| 1. |
- Bulgakov, Alexander, 1956, et al.
(författare)
-
Phosphorus cluster production by laser ablation
- 2004
-
Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 79, s. 1369-1372
-
Tidskriftsartikel (refereegranskat)abstract
- Neutral and charged phosphorus clusters of a wide size range have been produced by pulsed laser ablation (PLA) in vacuum at 532, 337, and 193 nm ablating wavelengths and investigated by time-of-flight mass spectrometry. The neutral Pn clusters are even-numbered with local abundance maxima at n=10 and 14, while the cationic and anionic clusters are preferentially odd-numbered with P7+, P21+, and P17- being the most abundant ions. The dominance of the magic clusters is more pronounced at 337-nm ablation that is explained by efficient direct ejection of their building blocks under these conditions. Nanocrystalline phosphorus films have been produced by PLA in ambient helium gas.
|
|
| 2. |
- Bulgakova, Nadya, 1956, et al.
(författare)
-
A general continuum approach to describe fast electronic transport in pulsed laser irradiated materials: the problem of Coulomb explosion
- 2005
-
Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 81, s. 345-356
-
Tidskriftsartikel (refereegranskat)abstract
- We present a continuum model, based on a drift-diffusion approach, aimed at describing the dynamics of electronic excitation, heating, and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, for near-infrared femtosecond irradiation, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, application of the model to UV nanosecond pulsed laser interaction with bulk silicon has pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) and material properties are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics.
|
|
