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Gerson Mette, [Kunie Ishioka](https://orcid.org/0000-0002-2285-8839), Steven Youngkin, Wolfgang Stolz, Kerstin Volz, Ulrich Hoefer

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[Interface-specific excitation of coherent phonons at the buried GaP/Si(001) heterointerface](https://mdr.nims.go.jp/datasets/1c695d83-6090-4b3a-8828-f9a4fdb8b9da)

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Interface‐Specific Excitation of Coherent Phonons at the Buried GaP/Si(001) HeterointerfaceRESEARCH ARTICLEwww.advmatinterfaces.deInterface-Specific Excitation of Coherent Phonons at theBuried GaP/Si(001) HeterointerfaceGerson Mette,* Kunie Ishioka, Steven Youngkin, Wolfgang Stolz, Kerstin Volz,and Ulrich Höfer*Ultrafast charge-carrier and phonon dynamics at the buried heterointerface ofGaP/Si(001) are investigated by means of two-color pump-probe reflectivitymeasurements. The carrier-induced reflectivity signal exhibits a resonantenhancement at a pump-photon energy of 1.4 eV, which is assigned to anoptical transition at the interface. In addition, the transient reflectivity ismodulated by a coherent oscillation at 2 THz, whose amplitude also becomesmaximum at 1.4 eV. The observed resonant behavior of the oscillation, incombination with the characteristic wavelength-dependencies of its frequencyand its initial phase, strongly indicates that the 2-THz mode is adifference-combination mode between a GaP-like and a Si-like phonon at theheterointerface and that the corresponding second-order Raman scatteringprocess can be enhanced by a double resonance involving the interfacialelectronic states.1. IntroductionThe coupling of charge and lattice degrees of freedom in semi-conductors is one of the key factors to determine their crys-talline structure and dominate the electronic, optical and ther-mal properties.[1] At surfaces of inorganic semiconductors, therearrangement of the atomic structure leads to well-defined elec-tronic and phononic surface states.[2] Although similar effectsare expected at deeply buried semiconductor interfaces, thoseG. Mette, S. Youngkin, W. Stolz, K. Volz, U. HöferFaculty of Physics and Materials Sciences CenterPhilipps-Universität Marburg35032 Marburg, GermanyE-mail: gerson.mette@physik.uni-marburg.de;hoefer@physik.uni-marburg.deK. IshiokaNational Institute for Materials ScienceTsukuba 305-0047, JapanU. HöferInstitute for Experimental and Applied PhysicsUniversity of Regensburg93040 Regensburg, GermanyThe ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/admi.202400573© 2025 The Author(s). Advanced Materials Interfaces published byWiley-VCH GmbH. This is an open access article under the terms of theCreative Commons Attribution License, which permits use, distributionand reproduction in any medium, provided the original work is properlycited.DOI: 10.1002/admi.202400573are more challenging to investigate dueto the experimental difficulty in detectingand isolating weak interface signaturesfrom dominant bulk signals. Highlyinterface sensitive nonlinear opticaltechniques such as second-harmonicgeneration (SHG) spectroscopy havebeen applied to study electronic inter-face states.[3] Phonons, however, areeven more difficult to investigate bySHG due to their tiny modulating sig-nals in the time domain.[4,5] In thisstudy, we therefore choose an alterna-tive approach to explore the ultrafastcharge-carrier and phonon dynamicsat a buried GaP/Si(001) heterointer-face: Instead of an interface-sensitivedetection, we apply an interface-specificexcitation and then detect the small signal modulations due tothe interface phonons with a linear optical technique.GaP/Si(001) has recently gained attention as an interestingmodel interface between a polar and a non-polar material.