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Unformatted text preview: Activity 2: Experimental uncertainties and unit analysis Topic 1: Uncertainties of many kinds in a real experimental situation: The thickness of a SiO 2 film Reading assignment: Preface of activity manual “Analysis of Experimental Errors” Your professor works on a two-dimensional atomically smooth material called graphene (Graphite, which is in your pencil, consists of many layers of graphene stacked together). In our lab, graphene sheets are deposited on Silicon Dioxide (SiO 2 ) films. These SiO 2 films are grown in a furnace. They are very smooth but not perfectly smooth. If you have the right kind of instrument, you can see a random distribution of hills and valleys on the surface. We wish to quantify the surface roughness (standard deviation of the thickness) of our SiO 2 films to understand its effect on the graphene layer placed on top. To measure the film thickness, we use a very precise instrument called an Atomic Force Microscope to scan the surface of the SiO 2 film and measure its height. The following image is a 3D rendering of a SiO 2 surface. A graduate student sampled the film thickness at different locations and acquired the following data set. The AFM is much more precise than a meter stick or a caliper, with an instrumental error of 0.03nm (1nm=1x10-9 m). This number is the intrinsic limit on the precision of the instrument. The number of significant figures in the data presented below reflects this limit. trial 1 2 3 4 5 6 t (nm)...
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This note was uploaded on 09/23/2008 for the course PHYS 211 taught by Professor Staff during the Fall '08 term at Pennsylvania State University, University Park.
- Fall '08