“…Raman analysis estimates morphological parameters such as crystallinity, strain, and size of the Si nanocrystals formed on the NWs array. FANTUM 21 (Fano and QCE) effect occurs for all the pristine NWs array, i.e., broadening of Raman line shape (FWHM) and shifting of Raman peak from the c-Si peak. Figure 5 shows higher FWHM of the NWs fabricated when using 0.001–0.005 Ω.cm resistivity as compared when using 0.01–0.02 Ω.cm resistivity of Si substrate, confirming the presence of higher amorphous content for lower resistivity substrate.…”
Section: Resultsmentioning
confidence: 99%
“…Asymmetrical broadening of FWHM indicates the formation of the Fano effect in the NWs. The Raman spectra of pristine NWs downshifts from the c-Si peak due to QCE 21 , 22 as the secondary etching or sidewalls etching creates Si nanostructures or nanocrystals on the NWs. Figure 5 Raman spectra of pristine and sintered NWs (@1000 °C) for ( a ) SiNWs_0.001, ( b ) SiNWs_0.01, ( c ) PSiNWs_0.001, ( d ) PSiNWs_0.01.…”
Section: Resultsmentioning
confidence: 99%
“…Dipping the NWs array in HF solution removes the oxide layer deposited on the surface during HNO 3 treatment, as shown in step—V. The NWs were rinsed with DI water again to remove the AgNPs further, as shown in step—VI 20 , 21 , 41 . Sintering is carried out in an Ar atmosphere to reduce the Ag remanence further, as shown in step—VII.…”
Metal-assisted chemical etching (MACE) is popular due to the large-area fabrication of silicon nanowires (SiNWs) exhibiting a high aspect ratio at a low cost. The remanence of metal, i.e., silver nanoparticles (AgNPs) used in the MACE, deteriorates the device (especially solar cell) performance by acting as a defect center. The superhydrophobic behavior of nanowires (NWs) array prohibits any liquid-based solution (i.e., thorough cleaning with HNO3 solution) from removing the AgNPs. Thermal treatment of NWs is an alternative approach to reduce the Ag remanence. Sintering temperature variation is chosen between the melting temperature of bulk-Ag (962 °C) and bulk-Si (1412 °C) to reduce the Ag particles and improve the crystallinity of the NWs. The melting point of NWs decreases due to surface melting that restricts the sintering temperature to 1200 °C. The minimum sintering temperature is set to 1000 °C to eradicate the Ag remanence. The SEM–EDS analysis is carried out to quantify the reduction in Ag remanence in the sintered NWs array. The XRD analysis is performed to study the oxides (SiO and Ag2O) formed in the NWs array due to the trace oxygen level in the furnace. The TG-DSC characterization is carried out to know the critical sintering temperature at which remanence of AgNPs removes without forming any oxides. The Raman analysis is studied to determine the crystallinity, strain, and size of Si nanocrystals (SiNCs) formed on the NWs surface due to sidewalls etching. An optimized polynomial equation is derived to find the SiNCs size for various sintering temperatures.
