Question
Refer to Example 28.6. Estimate the percentage change in the tunneling current if the distance between the sample surface and the STM tip increases $2.0 \%$.
Step 1
Step 1: Recall the formula for the tunneling current in an STM: $I \propto e^{-2\alpha d}$ where $I$ is the tunneling current, $\alpha$ is a constant, and $d$ is the distance between the sample surface and the STM tip. Show more…
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Refer to Example $28.6 .$ Estimate the percentage change in the tunneling current if the distance between the sample surface and the STM tip increases $2.0 \%$
Suppose that an STM scans a surface at a distance of a = 1.500 nm. Take the height of the potential energy barrier to be U0 - E = 1.70 eV. If the distance between the surface and the STM tip decreases by 1.6% estimate the percentage change in the tunneling current. (Here is how you should enter your answer: if the change is 5% write 5.00 and if 20.7% write 20.7 and so on)
Make a semilog plot showing tunneling current versus tip-sample separation for an STM. Assume that the tunneling depth is $\lambda=0.1 \mathrm{~nm}$ and the tunneling current is $1 \mathrm{nA}$ when the separation is $z=0.2 \mathrm{~nm} .$ In an STM the circuitry usually limits the measurable currents to the range between $100 \mu \mathrm{A}$ and $10^{-14} \mathrm{~A}$.
Solids-Applications
The Scanning Tunneling Microscope
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