Ferroelectricity and quantum-mechanical electron tunneling are well-known physical phenomena that have been studied for as long as a century. During this long period, scientific research has been restricted either to ferroelectricity or to electron tunneling. Never before have these subjects been combined into a new phenomenon based on their interaction. Within this work, I present the novel concept of a ferroelectric tunnel junction, where the term ferroelectric refers to a property of the barrier material. This device consists of a ferroelectric layer sandwiched between metal electrodes. The thickness of the ferroelectric layer is thin enough to allow for electron tunneling. For the first time, the influence of macroscopic parameters, such as the spontaneous polarization and strain on quantum-mechanical electron tunneling through a ferroelectric tunnel barrier is studied experimentally. In addition, the experimental work is accompanied by theoretical ideas and predictions concerning the manifestation of piezoelectricity or ferroelectricity in direct electron tunneling
