Recent developments in spectroscopy of quantum structures

Arora, B. M.; Ghosh, Sandip; Datta, Shouvik; Kumar, Shailendra

doi:10.1016/s1369-8001(02)00007-0

Cited by 6 publications

(6 citation statements)

References 28 publications

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“…However, they claim not having observed a complete conversion since phase coexistence persisted up to 490 °C, the highest measured temperature in their experiment. Probably, it is due to the consideration of the peak at near 340 cm −1 as belonging to MoO 2 phase while there is a peak very close to it that actually belong to MoO 3 [11]. The spectrum at the top was measured after cooling the sample, it can be noted that the MoO 3 phase is preserved, indicating the expected not reversible character of the MoO 2 /MoO 3 phase transformation in air.…”

Section: Transformation From Moo 2 To Moo 3 By Annealing In Airmentioning

confidence: 99%

“…SPS was performed at room temperature in a lab-made automated experimental setup; comprising a halogen lamp coupled with a grating monochromator, a lock-in amplifier and an optical chopper [10]. The sample was located between a transparent indium-tin-oxide (ITO) electrode and a copper plate which acts as a sample holder and the bottom ground electrode [11]. Then, the surface photovoltage (SPV) signal measured as a function of incident photon energy provided the SPV spectra.…”

Section: Experimental Details and Characterizationmentioning

confidence: 99%

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Optical and electrical properties of MoO₂ and MoO₃ thin films prepared from the chemically driven isothermal close space vapor transport technique

Melo

González

Climent‐Font

et al. 2019

J. Phys.: Condens. Matter

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Chemically -driven isothermal close space vapour transport was used to prepare pure MoO2 films which were eventually converted to MoO3 by annealing in air. According to temperaturedependent Raman measurements, the MoO2/MoO3 phase transformation was found to occur in the 225 -350 o C range; no other phases were detected during the transition. A clear change in composition and Raman spectra, as well as noticeable modifications of the band gap and the absorption coefficient confirmed the conversion from MoO2 to MoO3. An extensive characterization of films of both pure phases was carried out. In particular, a procedure was developed to determine the dispersion relation of the refractive index of MoO2 from the shift of the interference fringes the used SiO2/Si substrate. The obtained refractive index was corrected taking into account the porosity calculated from elastic backscattering spectrometry. The Debye temperature and the residual resistivity were extracted from the electrical resistivity temperature dependence using the Bloch -Grüneisen equation. MoO3 converted samples presented very high resistivity and a typical semiconducting behaviour. They also showed intense and broad luminescence spectra, which were deconvoluted considering several contributions; and its behaviour with temperature was examined. Furthermore, surface photovoltage spectra were taken and the relation of these spectra with the photoluminescence is discussed.

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Section: Transformation From Moo 2 To Moo 3 By Annealing In Airmentioning

confidence: 99%

Section: Experimental Details and Characterizationmentioning

confidence: 99%

Optical and electrical properties of MoO₂ and MoO₃ thin films prepared from the chemically driven isothermal close space vapor transport technique

Melo

González

Climent‐Font

et al. 2019

J. Phys.: Condens. Matter

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“…The measured ac SPV response amplitude reflects the mean potential change between the electrodes during a light-chopping period. This method has been shown effective in investigations on azo pigments, 39 quantum structures, 40 ZnO nanocrystals, 41 Fe 2 O 3 nanocrystals, 42 and TiO 2 powder. 43 The phase value of the ac photovoltage signal correlated to the light modulation benefits analysis of the kinetics of the SPV generating process.…”

Section: Introductionmentioning

confidence: 99%

Size- and Orientation-Dependent Photovoltaic Properties of ZnO Nanorods

et al. 2007

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ZnO nanorod arrays on an ITO substrate and nanorod powder have been prepared via a chemical method in aqueous solution at low temperature. Two dimensions of composite nanorods in the arrays were obtained by controlling the reaction time. SEM, XRD, UV-vis transmission, and PL measurements have been utilized to characterize the samples. The surface photovoltage (SPV) spectra of the three samples have been comparatively investigated by a lock-in amplifier with dc bias and Kelvin probe (KP) based measurements. The kinetic features of SPV responses are interpreted in terms of ac SPV phase spectra and SPV transients on a KP. We demonstrate that the photovoltaic properties of ZnO nanorods not only depend on the rod size, but also rely on the crystallographic orientation. The mechanisms therein have been discussed in detail. Our results could lead to better understanding of the photovoltaic properties in ZnO nanostructures.

