Dominador Tan

Areas Dominador Tan is Knowledgeable in:

Techniques Dominador Tan Uses:

Dominador Tan's Problem Solving Experience:

1. By how much does the tunneling current through the tip of an STM change if the tip rises 0.020 nm from some initial height above a sodium surface with a work function W0=2.28eV? [Hint: Let the work function (see Section 37-2) equal the energy needed to raise the electron to the top of the barrier.]
   
   
   Solution:
   
   In this problem, we are given a scanning tunneling microscope for which we want to estimate the change of the tunneling current if the tip of the microscope moves away for 0.020 from the sodium surface.
   
   T1= Ae^-2GI
   
   and
   
   T2= Ae^-2G (l + deltal)
   
   Next, drop in transmission which is going to be defined as,
   
   T2/T1= Ae^-2G(l + deltal)/ Ae^-2GI= e^-2Gdelta l
   
   
   Next, Calculate the exponent:
   
   exp= 2 x 0.0x10^-9 x squareroot 2 x 9.11x10^-31 x 2.28 x 1.6x10^-19/ h
   
   exp= -0.3091
   
   Finally, get the ratio between tunneling current:
   
   T2/T1= e^-2Gdeltal= e^-0.3091
   
   T2/T1= 0.73
   
   Therefore, the current drops for about 27%.