“…Raman analysis estimates morphological parameters such as crystallinity, strain, and size of the Si nanocrystals formed on the NWs array. FANTUM 21 (Fano and QCE) effect occurs for all the pristine NWs array, i.e., broadening of Raman line shape (FWHM) and shifting of Raman peak from the c-Si peak. Figure 5 shows higher FWHM of the NWs fabricated when using 0.001–0.005 Ω.cm resistivity as compared when using 0.01–0.02 Ω.cm resistivity of Si substrate, confirming the presence of higher amorphous content for lower resistivity substrate.…”
Section: Resultsmentioning
confidence: 99%
“…Asymmetrical broadening of FWHM indicates the formation of the Fano effect in the NWs. The Raman spectra of pristine NWs downshifts from the c-Si peak due to QCE 21 , 22 as the secondary etching or sidewalls etching creates Si nanostructures or nanocrystals on the NWs. Figure 5 Raman spectra of pristine and sintered NWs (@1000 °C) for ( a ) SiNWs_0.001, ( b ) SiNWs_0.01, ( c ) PSiNWs_0.001, ( d ) PSiNWs_0.01.…”
Section: Resultsmentioning
confidence: 99%
“…Dipping the NWs array in HF solution removes the oxide layer deposited on the surface during HNO 3 treatment, as shown in step—V. The NWs were rinsed with DI water again to remove the AgNPs further, as shown in step—VI 20 , 21 , 41 . Sintering is carried out in an Ar atmosphere to reduce the Ag remanence further, as shown in step—VII.…”
Metal-assisted chemical etching (MACE) is popular due to the large-area fabrication of silicon nanowires (SiNWs) exhibiting a high aspect ratio at a low cost. The remanence of metal, i.e., silver nanoparticles (AgNPs) used in the MACE, deteriorates the device (especially solar cell) performance by acting as a defect center. The superhydrophobic behavior of nanowires (NWs) array prohibits any liquid-based solution (i.e., thorough cleaning with HNO3 solution) from removing the AgNPs. Thermal treatment of NWs is an alternative approach to reduce the Ag remanence. Sintering temperature variation is chosen between the melting temperature of bulk-Ag (962 °C) and bulk-Si (1412 °C) to reduce the Ag particles and improve the crystallinity of the NWs. The melting point of NWs decreases due to surface melting that restricts the sintering temperature to 1200 °C. The minimum sintering temperature is set to 1000 °C to eradicate the Ag remanence. The SEM–EDS analysis is carried out to quantify the reduction in Ag remanence in the sintered NWs array. The XRD analysis is performed to study the oxides (SiO and Ag2O) formed in the NWs array due to the trace oxygen level in the furnace. The TG-DSC characterization is carried out to know the critical sintering temperature at which remanence of AgNPs removes without forming any oxides. The Raman analysis is studied to determine the crystallinity, strain, and size of Si nanocrystals (SiNCs) formed on the NWs surface due to sidewalls etching. An optimized polynomial equation is derived to find the SiNCs size for various sintering temperatures.
“…Further, micro-Raman studies were performed to study the restraint effect of etching parameters on NWs formation. In the direction of Raman studies, Sahoo and Kale observed the Raman line broadening and blue shift in SiNWs prepared at various etching temperature . The stated Raman effects in the sample are due to amorphous content (<20%), stress, and FANTUM effect (i.e., Fano effect + quantum confinement effect).…”
Section: Metal Nanoparticles Decorated Silicon Nanowiresmentioning
confidence: 99%
“…In the direction of Raman studies, Sahoo and Kale observed the Raman line broadening and blue shift in SiNWs prepared at various etching temperature. 98 The stated Raman effects in the sample are due to amorphous content (<20%), stress, and FANTUM effect (i.e., Fano effect + quantum confinement effect). The observed 0.25% tensile strain and 80% crystallinity fraction of NWs have significantly validated the device requirements.…”
This
review presents a comprehensive synopsis of the recent developments
and achievements in the research of nanosensors composed of plasmonic
nanoparticles (NPs) and silicon nanostructures (NSs) for effective
trace-level molecular detection. This review focuses intensively on
the methodologies for the preparation and enforcement of a variety
of SiNSs including (a) metal nanoparticles decorated silicon nanowires
(NWs), (b) metal nanodendrites (NDs) on Si substrate, (c) plasmonic
NPs decorated nanocrystalline porous silicon (pSi), and (d) silicon
composed hybrid nanostructures with favorable parameters of importance
in sensing. Furthermore, their potency in wide molecular sensing applications,
especially chemical, biological, and explosive molecules based on
surface enhanced Raman scattering (SERS) phenomenon is discussed in
detail. Various demonstrations and categorizations are provided on
the topic of Si-based NSs for a clear understanding to diverse readers.
A roadmap is also provided at the end for achieving superior sensing
materials or devices in the future.
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