Effect of silicon crystal structure on spin transmission through spin electronic devices

Spin injection into and spin transport through silicon spacer layers in iro n/silicon/cobalt structures has been investigated. Ultrahigh vacuum evapora ted silicon spacers of varying crystal quality from amorphous to epitaxial of thicknesses from 10 to 200 Angstrom were shown to improve their electric al conduction with increasing crystallinity, but no spin dependent transpor t was observed through the structure. Silicon and iron interdiffusion was a lso observed at the interfacial region. Device quality silicon was studied using 460 and 540 mu m doped silicon wafers of resistivity 0.1 and 1 Omega cm, respectively, polished on both sides, onto which were deposited iron an d cobalt layers. Sharp metal-semiconductor interfaces were achieved in this way, but no spin dependent transport, putting an upper limit on the spin d iffusion length in device quality silicon wafers. (C) 2000 American Institu te of Physics. [S0021-8979(00)92808-1].