Scanning gate microscopy : A new tool for nanoelectronics
UCL, Louvain-la-neuve, Belgium - Chair of Excellence of the Foundation Nanosciences
Thu, Dec. 18th 2008, 16:00
Amphi P015, PHELMA Polygone
Traditionally, the understanding of device physics has relied on the measurement of macroscopic properties, such as conductance, magnetization,... Although powerful when coupled to microscopic theories and statistical physics, this approach cannot provide a detailed image of ‘how electrons behave down there’. Until recently, microscopic properties such as the density of states, the presence of dopants,... could not be measured directly in real space, meaning that the microscopic theories of conduction, of first importance for nanoelectronics, could not be checked experimentally.
The first breakthrough towards a local investigation of electronic properties came shortly afer the discovery of the scanning tunneling microscope (STM) by G. Binnig and H. Rohrer. Suddenly, local scale studies at the surface of conducting materials were made possible. Even atomic manipulation was demonstrated as well as the first real-space observation of electron wavefunctions. However, STM is limited to surface properties of conductors and is of no help for electron devices that are embedded in semiconductor materials. More recently, progress was made towards the direct observation of electron properties in nano-devices by combining scanning probe techniques, i.e. atomic force microscopy (AFM), with transport measurements. This is the so-called scanning gate microscopy (SGM) that maps the change in conductance of a device as the polarized conducting tip of the AFM, acting as a tunable nano-gate,
scans at some distance above the embedded electrons.