[6–12]Since the two semiconductors have only a small mismatch intheir lattice constants, the interface can serve as a template forSi-based III/V optoelectronics.[6–8] The atomic structure and mor-phology of the interface is well characterized.[6,7,10–12] For a widerange of growth conditions, the interface mainly consists ofcharge-neutral (112) and (111) pyramidal facets extending overseven lattice planes.[11] A recent SHG study revealed an opti-cal resonance of the interface at 1.4 eV.[13] This resonance hasbeen attributed to interface electronic states which lie energet-ically in the optical band gap of the two semiconductors.[13–15]Previous transient reflectivity measurements at GaP/Si(001) het-erostructures with above-bandgap photoexcitation of GaP and Siat 3.1-eV photon energy[16–18] revealed the generation of coher-ent longitudinal optical and acoustic phonons of the respectivebulk semiconductors.[16,18] The main effect of the interface wasthe generation and observation of acoustic strain pulses,[17,18]however, no phonon mode characteristic to the heterointerfacewas observed.In the present study, we make use of short-pulsed, tun-able near-infrared pump light in order to resonantly excite theinterface for the investigation of the interfacial charge-carrierand phonon dynamics with transient reflectivity measurements.The measured carrier-induced reflectivity response exhibits aclear resonance at 1.4 eV in agreement with the previous SHGresults.[13] Moreover, the transient reflectivity signals are mod-ulated by an oscillation at 2 THz, whose amplitude follows theAdv. Mater. Interfaces 2025, 2400573 2400573 (1 of 6) © 2025 The Author(s). Advanced Materials Interfaces published by Wiley-VCH GmbHhttp://www.advmatinterfaces.demailto:gerson.mette@physik.uni-marburg.demailto:hoefer@physik.uni-marburg.dehttps://doi.org/10.1002/admi.202400573http://creativecommons.org/licenses/by/4.0/http://crossmark.crossref.org/dialog/?doi=10.1002%2Fadmi.202400573&domain=pdf&date_stamp=2025-02-09www.advancedsciencenews.com www.advmatinterfaces.deFigure 1. a) Interface-contribution in transient reflectivity of the GaP/Si heterostructure pumped at different wavelengths and probed at 800 nm. Tracesare offset for clarity. b) Height of the initial drop ΔRmax of the interface contribution of GaP/Si as a function of the pump wavelength in comparison tobulk Si. Filled and open symbols are obtained with two different light sources. The latter are multiplied by 1.7 to scale to the former. Curves are to guidethe eye. c) Schematic band diagram of the GaP/Si interface with IS indicating an occupied interface state.[13]same resonance as the carrier-induced response and which is ab-sent in the reflectivity signals of the bulk semiconductors. Theconsistent resonant behavior unambiguously proves that this os-cillation is an interface phonon mode. The observed wavelength-dependencies of, both, frequency and initial phase of the 2-THz mode furthermore suggest that the interfacial phonon isenhanced by a double resonance involving the interface elec-tronic states.2. Results and DiscussionThe as-measured transient reflectivity signals ΔR from theGaP/Si sample (cf. Figure S2a, Supporting Information) containcontributions not only from the GaP overlayer/heterointerfaceΔRint but also from the Si substrate ΔRsub.[19] Therefore, we ex-tract the former contribution by subtracting the latter from the as-measured signal (ΔRint ≡ΔR−ΔRsub) as described in more detailin Section III (Supporting Information). Please note, that a coher-ent upgoing spike at t = 0 originating from a contribution of theSi substrate[20] was not completely eliminated by the subtractionfor some of the transients. Pump-induced reflectivity changes ingeneral can be associated with changes in the dielectric functiondue to the presence of free charge carriers (electron–hole plasma)as well as interband transitions (state-filling effect).