Patent ID: 7399987

Claim:
An article comprising an element having a first and a second surface, wherein the first surface is adapted to hold a first electrical charge, and wherein the second surface is adapted to hold a second electrical charge, the first surface being substantially parallel to the second surface, means for providing an electric field across at least part of the element, said means comprising means for providing the first electrical charge to the first surface of the element, and means for providing the second electrical charge to the second surface of the element, the second electrical charge being different from the first electrical charge in order to move electrons in a direction substantially perpendicular to the first or the second surface, wherein the element comprises a material or a material system being prepared so as to reduce electron scattering within the material or material system by having a predetermined crystal orientation perpendicular to the first or second surface, and by having an impurity concentration of less than 10 14 cm −3 , and the material layer has a thickness in a direction at least substantially perpendicular to the first or the second surface, which is equal to or larger than 0.2 μm.