  We report experimentally that the electricity is generated from ambient
thermal fluctuations across a non-ideal diode consisted of a silicon tip and an
aluminum surface. The output is tuned by the contact force which modulates
Schottky barrier heights as well as rectifying ratios of the diodes. The
interaction regime between the silicon and the aluminum locates at the
quantum-classical boundary where thermal fluctuations are appreciable, and the
rectification of thermal fluctuations leads to the electricity generation. This
finding offers an innovative approach to environmental energy harvesting.
