Expansion of an ablation plume in a buffer gas and cluster growth

Bailini, A.; Ossi, P.M.

doi:10.1209/0295-5075/79/35002

Cited by 41 publications

(27 citation statements)

References 29 publications

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“…(* pg is the Ar pressure, ng is the number density of Ar gas atoms, na is the average number density of ablated atoms, σa-g and σa-a are the geometric cross-sections for ablated particle -ablated particle and for ablated particle -gas atom binary collisions respectively, ν0 is the initial plasma velocity, <ν> is the average velocity of plume particles, tf is the cluster formation time, xaggr is the distance travelled by the plume during cluster growth, d and <d> are the nanoparticle sizes theoretical and experimental respectively.) In order to verify our observation, theoretical calculations were done based on modelling of plasma expansion [15,16,18]. For this, images obtained by the fast imaging iCCD camera were introduced to MATLAB.…”

Section: Resultsmentioning

confidence: 91%

“…The important criterion for SERS is that the substrate surface has to be a roughened feature [10,11] since the magnitude of SERS not only depends on nanoparticle dimensions but also the size, shape, spatial density and distribution of these nanoparticles [12,13]. We propose a method of production of such excellent featured substrates using Pulsed Laser Ablation (PLD) based on Bottom Up approach [14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

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Ag and Au nanoparticles for SERS substrates produced by pulsed laser ablation

Agarwal

Fazio

Neri

et al. 2011

Cryst. Res. Technol.

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A method for the growth of films consisting of Nanoparticles (NP) of Ag and Au is presented. Nanostructured films were obtained by means of nanosecond pulsed laser ablation of a metallic target in presence of a controlled Ar atmosphere. The morphology of these films from island structures to isolated nanoparticles, measured by SEM, depends on the varying gas pressure (10-100 Pa) and on the number of laser pulses (500-30000), keeping other deposition parameters such as the target to substrate distance, incidence angle, laser wavelength, laser fluence constant. Fast imaging of the plasma, performed using a intensified and gateable CCD camera at different time delays with respect to the arrival of the laser pulse, allows revelation of the propagation regime of the ablation plume and inference of plasma initial velocity. This data along with the measured average ablated mass per pulse were taken as inputs to a model to estimate the average size of NPs grown in the expanding plume. The theoretical NP sizes were compared with sizes measured from TEM images. These images indicate narrow gradients of NP sizes. Hence strict control of growth parameters aids fine tuning of NP size that is essential for many applications, including Surface Enhanced Raman Spectroscopy (SERS) active substrates. UV-Visible Spectroscopy helped in determination of appropriate laser wavelength for resonant excitation of the localized surface plasmon. SERS Spectra obtained with increasingly lower concentrations of reference dye Rhodamin 6G (Rh6G) and medical drug Apomorphine, are discussed as a perspective of application to biomedical sensors.

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Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Ag and Au nanoparticles for SERS substrates produced by pulsed laser ablation

Agarwal

Fazio

Neri

et al. 2011

Cryst. Res. Technol.

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“…The diameters, although larger than those obtained in ps laser deposition in vacuum, increase in size with laser fluence for all laser wavelengths, as in the case of using a ps laser [13]. The formation of these nano-sized droplets is believed to be different from those grown in various background gases with a size of 1-10 nm; here the formation was related to plasma plume confinement from the background/buffer gas that enhanced collision and promoted aggregate formation [24]. In addition, the process should be different from fs laser ablation of Si in vacuum, where the formation is related to the sudden expansion upon laser irradiation instead of condensation in gas phase [16].…”

Section: Resultsmentioning

confidence: 88%

Nanosecond laser ablation and deposition of silicon

et al. 2011

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Nanosecond-pulsed KrF (248 nm, 25 ns) and Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) lasers were used to ablate a polycrystalline Si target in a background pressure of <10 −4 Pa. Si films were deposited on Si and GaAs substrates at room temperature. The surface morphology of the films was characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Round droplets from 20 nm to 5 µm were detected on the deposited films. Raman Spectroscopy indicated that the micron-sized droplets were crystalline and the films were amorphous. The dependence of the properties of the films on laser wavelengths and fluence is discussed.

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“…These observations were attributed to stronger plasma excitation in argon. Similar to DP-LIBS, expansion of a laser produced plume in a background or buffer gas is also complicated and difficult to model thoroughly [41,50]. This can be further complicated when changes in pressure are included [46].…”

Section: Introductionmentioning

confidence: 99%

Effect of atmosphere on collinear double-pulse laser-induced breakdown spectroscopy

Effenberger

Scott

2011

Anal Bioanal Chem

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Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) has been shown to enhance LIBS spectra. Several researchers have reported significant increases in signal-to-noise (S/N) and/or spectral intensity compared to single-pulse (SP) LIBS. In addition to DP-LIBS, atmospheric conditions can also increase sensitivity. Thus, in this study, a collinear DP-LIBS scheme was used along with manipulation of the atmospheric conditions. The DP-LIBS scheme consisted of an initial 45 mJ pulse at 1064 nm fired into a sample contained in a controlled atmospheric/vacuum chamber. A second analytical 45 mJ pulse at 1064 nm was then fired 0 to 200 μs after and along the same path of the first pulse. Ar, He, and air at pressures ranging from atmospheric pressure to 1 Torr are introduced during DP-LIBS and SP-LIBS experiments. For a brass sample, significant increases in the spectral intensities of Cu and Zn lines were observed in DP-LIBS under Ar compared to DP-LIBS in air. It was also found that Cu and Zn lines acquired with SP-LIBS in Ar are nearly as intense as DP-LIBS in air. While collinear DP-LIBS is effective for increasing the sensitivity for some reduced atmospheres (i.e., Ar and air at 630 to 100 Torr and He at 300 Torr), the enhanced spectral intensity ultimately dropped off as the pressure was reduced below 10 Torr for all atmospheric compositions in the experimental arrangement used in this study. At all pressures of air and Ar, the plasma temperature remained rather constant with increased inter-pulse delays; however, the plasma temperature was more variable for different He gas pressures and inter-pulse delays.

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Expansion of an ablation plume in a buffer gas and cluster growth

Cited by 41 publications

References 29 publications

Ag and Au nanoparticles for SERS substrates produced by pulsed laser ablation

Ag and Au nanoparticles for SERS substrates produced by pulsed laser ablation

Nanosecond laser ablation and deposition of silicon

Effect of atmosphere on collinear double-pulse laser-induced breakdown spectroscopy

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