Ion beam crystallography of surfaces and interfaces

Almost all metal-semiconductor or Schottky contacts exhibit rectifying behaviour which is caused by a depletion layer on the semiconductor side of the interface. The electronic properties of a Schottky diode are characterised by its barrier height which is the energy difference between the top of the valence band of the semiconductor and the Fermi level at the interface. The physical mechanism primarily determining barrier height is provided by the decay of the metal's electron wavefunctions into the semiconductor in the energy range between the top of the valence band and the Fermi level where the metal conduction band overlaps the semiconductor band gap. These wavefunction tails are described as the continuum of metal-induced gap states (MIGS) which are derived from the virtual gap states of the complex semiconductor band structure.

https://iopscience.iop.org/article/10.1088/0034-4885/53/3/001/pdf

On the physics of metal-semiconductor interfaces

Electronic properties on silicon-transition metal interface compounds

Microscopic properties and behavior of silicide interfaces

Diodes formed from semiconductor/metal interfaces often display non-ideal electronic properties. For instance, silicon/metal (Schottky) diodes made from n-type silicon and a variety of contacting metals exhibit only small differences in their rectification properties, despite theoretical and practical expectations that changes in the metal should effect changes in device properties. Similarly, Schottky diodes formed on p-type silicon generally exhibit ohmic behaviour with poor rectification characteristics. This lack of electrical response to changes in the properties of the contacting metal phase is generally attributed to interfacial reactions that take place during the high-temperature thermal or electron-beam deposition of metals onto silicon. Here we describe the fabrication of diodes using a low-temperature chemical procedure, in which contact to the semiconductor is made by a layer of the conducting organic polymer, polyacetylene. Unlike conventional metals, the electrical properties of polyacetylene can be manipulated through choice of the polymer dopant. The resultant organic/inorganic interfaces behave more ideally than contacts with conventional metals, in that changes in the electrical properties of the conducting polymer exert a large and predictable effect on the electrical properties of the resulting semiconductor/polymer diodes.

Electronic properties of junctions between silicon and organic conducting polymers

Chemical reaction and Schottky-barrier formation at V/Si interfaces

Synchrotron radiation photoemission measurements have been used to study the behavior of the Schottky barrier height φ bn and electronic structure of the V/Si interface for both cleaved Si(111)- (2X1) and sputter-cleaned Si(111)—(7 X 7) surfaces. Although the Schottky barrier height φ bn of the clean surface is influenced by surface reconstruction (and by steps), the barrier becomes pinned at low (~ 2 A) V coverage at a position essentially independent of the initial clean surface structure. Formation of the bulk V metal band structure is not complete until ∼ 30–40 A V coverage, indicating coverage-dependent structural effects in the growth of the metal film. These effects also seem to produce secondary influences on φ bn ,which are manifested as a gradual increase of φ bn ,with higher coverage or mild (~200°C) annealing. However, upon higher temperature annealing (>350°C) the trend reverses, with φ bn decreasing to a value (∼0.64 eV) characteristic of the bulk VSi2contact which is formed at 500–550 °C; this change in the behavior of φ bn is directly correlated with the onset of atomic mixing across the interface.

J. G. Clabes

Papers

Chemical reaction and Schottky-barrier formation at V/Si interfaces

The formation of the Schottky barrier at the V/Si interface

Summary Abstract: Schottky barrier formation at Pd/Si(111) and V/Si(111) interfaces

The formation of the Schottky barrier at the V/Si interfacea)