The Point Contact Transistor invented by Bardeen and Brattain contained a triangle covered in gold foil and a crystal of germanium on a spring. Brattain attached a single strip of gold foil over the point of a plastic triangle, and then used a razor blade to slice through the gold right at the tip of the triangle. When the contraption was complete, it successfully directed electrical current from one gold contact to the other, and in the process enable the current to emerge from the second gold contact stronger than it was when it entered the first.
The crystal of germanium was the semiconductor present in Bardeen and Brattain's transistor. It sat on a metal plate attached to a voltage source. As a semiconductor, germanium can either let a great deal of electrical current through or none at all, depending on how it is treated. The germanium used by Bardeen and Brattain had an excess of electrons, but the scientists soon discovered that, when an electric signal traveled in through the gold foil, it injected holes (positive particles, the opposites of electrons) into the surface. This created a thin layer along the top of the germanium that contained too few electrons.