a) Assume that the growth of the solidification front of a pure metal is limited by heat conduction. In the following cases, when do you expect to observe dendrite structures to form? Why? Also, explain briefly how dendrites form? Tm Solid | Liquid T m Solid | Liquid x i b) Consider a situation where you are growing a thin film on a substrate using pulsed laser deposition. In this process, you use a short pulse (-10-30 ns) laser to ablate a material and can control the number of pulses per second. Assume that I will do the growth at 1 Hz pulse rate (only one pulse per second) and the incoming flux of atoms is of sub-monolayer atomic density (the coverage you can get for a pulse is only a fraction of the atomic density on the surface of the substrate, hence 2D growth is dominant). Let us assume that the lattice constant of the film and the substrate are ~4 . Assume that I use a substrate with a miscut of 1 to the (001) face of the crystal and the surface diffusivity of incoming flux is 10-10 cm/s at 700C along this face irrespective of the miscut. Which is the dominant growth mechanism among (a) step flow growth or (b) layer-by-layer growth for this case? Why? Can you name two parameters you can control to change the growth mode from one to another?