Carrier Dynamics In Stacked Inpgaas Quantum Dots

We investigated two stacked layers of InPGaAs type-II quantum dots by transmission electron microscopy and optical spectroscopy. The results reveal that InP quantum dots formed in two quantum dot layers are more uniform than those from a single layer structure. The thermal activation energies as well as the photoluminescence decays are rather independent of the separation between quantum dot layers and the presence of the second layer. The quantum dot optical emission persists for thermal activation energy larger than the calculated exciton binding energy. The photoluminescence decay is relatively fast for type-II alignment. © 2007 American Institute of Physics.9112Goldstein, L., Glas, F., Marzin, M.J.Y., Charasse, N., Le Roux, G., (1985) Appl. Phys. Lett., 47, p. 1099Xie, Q., Madhkar, A., Chen, P., Kobayashi, N., (1995) Phys. Rev. Lett., 75, p. 2542Ledentsov, N.N., Shchukin, V.A., Grundmann, M., Kirstaedter, N., Böhmer, J., Schmidt, O., Bimberg, D., Heydenreich, J., (1996) Phys. Rev. B, 54, p. 8743Solomon, G.S., Trezza, J.A., Marchall, A.F., Harris Jr., J.S., (1996) Phys. Rev. Lett., 76, p. 952Sugiyama, Y., Nakata, Y., Futatsugi, T., Sugawara, M., Awano, Y., Yokoyama, N., (1996) Jpn. J. Appl. Phys., Part 2, 36, p. 158Schmidt, O.G., Kienzie, O., Hao, Y., Eberl, K., (1999) Appl. Phys. Lett., 74, p. 1272Chang, W.-H., Chen, W.-Y., Chou, A.-T., Hsu, T.-M., Chen, P.-S., Pei, Z., Lai, L.-S., (2003) J. Appl. Phys., 93, p. 4999Susuki, K., Hogg, R.A., Arakawa, Y., (1999) J. Appl. Phys., 85, p. 8349Sun, C.-K., Wang, G., Bowers, J.E., Brar, B., Blank, H.-R., Kroemer, H., Pilkuhn, M.H., (1996) Appl. Phys. Lett., 68, p. 1543Hatami, F., Grundmann, M., Ledentsov, N.N., Heinrichsdorff, F., Heitz, R., Böhrer, J., Bimberg, D., Alferov Zh., I., (1998) Phys. Rev. B, 57, p. 4635De Godoy, M.P.F., Gomes, P.F., Nakaema, M.K.K., Iikawa, F., Brasil, M.J.S.P., Caetano, R.A., Madureira, J.R., Bittencourt, A.C.R., (2006) Phys. Rev. B, 73, p. 033309Wang, B., Chua, S.-J., (2001) Appl. Phys. Lett., 78, p. 628Nakaema, M.K.K., Iikawa, F., Brasil, M.J.S.P., Ribeiro, E., Medeiros-Ribeiro, G., Carvalho Jr., W., Maialle, M.Z., Degani, M.H., (2002) Appl. Phys. Lett., 81, p. 2743Zundel, M.K., Specht, P., Eberl, K., Jin-Phillipp, N.Y., Phillipp, F., (1997) Appl. Phys. Lett., 71, p. 2972Sanguinetti, S., Henini, M., Grassi Alessi, M., Capizzi, M., Frigeri, P., Franchi, S., (1999) Phys. Rev. B, 60, p. 827

The interaction of cavities in silicon with moving amorphous–crystalline interfaces

A detailed transmission electron microscopy (TEM) study has been carried out on the effect on helium-filled cavities (bubbles), contained entirely within a buried amorphous layer in silicon, of the recrystallisation of the layer by solid-phase epitaxial growth. On annealing to temperatures in the range 550–600 °C, recrystallisation took place at both amorphous–crystalline interfaces which, as they moved, were observed to sweep the cavities, keeping them initially confined within the amorphous region. The recrystallisation also gave rise to the formation of microtwin lamellae which clearly did not nucleate on the bubbles; contrary to previous reports. This paper seeks to explain aspects of the interaction of both cavities and microtwins with the advancing a/c interface in terms of defects within the amorphous layer

In-situ transmission electron microscopy growth of nanoparticles under extreme conditions

