Role of defects and grain boundaries in the thermal response of wafer-scale hBN films

Bera, Kousik; Roy, Anushree; Chugh, Dipankar; Wong‐Leung, Jennifer; Tan, Hark Hoe; Jagadish, Chennupati

doi:10.1088/1361-6528/abc286

Cited by 8 publications

(15 citation statements)

References 68 publications

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“…This additional effect does not allow for reliable parameters modeling because of an unknown temperature-dependent behaviour of defects. It is suggested that the defect contribution should be linear [28]. Adding a further linear or quadratic term to the model would strongly influence other parameters which at this point are in good agreement with the literature values.…”

Section: Resultssupporting

confidence: 81%

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Temperature induced giant shift of phonon energy in epitaxial boron nitride layers

Iwański¹,

Tatarczak²,

Tokarczyk³

et al. 2022

Preprint

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The recent progress in the growth of large-area boron nitride epilayers opens up new possibilities for future applications. However, it remains largely unclear how weakly attached two-dimensional BN layers interact with their substrate and how their properties are influenced by defects. In this work, we investigate hBN layers grown by Metal Organic Vapor Phase Epitaxy (MOVPE) using Fourier-transform Infrared (FTIR) spectroscopy in the temperature range of 160-540 K. Our measurements reveal strong differences in the character of layer-substrate interaction for as-grown and delaminated epitaxial layers. A much weaker interaction of as-grown layers is explained by wrinkles formation that reduces strain at the layer-substrate interface, which for layers transferred to other substrates occurs only in a limited temperature range. The most striking result is the observation of a giant increase in the E1u phonon energy of up to ∼ 6 cm −1 in a narrow temperature range. We show that the amplitude and temperature range of the anomaly is strongly modified by UV light illumination. The observed giant effect is explained in terms of strain generation resulting from charge redistribution between shallow traps and different defects, which can be interpreted as a result of strong electron-phonon coupling in hBN. The observed narrow temperature range of the anomaly indicates that the effect may be further enhanced for example by electrostrictive effects, expected for sp 2 boron nitride.

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Section: Resultssupporting

confidence: 81%

“…The peak position at about 1367 cm −1 corresponds to the E 1u phonon mode of sp 2 hybridized boron nitride [26]. The high quality is manifested by the values of the γ BN parameter for the E 1u mode, which are relatively small compared to the values reported for epitaxial layers [18,[27][28][29]. The inset in FIG.…”

Section: Characterization Methodsmentioning

confidence: 88%

Temperature induced giant shift of phonon energy in epitaxial boron nitride layers

Iwański¹,

Tatarczak²,

Tokarczyk³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…The peak position at about 1367 cm −1 corresponds to the E 1u phonon mode of sp 2 hybridized boron nitride [26]. The high quality of our epitaxial samples is manifested by the values of the γ BN parameter for the E 1u mode, which are similar to the values of the Raman E 2g peak width for high-quality epitaxial layers reported by other groups [18,[27][28][29]. The IR-active mode is nearly degenerated with the E 2g Raman-active mode and decays with the same channels [30].…”

Section: Characterization Methodssupporting

confidence: 83%

“…Since the phonon energy is a good indicator for strain [28], we investigated as-grown and delaminated samples. Due to the delamination process, both samples should exhibit different layer-substrate interactions.…”

Section: Resultsmentioning

confidence: 99%

Temperature induced giant shift of phonon energy in epitaxial boron nitride layers

et al. 2022

View full text Add to dashboard Cite

The recent progress in the growth of large-area boron nitride epilayers opens up new possibilities for future applications. However, it remains largely unclear how weakly attached two-dimensional BN layers interact with their substrate and how their properties are influenced by defects. In this work, we investigate hBN layers grown by Metal Organic Vapor Phase Epitaxy (MOVPE) using Fourier-transform Infrared (FTIR) spectroscopy in the temperature range of 160-540 K. Our measurements reveal strong differences in the character of layer-substrate interaction for as-grown and delaminated epitaxial layers. A much weaker interaction of as-grown layers is explained by wrinkles formation that reduces strain at the layer-substrate interface, which for layers transferred to other substrates occurs only in a limited temperature range. The most striking result is the observation of a giant increase in the E1u phonon energy of up to ∼ 6 cm−1 in a narrow temperature range. We show that the amplitude and temperature range of the anomaly is strongly modified by UV light illumination. The observed giant effect is explained in terms of strain generation resulting from charge redistribution between shallow traps and different defects, which can be interpreted as a result of strong electron-phonon coupling in hBN. The observed narrow temperature range of the anomaly indicates that the effect may be further enhanced for example by electrostrictive effects, expected for sp2 boron nitride.

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“…From the position of the E 2g mode and its FWHM obtained by fitting the Lorentzian function, conclusions can be drawn about the quality and strain in the examined material [29]. The lower the value of the FWHM, the lower the concentration of defects in the boron nitride structure.…”

Section: Raman Measurements For Two-stage Samples With Off-cutmentioning

confidence: 99%

Effective substrate for the growth of multilayer h-BN on sapphire—substrate off-cut, pre-growth, and post-growth conditions in metal-organic vapor phase epitaxy

et al. 2023

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The substrate is one of the key components that determines the quality of the epitaxial layers. However, the implications of growing two-dimensional layers on three-dimensional bulk substrates have not yet been fully understood, and these implications need to be studied for different combinations of materials and substrates. Here, we present a study that addresses the influence of the sapphire substrate off-cut angle on the final growth of two-dimensional layers of hexagonal boron nitride (h-BN) by metal-organic vapor phase epitaxy (MOVPE). A two-step wafer-scale process was used in one epitaxial MOVPE procedure. The main process starts with a self-limiting continuous growth of a BN buffer followed by flow-modulated epitaxy in the second step, and is used to study substrates with different off-cuts angles, pre-growth nitridation steps, and post-growth annealing. An initial nitridation step at the growth temperature allowed for the growth of an AlN sublayer. This layer is shown to smooth out the underlying sapphire and establishes an “effective” sapphire/AlN substrate. This step is also responsible for enforcing a specific growth of the BN layer in a crystallographic orientation, which is shown to strongly deviate from the substrate for off-cut angles larger than 0.3°. A substrate with off-cut angle of 1° clearly yields the highest quality of h-BN layers as evidenced by the lowest amount of debris on the surface, most intense x-ray diffraction signal, minimal Raman phonon linewidth and thinnest amorphous BN (a-BN) at the interface with the effective substrate. Our study shows that the off-cut angles of sapphire substrates strongly influence the final epitaxial h-BN, clearly indicating the importance of optimal substrate preparation for the growth of two-dimensional BN layers. Post-growth annealing in N2 atmosphere at 800 °C improves the top surface morphology of the final stack, as well as suppresses further the presence of a-BN.

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Role of defects and grain boundaries in the thermal response of wafer-scale hBN films

Cited by 8 publications

References 68 publications

Temperature induced giant shift of phonon energy in epitaxial boron nitride layers

Temperature induced giant shift of phonon energy in epitaxial boron nitride layers

Temperature induced giant shift of phonon energy in epitaxial boron nitride layers

Effective substrate for the growth of multilayer h-BN on sapphire—substrate off-cut, pre-growth, and post-growth conditions in metal-organic vapor phase epitaxy

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