Stress redistribution in individual ultrathin strained silicon nanowires: a high-resolution polarized Raman study

Tarun, Alvarado; Hayazawa, Norihiko; Balois, Maria Vanessa; Kawata, Satoshi; Reiche, M.; Moutanabbir, Oussama

doi:10.1088/1367-2630/15/5/053042

Cited by 10 publications

(10 citation statements)

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“…Raman back-scattering from a (001) silicon surface allows only the longitudinal optical (LO) mode to be observed [56], while using a high NA objective with small spot size allows measurement of the two transverse optical (TO) modes as well [54]. Although Tarun et al showed that prestrained SiNWs retain a complex strain distribution when patterned on oxide [54], only uniaxial strain is expected to remain after suspension of the SiNWs, whereby the free surfaces of the SiNW are allowed to relax. Gridlines for uniaxial elastic strain in intervals of 0.5% are plotted in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…For SiNWs below 15 nm, quantum confinement begins to have an observable effect, causing peak shifts and asymmetric peak broadening [51][52][53]. It is also known that strain, depending on the crystal direction, can be related to peak shifts for the different optical mode phonons [54][55][56]. Much of the work done using Raman on SiNWs has been on chemically synthesized or chemically etched SiNWs, which typically * daniel.fan@psi.ch exhibit a size, position, and orientation distribution.…”

Section: Introductionmentioning

confidence: 99%

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Strain and thermal conductivity in ultrathin suspended silicon nanowires

et al. 2017

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We report on the uniaxial strain and thermal conductivity of well-ordered, suspended silicon nanowire arrays between 10 to 20 nm width and 22 nm half-pitch, fabricated by extreme-ultraviolet (UV) interference lithography. Laser-power-dependent Raman spectroscopy showed that nanowires connected monolithically to the bulk had a consistent strain of ∼0.1%, whereas nanowires clamped by metal exhibited variability and high strain of up to 2.3%, having implications in strain engineering of nanowires. The thermal conductivity at room temperature was measured to be ∼1 W/m K for smooth nanowires and ∼0.1 W/m K for rougher ones, similar to results by other investigators. We found no modification of the bulk properties in terms of intrinsic scattering, and therefore, the decrease in thermal conductivity is mainly due to boundary scattering. Different types of surface roughness, such as constrictions and line-edge roughness, may play roles in the scattering of phonons of different wavelengths. Such low thermal conductivities would allow for very efficient thermal energy harvesting, approaching and passing values achieved by state-of-the-art thermoelectric materials.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Strain and thermal conductivity in ultrathin suspended silicon nanowires

et al. 2017

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“…The autofocusing system proved to be invaluable as the detected TO signal was very weak especially for the 30 nm nanowires. Characterization of the anisotropic stress relaxation by both LO [3] and TO [4] phonon modes was performed. It was found that both cases suggest a complex redistribution of stress within the nanowire, which is contrary to the prevalent belief that stress is fully relaxed along the narrow width of the nanowire [5].…”

Section: Resultsmentioning

confidence: 99%

Precise and stable polarization control in a tightly focusing system for accurate characterization of strained Silicon nanostructures

Balois

Hayazawa

Tarun

et al. 2013

JSAP-OSA Joint Symposia 2013 Abstracts

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IntroductionRecently, it was demonstrated that it is possible to excite and observe the "forbidden" TO phonons in ultrathin strained silicon (ε-Si) nanostructures using high-resolution polarized Raman spectroscopy [1]. While the allowed LO phonon observation is sufficient for isotropic strain characterizations, TO phonon is important for characterizing anisotropic strain relaxation, which is particularly present upon patterning nanostructures such as nanowires. Raman imaging of such ε-Si nanostructures requires very precise polarization control and highly stable focus positioning relative to the nanostructures within the focus. Moreover, as these structures become very small in size, a weaker signal is detected, thus needing longer exposure time at each position. Also, scanning over a large area with a number of nanostructures for better data sampling requires long duration experiments. In such situations, focus stability becomes a key concern due to the combination of thermal, vibrational and electrical noise, which compounds over time, limiting the spatial resolution in the submicron scale, hence worsening the contrast of the image.In this study, Raman imaging of ultrathin ε-Si nanostructures was realized using highly precise polarization control in a tightly focusing system that ensures focus stability within ± 1 nm for long duration experiments [2], and can easily be an add-on to any kind of microscope set up. Three-dimensional mathematical analysis of the incident and scattered electric field intensity distribution was demonstrated. In these simulations, polarization, sample geometry and depolarization were considered for a more concise analysis of Raman spectra, longitudinal optical (LO) and transverse optical (TO) phonon behavior.

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“…Recent progress in probing the strain distribution in nanostructures includes utilizing Raman spectroscopy, transmission electron microscopy (TEM) based techniques, and x‐ray diffraction based techniques, such as microbeam x‐ray diffraction, high resolution x‐ray diffraction, and grazing incidence x‐ray diffraction (GIXRD) . Raman spectroscopy provides a fairly good spatial resolution and does not require any specific sample preparation, but it is limited to bare Si structures as the top metallic layer in the device prohibits the laser penetration.…”

Section: Strain Distribution In Silicon‐on‐insulator (Soi) Structuresmentioning

confidence: 99%

Coherent X‐Ray Diffraction Imaging and Characterization of Strain in Silicon‐on‐Insulator Nanostructures

et al. 2014

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Coherent X-ray diffraction imaging (CDI) has emerged in the last decade as a promising high resolution lens-less imaging approach for the characterization of various samples. It has made significant technical progress through developments in source, algorithm and imaging methodologies thus enabling important scientific breakthroughs in a broad range of disciplines. In this report, we will introduce the principles of forward scattering CDI and Bragg geometry CDI (BCDI), with an emphasis on the latter. BCDI exploits the ultra-high sensitivity of the diffraction pattern to the distortions of crystalline lattice. Its ability of imaging strain on the nanometer scale in three dimensions is highly novel. We will present the latest progress on the application of BCDI in investigating the strain relaxation behavior in nanoscale patterned strained silicon-on-insulator (sSOI) materials, aiming to understand and engineer strain for the design and implementation of new generation semiconductor devices.

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Stress redistribution in individual ultrathin strained silicon nanowires: a high-resolution polarized Raman study

Cited by 10 publications

References 20 publications

Strain and thermal conductivity in ultrathin suspended silicon nanowires

Strain and thermal conductivity in ultrathin suspended silicon nanowires

Precise and stable polarization control in a tightly focusing system for accurate characterization of strained Silicon nanostructures

Coherent X‐Ray Diffraction Imaging and Characterization of Strain in Silicon‐on‐Insulator Nanostructures

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