Half a year here is no sun, and that is when it is really needed. On cold winter days wind doesn't blow either, although we do have quite a lot wind turbines. Many of them waiting to be connected to the main grid.
I also have a Jolla phone and preordered Jolla tablet. You can definitely install Google Play to it.
Sailfish might not be OS for everyone, but for long time linux user like myself, it is great compared to alternatives. Needs some work to get it just right, but after that I really like it.
The tunneling goes through different kind of defects in the oxide material (crystal imperfections impurities etc). I guess in this case the RTA (rapid thermal annealing) improves the oxide quality by removing the crystal imperfections ( by rearraging the oxide in high temperature) and maybe by gathering the impurities by diffusion...