脉冲激光沉积(PLD)技术和应用剖析

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AUTOMATED EM SENSOR
• Exact transfer of complicated materials • Flexible, variety, easy to implement • Easy to prepare target • Epitaxy at low temperature • Fast growth rate
PRESSURE TRANSDUCER
YBCO TARGET
ROTATION MOTOR
Slot 6
PLUME VALVES TO VACUUM & O 2
HEATER WITH THERMOCOUPLE
VIDEO CAMERA
TOP WINDOW
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晑
WINDOW
Slot 13
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Slot 6
RAMAN SENSOR
III. Basic Theory of PLD
IV. Opportunities
Thin Film Deposition
Transfer atoms from a target to a vapor (or plasma) to a substrate
Thin Film Deposition
Transfer atoms from a target to a vapor (or plasma) to a substrate
smoother films at lower substrate temperatures, but may get intermixing
Target: metals, semiconductors… Laser: UV, 10 ns pulses Vacuum: Atmospheres to ultrahigh vacuum Film thickness: typically 100-200 nm. Deposition rate: 0.1 nm/pulse
SERVO-CONTROLLED MIRROR
INSERTABLE BEAM ATTENUATOR
WINDOWS
MANUAL EM SENSOR
BEAM CONDITIONING & FOCUSING
SUBSTRATE
EXCIMER LASER l = 248 nm
DEPOSITION CHAMBER
Chemical vapor deposition-CVD
substrate Ar+
target
substrate gas
Sputtering
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Low energy deposition (MBE): ~0.1 eV
High energy deposition (Sputtering ~ 1 eV)
Expansion of plume causes sudden drop in pressure just above surface
Shock wave pulls droplets of liquid off of surface
Thermal shock causes irregularities in surface to break off
Low energy deposition (MBE): ~0.1 eV
High energy deposition (Sputtering ~ 1 eV)
may get islanding unless you pick right substrate or heat substrate to high temperatures
may get islanding unless you pick right substrate or heat substrate to high temperatures
smoother films at lower substrate temperatures, but may get intermixing
• Uneven coverage • High defect or particulate concentration • Not well suited for large-scale film growth • Mechanisms and dependence on parameters
not well understood
Want sufficient diffusion for atoms to find best sites. Either use energetic atoms, or heat the substrate.
substrate
target
Evaporation (Molecular beam epitaxy-MBE)
After an atom is on surface, it diffuses according to: D=Doexp(-eD/kT)
eD is the activation energy for diffusion ~ 2-3 eV kT is energy of atomic species.
Pulsed Laser Deposition (PLD)
Huang Yan Wang Jianlin Ge Wen Zhao Yuan Yun Yu
UNIVERSITY OF SCIENCE AND TECHNOLOGY OF CHINA
I. Thin Film Deposition
II. Pulsed Laser Deposition a) Compared to other growth techniques b) Experimental Setup c) Advantages and Disadvantages
Subsurface Boiling
Laser superheats subsurface layer before surface reaches evaporation point
Surface breaks apart into large (micronsized) globule particles when the subsurface expands.