Properties of SiC.• Wide-gap semiconductor.
• High thermal conductivity.
• Low thermal expansion coefficient.
• High melting point.
• High hardness.
• High breakdown electric field.
• High electron saturation.
• Suitable for high temperature, power and frequency applications.
Photetching of SiC by VUV-266nm Multiwavelength.
Zhang, et. Al., 1996, “Direct photoetching of single crystal SiC by VUV-266 nm multiwavelength laser ablation”, Appl. Phys. A,64, p.367.
Femtosecond Pulsed Laser Induced 3C/SiC surface Morphology.
Pulse duration = 120 fs; wavelength = 800 nm
Dong.Y., and Molian. P., 2003, “Femtosecond pulsed laser ablation of 3C-SiC thin film on Silicon”, Appl. Phys. A, 77, p. 839
Monolayer of SiO2 Nano-spheres on SiC.
SEM micrograph of the monolayer of silica spheres diameters (a) 1.76 µm and (b) 640 nm.
Experimental Setup.
LaserHarmonic Separator
Lens
XY Stage
Aperture
SiC Substrate
Silica Nanospheres
Laser
Schematic of (a) experimental setup, (b) Irradiation of the spheres on SiC.
Features for 355 nm Laser on Bulk SiC.
Features formed on the SiC substrate with a 355 nm laser (a) 1.76 µm diameter spheres and 950 mJ/cm2 and (b) 640 nm diameter spheres and 850 mJ/cm2.
AFM Results for 355 nm Laser.
Variation in the feature size with respect to the laser intensity for 355 nm laser and 1.76 µm spheres.
Features for 532 nm Laser on Bulk SiC.
750 nm1 µm
Features formed on the SiC substrate with a 532 nm laser (a) 1.76 µm diameter spheres and 2 J/cm2 and (b) 640 nm diameter spheres and 6 J/cm2.
AFM Results for 532 nm Laser.
AFM cross section view of the features obtained with 532 nm laser and 1.76 µm spheres.
Ablation Mechanism.• At low laser fluence the formation of laser-induced nanostructures
are from defect-activation.
• The pre-existing defects facilitate local absorption of incident laser.
• This results crystalline SiC to lattice disorder due to electronic excitation.
• Weakens interatomic bonding and thus lower the vibrational energy required for lattice disorder.
• With increasing laser-induced lattice defects, the formation of grain boundries results in polycrystallization of SiC film.