Depending on the geometry and the material used for fabrication, the operation mechanisms are governed either by quantum tunnelling or thermal activation.
"[2] But due to fabrication difficulties, two decades passed before the first device could be successfully created.
Some of the first MIM diodes to be fabricated came from Bell Labs in the late 1960s and early 1970s[3] Brinkman et al. demonstrated the first zero-bias MIM tunneling diode with significant responsivity.
As soon as 1974, this diode was reportedly used as a mixer at 88 THz in a setup of the National Institute of Standards and Technology.
[5] Today MIM diode is the cornerstone of the ongoing nantenna developments.