y SUBSTRATE (b)Using above expression,calculate the rate of Si deposition on the substrate when I mole percent SiH4 and hydrogen gas mixture flows through the reactor. The substrate is maintained at 1000C.State any assumptions you make. Given:Diffusivity,DsiH4-H2(1000c)=2.5cm/sec Boundary layer thickness =0.02 cm Molecular wt.of SiH4 =32 10.(1)Consider a compound MX whose composition of existence includes the stoichiometric composition.Discuss thermodynamic and transport parameters which decide whether the compound is an ionic conductor,an electronic conductor.or a mixed conductor. (2)Tracer diffusion measurements for Cr2C3 at high P(O2)and high temperatures show that the dominant electrical neutrality condition is 3[Vcr]=[h].At low PO2,dissolved TiO2 dopant is compensated by excess electrons,[Ticr]=[e']. Consider a Cr2O3 specimen saturated with TiO2 and containing a small amount of excess TiO2: (a)How will the solubility of TiO2 depend upon P(O2)at low P (b)How will the electrical conductivity for TiO2-saturated Cr2O3 depend upon P(O2)2 11.Consider a localized adsorbate of methane on a substrate.In terms of absolute rate theory,present a detailed expression for the rate of desorption into the vapor. List and discuss all assumptions.Are there alternative descriptions of the activated state for this reaction? 12.Sulfur will segregate to grain boundaries in steel during annealing in the temperature range of 450-550C,causing grain boundary embrittlement. (a)If the sulfur atoms jump with a frequency of 108/s at 500C,give an estimate of the diffusion coefficient D,in cm /s in the lattice. (b)If the atom fraction of S in solution in the steel at 500C is 10 estimate how long it will take for enough diffusion to occur to form a monolayer of S on the grain boundary.(A monolayer consists of 1 sulfur atom per iron atom on the boundary.) 13.It has been postulated that in a certain temperature range the rate of the oxidation of nickel is limited by the rate of diffusion(mass transport)along grain boundaries,and not by diffusion through the lattice of the grains themselves.From your knowledge of lattice and grain boundary diffusion describe two types of(b) Using above expression, calculate the rate of Si deposition on the substrate when 1 mole percent SiH4 and hydrogen gas mixture flows through the reactor. The substrate is maintained at 1000°C. State any assumptions you make. Given: Diffusivity, DSiH4-H2(1000C)=2.5cm2 /sec Boundary layer thickness = 0.02 cm Molecular wt. of SiH4 =32 10. (1) Consider a compound MX whose composition of existence includes the stoichiometric composition. Discuss thermodynamic and transport parameters which decide whether the compound is an ionic conductor, an electronic conductor, or a mixed conductor. (2) Tracer diffusion measurements for Cr2C3 at high P(O2) and high temperatures show that the dominant electrical neutrality condition is 3[VCr"'] = [h0 ]. At low PO2, dissolved TiO2 dopant is compensated by excess electrons, [Ti0 Cr] = [e']. Consider a Cr2O3 specimen saturated with TiO2 and containing a small amount of excess TiO2: (a) How will the solubility of TiO2 depend upon P(O2) at low P^^ (b) How will the electrical conductivity for TiO2-saturated Cr2O3 depend upon P(O2)? 11. Consider a localized adsorbate of methane on a substrate. In terms of absolute rate theory, present a detailed expression for the rate of desorption into the vapor. List and discuss all assumptions. Are there alternative descriptions of the activated state for this reaction? 12. Sulfur will segregate to grain boundaries in steel during annealing in the temperature range of 450 - 550°C, causing grain boundary embrittlement. (a) If the sulfur atoms jump with a frequency of 108/s at 500°C, give an estimate of the diffusion coefficient D, in cm2 /s in the lattice. (b) If the atom fraction of S in solution in the steel at 500°C is 10-5, estimate how long it will take for enough diffusion to occur to form a monolayer of S on the grain boundary. (A monolayer consists of 1 sulfur atom per iron atom on the boundary.) 13. It has been postulated that in a certain temperature range the rate of the oxidation of nickel is limited by the rate of diffusion (mass transport) along grain boundaries, and not by diffusion through the lattice of the grains themselves. From your knowledge of lattice and grain boundary diffusion describe two types of