Are quantum dots in unexpected locations due to strain?

It is a fairly common occurrence that, in top-gated Si quantum dots, the dots appear in reproducible but unexpected positions.~ For instance, sometimes a group will make gates in order to electrostatically generate tunnel barriers, but discover that the quantum dot is formed underneath the gate rather than between two barrier gates.~ We will discuss the possibility that such quantum dots arise from the mechanical strain induced by the gate.~ The model is simple:~ i) We simulate metal or polysilicon gates on top of a Si/SiO{\$}\textunderscore 2{\$} wafer, and calculate the stress and strain from differential thermal contraction of the materials; ii) Using the fact that the energy of the Si conduction band depends on strain through the deformation potential, we then convert the strain modulation to a potential energy modulation.~ As an example, we find that, for a single Al gate, there is a potential well directly underneath the gate with the size of a few meV, in agreement with recent experimental results.~ We also show that polysilicon gates will not produce such strain-induced quantum dots.