Influence de la température de recuit sur les queues d'absorption optique exponentielle de couches minces de silicium amorphe hydrogéné déposé par “glow discharge”

Berger, J.M.; Chelle, F. De; Ferraton, J.P.; Donnadieu, A.

doi:10.1016/0040-6090(83)90199-2

Cited by 7 publications

(6 citation statements)

References 9 publications

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“…The higher the size quantization effects (which are often accompanied by higher ε and δ values), the higher the value of X in , as revealed by a direct comparison of the nanostructured systems addressed in our present and previous studies. It is worth noting, however, that such high values for the Urbach energies (i.e., Urbach tails with large widths) have been already found for particular materials, mostly with amorphous or partially crystalline character. − Nanostructured thin films, therefore, behave similarly as amorphous materials in this respect.…”

Section: Resultsmentioning

confidence: 87%

“…As already implied, however, though the sub-band gap absorption has been studied a lot in the case of macrocrystalline and amorphous materials, − emphasizing many aspects as well as the influence of a number of external parameters on the UM absorption tails, the number of studies has been much smaller in the case of nanostructured semiconductors (3D QD assemblies, in particular) and also in the case of thin films. As we have already argued before, however, it is of certain importance for both fundamental aspects of physical chemistry, materials science, and the potential applications of semiconductor quantum dot thin films to follow the evolution of the sub-band gap absorption tails with both temperature and controlled particle size reduction.…”

Section: Introductionmentioning

confidence: 99%

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Nanostructured CdSe Films in Low Size-Quantization Regime: Temperature Dependence of the Band Gap Energy and Sub-Band Gap Absorption Tails

Pejova

Abay

2011

J. Phys. Chem. C

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Temperature dependence of the band gap energy and sub-band gap absorption tails in 3D assemblies of close packed weakly quantized CdSe quantum dots deposited as thin films was studied. The range from cryogenic temperatures (∼10 K) up to 340 K was covered. Excitonic absorption peaks were not observed even at temperatures as low as 11 K, which was attributed to the finite particle size distribution and interdot electronic coupling effects. The temperature coefficient of the band gap energy of the nanostructured films of 9.4 Â 10 À4 eV K À1 is higher by a factor of 1.35 than the corresponding value for the bulk CdSe specimen. As compared to the case of films constituted of strongly quantized ZnSe QDs, where the factor α nanocrystal /α bulk was found to be 1.82 (Pejova, B.; Abay, B.; Bineva, I. J. Phys. Chem. C 2011, 115, 37), the present findings imply that this ratio increases upon enhancement of size quantization effects in semiconductor nanocrystals. Analysis of the temperature-dependent optical absorption data within the Bose-Einstein model implies that no phonon confinement effects influence the phonon spectrum in the presently studied material due to the very small size-quantization effects. This situation is opposite to what we have recently found in the case of 3D arrays of strongly quantized ZnSe films. The characteristic Einstein temperature of the presently studied material corresponds to phonon frequency of about 220 cm À1 , in excellent agreement with the LO mode frequency of bulk CdSe (210À214 cm À1 ). It is demonstrated that the Urbach rule is valid in the presently studied nanostructured material in low size-quantization regime. Urbach energies are several times higher than the values characteristic for macrocrystalline materials, due to the relatively high degree of inherent structural disorder in the studied QD solids. At the same time, however, these values are approximately three times smaller than those reported for strongly quantized ZnSe films in our previous study. The dynamical (temperature-dependent) term accounts for only about 22% of the overall Urbach energy values, though this value is higher than the corresponding ratio in the case of strongly quantized ZnSe films.

