Figure 13 may be a photograph or a 3D computer model but it is clearly intended to represent the microscopic world. A square piece of silicon is shown as a ridged but otherwise flat surface that is lightly covered in small specks of other substances. The two electrodes are shown as additional substantial lines of material on the surface, starting at opposite corners and laid out along a common diagonal line. They are not long enough to meet and in the middle of the gap between them there is a single atom of phosphorus.