[20] For Si bulksamples and low excitation densities, one would expect a pump-induced decrease of the reflectivity from both contributions in ac-cordance with our results obtained on Si without a GaP overlayer(Figure S2b, Supporting Information) and previous studies.[20–22]Figure 1a compares the obtained overlayer/interface-contribution ΔRint/R for different pump wavelengths. Thetransients show an abrupt drop at t = 0 which is followed bya double exponential increase. The height of the initial dropΔRmax gives a semi-quantitative measure for the photoexcitedcharge-carrier density in the overlayer and at the heterointerface.ΔRmax exhibits a distinct resonance peak at 𝜆pump ≃900 nm(photon energy of 1.4 eV) on top of the monotonic decreasewith increasing wavelength (decreasing pump-photon energy)as plotted in Figure 1b. This resonance behavior coincides withAdv. Mater. Interfaces 2025, 2400573 2400573 (2 of 6) © 2025 The Author(s). Advanced Materials Interfaces published by Wiley-VCH GmbH 21967350, 0, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/admi.202400573 by National Institute For, Wiley Online Library on [11/02/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advmatinterfaces.dewww.advancedsciencenews.com www.advmatinterfaces.deFigure 2. a) Oscillatory part of transient reflectivity of GaP/Si pumped at different wavelengths and b) the corresponding fast Fourier transform (FFT)spectra. Traces are offset for clarity. c) Amplitude, d) frequency, and e) initial phase of the low-frequency mode (LFM) as a function of the pumpwavelength. Filled and open symbols in each panel represent the results obtained with two different light sources. In (c) the latter are multiplied by1.7 to scale to the former. Curves are to guide the eye.the resonance of the fast SHG component obtained in ourprevious study on a thin (d = 4.5 nm) GaP film on Si(001).[13]Indeed, it is in apparent contrast to the initial drop height ofbulk Si (transient signals shown in Figure S2b, SupportingInformation), which decreases monotonically with decreasingphoton energy, as plotted in the same figure. We thereforeattribute the 1.4-eV resonance to an optical transition at theinterface[13] as schematically shown in Figure 1c. After the initialdrop of the reflectivity induced e.g. by a state-filling effect of theinvolved electronic states, the following increase of ΔRint/R canbe fitted to a multiple exponential function. The time constantfor the fast rise of ≈0.2 ps is comparable to the fast decay ofthe SHG signal observed previously[13] and it is assigned tothe relaxation of the excited electronic states. The slower riseoccurs on a similar time scale to that of bulk Si (cf. Figure S2b,Supporting Information), ≈40 ps, and is therefore attributedto carriers photoexcited in the Si substrate and recombining atthe GaP/Si interface.[19,20,23]The transient reflectivity signals of the GaP/Si sample also ex-hibit an apparent periodic modulation, as extracted in Figure 2aafter subtracting a multi-exponential baseline. This oscillation isnot seen for bulk Si (Figure S2b, Supporting Information) or bulkGaP (not shown) measured under the same conditions. Indeed,the frequency of this oscillation, 2 THz, has no counterpart inthe previously reported first- and second-order Raman spectra ofbulk GaP or Si.