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Section: Resultsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Nanostructured CdSe Films in Low Size-Quantization Regime: Temperature Dependence of the Band Gap Energy and Sub-Band Gap Absorption Tails

Pejova

Abay

2011

J. Phys. Chem. C

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“…[35][36][37][38][39][40][41][42] It is worth noting, however, that such high values for the Urbach energies (i.e., Urbach tails with large widths) have been already found for particular materials, mostly with an amorphous or partially crystalline character. [44][45][46][47][48][49][50][51][52][53] It could be, therefore, concluded that nanocrystalline thin films behave similarly as amorphous materials in this respect. To the best of our knowledge, however, this is the first experimental study in which the validity of the Urbach-Martienssen rule in the case of nanocrystalline thin films has been demonstrated.…”

Section: Urbach-martienssen Absorption Tails In the Optical Spectra O...mentioning

confidence: 99%

“…Also, comparative studies of the Urbach and exciton absorption in the case of undoped and doped metal chalcogenide compounds (such as GaSe and Ga-doped GaSe as well as InSe and Er-doped InSe) − at various temperatures have been performed. The doping, hydrogenation, and postdeposition annealing influences on the optical absorption edge of various amorphous materials have been studied as well. − It is, however, of certain importance for both the fundamental physical chemistry and materials science and the potential applications of the semiconductor QD thin films to follow the evolution of these absorption tails upon controlled particle size reduction as well. It is exactly this aspect of semiconducting nanocrystalline materials that the present paper is devoted to.…”

Section: Introductionmentioning

confidence: 99%

“…The doping, hydrogenation, and postdeposition annealing influences on the optical absorption edge of various amorphous materials have been studied as well. [44][45][46][47][48][49][50][51][52][53] It is, however, of certain importance for both the fundamental physical chemistry and materials science and the potential applications of the semiconductor QD thin films to follow the evolution of these absorption tails upon controlled particle size reduction as well. It is exactly this aspect of semiconducting nanocrystalline materials that the present paper is devoted to.…”

Section: Introductionmentioning

confidence: 99%

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Temperature Dependence of the Band-Gap Energy and Sub-Band-Gap Absorption Tails in Strongly Quantized ZnSe Nanocrystals Deposited as Thin Films

2010

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The temperature-dependent optical absorption of 3D arrays of close-packed strongly quantized ZnSe QDs, deposited in thin film form, is studied in the interval from 11 to 340 K. Because of the particle size distribution and interdot coupling between proximal QDs within the QD arrays, the excitonic peaks are not visible at all, even at temperatures as low as 11 K. The temperature coefficient of the band-gap energy in the strongly quantized QD arrays was found to be twice larger than the value characteristic of a bulk ZnSe specimen. The Debye temperature, on the other hand, is shown to decrease by about 15% in comparison with the bulk value, which is attributed to the phonon confinement effects. It is shown that the sub-band-gap exponential absorption tails in the strongly quantized 3D QD arrays obey the Urbach−Martienssen rule. The temperature dependence of the Urbach energy and the relation between this quantity and the band-gap energy of the films could be excellently fitted to the predictions of the Cody’s model. However, in contrast to the macrocrystalline semiconductors, the temperature-dependent component of the Urbach energy accounts for less than 15% of the overall value, which is attributed to the very high degree of inherent structural disorder in the QD arrays. This is in line with the conclusions derived from analyses of the temperature dependence of the steepness parameter, σ, which imply a rather high energy of the phonons contributing to the Urbach−Martienssen tails in the optical absorption of the QD arrays.

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Urbach tail and optical gap of G D a-Si:H films: Temperature and doping effects

Ferraton¹,

Donnadieu²,

Berger³

et al. 1983

Journal of Non-Crystalline Solids

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Influence de la température de recuit sur les queues d'absorption optique exponentielle de couches minces de silicium amorphe hydrogéné déposé par “glow discharge”

Cited by 7 publications

References 9 publications

Nanostructured CdSe Films in Low Size-Quantization Regime: Temperature Dependence of the Band Gap Energy and Sub-Band Gap Absorption Tails

Nanostructured CdSe Films in Low Size-Quantization Regime: Temperature Dependence of the Band Gap Energy and Sub-Band Gap Absorption Tails

Temperature Dependence of the Band-Gap Energy and Sub-Band-Gap Absorption Tails in Strongly Quantized ZnSe Nanocrystals Deposited as Thin Films

Urbach tail and optical gap of G D a-Si:H films: Temperature and doping effects

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