Effect of Dopant Concentration

Davis et al. reported the successful etching of PTFE using single-photon energies in the quartz UV (308 nm and a pulse duration of 25 ns) by sensitizing the fluoropolymer with polyimide. The number of pulses varied depending on fluence and material composition in order to achieve ablated features whose depths were reproducible as measured by a stylus-type profilometer. The pulse repetition rate was on the order of about 200 Hz. In that study, dopant levels 

Upilex-S is a registered trademark of Ube Industries, Ltd., Tokyo, Japan. 

Estimates of fZhicud using a rule-of-mixtures relationship are 3.0 X 10 and 

2 X 10 cm lor 0.2 and 5.0% polyimide, respectively. This dependence of the optimum absorption coefficient (in terms of ablation rate), Omax on fluence is consistent with the observations of Chuang et al. for ablation of several UV-transparent (at 308 nm) polymers sensitized with low-molecular-weight dopants, e.g., PMMA doped with pyrene. For the pyrene-PMMA system, Chuang et reported maximum etch rates for 1.2 J/cm at a = 7 x 10 cm i. It should not be expected that different dopant-matrix systems would yield the same optimum absorption coefficient for a given fluence level since the thermal properties for different polymers may vary significantly. 

The threshold fluence decreases with increasing dopant concentration and for the lowest concentration where ablation is observed (0.2% polyimide) the threshold fluence is about 0.7 J/cm at 248 nm and about 0.9 J/cm at 308 nm. Additionally, at fluences around 10. J/cnP, the maximum measured etching rates at 248 and 308 nm are about 3 and 6 pm/pulse, respectively. While the etching rate for the 248 nm ablation of the 0.2% polyimide-doped sample has begun to saturate, the corresponding curve for the 308-nm ablation is still increasing. In comparison, the tlireshold fluence for the ablation of neat PTFE using 300 fs 

---

Equation 9 quantifies the effects of dopant concentrations on the temperature required for the onset of martensite formation, Mg. The greatest effects are seen for the austenite-forming elements of C, Mn, and Ni where even small concentrations result in a sharp decrease in Mg. Whereas pure y-iron may be converted to martensite at temperatures in excess of 500°C, hypereutectoid steel is not transformed to martensite until a temperature of ca. 160°C is reached during quenching. At carbon concentrations above 0.7%, martensite is still being formed at temperatures well below 0°C. Hence, high-C steels must be quenched in low-temperature media e.g., dry ice/acetone, liquid nitrogen) to ensure full conversion of austenite to martensite. 

FIGURE 8.52. The effect of dopant concentration on the PS density. After Arita and Sunahama. (Reproduced by permission of The Electrochemical Society, Inc.)... 

Zhang, T.S. et al.. Effects of dopant concentration and aging on the electrical properties of Y-doped ceria electrolytes. Solid State Science 5 (2003) 1505-1511. 

Patra A, Baker GA, Baker SN. Effects of dopant concentration and annealing temperature on the phosphorescence from Zn2Si04 Mn2+ nanocrystals, J Lumin 2005 111 105-11. 

Sabbagh Alvani AA, Moztarzadeh F, Sarabi AA (2005) Effects of dopant concentrations on phosphorescence properties of Eu/Dy-doped Sr3MgSi20g. J Lumin 114 131-136... 

What is the effect of pH on voltammetric parameters of protonable CP systems The effect of dopant concentration in the electrolyte on other CP systems ... 

For the first two series of experiments, the coupon was submerged completely in one of the two test contaminants, patted lightly with a lint-free tissue to remove excess material, and weighed. Loading was controlled to 0.005 g from run to run to minimize effects of surface concentration differences. In later series, dopants were applied to one side of the coupon which was marked to designate an area so that the contaminated area would remain constant from run to run. The contaminants were applied to this area with a small, short-bristled paint brush. Contaminant mass for each of these series was kept constant from run to run to within 0.0001 g. 

Measurements of Rs transients were conducted in order to assess the effect of dopants / plating parameters on the kinetics of the transformation of electroplated copper [8]. Results are shown in Figure 6. For a constant bath temperature, the parameters that affect dopant incorporation the most are current density, rotation speed, and additive concentration. It is seen that an increase in additive concentration and rotation speed leads to a delay in the resistance transformation and to an increase in dopant content. Similarly, an increase in plating current density causes an acceleration of the resistance transformation and a decrease in dopant incorporation. It is thus concluded that dopant content increase causes delays in the resistance transformation of plated copper in accordance with the observations of Harper et al [8]. Results shown in Figs. 7 and 8 corresponding to different bath temperatures as well as plating from three different commercial chemistries are consistent with this correlation. 

In this paper, we report the result of an investigation on the relationship among the dopant concentration and the charge carriers as well as the associated molecular and electronic structure of the doped polyanilines. It is hoped that a study relating various data associated with the variations of molecular and electronic structures as well as the spin signals of the samples as functions of dopant concentration may provide a more comprehensive understanding of the doping effects in polyanilines. 

Four-probe dc conductivity of ES-I, as a function of protonation level, showed [21] a conductivity proportional to exp[-(T/T)i ]. The slope of the conductivity vs T / curves is independent of dopant concentration for x s [C1]/[N] 0.3. Given the behavior of susceptibility vs. protonation level for the ES-I family, the conductivity is best understood in terms of charging-energy-limited tunneling among the small metal islands [43]. For [C1]/[N] > 0.3, it appears that the barriers between the islands remain the same, while the number of pathways increases. Together wiA the electric field dependence of the conductivity, T can be used to estimate [21] the separation among the metallic islands as 100 A, in accord with later x-ray diffraction studies [20]. The temperature-dependent thermoelectric power, as a function of protonation level, shows a clear crossover in behavior, as a function of protonation level [21]. Analysis of the data is consistent with effective medium theory for a metallic phase embedded in a nonmetallic phase [44]. 

---