[24,25] Hereafter we refer to the 2-THz oscillationas “low-frequency mode (LFM).” In the fast Fourier-transform(FFT) spectra in Figure 2b, we also see a small overtone of theLFM at ≈4 THz for 𝜆pump <800 nm.The oscillatory reflectivity in Figure 2a can be fitted reasonablyto a damped harmonic oscillation:f (t) = ALFM exp(−ΓLFMt) sin(2𝜋𝜈LFMt + 𝜙LFM) (1)The obtained fitting parameters ALFM, ΓLFM, 𝜈LFM and ϕLFM areplotted as a function of 𝜆pump in Figure 2c–e. The amplitudeALFM in Figure 2c exhibits a distinct resonant peak at 𝜆pump≃900 nm (photon energy of 1.4 eV). This resonance behaviorcoincides with that of ΔRmax in Figure 1b, indicating a strongcoupling of the LFM with the interface electronic state. Wetherefore assign the LFM as an interface phonon mode cou-pled with the electronic transition at the GaP/Si interface. Wenote that the frequency 𝜈LFM (Figure 2d) exhibits a small but dis-tinct jump, whereas the initial phase ϕLFM (Figure 2e) shows ashift by 𝜋, both at 𝜆pump ∼800 nm, which corresponds to ourprobe wavelength.As for the microscopic origin of the 2-THz interface phononmode, it might be natural to consider Ga-Si or P-Si bonds atthe heterointerface, where the electronic interface states are ex-pected to be localized.[14] Stretching vibrations of these “wrong”bonds would appear at frequencies comparable to those of theoptical phonons of bulk GaP and Si, however, which are in theAdv. Mater. Interfaces 2025, 2400573 2400573 (3 of 6) © 2025 The Author(s). Advanced Materials Interfaces published by Wiley-VCH GmbH 21967350, 0, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/admi.202400573 by National Institute For, Wiley Online Library on [11/02/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advmatinterfaces.dewww.advancedsciencenews.com www.advmatinterfaces.deFigure 3. a) Schematic illustration of doubly resonant second-order Ra-man scattering at the GaP/Si interface (arrows). Left: Calculated projectedband structures of GaP(001)[35] (shaded in orange) and Si(001)[36] (grey)superposed with a valence band offset of 0.8 eV. The conduction bandswere both shifted to represent the actual band gaps of Si (1.12 eV) andGaP (2.24 eV). IS indicates an occupied interface state near the Γ-point.[13]Right: Calculated bulk band structure of GaP[37] (red dotted curves) andSi[27] (grey solid curves) superposed with the same valence band offset of0.8 eV. b) Phonon dispersion curves of Si and GaP taken from refs. [38,39]with an example of a pair of Si and GaP optical phonons participating inthe second-order scattering (black arrows).much higher frequency range of 12−15 THz.[26,27] It is highlyunlikely that the chemical bonds at the interface can be weakenedso much as compared to the bulk that their frequency lowers bya factor of five or more. Instead, one could consider a combina-tion mode among the interface vibrational modes. Previous Ra-man studies on GaAs/AlAs superlattices reported higher-orderscattering by multiple phonons in addition to the first-order scat-tering by a single phonon.[28–34] The intensities of the higher-order Raman scattering are usually much smaller than those ofthe first-order, but the former can be enhanced significantly bytuning the incident photon energy to the transition between thesub-bands of a quantum well, for example. Multiple scatteringcan involve not only phonons within the same crystal, but alsothose from two different materials, e.g. GaAs and AlAs. Whereasmost of these studies focused on sum-frequency combinationmodes appearing at high frequencies, there was also a report ona Raman peak appearing at a low frequency of 108 cm−1 (3.2THz).