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MBE1

Growth System MBE 1 (SiGe)

Paola De Padova  -

Carlo Ottaviani  -

Sandro Priori  -

Laboratory: IC11

Rome - Tor Vergata
 
 
The heart of an MBE apparatus resides into the Knudsen effusion cells (called K-cells or effusion cells) and in a system to monitor the epitaxy and/or film crystallinity. This is, for instance, the reflection high energy electron diffraction (RHEED) system. In this case the RIBER K-cells are designed for an operating temperature up to 1200°C, pyrolytic BN, or at 1400°C C-pyrolytic BN. Conventional temperature control based on the proportional–integral–derivative (PID) device join to a thermocouple feedback, provides a temperature stability ΔT of few °C
 
 

TECHNICAL SPECIFICATIONS

  • Working pressure ~10-11-11 mbar
     
  • Si(C-BN-1400 °C), Ge(BN-1200 °C, Mn(BN-1200 °C) K-cells; Si (flux=0.04 Å/min); Ge (flux=0.16 Å/min);
     
  • Sb, As, Bi- Surfactants effusion cells;
     
  • Ag, Au- Capping Layer effusion cells;
     
  • DC direct sample heating (RT-1200 °C) and Indirect heating (RT-450 °C ) systems;
     
  • Air-vacuum Fast Load-lock Sample Transfer System;
     
  • Variable e- HV (0-15 KeV) for RHEED system;
     
  • Hi-Speed Camera for real-time data diffraction acquisition (Image-software-MAC).

AVAILABLE TECHNIQUES

  • RHEED Ultra-High Vacuum (UHV) System for Surface Science Investigations; 
  • Cleaning Semiconductor (SC), Metal (M)-Surfaces reconstruction;
  • Epitaxial growth SC/SC, SC/Metal/SC;
  • Homo- and Hetero-structures growth: 1D, 2D and 3D Materials.
 

SAMPLES

  • Sample lateral dimensions: 10 x 5 mm (ideal), 3 x 3 mm (minimal), 10 x 10 mm (maximal);

  • Sample thickness: ideally up to 2 mm (thicker and/or smaller samples also feasible).
 

USED FOR

  • Fundamental Surface Science study;

  • Artificial Atomic Epitaxial Growth;;

  • Discovery of new 1D, 2D and 3D epitaxial   SC/SC; M/SC for micro-nanoelectronics and solar cells purposes;

  • Semiconductors for Microelectronics;

  • Microcircuits;

  • Ultra-thin Films;

  • Samples Cleaning;
     
  • Thin-film Stability;
     
  • Barrier Layers;
     
  • Lubrication;
     
  • Chemical Industry;
     
  • Coatings/Catalysis.
 
 

CASE STUDIES

Cross-sectional high-resolution transmission electron microscopy (HRTEM) image of a Mn0.06Ge0.94 film grown on a Ge(001)2✕1 substrate held at 520 K0.06Ge0.94 on Ge(001)2✕1

The structural, electronic, and magnetic properties of the Mn0.06Ge0.94 diluted magnetic semiconductor0.06Ge0.94, grown at 520 K by molecular-beam epitaxy on Ge(001)2✕1, have been investigated. Diluted and highly ordered alloys, containing Mn5Ge3 nanocrystals5Ge3. The valence band photoelectron spectrum of Mn0.06Ge0.94 shows a feature located at −4.2 eV below the Fermi level, which is the fingerprint of substitutional Mn atoms in the Ge matrix. Magnetization measurements show the presence of a paramagnetic component due to substitutional Mn atoms and of a ferromagnetic like component due to Mn5Ge3. The Mn L2,3 x-ray absorption spectrum of this polyphase film shows no marked multiplet structure, but a bandlike character.

See: P. De Padova, et al., Phys. Rev. B 77,  045203 (2008).

 
Immagine ad alta risoluzione in sezione-trasmessa ottenuta al microscopio elettronico a trasmissione (HRTEM) sul film di Mn0.06Ge0.94 cresciuto sul substrato di Ge(001)2✕1 tenuto ad una temperatura di 520 K.
 
 
Immagine ad alta risoluzione in sezione-trasmessa ottenuta al microscopio elettronico a trasmissione (HRTEM) di un film di Mn5Ge3 cresciuto sul substrato di Ge(111), misurata lungo la direzione di asse di zona [-1-12] del substrato di Ge(111). (b) Vista laterale a sfere e sticks di un'epitassia coerente tra il film di Mn5Ge3 e il substrato di Ge.
 

Spettri di assorbimento a raggi-X di L2,3 di Mn misurati per polarizzazione circolare della luce destra [σ+ (linea rossa)] and sinistra [σ− (blue dashed line)] e il corrispondente segnale XMCD (σ+ − σ−) (linea nera).

 

See: W. Ndiaye et al., Phys. Rev. B 91, 125118 (2015).

 

Mn5Ge3 film on Ge(111)

An investigation of the structural, magnetic and electronic properties of≈3 nm thick Mn5Ge3 grown on a Ge(111)-c(2✕8) reconstructed surface is reported. High resolution transmission electron microscopy and selected area electron diffraction give evidence of 2.2% in-plane compressive strain between the Mn5Ge3 and the Ge substrate. Magneto optical Kerr effect measurements show that the films are ferromagnetic with a Curie temperature of ≈325 K. The analysis of Ge 3d core level photoelectron spectra of the Mn5Ge3 allows determining an upper limit of 76 meV for the Ge 3d5/2 core-hole lifetime broadening Ge 3d5/2. The Ge 3d3/2 core-hole lifetime broadening is found to be 15 meV larger than that of the Ge 3d5/2 core hole3/2 5/2, because of the existence of a Coster–Kronig decay channel due to the metallic character of Mn55Ge3.

See: P. De Padova, et al., Phys. Rev. B 77,  045203 (2008).

 
 
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