Observation of CuCl clusters in NaCl by scanning near-field optical microscopy

Diegeler, A.; Haselhoff, M.; Rammensee, W.; Weber, Helmut

doi:10.1016/s0038-1098(97)10071-0

Cited by 6 publications

(7 citation statements)

References 19 publications

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“…16 Images of CuCl in NaCl taken with a scanning near-field microscope demonstrated the existence of deformation fields around the embedded nanocrystals. 17 In agreement with this microscopic observation, the increments of the elastic constants in the composite material could be explained by a prestressed NaCl lattice. 16 In the present work we elucidate the potential of copperdoped alkali halides and of the exciton spectroscopy for studying kinetic processes in the course of phase separation in a eutectic system.…”

Section: Introductionsupporting

confidence: 79%

“…We expect the unwanted nucleation, which reduces the experimental accuracy, to depend on the presence of structural defects. The influence of defects on the nucleation process was also concluded from observations in the optical near-field microscope 17 and it is the most natural explanation for the appearance of the bulk excitons in the spectra at 78-250 K and at 550 K of Fig. 4.…”

Section: A Accuracy Of the Decompositon Proceduresmentioning

confidence: 70%

“…Recently, we observed in a scanning near-field optical microscope that the growth of big clusters is related to a local assembly of Schottky defects. 17 Such assemblies of defects are able to reduce the diffusion path and the diffusion coefficient drastically and they should influence the primary nucleation of seeds strongly. A nucle-ation process related to nonideal and disturbed lattices is called heterogenous nucleation.…”

Section: B On the Comparison Of Growth Experiments With Classical Grmentioning

confidence: 99%

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Nanocrystal growth in alkali halides observed by exciton spectroscopy

Haselhoff

Weber

1998

Phys. Rev. B

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We have developed a method to study the growth of CuCl and CuBr nanocrystals in alkali halides by in situ absorption spectroscopy. Exciton lines are used as a signature of crystallinity and a broad absorption peak measures the number of Cu ϩ ions. The mean radius R and the concentration x cr of nanocrystals are determined simultaneously, which in turn enables the determination of the particle density N of crystals as a function of time. Neither the size-distribution function nor R(t) follow the prediction of the classical growth theory. x cr (t) reveals two different growth mechanisms, one for high and one for low growth temperatures. N(t) demonstrates that the growth of big crystals at the expense of small crystals happens from the beginning of the growth process. This result contradicts the traditional view of Ostwald ripening as a final stage of precipitation and stresses the dynamical character of cluster growth. The experimental data are described by a set of empirical parameters that can be used as a guide for controlled growth of CuCl nanocrystals in NaCl. The smallest nanocrystals detected by exciton spectroscopy consist of 50 unit cells. The kinetic properties of KCl and NaBr crystals doped with CuCl and CuBr are very similar to those observed in NaCl doped with CuCl.

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Section: Introductionsupporting

confidence: 79%

Section: A Accuracy Of the Decompositon Proceduresmentioning

confidence: 70%

Section: B On the Comparison Of Growth Experiments With Classical Grmentioning

confidence: 99%

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Nanocrystal growth in alkali halides observed by exciton spectroscopy

Haselhoff

Weber

1998

Phys. Rev. B

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“…3. This presumption is supported by the observation of local assemblies of Schottky defects related to big nanocrystals in a scanning near-field optical microscope (Diegeler et al, 1998). No matter how, it must be assumed that in the beginning of the heat treatment at the different growth temperatures the sample contains a certain number of athermal nuclei.…”

Section: Figurementioning

confidence: 97%

Small-angle X-ray scattering study of the growth kinetics of CuCl nanocrystals in NaCl

Kranold¹,

Kriesen²,

Haselhoff³

et al. 2003

J Appl Cryst

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The precipitation of CuCl nanocrystals in a NaCl matrix has been studied by time-resolved small-angle X-ray scattering. The experimental results suggest that the nucleation process is accelerated by lattice defects of the matrix remaining in the NaCl lattice after the dissolution of previous nanocrystals at high temperature. The evolution of structural parameters calculated from the scattering curves, such as volume fraction, mean radius and particle number density of the nanocrystals, is discussed in terms of a classical phase separation process but with specific concern for the effect of elastic strains. It was found that Ostwald ripening is effective during the whole period of observation. The effect of elastic strains results in an increase of the critical radius and a decrease of the coarsening rate. The results of the scattering experiments confirm the miscibility gap data determined by exciton spectroscopy.

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“…23 The elastic interaction between the nanocrystals and the surrounding lattice was studied and the existence of deformation fields around the nanocrystals was observed by means of a scanning near-field microscope. 24,25 These results show that the surface of CuCl nanocrystals in NaCl is highly strained and the atomic arrangement at the interface between the nanocrystals and the matrix NaCl is more regular than those at the interfaces between the nanocrystals and the surrounding glass and KCl, perhaps resulting in the formation of cubic nanocrystals in NaCl. As a result, CuCl nanocrystals interact with the surrounding NaCl and cannot vibrate freely, similarly to damped oscillators, leading to the softening of the frequencies of the low-frequency vibrations.…”

mentioning

confidence: 89%