A mean field theory for relaxor piezoelectrics and the piezoelectric transistor

IBM TJ Watson is working on a solution to the slowing down of Moore's law, in the form of a piezoelectric transistor (PET). In essence, a PET is a piezoresistive material sitting atop of a piezoelectric material, being clamped together by a material with a high tensile strength. Applying an electric field to a piezoelectric material causes it to expand, compressing the piezoresistive material. If the piezoresistor is chosen such that a small pressure change leads to a large resistive change and the piezoelectric such that a small voltage leads to a large pressure, the combination results in a fast, low voltage switch that can be used as a building block for logic gates and microchips.

A key component to a PET is a material with a large piezoelectric coefficient. A category of materials called relaxor piezoelectrics show such behaviour. They are solid mixtures of two perovskites, an example being lead magnesium niobate - lead titanate (PMN-PT). When the composition of PT is close to 33% (called the morphotropic phase boundary), these materials show a large piezoelectric response, dependant on their domain structure.

In this talk, I'll present ongoing efforts and open questions in theoretically understanding the behaviour of relaxor piezoelectrics such as PMN-PT