International audienceThe formation and time resolved behavior of individual Pb nanoparticles embedded in silica have been studied by in-situ transmission electron microscopy observations at high temperatures (400-1100 degrees C) and under 200 keV electron irradiation. It is shown that under such extreme conditions, nanoparticles can migrate at long distances presenting a Brownian-like behavior and eventually coalesce. The particle migration phenomenon is discussed considering the influence of the thermal energy and the electron irradiation effects on the atomic diffusion process which is shown to control particle migration. These results and comparison with ex-situ experiments tackle the stability and the microstructure evolution of nanoparticles systems under extreme conditions. It elucidates on the effects of energetic particle irradiation-annealing treatments either as a tool or as a detrimental issue that could hamper their long-term applications in radiation-harsh environments such as in space or nuclear sectors. (c) 2016 AIP Publishing LLC

Nanocavities induced by neon Plasma Based Ion Implantation in silicon

Nanocavities formed by neon Plasma Based Ion Implantation (PBII) in Si have been studied in comparison with conventional ion implantation (CI). Interstitial-type defects are also investigated. To avoid amorphisation, neon implantations were performed at 250 °C with a fluence of ≈5 × 1016 cm−2. Using PBII a rather uniform layer of cavities is observed from the surface while a three layer structure is present using the CI. However, the mean diameter of cavities is smaller due to the interaction with the interstitial-type defects. After annealing at 800 °C, bubbles grow and extended defects identified as {1 1 3} defects are formed

Nanoscale organization by elastic interactions between H and He platelets in Si

International audienceWe used ion implantation of H and He in Si and thermal treatments to produce two systems allowing to study the effects of global and local mechanical stress fields on the formation energy of H-precipitates called H-platelets. In the first part of the work, the depth-distribution of different crystallographic orientations of the precipitates formed along the implanted layer was characterized by transmission electron microscopy. The global strain in the region was measured by X-ray diffraction, and the depth distribution of strain was reconstructed using a dynamical-theory-based code. Elasticity theory was used to develop a model based on mechanical interactions, explaining the preferential presence of (001)-oriented precipitates in the more stressed region of the implanted layer. In a second part, local sources of stress of nanometer size and cylindrical symmetry were introduced in a deeper region of the matrix, before the nucleation of H-platelets. The local stresses were embodied by (001) He-plate precipitates. Upon annealing, a specific arrangement of crystallographic variants of {111}-oriented H-platelets in a four-fold configuration was observed. To explain these experimental observations, and to calculate the variations of the formation energy of the precipitates under the presence of local stress tensors components, analytical and numerical (finite element method) approaches were used to develop 2D and 3D models based on elasticity theory. The concepts and modeling strategy developed here paves the way for determining the required conditions to create controlled architecture of precipitates at the nanoscale using local stress engineering

Formation of neon induced cavities in silicon by plasma based ion implantation

Nanocavities and interstitial-type defects formed by neon plasma based ion implantation (PBII) in Si followed by annealing at 900 °C have been studied in comparison with conventional ion implantation. Implantations were performed at 250 °C and high fluence of ≈5 × 1016 cm−2. Using PBII, a rather uniform layer of cavities is observed from the surface. However, the mean diameter of cavities is smaller due to the interaction with the interstitial-type defects. In contrast with conventional implantation, these latter are created all over the cavity band because of the ion energy distribution that is characteristic of plasma based ion implantation

A New Approach to Study the Damage Induced by Inert Gases Implantation in Silicon

In the present work, we report on the effects of the implantation temperature on the formation of bubbles and extended defects in Ne+-implanted Si(001) substrates. The implantations were performed at 50 keV to a fluence of 5x1016 cm-2, for distinct implantation temperatures within the 250°C≤Ti≤800°C interval. The samples are investigated using a combination of cross-sectional and plan-view Transmission Electron Microscopy (TEM) observations and Grazing Incidence Small-Angle X-ray Scattering (GISAXS)measurements. In comparison with similar He implants, we demonstrate that the Ne implants can lead to the formation of a much denser bubble system

Role of Thermodynamics in the Shape Transformation of Embedded Metal Nanoparticles Induced by Swift Heavy-Ion Irradiation

International audienceSwift heavy-ion irradiation of elemental metal nanoparticles (NPs) embedded in amorphous SiO2 induces a spherical to rodlike shape transformation with the direction of NP elongation aligned to that of the incident ion. Large, once-spherical NPs become progressively more rodlike while small NPs below a critical diameter do not elongate but dissolve in the matrix. We examine this shape transformation for ten metals under a common irradiation condition to achieve mechanistic insight into the transformation process. Subtle differences are apparent including the saturation of the elongated NP width at a minimum sustainable, metal-specific value. Elongated NPs of lesser width are unstable and subject to vaporization. Furthermore, we demonstrate the elongation process is governed by the formation of a molten ion-track in amorphous SiO2 such that upon saturation the elongated NP width never exceeds the molten ion-track diameter