution of lithium perchlorate in propylene carbonate, here abbreviated to LiC104-PC) and suitable counter (e.g. lithium metal) and reference (e.g. again Li) electrodes, can be used. 

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