Nanoscale mapping of the W/Si(001) Schottky barrier

Abstract

The W/Si(001) Schottky barrier was spatially mapped with nanoscale resolution using ballistic electron emission microscopy (BEEM) and ballistic hole emission microscopy (BHEM) using n-type and p-type silicon substrates. The formation of an interfacial tungsten silicide is observed utilizing transmission electron microscopy and Rutherford backscattering spectrometry. The BEEM and BHEM spectra are fit utilizing a linearization method based on the power law BEEM model using the Prietsch Ludeke fitting exponent. The aggregate of the Schottky barrier heights from n-type (0.71 eV) and p-type (0.47 eV) silicon agrees with the silicon band gap at 80 K. Spatially resolved maps of the Schottky barrier are generated from grids of 7225 spectra taken over a 1 lm  1 lm area and provide insight into its homogeneity. Histograms of the barrier heights have a Gaussian component consistent with an interface dipole model and show deviations that are localized in the spatial maps and are attributed to compositional fluctuations, nanoscale defects, and foreign materials. V C 2014 AIP Publishing LLC. [http://dx

Nanoscale Schottky barrier visualization utilizing computational modeling and ballistic electron emission microscopy

“…This would cause unintentional radiative heating of the substrate due to its proximity to the source which would promote intermixing and the formation of a silicide. The TEM images support this finding as they show a more intermixed interface for the e-beam sample [42] when compared to sputter sample, which shows a very abrupt interface as seen in Fig. 4.1.…”

“…Fig. 4.1 showed TEM and EDX profiling of a 10 nm wide cross section of the e-beam sample, showing a significantly intermixed tungsten-silicon region when compared to the sputter sample, which showed an abrupt tungsten to silicon transition [42,44]. The presence of a small amount of gold in the model suggests that either gold is in contact with the silicon or that a sub-nm-thick tungsten layer might not be able to "screen" the gold from affecting the barrier height in some regions.…”

Relating spatially resolved maps of the Schottky barrier height to metal/semiconductor interface composition

“…Mapping of the SBH is achieved by fitting the spatially resolved transmission as a function of tip bias to extract the local SBH at individual tip locations and can achieve nanoscale resolution [15][16][17][18][19][20][21] [20]. However, no studies have measured the Schottky interface of mixed Au and Ag on the Si(001) substrate, which would be insightful for pinch-off effects due to the large differences in their barrier height's (∼ 0.2 eV) and their miscibility [25].…”

First-Principles View on Photoelectrochemistry: Water-Splitting as Case Study

“…Conventional models all assume a uniform dopant distribution, and it remains unclear how the composition and atomic structure of the semiconductor affect the electronic structure, i.e., barrier height and band bending, on the atomic level. It should be noted, however, that recent advances [96][97][98][99] have made it possible to characterize the Schottky band bending at the nanometer scale and have revealed important deviations from predictions made on the conventional Schottky model [100]. Instead, the results, which depend on materials' properties, dopant compositions and concentrations, can be qualitatively interpreted in the inhomogeneous Schottky barrier height model [101][102][103].…”