Porous Silicon's fractal nature revisited

Yogi, Priyanka; Saxena, Shailendra K.; Chaudhary, Anjali; Pathak, Devesh K.; Mishra, Suryakant; Mondal, Puspen; Joshi, Bipin; Sagdeo, Pankaj R.; Kumar, Rajesh

doi:10.1016/j.spmi.2018.05.026

Cited by 16 publications

(14 citation statements)

References 45 publications

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“…The nature of junction (ohmic or schottky) play a role because the movement of holes and its flux is associated with the nature of band bending in a given metal/Si junction 46 . In the present study, two different Generally, porosified Si wafers prepared using H 2 O 2 /HF solution shows fractal nature 47,48 which consists of Si NSs at microscopic level present in the wire like structures. These Si NSs often are small enough (~ a few nanometers) to show quantum confinement effects.…”

Section: R a F Tmentioning

confidence: 62%

Parallel or interconnected pores’ formation through etchant selective silicon porosification

et al. 2022

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Effect of oxidizer, present in the etching solution, on the surface morphology and microstructure obtained after porosification of p-type silicon wafer using metal assisted chemical etching has been studied here. The morphologies of Si wafers porosified using two different solutions namely HF/ H2O2 and HF/KMnO4 have been compared to establish how either of the oxidizers (H2O2 or KMnO4) should be chosen depending on the desired application. The comparative study reveals that either parallel pores with wire like structures or interconnected pores with cheese like structures can be obtained when H2O2 or KMnO4 respectively are chosen. Careful analysis of SEM images has been carried out using ImageJ to establish that samples prepared using KMnO4 are more porous due to aggressive etching. Additionally, experimental and theoretical Raman spectroscopic studies have been utilized to study the presence of low dimensional Si nanostructures of a few nanomaters size at the microscopic level in the porosified silicon.

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Section: R a F Tmentioning

confidence: 62%

Parallel or interconnected pores’ formation through etchant selective silicon porosification

et al. 2022

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“…The Si wafer etched by using MIE becomes porous and shows a fractal nature 49,56,57 as can be seen by using electron microscopy (Figure 1a). A low-resolution top surface SEM confirms (Figure 1a) the formation of porous silicon in wirelike structure formed as a consequence of reaction between the Si wafer and the etching solution (eqs R1−R3, Supporting Information).…”

mentioning

confidence: 84%

“…An increasing Fano coupling parameter (with decreasing size), obtained by using Fano line shape fitting of Raman spectra, is noticed which actually was found to be consistent with the known size-dependent Fano effect as established by careful deconvolution of the Raman line shape by incorporating the effect of gradual nanosize variation along the Si microwires. The wire-like structures, prepared by using metal-assisted etching, exhibit depletion of dopants as a consequence of the fabrication process − due to the fractal nature of the Si NSs. The quantum effect was found to exhibit a dual role of a typical band gap enhancement and atypical zonal dopant depletion with the latter being dominating.…”

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confidence: 99%

Pseudo-Anomalous Size-Dependent Electron–Phonon Interaction in Graded Energy Band: Solving the Fano Paradox

Tanwar

Pathak

Chaudhary

et al. 2021

J. Phys. Chem. Lett.

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Quantum size effects on interferons (electron–phonon bound states), confined in fractal silicon (Si) nanostructures (NSs), have been studied by using Raman spectromicroscopy. A paradoxical size dependence of Fano parameters, estimated from Raman spectra, has been observed as a consequence of longitudinal variation of nanocrystallite size along the Si wires leading to local variations in the dopants’ density which actually starts governing the Fano coupling, thus liberating the interferons to exhibit the typical quantum size effect. These interferons are more dominated by the effective reduction in dopants’ density rather than the quantum confinement effect. Detailed experimental and theoretical Raman line shape analyses have been performed to solve the paradox by establishing that the increasing size effect actually is accompanied by receding Fano coupling due to the weakened electronic continuum. The latter has been validated by observing a consequent variation in the Raman signal from dopants which was found to be consistent with the above conclusion.

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“…Porous Si, when prepared using MACE, has been reported to have SiNWs showing fractal nature that consists of two‐dimensional SiNSs at microscopic level, whereas at macroscopic level, parallel microwires of Si [ 116 ] are present. Figure 7a shows schematic of these SiNSs containing porous wires for the case of n‐type Si seen in cross‐sectional geometry.…”

Section: Raman Microscopic Evidence Of Size‐dependent Fano Interactionmentioning

confidence: 99%

“…(b) Raman image recorded using 633-nm excitation laser from heavily doped n-type silicon nanostructures (SiNSs) (resistivity 0.01 Ω-cm). Reprinted with permission from Tanwar et al [68] Copyright (2020) American Chemical Society consists of two-dimensional SiNSs at microscopic level, whereas at macroscopic level, parallel microwires of Si [116] are present. Figure 7a shows schematic of these SiNSs containing porous wires for the case of n-type Si seen in cross-sectional geometry.…”

Section: Raman Microscopic Evidence Of Size-dependent Fano Interactionmentioning

confidence: 99%

Effect of some physical perturbations and their interplay on Raman spectral line shapes in silicon: A brief review

Kumar

Tanwar

2021

J Raman Spectroscopy

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Raman spectroscopy is a proven versatile tool for characterization of materials spanning almost all areas of science because of its ability to non-invasively extract information about materials. This technique is able to detect any perturbation in a system that can affect the phonons. A detailed discussion on various factors that affect the Raman line shape for a material has been summarized here by taking the example of silicon. Methods to identify the actual reason(s) behind the observed Raman spectral line shape have also been briefly discussed. Raman line shape obtained from silicon nanostructures when analyzed closely along with their bulk counterparts, reveals important information about the quantum confinement in such systems characterized by the Bohr's exciton radius. Raman line-shape parameters are analyzed closely to understand the influence of any perturbation like quantum confinement, heavy doping, temperature rise, pressure, excitation wavelength, electronphonon interaction, and so on. Current review briefly deals with the origin of asymmetric Raman line shapes in (nano-) silicon due to various physical perturbations and their interplays, which becomes the origin of different line shapes. Advantages of using Raman microscopy in analyzing subtler physical processes taking place in a semiconductor have also been underlined.

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Porous Silicon's fractal nature revisited

Cited by 16 publications

References 45 publications

Parallel or interconnected pores’ formation through etchant selective silicon porosification

Parallel or interconnected pores’ formation through etchant selective silicon porosification

Pseudo-Anomalous Size-Dependent Electron–Phonon Interaction in Graded Energy Band: Solving the Fano Paradox

Effect of some physical perturbations and their interplay on Raman spectral line shapes in silicon: A brief review

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