Melting in Superheated Silicon Films Under Pulsed-Laser Irradiation
- Melting in Superheated Silicon Films Under Pulsed-Laser Irradiation
- Wang, Jin Jimmy
- Thesis Advisor(s):
- Im, James Sungbin
- Ph.D., Columbia University
- Materials Science and Engineering
- Persistent URL:
- This thesis examines melting in superheated silicon ﬁlms in contact with SiO₂ under pulsed laser irradiation. An excimer-laser pulse was employed to induce heating of the ﬁlm by irradiating the ﬁlm through the transparent fused-quartz substrate such that most of the beam energy was deposited near the bottom Si-SiO₂ interface. Melting dynamics were probed via in situ transient reﬂectance measurements. The temperature proﬁle was estimated computationally by incorporating temperature- and phase-dependent physical parameters and the time-dependent intensity proﬁle of the incident excimer-laser beam obtained from the experiments.
The results indicate that a signiﬁcant degree of superheating occurred in the subsurface region of the ﬁlm. Surface-initiated melting was observed in spite of the internal heating scheme, which resulted in the ﬁlm being substantially hotter at and near the bottom Si-SiO₂ interface. By considering that the surface melts at the equilibrium melting point, the solid-phase-only heat-ﬂow analysis estimates that the bottom Si-SiO₂ interface can be superheated by at least 220K during excimer-laser irradiation.
It was found that at higher laser ﬂuences (i.e., at higher temperatures), melting can be triggered internally. At heating rates of 10¹⁰ K/s, melting was observed to initiate at or near the (100)-oriented Si-SiO₂ interface at temperatures estimated to be over 300K above the equilibrium melting point. Based on theoretical considerations, it was deduced that melting in the superheated solid initiated via a nucleation and growth process. Nucleation rates were estimated from the experimental data using Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis. Interpretation of the results using classical nucleation theory suggests that nucleation of the liquid phase occurred via the heterogeneous mechanism along the Si-SiO₂ interface.
- Excimer lasers
Thin films--Effect of radiation on
Thin films--Thermal properties
Silicon oxide films
Chemistry, Physical and theoretical
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- Suggested Citation:
- Jin Jimmy Wang, 2016, Melting in Superheated Silicon Films Under Pulsed-Laser Irradiation, Columbia University Academic Commons, https://doi.org/10.7916/D8NV9J7Q.