Ohmic contacts contact resistivity

P Evaporation Al Ohmic Specific contact resistance 1.51 x 10 Kanungo et al. 2009a... 

P Screen printing Ag Ohmic Specific contact resistance 0.0736 Vinod2005... 

P Screen printing firing at 800 °C in air anneahng at 450 °C in N2 Ag electroplating Ag Ohmic Specific contact resistance 1.01 x 10 Vinod2009... 

P Screen printing baking at 240 °C in inert ambient firing at 725 °C in air annealing at 450 °C in N2 —> Ag electroless Ag Ohmic Specific contact resistance 1.025 x lO " (before electroless Ag deposition) 3.25 X 10 (After electroless Ag deposition) Vinod2013... 

Reduction in resistive and capacitive (RC) delays is continuing by the use of higher conductivity materials and improved ohmic contact. 

Ohmic losses AEohmic originate from (i) membrane resistance, (ii) resistance of CLs and diffusion layers, and (iii) contact resistance between the flow field plates. Although it is common practice to split current-voltage characteristics of an MEA into three regions— kinetic (low currents), ohmic (intermediate currents), and mass transport (high currents) [Winter and Brodd, 2004]—implicit separation of vt Afiohmic is not always straightforward, and thus studies of size and... 

The Schottky-Mott theory predicts a current / = (4 7t e m kB2/h3) T2 exp (—e A/kB 7) exp (e n V/kB T)— 1], where e is the electronic charge, m is the effective mass of the carrier, kB is Boltzmann s constant, T is the absolute temperature, n is a filling factor, A is the Schottky barrier height (see Fig. 1), and V is the applied voltage [31]. In Schottky-Mott theory, A should be the difference between the Fermi level of the metal and the conduction band minimum (for an n-type semiconductor-to-metal interface) or the valence band maximum (for a p-type semiconductor-metal interface) [32, 33]. Certain experimentally observed variations of A were for decades ascribed to pinning of states, but can now be attributed to local inhomogeneities of the interface, so the Schottky-Mott theory is secure. The opposite of a Schottky barrier is an ohmic contact, where there is only an added electrical resistance at the junction, typically between two metals. 

A resistance Rv due to the sum of the ohmic contact resistance, the silicon bulk resistance and in part to the electrolyte resistance. 

Prasarma et al. [185] were also able to observe an optimum thickness of DLs for fuel cells experimentally. They demonstrated that the thicker DLs experience severe flooding at intermediate current densities (i.e., ohmic region) due to low gas permeation and to possible condensation of water in the pores as the thickness of the DL increases. On the other hand, as the thickness of the DL decreases, the mass transport losses, contact resistance, and mechanical weakness increase significantly [113,185]. Through the use of mathematical modeling, different research groups have reported similar conclusions regarding the effect of DL thickness on fuel cell performance [186-189]. 

Figure 2 Schematic diagram of applied contact pads with gold film, silver paste and gold wire. (Ref. Sugimoto, I., Tajima, Y., Hikita, M., Low Resistance Ohmic Contact for Oxide Superconductor Eu-Ba-Cu-O, Jpn. J. Appl. Phys. 27 L864 (1988).

Single-crystal Sb-doped, polished n-type Si wafers ((111) face exposed) were obtained from General Diode Co., Framingham, MA. The wafers were 0.25 mm thick and had resistivities of 4-5 ohm-cm. Electrodes were fashioned as previously reported (12). Ohmic contacts were achieved by rubbing Ga-In eutectic onto the back side of the electrode after a 48% HF etch and H2O rinse. The electrode was attached to a Cu wire with Ag epoxy, and the Cu wire was passed through a 4 mm Pyrex tube. 

This type of sensor utilizes a drastic increase in resistance at the point of dew condensation, since water absorption swells the polymers to counteract ohmic contact between carbon particles. This type sensor is now widely applied to humidity controling systems of video tape recorders or car windows. 

Another possible effect of PdAu deposits on PdAu/SnOx sensors is through the formation of a Schottky barrier between PdAu and SnOx, as in the case of the Pd/CdS hydrogen sensor. If such a barrier is formed, then a depletion layer is created inside the semiconductor tin oxide. Since the Pd work function can be reduced by hydrogen absorption through dipole or hydride formation (14,15), the width of the depletion layer in tin oxide may be reduced. The reduction of the depletion layer width causes the sample resistance to decrease. Such a possibility was checked and was ruled out, because a good ohmic contact was obtained between Pd (-50 nm thick) and SnOx- It is also commonly known that gold forms an ohmic contact with tin oxide. 

CellRes ohmCm2 Constant=0.05 %ohm-cm2 — this is a fixed ohmic loss (e.g., contact resistance)... 

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