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“…The SPV amplitude related to QW transitions in region‐III can be explained by the absorption of photons using the following relation [ 41 ]

| SPV {false|}_{abs} = \frac{k_{B} T}{e} \frac{A η^{*} e Φ_{0} (1 - R^{*})}{h ν} [1 - e^{- α^{*} l_{w}}]

…”

Section: Resultsmentioning

confidence: 99%

“…In previous studies, it was shown that the SPV amplitude × hν can be used to study the fundamental parameters of the material system, i.e., absorption coefficient, diffusion length, etc. [ 40–42 ] Moreover, the matrix elements related to an optical transition become independent of energy when the absorption coefficient, which is proportional to SPV, is multiplied with hν . [ 43,44 ] In the present investigation, the transition energy ( hν ) related to HH and LH features significantly varies for different thicknesses of QW.…”

Section: Resultsmentioning

confidence: 99%

Photovoltaic Response and Charge Redistribution Processes in GaAs/AlGaAs Multiple‐Quantum Wells Structure

Haldar

Kumar

Roychowdhury

et al. 2020

Physica Status Solidi (b)

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The impact of radiative and non‐radiative processes on the photovoltaic response of GaAs/AlGaAs multiple‐quantum wells is investigated by temperature, excitation power, and chopping‐frequency‐dependent surface photovoltage (SPV) measurements. It is shown that a systematic study of SPV amplitude along with phase spectra can provide important information on thermal escape, carrier localization, and spatial redistribution of charge carriers. Characteristic features in SPV‐phase spectra related to quantum well (QW) transitions and their variation under an external perturbation are explained by the electron–electron interaction. It is found that a many‐body interaction inside the QW is responsible for the capture of charges at the heterointerfaces, which builds up an interface electric field and hinders the drift/diffusion of charges. Such an effect becomes dominant under higher excitation powers, causing a sub‐linear enhancement of photovoltage amplitude and an increase in phase delay as a function of photon flux. From the chopping‐frequency‐dependent SPV measurements, it is concluded that carriers during the drift in barrier layers are repeatedly captured by point defects and other QWs, which enhances the effective time response of the photovoltage signal. Results obtained in this study are beneficial in the engineering of quantum structures for high‐efficiency photovoltaics and non‐invasive characterization of electro‐optical processes.

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Recent developments in spectroscopy of quantum structures

Cited by 6 publications

References 28 publications

Optical and electrical properties of MoO₂ and MoO₃ thin films prepared from the chemically driven isothermal close space vapor transport technique

Optical and electrical properties of MoO₂ and MoO₃ thin films prepared from the chemically driven isothermal close space vapor transport technique

Size- and Orientation-Dependent Photovoltaic Properties of ZnO Nanorods

Photovoltaic Response and Charge Redistribution Processes in GaAs/AlGaAs Multiple‐Quantum Wells Structure

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Recent developments in spectroscopy of quantum structures

Cited by 6 publications

References 28 publications

Optical and electrical properties of MoO2 and MoO3 thin films prepared from the chemically driven isothermal close space vapor transport technique

Optical and electrical properties of MoO2 and MoO3 thin films prepared from the chemically driven isothermal close space vapor transport technique

Size- and Orientation-Dependent Photovoltaic Properties of ZnO Nanorods

Photovoltaic Response and Charge Redistribution Processes in GaAs/AlGaAs Multiple‐Quantum Wells Structure

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Optical and electrical properties of MoO₂ and MoO₃ thin films prepared from the chemically driven isothermal close space vapor transport technique

Optical and electrical properties of MoO₂ and MoO₃ thin films prepared from the chemically driven isothermal close space vapor transport technique