Doped poly diffusion

Because of the above-mentioned difficulties in trying to dope poly with phosphorus in situ, such films have traditionally been deposited undoped. Doping can then be accomplished by ion implantation or diffusion. 

H NMR study of I2 doped poly[2-buthoxy-5-methoxy phenylene vinylene] (PBMPV) has been carried out by Lee et al.114 They found magnetization recovery to follow a stretched-exponential form M(f) =Mo[l — exp(f/Ti) ] with n = 0.8 0.03, which is characteristic of a system with distribution of the correlation time. 1/Tj versus/ 172 in samples with different conductivity follows/ 172 dependence over 20 40 MPIz range indicating the main SLR is ID spin diffusion. A correlation between 1/T1 and dc conductivity has been made which is found follow a simple power law. 

H. Randriamahazaka, V. Noel and C. Chevrot, Anomalous diffusion on the active zone of p-doped poly(3,4-ethylenedioxythiophene) modified electrodes, J. Electroanal. Chem. 556, 35-42 (2003). 

Diffusion in films which were as thin as 3.5nm was studied by using doped poly-Si/Si02/Si samples. The data for As diffusion could be described ... 

Figure 4 Effect on the serum stability of the incorporation of 5% cholesterol poly(ethy-lene glycol) (PEG) into cationic lipoplexes [hpopolyamine RPR209120/DOPE1/1, ratio (mol) lipid/DNA = 10 in 150 mM NaCl]. Lipoplexes were incubated in DMEM + 10% SVF, at 37°C, aliquots were regularly sampled and monitored by dynamic diffusion. Results represent a mean between three measurements. Error bars are not presented to simplify the graph, but differences among PEG, PEG-1, and PEG-2 are significant. Abbreviations PEG, poly(ethylene glycol) DOPE, dioleylphosphatidylethanolamine DMEM, Dulbecco s Modified Eagle Medium.

Attempts to dope organic semiconductors have been made very early in the field, motivated by the prospect of possibly reaching metallic conductivities [108, 109]. These synthetic metals, however, have not been realized. While p-type doping could be obtained, for example, with iodine gases for poly-p-phenylene vinylene (PPV) derivatives, and n-type doping was demonstrated with sodium for a cyano-derivative of PPV, the doping levels obtained were not stable with time. The dopant molecules readily diffused into the organic semiconductor, yet also out of it. Due to the lack of stability, these approaches were not suitable for commercial applications. 

Heavily doped (>1018/cm3) n-type Si and poly-Si etch faster in Cl- and F-containing plasmas than do their boron-doped or undoped counterparts (103a, 105, 111, 112). Because ion bombardment is apparently not required in these cases, isotropic etch profiles (undercutting) in n + poly-Si etching often occur. Although the exact mechanisms behind these observations are not completely understood, enhanced chemisorption (103b, 111) and space charge effects on reactant diffusion (112) have been proposed. 

Investigation of the microscopic origin of these TLSs has demonstrated the feasibility of modulating resonance shifts in a single molecule by interrogation of neighboring solvent molecules coupled to the system.1158 In poly(methyl methacrylate) doped with free base phthalocyanine and small amounts of water, it has been shown that reorientation of nearby water molecules is the source of spectral diffusion observed in the phthalocyanine. 

Figure 2.16. Left oxygen diffusion data of various ceria-coniaining materials 1 CeOj. single crystal 2 CeOj poly crystalline sample 3 CeogYojOiv 4 CCo Yo Oig 5 CeO,g 6 Ceo9Cao,0,/ 7 (0.3%)Od doped CcOj 8 Ce02. shaded area corresponds to oxygen diffusion values calculated from ionic conductivity of rare-earth doped ceria CC. M 02.o,. with x 0.2 and 0.3 using Eq. 2.29. Right details of oxygen diffusion coefficients of rare-earth doped ceria with x=0,3 from top to the bottom (M=Eu,Nd.Ho,Gd.Er.Sm,Y.La.Yb,Dy).

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