Too thin oxide layer looks light, up to the color of metallic copper.
Copper can be sealed to glass without the oxide layer, but the resulting joint is less strong.
The bond strength is also governed by the character of the oxide layer on its surface.
In a vacuum, however, this renewal of the oxide layer does not occur.
It does not oxidize any more than the oxide layer.
This oxide layer is stable and has a high emission coefficient.
The two transistors are separated from each other by a thin oxide layer.
This oxide layer must be removed for welding to occur.
A light oxide layer on the outside, a few trace elements below.
An insulating oxide layer is grown on top of the silicon.