Problem 2 - Scanning Tunneling Microscopy -20 points (6/10/4) (a) Why will an ideally sharp step edge ( 90 angle to the surface) with a height of a nanometer or more not appear equally sharp in the STM images? Please add a sketch to clarify your thought process, include your knowledge about the tunneling process. (6 points) (b) Calculate the work function () for all 5 curves shown below which show measurements of the tunneling current as a function of distance between sample and tip. Use the value of A=1.025A1eV1/2. This measurement is done on the same surface for all curves and as such the density of states can be taken as constant. Note that the x-axis is given in relative displacement and does not show an absolute height. The tip is made of tungsten. (10 points) (c) How do you interpret the change moving from A to E ? The jump in curve B in the upward measurement is due to an experiment glitch and can be disregarded. (4 points)