Ultraviolet laser patterning of porous silicon

Journal Article · Wed May 14 04:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4875378· OSTI ID:22275573

Vega, Fidel ^[1]; Peláez, Ramón J.; Kuhn, Timo; Afonso, Carmen N. ^[2]; Recio-Sánchez, Gonzalo; Martín-Palma, Raúl J. ^[3]

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1. Departament d'Òptica i Optometria, UPC, Violinista Vellsolà 37, 08222 Terrasa (Spain)
2. Laser Processing Group, Instituto de Óptica, CSIC, Serrano 121, 28006 Madrid (Spain)
3. Departamento de Física Aplicada, UAM, Campus de Cantoblanco, 28049 Madrid (Spain)

This work reports on the fabrication of 1D fringed patterns on nanostructured porous silicon (nanoPS) layers (563, 372, and 290 nm thick). The patterns are fabricated by phase-mask laser interference using single pulses of an UV excimer laser (193 nm, 20 ns pulse duration). The method is a single-step and flexible approach to produce a large variety of patterns formed by alternate regions of almost untransformed nanoPS and regions where its surface has melted and transformed into Si nanoparticles (NPs). The role of laser fluence (5–80 mJ cm{sup −2}), and pattern period (6.3–16 μm) on pattern features and surface structuring are discussed. The results show that the diameter of Si NPs increases with fluence up to a saturation value of 75 nm for a fluence ≈40 mJ cm{sup −2}. In addition, the percentage of transformed to non-transformed region normalized to the pattern period follows similar fluence dependence regardless the period and thus becomes an excellent control parameter. This dependence is fitted within a thermal model that allows for predicting the in-depth profile of the pattern. The model assumes that transformation occurs whenever the laser-induced temperature increase reaches the melting temperature of nanoPS that has been found to be 0.7 of that of crystalline silicon for a porosity of around 79%. The role of thermal gradients across the pattern is discussed in the light of the experimental results and the calculated temperature profiles, and shows that the contribution of lateral thermal flow to melting is not significant for pattern periods ≥6.3 μm.

• OSTI ID: 22275573
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 18 Vol. 115; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
77 NANOSCIENCE AND NANOTECHNOLOGY
EXCIMER LASERS
FABRICATION
INTERFERENCE
LAYERS
MELTING
MELTING POINTS
NANOSTRUCTURES
PARTICLES
POROSITY
POROUS MATERIALS
PULSED IRRADIATION
SILICON
SURFACES
TEMPERATURE GRADIENTS
ULTRAVIOLET RADIATION