Raman-based measurement of carrier concentration in n-type ZnO thin films under resonant conditions

Mao, Zhuang; Fu, Cong; Pan, Xinhua; Chen, Xiangyang; He, Haiping; Wang, Wei; Zeng, Yu‐Jia; Ye, Zhizhen

doi:10.1016/j.physleta.2019.126148

Cited by 12 publications

(11 citation statements)

References 41 publications

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“…According to the cascade model [63], impurities do not influence the second-order scattering process, but they are still affected by phonon-plasmon coupling. Therefore, the Raman shift of the 2A 1 -LO modes can be used for measurements of the charge carrier concentration [56]. In our case, the shift of the 2A 1 -LO from 1148 ± 2 to 1144 ± 2 cm −1 for the undoped and RE-doped ZnO, respectively, could be caused by an increase in the charge carrier concentration upon doping.…”

Section: Raman Spectroscopymentioning

confidence: 64%

“…According to Alim et al [55], there are three main mechanisms leading to the red (downward) peak shifts of the phonon frequencies in NCs, namely, the spatial confinement within the boundaries of the nanocrystals, defects that are responsible for the phonon localization, and localized heating by the laser. Mao et al showed that for heavily doped ZnO, the first-and secondorder A 1 -LO modes are red-shifted due to phonon-plasmon coupling [56]. In the case of doping, a mass effect of foreign atoms and strain should be considered [57].…”

Section: Raman Spectroscopymentioning

confidence: 99%

“…Large RE atoms may deteriorate the lattice and create additional defects that are partially corroborated by the decrease in the PL intensity and the shift of the absorption edge. Lattice defects are thus also one of the possible scenarios responsible for the observed broadening and shift of the Raman peaks [55,56]. The nominal doping ratio of RE/Zn was set as 1:100.…”

Section: Raman Spectroscopymentioning

confidence: 99%

“…The inclusion of such a large amount of dopant was inconsistent with the ZnO lattice, so the mass effect may have contributed to the shift, but it cannot be the sole cause. Finally, the red shift of the first A 1 -LO mode together with the point defects could have been caused the interaction of the longitudinal phonons with plasmons generated by free charge carriers [56]. According to the cascade model [63], impurities do not influence the second-order scattering process, but they are still affected by phonon-plasmon coupling.…”

Section: Raman Spectroscopymentioning

confidence: 99%

“…In our case, the shift of the 2A 1 -LO from 1148 ± 2 to 1144 ± 2 cm −1 for the undoped and RE-doped ZnO, respectively, could be caused by an increase in the charge carrier concentration upon doping. Using the values of the shift of the 2A 1 -LO mode reported in [56], one can estimate the charge carrier concentration as ~8•10 18 and ~4•10 19 cm −3 for the pristine and RE-doped ZnO NCs, respectively. Thus, excluding factors such as laser heating, phonon confinement, and stress, the shift of the A 1 mode of the RE-doped ZnO NCs (RE = Nd, Gd, and Er) can be partly explained by the mass effect of heavy RE atoms and mostly by additional point defects and charge carrier concentration increases in the ZnO NCs created by doping.…”

Section: Raman Spectroscopymentioning

confidence: 99%

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Optical and Structural Characteristics of Rare Earth-Doped ZnO Nanocrystals Prepared in Colloidal Solution

et al. 2022

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ZnO nanocrystals doped with Nd, Gd, and Er were synthesized using a soft chemical process in ambient atmosphere. Pseudospherical and hexagonal nanocrystals (NC) of the wurtzite phase with a mean size of (7.4 ± 1.7) nm were obtained. The presence of rare earth (RE) dopants was confirmed by X-ray fluorescence (XRF) spectroscopy. The ZnO nanocrystals exhibited simultaneously narrow excitonic- and broad trap/surface-related photoluminescence (PL), both of which were affected by doping with RE atoms. Doping reduced the total PL intensity, suppressing the excitonic emission by a greater extent than the broad band PL. Also, doping resulted in a blue shift of the trap/surface-related emission, while the energy of the excitonic peak remained unchanged. Resonant Raman spectra additionally confirmed the wurtzite phase of ZnO NCs and revealed a shift of the A1-LO mode towards lower frequency upon doping that could be caused by the mass effect of RE atoms, point defects, and increases in charge carrier concentration. Fitting of the spectra with Voigt profiles showed better results with two surface optical (SO) phonon modes that were previously theoretically predicted for the wurtzite ZnO phase. The influence of RE doping on PL and Raman spectra can be explained by the incorporation of RE ions into the ZnO nanostructures, where the dopants act as non-radiative defects.

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Section: Raman Spectroscopymentioning

confidence: 64%

Section: Raman Spectroscopymentioning

confidence: 99%

Section: Raman Spectroscopymentioning

confidence: 99%

Section: Raman Spectroscopymentioning

confidence: 99%

Section: Raman Spectroscopymentioning

confidence: 99%

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Optical and Structural Characteristics of Rare Earth-Doped ZnO Nanocrystals Prepared in Colloidal Solution

et al. 2022

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Validation of Raman spectroscopy as a tool for mapping transport parameters in inhomogeneous N‐doped 4H‐SiC

Hergert

Elm

Klar

2023

J Raman Spectroscopy

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We assess Raman spectroscopy as a tool for fast and non‐invasive mapping of charge carrier density and carrier mobility in inhomogeneously doped 4H‐SiC. For this purpose, we compare values of these transport parameters obtained by magneto‐transport and Raman measurements of N‐doped 4H‐SiC. The comparison is not straightforward. The effective charge density and mobility, which are obtained from resistivity and Hall measurements by employing the commonly used effective one‐band model, deviate from the values extracted by applying the established line‐shape models for describing the longitudinal optical phonon coupled (LOPC) modes in the Raman spectra. Differentiating between free and localized carriers in the framework of a three‐band transport model confirms that only the free charge carriers in the conduction band of N‐doped 4H‐SiC contribute to the LOPC Raman signal and their density agrees well with that obtained by the line shape analysis. The agreement of the mobility values is good keeping in mind that different frequencies of the applied electric fields are used in the two approaches, i.e., dc‐transport measurements at 0 Hz and ac‐fields of the exciting laser at about 500 THz. Moreover, the excitation of electrons into the conduction band by the laser, which is inherent to the Raman experiment, causes differences in the temperature dependence of the carrier density compared with the electrical transport data.

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Investigation of structural and optical parameters of yttrium-doped ZnO thin films prepared via spin coating of simple aqueous solution

et al. 2021

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Raman-based measurement of carrier concentration in n-type ZnO thin films under resonant conditions

Cited by 12 publications

References 41 publications

Optical and Structural Characteristics of Rare Earth-Doped ZnO Nanocrystals Prepared in Colloidal Solution

Optical and Structural Characteristics of Rare Earth-Doped ZnO Nanocrystals Prepared in Colloidal Solution

Validation of Raman spectroscopy as a tool for mapping transport parameters in inhomogeneous N‐doped 4H‐SiC

Investigation of structural and optical parameters of yttrium-doped ZnO thin films prepared via spin coating of simple aqueous solution

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