Isomerization of fluorophors on a treated silicon surface

Journal Article · Thu Mar 02 04:00:00 EST 2000 · Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical

DOI:https://doi.org/10.1021/jp9933469· OSTI ID:20017519

Gole, J L; Dixon, D A

In contrast to the green and familiar orange-red emissions associated with UV excited porous silicon (PS), the origins of the longer wavelength photoluminescence (PL) excited in the visible and near-infrared regions on a PS surface at 298 K are considered within an alternate molecular model. Ab initio molecular orbital theory is used to suggest that the longest wavelength PL observed as a result of the nitrogen laser pumping of post-etch dye and HCI treated PS samples and that accessed with near-infrared excitation sources (PLE) at 298 K arises in large part from singlet-triplet transitions in silylene-based moieties (:SiRY) attached to the PS surface or present as uncoupled defect sites at or near the surface. This long-wavelength PL is distinct from the ultraviolet light excited PL associated with PS which has previously been attributed to a silanone-based silicon oxyhydride moiety attached to the surface. Ab initio molecular theory at the MP2 level with polarized double-basis sets (MP2/DZP) has been used to calculate the singlet-triplet separation for a number of silylenes with a variety of combinations of R, Y=H, OH, SiH{sub 3}, Cl, and NH{sub 2} and to evaluate their thermodynamic stability relative to the silanones. The calculations show that the singlet silylene is always more stable than its triplet with transition wavelengths ranging from 1,100 to 420 nm, where the highest transition energies are found to correlate with the most electronegative substituents. The silylene isomers are found to be more stable than the corresponding silanones in most cases. The relative stabilities are strongly coupled to the electronegativity of the substituents and to the formation of an Si-O bond in the silylene as compared to the much weaker Si-Si bond in the silanone.

• Research Organization: Georgia Inst. of Tech., Atlanta, GA (US)
• Sponsoring Organization: US Department of Energy
• OSTI ID: 20017519
• Journal Information: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 8 Vol. 104; ISSN 1089-5647; ISSN JPCBFK
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ETCHING
ISOMERIZATION
MOLECULAR ORBITAL METHOD
PHOTOLUMINESCENCE
POROSITY
SILICON