A. Kadyshevitch

Molecular control of a GaAs transistor

Abstract The interactions between adsorbed organic molecules and the electronic charge carriers in specially made GaAs structures are studied by time- and wavelength-dependent measurements of the photocurrent. The adsorption of the molecules modifies the photocurrent decay time by orders of magnitude. The effects are molecularly specific, as they depend on the electronic properties and absorption spectrum of the molecules. These observations are rationalized by assuming that new surface states are created upon adsorption of the molecules and that the character of these states is controlled by the relative electronegativity of the substrates and the adsorbed molecules. The relevance for surface passivation and for construction of semiconductor-based sensors is indicated.

Electron transmission through band structure in organized organic thin films

Direct evidence for the electronic band structure of thin organized organic layers is presented. The experimental results indicate that the electron-organic film system has to be described in quantum mechanical terms and that classical concepts fail. Quantum mechanical simulations on a generic system are also presented. They indicate that this type of simulation provides insight into the system studied experimentally.

THE ROLE OF THREE DIMENSIONAL STRUCTURE IN ELECTRON TRANSMISSION THROUGH THIN ORGANIC LAYERS

In this work we probe the effect of the three dimensional structure of the medium on the efficiency of electron transmission (ET) through it, and demonstrate that all three dimensions are playing a crucial role in the ET through thin films. By producing Langmuir–Blodgett layers from two type of amphiphiles we could vary the order in the plane perpendicular to the direction of electron propagation. It was found that the order in this plane affects the low energy electron transmission efficiency. The results are explained by the long wavelength associated with the low energy electrons.

The interactions of electrons with organized organic films studied by photoelectron transmission

Abstract The interaction between electrons and organized organic thin films was investigated by measuring the energy distribution of photoelectrons injected from a thin silver film coated with thin organic layers. Electrons with an energy above approximately 0.8 eV were transmitted ballistically through an organic layer containing up to five monolayers each about 2 nm thick. The transmission of low-energy electrons is controlled mainly by an electrostatic barrier perpendicular to the surface. Both elastic and nonelastic scattering were found to be unimportant on the scale of a single monolayer. The mean free path for electrons with an energy of 1.15 eV was found to be about 26 nm.

Electron Transmission Through Thin Organized Organic Films

The interaction between electrons and organized organic thin films was investigated by measuring the energy distribution of photoelectrons injected from a thin silver film coated with thin organic layers Electrons with energy above ∼0.8 eV were transmitted ballistically through an organic layer that contains up to five monolayers, each ∼2 nm thick. Elastic scattering processes contribute significantly to the electron energy distribution only for thicker layers. The transmission of low-energy electrons is controlled mainly by an electrostatic barrier perpendicular to the surface. A signature of a band structure in the organic layer was observed when the electrons were transmitted through 13 layers.

The effect of molecular structure and of three-dimensional order on electron transmission through thin organic layers

Abstract The electron transmission through thin organic films was investigated in order to reveal the effect of the chemical nature of the molecules composing the thin organic layer and the role of the three-dimensional structure of the film on the electron transmission efficiency. By preparing Langmuir–Blodgett layers from two types of amphiphile and a film which is a mixture of both, we could vary the chemical properties of the film and the order in the plane perpendicular to the direction of electron propagation. It was found that the electron transmission yield depends on the chemical nature of the film and varies with the film thickness in a non-trivial way. In the case of the mixed film, the electron transmission is reduced dramatically compared to the films composed from one type of molecule. The results are explained by the long wavelength associated with the low-energy electrons.