[33] Based on its resonance behavior it was attributed toa difference-frequency combination mode involving GaAs andAlAs optical phonons.In the present study we similarly attribute the observed LFMto a difference-frequency combination mode between a GaP-like and a Si-like optical phonon. Because the optical phononbranches of GaP and Si have comparatively small dispersionalong the Γ − X direction of the Brillouin zone as shown inFigure 3b, there is a relatively high density-of-states for a pairof Si and GaP optical phonons to simultaneously satisfy energyand momentum conservation, i.e., 𝜈Si − 𝜈GaP = 2 THz and kSi =−kGaP. An exemplary second-order Raman scattering process thatwould give rise to such a difference-frequency combination modeis shown schematically in Figure 3a. It is initiated by the creationof electron-hole pairs upon optical excitation at the Γ-point, fol-lowed by the large-k scattering of a Si-like and a GaP-like opticalphonon and finally terminated by the charge-carrier recombina-tion.As a combination phonon mode, the coherent LFM is de-tected with an extraordinarily large amplitude. We attribute thesignificant enhancement to a double (or multiple) resonance in-volved in the second-order Raman scattering. Figure 3a illus-trates an example of such a doubly resonant second-order scat-tering, in which the excited state at the Γ-point and the GaPconduction band near the X-point contribute as real intermedi-ate states. Here, the excited state at the Γ-point originates fromGaP conduction band states projected to the (001) interface asschematically shown in the left part of Figure 3a. Alternatively,one could also consider the existence of unoccupied electronic in-terface states as DFT band structure calculations have predictedthe existence of both occupied and unoccupied electronic inter-face states at the GaP/Si interface.[14] The involvement of a dou-ble resonance can also explain the small discontinuity in the LFMfrequency at 𝜆pump ≃ 𝜆probe shown in Figure 2d. The 𝜋-phase shiftobserved in Figure 2e is an indication of Stokes and anti-Stokesscattering dominating the detection process in the short (𝜆probe< 𝜆pump) and long (𝜆probe > 𝜆pump) probe wavelength regimes,respectively.[40] A small frequency disparity between Stokes andanti-Stokes scattering can be explained as a result of different in-termediate electronic states contributing to the double (or mul-tiple) resonance, as reported for the disorder-induced Ramanbands (D, D′, D″ and their combination modes) of graphiticmaterials.[41–45]3. ConclusionIn conclusion, our two-color transient reflectivity measurementsapplied an interface-specific excitation to explore the ultrafastcharge-carrier and phonon dynamics at the buried heterointer-face of GaP/Si(001). By using tunable near-infrared pump light,an interface phonon mode was unambiguously resolved as aperiodic modulation at ≈2 THz, whose amplitude was reso-nantly enhanced by an optical transition involving electronic in-terface states. The oscillation was interpreted as a difference-frequency combination mode between a GaP-like and a Si-likeoptical phonon. Its unusually large amplitude, together with itsphoton-energy dependent frequency, indicated the involvementof a multiple resonance in the second-order Raman scattering.We thus demonstrated electron-phonon coupling that is char-acteristic to a heterointerface of polar and non-polar inorganicsemiconductors.Adv. Mater. Interfaces 2025, 2400573 2400573 (4 of 6) © 2025 The Author(s). Advanced Materials Interfaces published by Wiley-VCH GmbH 21967350, 0, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/admi.202400573 by National Institute For, Wiley Online Library on [11/02/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advmatinterfaces.dewww.advancedsciencenews.com www.advmatinterfaces.de4. Experimental SectionThe studied sample was a nominally undoped 10-nm thick GaP nucle-ation layer grown at 450°C on n-type Si(001) by using flow-rate modulatedmetal-organic vapor phase epitaxy (MOVPE).