PhD at INAC-CEA, France

Institute for Nanoscience and Cryogenics (INAC), France

1.Atomistic simulation of GeMn magnetic semiconductors

Spintronic is a very active field in condensed matter research. A new magnetic semiconductor GeMn has been recently grown by means of molecular beam epitaxy in the laboratory [Nature Materials, 5 653 (2006)]. It consists of Mn-rich nanocolumns embedded in an almost purely Ge diamond matrix. The structure and the good magnetic properties of these Mn-rich nanocolumns are still puzzling. Our recent Extended X-Ray Absorption Fine Structure study reveals that these nano-columns show a complex local structure that does not correspond to any known stable GeMn compound [Applied Physics Letters, Vol. 92 242510 (2008)]. Electronic structure calculations give information about the magnetic and structural properties of a possible Ge1-xMnx compound which may form inside the nano-columns. The goal of this thesis is to study the kinetics of the nanocolumns growth as well as their transformation into stable compound upon annealing. This will be done by means of Monte Carlo simulations for the MBE growth and of Molecular Dynamics for the nanocolumns annealing. Both simulations will be based on an energy model that will be derived from ab initio calculations on stable compounds that should also reproduce magnetic ordering whitin theses compounds.For more details about ongoing work, see the web page of the laboratory: http://inac.cea.fr/L_Sim/The position is for three years. The start date is October 2009. Applications are being considered now. A master or equivalent diploma in either physics or chemistry or applied mathematics is required. The applicant must have strong skills in quantum physics, atomistic simulations and solid state physics. A good knowledge of computer programming and environment is essential.Interested candidates should send curriculum vitae, motivation letter and arrange for one to two references.

2.Atomistic modeling of the transport properties of semiconductor nanowires

Semiconductor nanowires are attracting much attention due to their promising properties and due to their possible applications in opto- and nano-electronics. The diameter of these nanowires ranges from a few to a few ten of nanometers, while their length can reach microns. These nanostructures provide many opportunities: For example, it is possible to vary the composition of the wires along their axis to introduce quantum dots or tunnel barriers whose width and position are well controlled. These nanowire “heterostructures” can then be connected to electrodes for charge transport measurements. Many such original experiments are being performed today to explore the potential of semiconductor nanowires for nano-electronics.The physics of semiconductor nanowires is complex and not yet fully understood. In this context, theory and modeling can bring valuable insights into the properties of these structures. The L_Sim laboratory is actively developing tools for the atomistic modeling of the electronic, optical and transport properties of semiconductor nanowires for a few years now (see web page below). We are now seeking a candidate for a PhD thesis on the modeling of the transport properties of semiconductor nanowires, using non-equilibrium Green function methods in an atomistic tight-binding framework. Various aspects such as the electron-phonon coupling, the treatment of contacts and open boundaries conditions, or charged defects might be explored during the thesis. These calculations will help achieving a better understanding of the physics of the nanowires and refining the interpretation of the experiments.The position is open for three years starting from October 2009. Applications are being considered now. A master or equivalent diploma in physics or material sciences will be required. The applicant must have strong skills in mathematics and quantum / solid state physics. A good knowledge of computer programming is essential.Interested candidates should send curriculum vitae, motivation letter and arrange for one to two references to:Yann-Michel Niquet,Laboratory of Atomistic Simulation (L_Sim),Institute for Nanosciencs and Cryogenics (INAC),CEA Grenoble,17, rue des Martyrs,38054 Grenoble cedex 9FranceE-mail : yniquet AT cea.frWeb pages : L_Sim : http://inac.cea.fr/L_Sim