The Origin and Implications of (111)-Textured Grains Obtained via Nucleation and Growth of Solids in Pulsed-Laser-Quench
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0979-HH11-50
The Origin and Implications of (111)-Textured Grains Obtained via Nucleation and Growth of Solids in Pulsed-Laser-Quenched Al Films on SiO2 J. B. Choi, Min H. Choi, U.-J. Chung, A. B. Limanov, and James S. Im Program in Materials Science, Applied Physics and Applied Mathematics, Columbia University, New York, NY, 10027
ABSTRACT We have investigated excimer laser irradiation of 2000-Å-thin as-deposited Al films on SiO2. Microstructural analysis of the irradiated films conducted with AFM and EBSD techniques reveals that there exists a wide energy density interval over which large equaxed grains with a strong (111) texture are obtained. Based on thermal, transformational, and microstructural considerations, we propose a heterogeneous nucleation model to account for the observed behaviors, and discuss the implication of the model on the phenomenon of heterogeneous nucleation of crystalline solids in condensed systems as regards the thermodynamic role played by the orientation of subcritical clusters. INTRODUCTION Pulsed-laser-induced rapid solidification of thin films represents an experimental area that continues to offer opportunities for attaining revealing results that are relevant to the field of discontinuous phase transitions [1,2]. In this paper, we report on findings that are obtained from single-pulse excimer laser irradiation of as-deposed thin Al films on SiO2; our interpretation of the observations that are made in this experimental investigation substantiates the notion that the orientation of subcritical clusters can be a factor of relevance in heterogeneous nucleation of crystalline solids occurring in condensed systems. EXPERIMENT The Al samples utilized in the present investigation consisted of 2000-Å-thick smallgrained polycrystalline Al films that were prepared via sputter deposition onto SiO2 coated glass substrates. Single-pulse irradiation experiments using an excimer laser (XeCl, FWHM 28 ns, 308 nm) were conducted in air, without any preheating of the substrate. The incident energy density of the beam was varied in increments of approximately 66 mJ/cm2 using a variableenergy attenuator. It was found that AFM and EBSD techniques, when used together in a complementary manner, were particularly effective in characterizing the microstructure of the irradiated Al films that were obtained in the present investigation; subsequently, they were employed extensively.
A variety features and trends were observed as the incident energy density was varied from values too low to induce any discernable microstructural or morphological changes up to the point at which noticeable physical damages are obtained. The overall behavior and trends — the details of which will be addressed elsewhere [3] — can be summarized as being primarily consistent with those findings and conclusions that were made in the course of studying excimer laser irradiation of thin Si films on SiO2 [4]. In this paper, we focus specifically on presenting and addressing a particular experimental regime (incident energy density
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