W. Olejniczak

Graphene on gold: Electron density of states studies by scanning tunneling spectroscopy

Graphene devices require electric contacts with metals, particularly with gold. Scanning tunneling spectroscopy studies of electron local density of states performed on mono-, bi-, and trigraphene layer deposited on metallic Au/Cr/SiO2/Si substrate shows that gold substrate causes the Fermi level shift downwards which means that holes are donated by metal substrate to graphene which becomes p-type doped. These experimental results are in good accordance with recently published density function theory calculations.

Sharp anomalies in the scanning tunneling microscope I–V characteristics at room temperature

A fine structure in the current-voltage characteristics of oxidized Zn, Cd, and Au measured by means of the room-temperature high stability STM technique is reported. The normalized second voltage derivatives obtained by numerical differentiation clearly reveal sharp anomalies near the voltages corresponding to the energies of oxide phonons. By analyzing the results, it is concluded that the physics of the effect involves the electron tunneling transfer via a series of quantum dots and the abrupt rearrangement of a dot local atomic structure accompanied by phonon emission.

Fine structure in differential conductance of oxidized nickel observed in a room temperature STM experiment

Direct measurements at room temperature of the current-voltage characteristics I(V) of a junction between a scanning tunnelling microscope tip made from W or Ni and an oxidized polycrystalline nickel surface are presented, with particular emphasis on a fine structure in the I(V) data. We show that it appears at voltages nearly corresponding to the energies of phonon and magnon excitations in tungsten, nickel and nickel oxide. We interpret the results obtained in terms of the mesoscopic dynamic processes that take place in tunnelling through specific atomic-scale surface sites.