Spatially resolved Raman spectroscopy study of uniform and tapered InAs micro‐nano wires: correlation of strain and polytypism

Abstract

The asymmetric peak ~212–218 cm−1 occurring in InAs micro‐nanowires (MNWs: diameter: 2 μm – 400 nm) is investigated using spatially resolved Raman spectroscopy of uniform, bent and long tapered MNWs grown on a Si (001) substrate. It is attributed to superposition of E2h phonon (wurtzite: WZ) and TO phonon (zinc blende: ZB) of InAs. Polarized and wavelength‐dependent spatially resolved Raman spectroscopy establishes the presence of WZ and ZB phases in these MNWs. However, formation of WZ phase for larger diameter InAs MNWs is not commensurate with existing growth mapping studies. Further, study of these MNWs suggests that the fraction of WZ to ZB content in a MNW depends not only on the diameter but also seems to be governed by local growth seeding/conditions. This in turn leads to either tapered or uniform MNW growth under the same (external) growth conditions. The variation of these wavenumbers that of bulk value is correlated to the residual stress present in ZB and WZ phases due to the presence of the other (WZ/ZB) phase. Consistently, temperature‐dependent Raman data show that there is a measurable contribution of stress to dω/dT, a positive for ZB and negative for WZ phonons, due to differences in their thermal expansions. Further, effective thermal expansion coefficient of WZ InAs in the presence of ZB phase is calculated to vary in the range 10–19 × 10−6/K from base to tip of a MNW at ~80 K, which is not possible to determine otherwise. Copyright © 2017 John Wiley & Sons, Ltd.

Understanding the effect of nanowire orientation on time evolution of Raman spectra from laser irradiated InAs nanowire surface

“…As we have studied earlier, Raman spectra for InAs NWs (dia. : 2 μm-200 nm and length: 80-4 μm) depicts Raman selection rules (RSR) in polarized Raman spectra [17,18]. However, we observe major differences in the time evolution of oxide related peaks in unpolarized Raman spectra for differently oriented InAs NWs for the same/ similar simulated temperature.…”

Effect of Flow Rate Scaling on SAE-InAs Crystal Phase and Integration of Self-Catalyzed InAs/InSb Heterostructure Nanowires on Si (111) Substrate by MOCVD

“…For sample-A, ZB crystal structure is dominated than WZ structure, while WZ crystal structure dominates for sample-B. 21 Further scaling in molar flow rates result to equally dominated WZ/ZB polytypes, which is inferred from intensities of WZ and ZB Lorentzian peaks.…”

“…Due to broken crystal symmetry in NW, two different peaks were observed, strong transverse-optical (TO) phonon spectra (∼212-218 cm -1 ) with some weak longitudinal-optical (LO) (A H ) (238 ∼ 240 cm −1 ) spectra. 21 Since absorption coefficient of InAs is high at 514.5 nm excitation wavelength, LO mode is less sensitive for the NWs with diameter larger than 32 nm. 22 To find possible of WZ and ZB prescience, spectra is deconvoluted with Lorentzian fit.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…Polarized and wavelength‐dependent spatially resolved Raman spectroscopy establishes the presence of wurzite (WZ) and zinc blend phases in these MNWs. However, they found that the formation of WZ phase for larger diameter InAs MNWs was not commensurate with existing growth mapping studies . Rivas‐Murias and Salgueirino described a thermodynamic CoOCo 3 O 4 crossover using Raman spectroscopy in magnetic octahedron‐shaped nanocrystals.…”

“…However, they found that the formation of WZ phase for larger diameter InAs MNWs was not commensurate with existing growth mapping studies. [95] Rivas-Murias and Salgueirino described a thermodynamic CoO-Co 3 O 4 crossover using Raman spectroscopy in magnetic octahedron-shaped nanocrystals. They found that above a certain value of the laser power and exposure time, CoO rock salt sample evolves clearly to the oxidized Co 3 O 4 normal spinel material because of the energy transfer and consequent local heating induced by the applied laser.…”