[46,47] The single crystallineGaP nucleation layer exhibited a small surface undulation with a lateralfeature size of ≤30 nm as shown in Figure S1 (Supporting Information).Two-color pump-probe reflectivity measurements were performed underambient conditions in the near back-reflection geometry. Details of the ex-perimental setups are described in Section II (Supporting Information).Two different sets of tunable femtosecond light sources with pulse dura-tions in the range of 30 − 50 fs were employed to cover the pump wave-length range of 720 − 1220 nm (photon energy of 1.02 − 1.72 eV). Pleasenote, that the used pulse durations were not short enough to observethe optical phonons of bulk GaP and Si (frequencies 12 and 15.6 THz,respectively).[26,27] The pump-photon energies were smaller than the in-direct bandgap of GaP (2.26 eV), but comparable with or larger than thatof Si (1.12 eV). The probe wavelength was fixed at 800 nm (1.55 eV). Thepump-induced change in the reflectivity ΔR/R was measured by detectingthe probe lights before and after the reflection by the sample with a pairof matched photodiodes. The time delay t between the pump and probepulses was scanned using a linear motor stage with a slow scan technique.Supporting InformationSupporting Information is available from the Wiley Online Library or fromthe author.AcknowledgementsThe authors gratefully acknowledge funding by the Deutsche Forschungs-gemeinschaft (DFG, German Research Foundation), Project-ID223848855-SFB 1083. The authors thank NIMS RCAMC and NAsPIII/V GmbH for AFM measurements.Conflict of InterestThe authors declare no conflict of interest.Data Availability StatementThe data that support the findings of this study are available from thecorresponding author upon reasonable request.Keywordsburied heterointerface, coherent phonons, experiment, GaP/Si(001), in-terface phonon, pump-probe, transient reflectivity, ultrafast dynamicsReceived: July 1, 2024Revised: December 9, 2024Published online:[1] P. Y. Yu, M. Cardona, Fundamentals of Semiconductors, 3rd ed.,Springer, Berlin 2005.[2] W. Mönch, Semicnductor Surfaces and Interfaces, Springer, Berlin2001.[3] T. F. Heinz, F. J. Himpsel, E. Palange, E. Burstein, Phys. Rev. Lett. 1989,63, 644.[4] Y. M. Chang, L. Xu, H. W. K. Tom, Phys. Rev. Lett. 1997, 78, 4649.[5] T. Nomoto, H. Onishi, Phys. Chem. Chem. Phys. 2007, 9, 5515.[6] A. Beyer, K. Volz, Adv. Mater. Interfaces 2019, 6, 1801951.[7] O. Supplie, O. Romanyuk, C. Koppka, M. Steidl, A. Nägelein, A.Paszuk, L. Winterfeld, A. Dobrich, P. Kleinschmidt, E. Runge, T.Hannappel, Progr. Cryst. GrowthCharact. Mater. 2018, 64, 103.[8] R. Saive, H. Emmer, C. T. Chen, C. Zhang, C. Honsberg, H. Atwater,IEEE J. Photovoltatics 2018, 8, 1568.[9] K. Brixius, A. Beyer, G. Mette, J. Güdde, M. Dürr, W. Stolz, K. Volz, U.Höfer, J. Phys.: Cond. Matter 2018, 30, 484001.[10] O. Supplie, M. M. May, G. Steinbach, O. Romanyuk, F. Grosse, A.Nägelein, P. Kleinschmidt, S. Brückner, T. Hannappel, J. Phys. Chem.Lett. 2015, 6, 464.[11] A. Beyer, A. Stegmüller, J. O. Oelerich, K. Jandieri, K. Werner, G.Mette, W. Stolz, S. D. Baranovskii, R. Tonner, K. Volz, Chem. Mater.2016, 28, 3265.[12] A. Lenz, O. Supplie, E. Lenz, P. Kleinschmidt, T. Hannappel, J. Appl.Phys. 2019, 125, 045304.[13] G. Mette, J. Zimmermann, A. Lerch, K. Brixius, J. Güdde, A. Beyer,M. Dürr, K. Volz, W. Stolz, U. Höfer, Appl. Phys. Lett. 2020, 117,081602.[14] O. Romanyuk, O. Supplie, T. Susi, M. M. May, T. Hannappel, Phys.Rev. B 2016, 94, 155309.[15] G. Steinbach, M. Schreiber, S. Gemming, Nanosci. Nanotechnol. Lett.2013, 5, 73.