Trends in the Interaction of the Strong Acids HCl, HBr, and HI with a Photoluminescing Porous Silicon Surface

Seals, Lenward; Dudel, Frank P.; Grantier, David R.; Gole, James L.; Bottomley, Lawrence A.

doi:10.1021/jp971178j

Cited by 16 publications

(14 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Silicon surfaces treated in an oxidative environment, especially high surface area porous silicon (PS) surfaces which are formed in wafer scale through electrochemical etching, display a variety of photoluminescent (PL) emissions upon excitation with a diversity of ultraviolet, visible, and near-infrared light sources. − These PL emissions, which have attracted considerable attention, are thought to originate from regions close to the treated silicon surface. , However, the origin of the PL is the source of some controversy as the efficiency and wavelength range of the emitted light can be affected by the physical and electronic structure of the surface, the nature of the etching solution, − and the nature of the environment into which the etched sample is placed. − In conjunction with detailed quantum chemical modeling of those fluorophors which might be present on a PS surface, ,− we have examined the derivatization 10,17 of this oxidizing surface. The results of these studies suggest that the commonly observed “orange−red” photoluminescence from a PS surface can be correlated with −OH or −OR bonded silanone-based silicon oxyhydrides.…”

Section: Introductionmentioning

confidence: 99%

Isomerization of Fluorophors on a Treated Silicon Surface

Gole

Dixon

2000

J. Phys. Chem. B

Self Cite

View full text Add to dashboard Cite

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 HCl 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 silanonebased 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 3 , OSiH 3 , Cl, and NH 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 1100 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.

show abstract

Section: Introductionmentioning

confidence: 99%

Isomerization of Fluorophors on a Treated Silicon Surface

Gole

Dixon

2000

J. Phys. Chem. B

Self Cite

View full text Add to dashboard Cite

show abstract

“…The light-induced PL from PS has been associated with a variety of mechanisms, including emission from quantum-confined silicon crystallites, − surface-localized states, ,, surface-confined defects , or surface-confined molecular − or molecule-like − emitters. The efficiency and wavelength range of the emitted light can be affected by the physical and electronic structure of the surface, the nature of the etching solution, ,, and the nature of the environment into which the etched sample is placed. − …”

Section: Introductionmentioning

confidence: 99%

“…The efficiency and wavelength range of the emitted light can be affected by the physical and electronic structure of the surface, 3 the nature of the etching solution, 22,23,25 and the nature of the environment into which the etched sample is placed. [26][27][28] The environment-dependent behavior of a PS surface suggests the possibility that several common fluorescent dyes whose radiative lifetimes are of the order of nanoseconds might be made to interact with the PS surface so as to considerably improve its observed luminescence rate. Here, we report a series of experiments designed to evaluate the interaction of select fluorescent dyes with PS samples of varying porosity and photovoltaic response.…”

Section: Introductionmentioning

confidence: 99%

Optical Pumping of Dye-Complexed and -Sensitized Porous Silicon Increasing Photoluminescence Emission Rates

1999

View full text Add to dashboard Cite

Distinctly structured nanoporous and combined hybrid macroporous−nanoporous porous silicon (PS) structures have been fabricated and treated with the dyes 3,3‘-diethyloxadicarbocyanine iodide (DODCI) and Rhodamine 700, both of which have negligible absorption at the wavelengths of maximum absorption for porous silicon. After an extended period of aging in darkness (air) these dye-treated samples are pumped (PLE) at 337.1 nm (nitrogen laser) near the maximum in the PS absorption spectrum (far from the major absorption regions of the impregnating dye) and the subsequent photoluminescence from these treated samples is monitored and compared to that obtained for the untreated PS structures. The first time-dependent photoluminescence (PL) histograms obtained for these systems indicate that the resulting luminescence, initiated through the pumping of a modified PS surface, displays the manifestation of a significant interaction between the surface-bound fluorophors which characterize PS and the dye (DODCI). It is suggested that this interaction results in the creation of a distribution of PS−dye complexes which greatly enhance the nominal PL emission rate from the untreated PS surface. This enhancement not only facilitates the observation of luminescence from a formed photoluminescing PS “green” precursor state but also the mapping of its time-dependent oxidation to form the more commonly observed “orange-red” emitter. Both emitters are attributed to surface-bound silanone-based silicon oxyhydride fluorophors. The degree of PS−dye interaction, in addition to being dye dependent, is found to be PS-structure dependent. Thus the photoluminescent histograms obtained in this study also appear to provide evidence for the influence of PS morphology on the surface interaction.

show abstract

“…While the luminescence is thought to occur near the PS surface, 6,7 the source of the visible emission is controversial as the efficiency and wavelength range of the emitted light can be affected by the physical and electronic structure of the surface, 3 the nature of the etching solution, [8][9][10] and the nature of the environment into which the etched sample is placed. [11][12][13] The luminescence from PS has been attributed to quantum-confined electrons and holes in columnar structures or undulating wires, [14][15][16][17] surface localized states, 6,7,18 and surface confined molecular emitters. [19][20][21][22][23] The tenets of quantum confinement assert that the luminescence results from the radiative recombination of confined electrons and holes possibly in columnar structures or undulating wires.…”

Section: Introductionmentioning

confidence: 99%

Resonantly excited photoluminescence from porous silicon and the question of bulk phonon replicates

Gole

Prokes

1998

Phys. Rev. B

Self Cite

View full text Add to dashboard Cite

High surface area porous silicon displays a light-induced visible photoluminescence ͑PL͒ in the 600-800-nm range, which has been associated with a variety of mechanisms, including emission from quantum confined silicon crystallites, surface-based states, surface confined defects, or molecular emitters. Key features used to support the quantum confinement hypothesis include the ''phonon replicates,'' which, while observed only at very low temperatures have been interpreted as proof of a silicon phonon-assisted radiative process within the Si crystallites. For the quantum confinement model to be valid, only 2 or fewer of these ''replicates'' should be observed. We offer an alternate interpretation of the observed replicate features, which is not only consistent with the data presented by the quantum confinement proponents, but also is commensurate with the observation of additional structure by a number of researchers in the field. It is suggested that the observed ''replicates'' can be ascribed to transitions involving surface bound fluorophors that are associated with the silanone-based silicon oxyhydrides. Support for this interpretation is provided by quantum chemical calculations of the various silanone species as well as a variety of experimental observations.

show abstract

Trends in the Interaction of the Strong Acids HCl, HBr, and HI with a Photoluminescing Porous Silicon Surface

Cited by 16 publications

References 30 publications

Isomerization of Fluorophors on a Treated Silicon Surface

Isomerization of Fluorophors on a Treated Silicon Surface

Optical Pumping of Dye-Complexed and -Sensitized Porous Silicon Increasing Photoluminescence Emission Rates

Resonantly excited photoluminescence from porous silicon and the question of bulk phonon replicates

Contact Info

Product

Resources

About