Ballistic electron emission spectroscopy of metals on GaP(110)
ABSTRACT Ballistic electron emission spectroscopy (BEES), a technique based on the scanning tunneling microscope (STM), was used to measure Schottky barrier heights of metals on cleaved n‐type GaP(110). The threshold voltages V 0 for current detection in the semiconductor were found to be uniform to within ±0.02 V over the sample surface for any given metal on GaP. A transport model for the current I c crossing the barrier, that includes both nonclassical transmission across the metal–semiconductor interface and electron scattering in the metal, yields I c ∝(V-V 0 )5/2 near threshold. The value of V 0 extracted from the data, which represents the Schottky barrier height, depends somewhat on the details of the transport model. Our best estimates of the Schottky barrier heights, within ±0.03 eV, are 1.07 (Mg), 1.11 (Ni), 1.14 (Bi), 1.25 (Cu), 1.31 (Ag), and 1.46 eV (Au).
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ABSTRACT: Hot electron transport of direct and scattered carriers across an epitaxial NiSi2/n-Si(111) interface, for different NiSi2 thickness, is studied using ballistic electron emission microscopy (BEEM). We find the BEEM transmission for the scattered hot electrons in NiSi2 to be significantly lower than that for the direct hot electrons, for all thicknesses. Interestingly, the attenuation length of the scattered hot electrons is found to be twice as large as that of the direct hot electrons. The lower BEEM transmission for the scattered hot electrons is due to inelastic scattering of the injected hot holes while the larger attenuation length of the scattered hot electrons is a consequence of the differences in the energy distribution of the injected and scattered hot electrons and the increasing attenuation length, at lower energies, of the direct hot electrons in NiSi2.Journal of Physics Condensed Matter 09/2013; 25(44):445005. · 2.36 Impact Factor
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ABSTRACT: Ballistic Electron Emission Microscopy (BEEM) can be a versatile spectroscopic technique to investigate electron scattering phenomena during transport across metal-semiconductor (M-S) interfaces. Two examples for obtaining numerical values of scattering parameters are discussed. In the first example the elastic and inelastic mean free paths of electrons in Pd are deduced over a 1-6eV energy range from model fits of the attenuation of the collector current with film thickness for thin Pd films deposited on Si(111) and Si(100) substrates. The results are used to demonstrate that electron scattering in the Pd film is insufficient to account for the spectral similarities for the two Si substrate orientations, which implies that the scattering occurs at the M-S interface and that transverse momentum is not conserved for electrons crossing the M-S interface. In the other example, the impact ionization quantum yield for electron-hole pair generation in Si is directly measured over an energy range from 1-7eV by injection of electrons through pin holes in thin NiSi2 layers grown epitaxially on Si(111). The quantum yield is in excellent agreement with existing model calculations, which can be used to determine the primary component of the collector current for any energetic BEEM spectrum. The primary component is shown to exhibit structure that is interpreted as arising from density-of-states effects in the semiconductor.Physica Scripta 01/2007; 1994(T55):90. · 1.03 Impact Factor
- Surface and Interface Analysis 01/1999; 27:517-520. · 1.22 Impact Factor