[16] K. Ishioka, K. Brixius, A. Beyer, A. Rustagi, C. J. Stanton, W. Stolz, K.Volz, U. Höfer, H. Petek, Appl. Phys. Lett. 2016, 108, 051607.[17] K. Ishioka, A. Rustagi, A. Beyer, W. Stolz, K. Volz, U. Höfer, H. Petek,C. J. Stanton, Appl. Phys. Lett. 2017, 111, 062105.[18] K. Ishioka, A. Beyer, W. Stolz, K. Volz, P. Hrvoje, U. Höfer, C. J.Stanton, J. Phys.: Cond. Matter 2019, 31, 094003.[19] K. Ishioka, E. Angerhofer, C. J. Stanton, G. Mette, K. Volz, W. Stolz,U. Höfer, Phys. Rev. B 2022, 105, 035309.[20] A. J. Sabbah, D. M. Riffe, Phys. Rev. B 2002, 66, 165217.[21] C. V. Shank, R. Yen, C. Hirlimann, Phys. Rev. Lett. 1983, 50, 454.[22] M. C. Downer, C. V. Shank, Phys. Rev. Lett. 1986, 56, 761.[23] A. J. Sabbah, D. M. Riffe, J. Appl. Phys. 2000, 88, 6954.[24] R. Hoff, J. Irwin, Can. J. Phys. 1973, 51, 63.[25] C. S. Wang, J. M. Chen, R. Becker, A. Zdetsis, Phys. Lett. A 1973, A 44,517.[26] M. Hase, M. Kitajima, A. Constantinescu, H. Petek, Nature 2003, 426,51.[27] K. Ishioka, K. Brixius, U. Höfer, A. Rustagi, E. M. Thatcher, C. J.Stanton, H. Petek, Phys. Rev. B 2015, 92, 205203.[28] M. H. Meynadier, E. Finkman, M. D. Sturge, J. M. Worlock, M. C.Tamargo, Phys. Rev. B 1987, 35, 2517.[29] V. V. Gridin, R. Beserman, H. Morkoc, Phys. Rev. B 1988, 37, 9061.[30] Z. V. Popovic, M. Cardona, E. Richter, D. Strauch, L. Tapfer, K. Ploog,Phys. Rev. B 1989, 40, 1207.[31] Z. V. Popovic, M. Cardona, E. Richter, D. Strauch, L. Tapfer, K. Ploog,Phys. Rev. B 1989, 40, 3040.[32] D. J. Mowbray, M. Cardona, K. Ploog, Phys. Rev. B 1991, 43, 11815.[33] J. Spitzer, I. Gregora, T. Ruf, M. Cardona, K. Ploog, F. Briones, M. I.Alonso, Solid State Commun. 1992, 84, 275.[34] S. L. Zhang, C. L. Yang, Y. T. Hou, Y. Jin, Z. L. Peng, J. Li, S. X. Yuan,R. Planel, J. Raman Spectroscopy 1996, 27, 249.[35] W. G. Schmidt, J. Bernholc, F. Bechstedt, Appl. Surf. Sci. 2000, 166,179.[36] P. Krüger, J. Pollmann, Phys. Rev. B 1993, 47, 1898.[37] K. S. Sieh, P. V. Smith, Phys. Stat. Sol. B 1985, 129, 259.[38] W. Weber, Phys. Rev. B 1977, 15, 4789.[39] P. H. Borcherds, R. L. Hall, K. Kunc, G. F. Alfrey, J. Phys. C 1979, 12,4699.[40] K. Mizoguchi, R. Morishita, G. Oohata, Phys. Rev. Lett. 2013, 110,077402.Adv. Mater. Interfaces 2025, 2400573 2400573 (5 of 6) © 2025 The Author(s). Advanced Materials Interfaces published by Wiley-VCH GmbH 21967350, 0, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/admi.202400573 by National Institute For, Wiley Online Library on [11/02/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advmatinterfaces.dewww.advancedsciencenews.com www.advmatinterfaces.de[41] P. Tan, Y. Deng, Q. Zhao, Phys. Rev. B 1998, 58, 5435.[42] P. Tan, L. An, L. Liu, Z. Guo, R. Czerw, D. L. Carroll, P. M. Ajayan, N.Zhang, H. Guo, Phys. Rev. B 2002, 66, 245410.[43] L. Cancado, M. A. Pimenta, R. Saito, A. Jorio, L. Ladeira, A. Grueneis,A. Souza Fiho, G. Dresselhaus, M. Dresselhaus, Phys. Rev. B 2002,66, 035415.[44] V. Zólyomi, J. Kürti, Phys. Rev. B 2002, 66, 073418.[45] I. Katayama, K. Sato, S. Koga, J. Takeda, S. Hishita, H.Fukidome, M. Suemitsu, M. Kitajima, Phys. Rev. B 2013, 88,245406.[46] K. Volz, A. Beyer, W. Witte, J. Ohlmann, I. Nemeth, B. Kunert, W. Stolz,J. Crystal Growth 2011, 315, 37.[47] A. Beyer, J. Ohlmann, S. Liebich, H. Heim, G. Witte, W. Stolz, K. Volz,J. Appl. Phys. 2012, 111, 083534.Adv. Mater. Interfaces 2025, 2400573 2400573 (6 of 6) © 2025 The Author(s). Advanced Materials Interfaces published by Wiley-VCH GmbH 21967350, 0, Downloaded from https://advanced.onlinelibrary.wiley.com/doi/10.1002/admi.202400573 by National Institute For, Wiley Online Library on [11/02/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.advmatinterfaces.de