Institut des
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Séminaire nanostructures et systèmes quantiques

Electronic States in Semiconductors Nanostructures probed by : Scanning Tunneling Microscopy and Spectroscopy

Jean-Christophe Girard

Probing at the atomic scale the electronic properties of low dimensional compounds and nanostructures is one of the major challenges in nanoscience and technology. Scanning Tunneling Microscopy and Spectroscopy (STM/STS) offer an unique opportunity to measure the spatial distribution of the local density of states at an nanometer scale together with an energy resolution in the meV range, if performed under combined low temperature cryogenic (T=4K) and ultra-high-vacuum (UHV) environment. In our recent Cross-Sectional Scanning Tunneling Microscopy (X-STM) experiments, epitaxially grown semiconductor nanostructures samples are cleaved in situ to expose their cross-section on (110) surfaces and offer access for STS spectroscopic measurements of their local density of states (LDOS). In this talk, I will present spectroscopic studies on cleaved QDs of InAs/GaAs(110) and InAs/InP(110). Discrete energy levels for confined carriers were clearly identified and mapping of their eigen wavefunction were acquired in real space with high spatial and energy resolution. For QDs on InP(001), electron ground state energy inferred from our STS results are systemically found at lower values in comparison with QDs on GaAs(001) case. These STS results are already in favor of a shift of the emission to higher wavelength.