The Molecular Beam Epitaxy (MBE) is a technique for the growth of epitaxial thin film. In MBE the desired elements are sublimated in special devices called evaporators (by thermal annealing) or introduced in the chamber in gas phase. In both cases the atoms stick on a substrate creating a solid solution in thin film form. The MBE can be performed only in Ultra High Vacuum (UHV) condition. The technique is characterized by a very small deposition rate (typically less than 1 nm per minute) that permit the deposition of thin film with the best possible thickness precision. Moreover this technique give rise to thin films with high purity stoichiometry and a high control on their crystal structure.
A cluster of UHV chambers that can exchange samples for growth and analysis is available for users projects. The cluster is composed by 3 different chambers: 2 MBE chambers (Oxide and Mask) and 1 XPS station. The MBE cluster growth facility is located in the area of the APE beamline inside the experimental hall of Elettra, is not directly connected with the APE-NFFA laboratory but can exchange samples via a UHV shuttle chamber (available soon).
The MBE-Oxide chamber allows for growth of complex oxides in pure ozone or oxygen as oxidizing ambient. The growth chamber is equipped with in-situ noninvasive measurement of atomic fluxes in real-time for single component materials (quartz crystal monitor) and for multi-component compound (atomic absorption spectroscopy). The deposition of individual monolayers is monitored by in situ reflection high energy electron diffraction (RHEED) system.
The MBE mask chamber allows for metal and simple rock-salt oxide depositions (masked or mask-less). The chamber is equipped for the standard tools for sample preparation in UHV conditions (sputtering with Ar ions, annealing stage by e-beam bombardment, quartz microbalance, leak valve for gas inlet and e-beam evaporators). Moreover the chamber will equipped with a shadow mask system that will allow the direct evaporation of patterned film of micrometric size. In the chamber there is also an AES/LEED system for the structural and chemical characterization and a MOKE apparatus (see MOKE section) for azymuthal Kerr magnetometry in UHV with fields up to 0.55T. Moreover thanks to a 2 contact sample-holder we can measure the transport properties (I vs V curve and magnetoresistance) of thin films and junctions.
The XPS analysis chamber is equipped with a double anode (Mg,Al) x-ray source and with a electrostatic hemispherical analyzer (mean radius 200 mm) to permit XPS measurements (see XPS section). The samples can be in situ transferred from the MBE chambers or can be directly introduced from external sources. In-situ with sputter/annealing surface treatments are available.
Complementary facilites at the co-located IOM-TASC clean-room are available for integrating lithography in the sample fabrication, in particular for "in-operando” type experiments.
|Ultrathin Layers on Surfaces|
|3d,4d,4f metals||Ferromagnetic metals|
|organic molecules||Moleculer magnets|
|MgO, Al2O3, NiO||Insulationg Oxides|
|Metallization and masked deposition|
|Au, Pt||Conductive metals|
|Perovskite structure compounds ABO3|
|Spinel structure compound AB2O4|
The Oxide growth chamber is operational since several years and is active in perovskite structure compounds deposition, like doped manganites, ferroelectric and multiferroic based thin films and heterostructures. The new MBE chamber is in the commissioning phase, the MOKE apparatus which is already operational has been used to study ferromagnetic oxides and magnetoelastic layers. The system will be devoted to the growth and characterization of multilayers with advanced functionalities for microelectronics. Thanks to the clean room facility at TASC the 2D samples will be structured by lithography in order to obtain prototypes of functioning devices. The system also permits the characterization of the electrical transport properties of a device.
|MBE Masked deposition|
|sample dimensions||5x5 mm|
|evaporation sources||up to 5 e-bombardment evaporators|
|annealing temperature||up to 950K|
|sample temperature control||35-300K|
|LEED / Auger spectroscopy||OCI BDL800IR|
|transport merasurements||Keithley 6487|
|MBE Oxide Growth|
|sample dimension||up to 10 mm x 10 mm|
|deposition temperature range||up to 800 K|
|deposition pressure in ozone/oxygen||up to 10^-5 mbar|
|deposition pressure without process gas||down to 10^-9 mbar|
|high temperature effusive cells (up to 1500°C)||3|
|conventional effusive cells||3|
|low temperature effusive cells||2|
|RHEED gun electron energy||10 kV|
|RHEED software analysis||KSA-400|
|RHEED spot size||100 micron diameter|
My research activity is focused on the investigation of the magnetic properties of nanostructure and thin films. The class of material that I study comprises: metals, diluted magnetic semiconductors and oxides, multiferroics and new functional materials.
My research activity is mainly devoted to the study of the interplay between magnetic and electronic-structural properties in highly correlated systems on the Cluster Growth at APE beamline (buried interfaces, 2D electron gases, ferroelectric and magnetic oxides heterostructures). I do also local contact activity on APE-HE beamline.
Research activity concern to oxide thin films and heterostuctures growth by means of molecular beam epitaxy, and its magnetic, transport and structural properties study in dependence on interface and surface state and/or interaction (exchange bias and tunneling structures).