About the technique

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.

 

Facility at APE

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.

 

 

 

Materials deposited by MBE

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
(La-Sr)(Co-Cu-Ti-Zn)O3 Conductive
(Ba-K)(Cu-Bi)O3 Superconducting
(Ba-Sr)(Ti-Zr)O3 di-/ferroelectric
(La-Ba)(Mn-Fe-Ni-Co)O3 Ferromagnetic
Bi(Fe-Mn)O3 multiferroic
Spinel structure compound AB2O4
ZnFe2O4 Antiferromagnetic
Fe3O4 Ferromagnetic
Inside view of MBE-Oxide chamber

Inside view of MBE-Oxide chamber

Ongoing research

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.

Optical microscope image of the pillar structures and gold pads

Optical microscope image of the pillar structures and gold pads

Schema of the double junction circuit obtained on Fe/MgO/FeGa multilayers by optical lithography.

Schema of the double junction circuit obtained on Fe/MgO/FeGa multilayers by optical lithography.

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Technical specifications

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

The map of techniques

at MM building at Q2 building at Elettra experimental hall at CNR-IOM cloud at Fermi-T-Rex laboratory Surface & Nano Science Lab, STM/STS PLD XPS & ambient pressure XAS ARPES & Spin ARPES MOKE & Masked deposition system XPS MBE Oxides SPRINT laboratory SEM XRD PVD data repository open data data analysis
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Scientists in charge