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Study of nanostructure growth with nanoscale apex induced by femtosecond laser irradiation at megahertz repetition rate.

Patel NB, Tan B, Venkatakrishnan K - Nanoscale Res Lett (2013)

Bottom Line: We have recently developed this unique technique to grow leaf-like nanostructures with such interesting geometry without the use of any catalyst.It was found to be possible only in the presence of background nitrogen gas flow.We observed a clear transformation in the kind of nanotips that grew for the given laser conditions.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Aerospace Engineering, Ryerson University, Victoria Street, Toronto, ON M5B 2K3, Canada. tanbo@ryerson.ca.

ABSTRACT
Leaf-like nanostructures with nanoscale apex are induced on dielectric target surfaces by high-repetition-rate femtosecond laser irradiation in ambient conditions. We have recently developed this unique technique to grow leaf-like nanostructures with such interesting geometry without the use of any catalyst. It was found to be possible only in the presence of background nitrogen gas flow. In this synthesis method, the target serves as the source for building material as well as the substrate upon which these nanostructures can grow. In our investigation, it was found that there are three possible kinds of nanotips that can grow on target surfaces. In this report, we have presented the study of the growth mechanisms of such leaf-like nanostructures under various conditions such as different laser pulse widths, pulse repetition rates, dwell times, and laser polarizations. We observed a clear transformation in the kind of nanotips that grew for the given laser conditions.

No MeSH data available.


Related in: MedlinePlus

Microholes drilled via different pulse-width sizes. Microholes drilled by femtosecond laser pulses with pulse widths of (a) 214 and (b) 714 fs at 16-W average laser power and 0.5-ms dwell time, 13-MHz repetition rate.
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Figure 3: Microholes drilled via different pulse-width sizes. Microholes drilled by femtosecond laser pulses with pulse widths of (a) 214 and (b) 714 fs at 16-W average laser power and 0.5-ms dwell time, 13-MHz repetition rate.

Mentions: Equation 1 gives the time at which the breakdown starts after the laser pulse has started interacting with the target surface at a given position in the focal region. From this point onward, the plasma starts to grow and expand, and covers the irradiated spot for few nanoseconds during which the second part of the laser pulse is still traveling toward the target surface. Using this equation, the time required for the breakdown to initiate is calculated to be 77, 189, and 325 fs for pulse widths of 214, 428, and 714 fs, respectively. The schematic representation of this time is shown in Figure 2. The amount of energy lost to the plasma before reaching the target surface depends on the amount of time the remaining portion, after breakdown initiation, of the pulse spends on traveling through the plasma. Shorter laser pulses (214 fs) reach threshold fluence very early since they possess high intensity, as depicted in Figure 2. However, they are very short and thus spend less amount of time in the plasma and thus loose less energy to the plasma and remove target material more efficiently compared to longer pulses (>214 fs). Hence, as can been seen from Figure 3a, the hole (approximately 12 μm in diameter) drilled by 214-fs pulse is closer in size to the laser beam spot diameter of 10 μm. Although we just worked with pulses in femtosecond regime (214 to 714 fs), the findings in the investigation by Stuart et al. are more relevant to our experiments as they worked with multiple pulses of laser with the wavelength of 1,053 nm in order to measure the damage threshold for SiO2[21]. Whatever results Stuart et al. achieved between picosecond and femtosecond pulses, we acquired it within the femtosecond pulse regime. For example, they discovered that the damage area generated by the 500-fs pulse in fused silica glass was twice as much smaller than that produced by the 900-ps pulse.


Study of nanostructure growth with nanoscale apex induced by femtosecond laser irradiation at megahertz repetition rate.

Patel NB, Tan B, Venkatakrishnan K - Nanoscale Res Lett (2013)

Microholes drilled via different pulse-width sizes. Microholes drilled by femtosecond laser pulses with pulse widths of (a) 214 and (b) 714 fs at 16-W average laser power and 0.5-ms dwell time, 13-MHz repetition rate.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3643873&req=5

Figure 3: Microholes drilled via different pulse-width sizes. Microholes drilled by femtosecond laser pulses with pulse widths of (a) 214 and (b) 714 fs at 16-W average laser power and 0.5-ms dwell time, 13-MHz repetition rate.
Mentions: Equation 1 gives the time at which the breakdown starts after the laser pulse has started interacting with the target surface at a given position in the focal region. From this point onward, the plasma starts to grow and expand, and covers the irradiated spot for few nanoseconds during which the second part of the laser pulse is still traveling toward the target surface. Using this equation, the time required for the breakdown to initiate is calculated to be 77, 189, and 325 fs for pulse widths of 214, 428, and 714 fs, respectively. The schematic representation of this time is shown in Figure 2. The amount of energy lost to the plasma before reaching the target surface depends on the amount of time the remaining portion, after breakdown initiation, of the pulse spends on traveling through the plasma. Shorter laser pulses (214 fs) reach threshold fluence very early since they possess high intensity, as depicted in Figure 2. However, they are very short and thus spend less amount of time in the plasma and thus loose less energy to the plasma and remove target material more efficiently compared to longer pulses (>214 fs). Hence, as can been seen from Figure 3a, the hole (approximately 12 μm in diameter) drilled by 214-fs pulse is closer in size to the laser beam spot diameter of 10 μm. Although we just worked with pulses in femtosecond regime (214 to 714 fs), the findings in the investigation by Stuart et al. are more relevant to our experiments as they worked with multiple pulses of laser with the wavelength of 1,053 nm in order to measure the damage threshold for SiO2[21]. Whatever results Stuart et al. achieved between picosecond and femtosecond pulses, we acquired it within the femtosecond pulse regime. For example, they discovered that the damage area generated by the 500-fs pulse in fused silica glass was twice as much smaller than that produced by the 900-ps pulse.

Bottom Line: We have recently developed this unique technique to grow leaf-like nanostructures with such interesting geometry without the use of any catalyst.It was found to be possible only in the presence of background nitrogen gas flow.We observed a clear transformation in the kind of nanotips that grew for the given laser conditions.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Aerospace Engineering, Ryerson University, Victoria Street, Toronto, ON M5B 2K3, Canada. tanbo@ryerson.ca.

ABSTRACT
Leaf-like nanostructures with nanoscale apex are induced on dielectric target surfaces by high-repetition-rate femtosecond laser irradiation in ambient conditions. We have recently developed this unique technique to grow leaf-like nanostructures with such interesting geometry without the use of any catalyst. It was found to be possible only in the presence of background nitrogen gas flow. In this synthesis method, the target serves as the source for building material as well as the substrate upon which these nanostructures can grow. In our investigation, it was found that there are three possible kinds of nanotips that can grow on target surfaces. In this report, we have presented the study of the growth mechanisms of such leaf-like nanostructures under various conditions such as different laser pulse widths, pulse repetition rates, dwell times, and laser polarizations. We observed a clear transformation in the kind of nanotips that grew for the given laser conditions.

No MeSH data available.


Related in: MedlinePlus