Ballistic electron emission microscopy (BEEM) has been performed on both $\mathrm{Au}∕{\mathrm{Fe}}_{81}{\mathrm{C}}_{19}∕\mathrm{Si}$ (001) and $\mathrm{Au}∕\mathrm{Fe}∕\mathrm{Si}$ (001) Schottky diodes at $80\mathrm{K}$. The Schottky heights were measured to be $0.68\pm 0.02\mathrm{eV}$ and $0.70\pm 0.02\mathrm{eV}$ for the ${\mathrm{Fe}}_{81}{\mathrm{C}}_{19}∕\mathrm{Si}$ (001) and $\mathrm{Fe}∕\mathrm{Si}$ (001) interfaces, respectively. In addition, a second threshold voltage was observed for the $\mathrm{Fe}∕\mathrm{Si}$ (001) interface at $1.29\pm 0.04\mathrm{eV}$ and attributed to an additional conduction band minimum at the interface that arises from the bonding of the Fe to the Si. The hot electron attenuation lengths at $1.25\mathrm{eV}$ were measured to be $3.5\pm 1.0\mathrm{nm}$ and $3.0\pm 0.9\mathrm{nm}$ for ${\mathrm{Fe}}_{81}{\mathrm{C}}_{19}$ and Fe, respectively. The attenuation length of the ${\mathrm{Fe}}_{81}{\mathrm{C}}_{19}$ showed a decrease with increasing energy consistent with the universal curve for electron-electron scattering. However, the attenuation length for the Fe showed this decrease only until the onset of the second threshold after which it increased. It is proposed that this increase is attributed to the parallel momentum distribution of the additional conduction band minimum at the $\mathrm{Fe}∕\mathrm{Si}$ (001) interface.

• Received 2 June 2006

DOI:https://doi.org/10.1103/PhysRevB.74.155328