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Molecular Beam
Epitaxy 101b
MBE SYSTEM COMPONENTS Section 1.2
MBE
• Substrate temperature • Effusion Cells
• Elemental sources fluxes • Flux control using shutters • Flux monitoring
• Very abrupt interfaces • RHEED in situ monitoring • Mass analyser • Cryogenic panels • Pumps • Vacuum gauges
Vacuum: Pumps
• Roughing
• Turbo
• Sorption
• Cryogenic
• LN2 cryogenic shroud
• Ion
• Diffusion
• Titanium Sublimation
4K
N
S
N
S
V+ V+
Epitaxy
• Ultrahigh vacuum conditions (base pressure ~10-10mbar) • Vaporised solid ultrapure elemental sources
• Group III: In, Ga, Al • Group V: (N), P, As, Sb, Bi •Dopants: Si and Be
• Condense onto a heated, rotated substrate
Knudsen Cells
• PBN crucible • Heater element • Thermocouple • Shutter
t/c
As cracker
• Ta crucible
• Heater elements
• Thermocouples
• Needle valve
Monitoring Ion gauge Beam flux monitor
• BEP
– Filament
– Grid
– Collector
+V
+V
-V
+V e
-V
THIN FILM GROWTH Section 1.3
• Frank-van der Merwe (2D) – Step flow – Islanding
• Stranski-Krastanov (S-K) • Volmer-Weber (3D)
Growth modes
Growth modes
• Frank-van der Merwe (2D) – Step flow – Islanding
• Stranski-Krastanov (S-K) • Volmer-Weber (3D)
• Frank-van der Merwe (2D) – Step flow – Islanding
• Stranski-Krastanov (S-K) • Volmer-Weber (3D)
Growth modes
• Frank-van der Merwe (2D) – Step flow – Islanding
• Stranski-Krastanov (S-K) • Volmer-Weber (3D)
Growth modes