Several features of the piezotronic effect are emphasized here. First, fundamental theory shows that the change of the Schottky barrier height is proportional to the piezoelectric charge density, which is proportional to the strain. Because the current depends exponentially on the Schottky barrier height, the relationship between strain and current flow is also exponential [20]. Second, the piezotronic effect is not a transient effect. As long as the strain holds, remnant piezoelectric charges can stay at the interface and the piezotronic effect will not disappear [44], although some slight decay over time was also observed [21]. Third, the piezotronic effect is an interface phenomenon, and should not be confused with the piezoresistive effect. The piezoresistive effect describes a change of the electrical conductivity of a semiconductor or metal when strain alters its bandgap, and thus it is a volume effect. Usually, the piezotronic effect has a more significant influence on the current flow than the piezoresistive effect when a Schottky barrier exists [45]