Early Stages of Pulsed-Laser Growth of Silicon Microcolumns and Microcones in Air and SF₆

Conference · Thu Jul 29 00:00:00 EDT 1999

OSTI ID:9120

Lowndes, Douglas H. ^[1]; Fowlkes, Jason D. ^[2]; Pedraza, Antonio J. ^[2]

---

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Univ. of Tennessee, Knoxville, TN (United States)

Dense arrays of high-aspect-ratio silicon microcolumns and microcones are formed by cumulative nanosecond pulsed excimer laser irradiation of single-crystal silicon in oxidizing atmospheres such as air and SF₆. Growth of such surface microstructures requires a redeposition model and also involves elements of self-organization. The shape of the microstructures, i.e. straight columns vs steeply sloping cones and connecting walls, is governed by the type and concentration of the oxidizing species, e.g. oxygen vs fluorine. Growth is believed to occur by a "catalyst-free" VLS (vapor-liquid-solid) mechanism that involves repetitive melting of the tips of the columns/cones and deposition there of the ablated flux of Si-containing vapor. Results are presented of a new investigation of how such different final microstructures as microcolumns or microcones joined by walls nucleate and develop. The changes in silicon surface morphology were systematically determined and compared as the number of pulsed KrF (248 nm) laser shots was increased from 25 to several thousand in both air and SF₆. The experiments in air and SF₆ reveal significant differences in initial surface cracking and pattern formation. Consequently, local protrusions are first produced and column or cone/wall growth is initiated by different processes and at different rates. Differences in the spatial organization of column or cone/wall growth also are apparent.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 9120
• Report Number(s): ORNL/CP-103769; KC 02 02 02 0; ON: DE00009120
• Resource Relation: Conference: European Materials Research Society Meeting, Strasbourg, France, June 1-4, 1999
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Silicon
Ablation
Deposition
Cones
Whiskers
silicon
pulsed laser
ablation
deposition
columns
cones
whiskers
nonequilibrium growth
surface modification