Evolution of crystalline domain size and epitaxial orientation of CdTe/Si(111) quantum dots

Suela, J.; Ribeiro, I. R. B.; Ferreira, S. O.; Malachias, A.; Fontes, Giselle N.; Montoro, Luciano A.; Ramírez, Antonio J.

doi:10.1063/1.3357292

Cited by 7 publications

(11 citation statements)

References 26 publications

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“…We performed the experiment growing CdTe films onto polymeric substrates (Kapton, Dupont) by hot wall deposition technique in high-vacuum (~10 −7 Torr). This growth technique has been chosen for its simplicity and for being demonstrated to yield high quality CdTe films with properties similar to films produced by molecular beam epitaxy 28 , 29 . Substrate temperature was set to T = 150 °C, and source temperature to 510 °C, yielding a growth rate F = 14.0(3) nm /min.…”

Section: Experimental Methodsmentioning

confidence: 99%

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

Almeida

Ferreira

Ferraz

2017

Sci Rep

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The Kardar-Parisi-Zhang (KPZ) class is a paradigmatic example of universality in nonequilibrium phenomena, but clear experimental evidences of asymptotic 2D-KPZ statistics are still very rare, and far less understanding stems from its short-time behavior. We tackle such issues by analyzing surface fluctuations of CdTe films deposited on polymeric substrates, based on a huge spatio-temporal surface sampling acquired through atomic force microscopy. A pseudo-steady state (where average surface roughness and spatial correlations stay constant in time) is observed at initial times, persisting up to deposition of ~10 4 monolayers. This state results from a fine balance between roughening and smoothening, as supported by a phenomenological growth model. KPZ statistics arises at long times, thoroughly verified by universal exponents, spatial covariance and several distributions. Recent theoretical generalizations of the Family-Vicsek scaling and the emergence of log-normal distributions during interface growth are experimentally confirmed. These results confirm that high vacuum vapor deposition of CdTe constitutes a genuine 2D-KPZ system, and expand our knowledge about possible substrate-induced short-time behaviors.The Kardar-Parisi-Zhang (KPZ) equationoriginally describes interface motion under conditions of no bulk conservation and exponentially fast relaxation 2 . The height field h(x, t) is measured from a d s -dimensional substrate at location x, with x ∈  d s at time t ≥ 0. ν, λ and D are phenomenological parameters, physically representing the surface tension, the excess of velocity in the growth, and the amplitude of a space-time white noise η, respectively.Although posed 30 years ago, outstanding advances on the understanding of the KPZ class have been made quite recently. Following seminal works on multiple-meaning stochastic models 3, 4 , long-awaited analytical solutions 2,5 , experiments 6, 7 and numerical simulations 7-9 came out to confirm that asymptotic 1D-KPZ height distributions (HDs) are related to statistics of the largest eigenvalues of random matrices 10 , while spatial covariances are dictated by the time-correlation of Airy processes 11 . Noteworthy, both HDs and covariances exhibit sensibility to initial conditions (ICs) 4, 11 , splitting the KPZ class into subclasses according to the ICs. This unanticipated feature was recently observed also in models for nonlinear molecular beam epitaxy class 12 . Similar scenario has been found for the 2D-KPZ case, based on numerical simulations [13][14][15] , although no analytical result is known for 2D-KPZ HDs and covariances and the existing theoretical approaches 16,17 for the scaling exponents disagree with numerical outcomes. In such arid landscape, the rare reliable experimental evidences of 2D-KPZ universality [18][19][20][21] turns to be precious achievements.The short-time roughening of systems exhibiting asymptotic KPZ scaling is also rich in behavior. For example, a transient scaling in the Edwards-Wilkinson 22 (EW) class, might appear whenev...

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Section: Experimental Methodsmentioning

confidence: 99%

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

Almeida

Ferreira

Ferraz

2017

Sci Rep

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“…Experimental methods. -CdTe (5N) was evaporated on Si(001) substrates by HWE, a well-controlled and highly reproducible growth technique [20,21]. The experimental HWE setup is described in detail in Ref.…”

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confidence: 99%

Temperature effect on (2 + 1) experimental Kardar-Parisi-Zhang growth

Almeida¹,

Ferreira²,

Ribeiro³

2015

EPL

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PACS 68.43.Hn -Structure of assemblies of adsorbates (two-and three-dimensional clustering) PACS 81.15.Aa -Theory and models of film growth PACS 05.40.-a -Fluctuation phenomena, random processes, noise, and Brownian motion Abstract -We report on the effect of substrate temperature (T ) on both local structure and long-wavelength fluctuations of polycrystalline CdTe thin films deposited on Si(001). A strong T -dependent mound evolution is observed and explained in terms of the energy barrier to intergrain diffusion at grain boundaries, as corroborated by Monte Carlo simulations. This leads to transitions from uncorrelated growth to a crossover from random-to-correlated growth and transient anomalous scaling as T increases. Due to these finite-time effects, we were not able to determine the universality class of the system through the critical exponents. Nevertheless, we demonstrate that this can be circumvented by analyzing height, roughness and maximal height distributions, which allow us to prove that CdTe grows asymptotically according to the Kardar-Parisi-Zhang (KPZ) equation in a broad range of T . More important, one finds positive (negative) velocity excess in the growth at low (high) T , indicating that it is possible to control the KPZ non-linearity by adjusting the temperature.

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“…As in the case of (Zn,Mn)Te/ZnSe QDs, described by Sellers et al 8 , the expected type II band alignment of CdTe/Si system would increase the carriers radiative life-time facilitating the formation of MPs. We have already shown that despite the big lattice mismatch around 19%, almost perfect CdTe QD can be grown on Si(111) 9 . The big advantage of using Si substrates is its compatibility with most processes used by the semiconductor industry.…”

Section: Introductionmentioning

confidence: 97%

Epitaxial growth of CdMnTe quantum dots directly on Si(111)

2014

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The presence of magnetic ions in a diluted magnetic semiconductor (DMS) leads to a variety of electronic, optical and magneto-optical properties. For instance, the exchange interaction between the magnetic ions spin and the spin of carriers leads to formation of bound magnetic polarons (BMPs). In a diluted magnetic quantum dot (DMQD), the possibility of tuning the three dimensional confinement originates new magnetic effects not present in bulk or quantum wells and makes MPs a very interesting system. Recently, formation of robust MPs has been observed in type-II DMQDs, due to the spatial separation of electrons and holes. In this work, we report the growth and structural characterization of CdMnTe/Si quantum dots. The samples were grown by molecular beam epitaxy directly on Si (111) substrates, in contrast with the previously studied systems, where the DMS islands were grown on II-VI buffers layers. The use of Silicon as substrates is advantageous for its compatibility with most processes of the microelectronic industry. We have used atomic force microscopy, high-resolution transmission electron microscopy and high-resolution x-ray diffraction to investigate the effect of growth time and temperature on the morphology and structural characteristics of the quantum dots. Our results show that this system follows the Volmer-Weber growth mode and almost perfect epitaxial islands can be grown despite a lattice mismatch around 19%. The introduction of a small concentration Mn ions improves the structural quality of the islands, as observed by high resolution x-diffraction around the (111) Bragg reflection.

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Evolution of crystalline domain size and epitaxial orientation of CdTe/Si(111) quantum dots

Cited by 7 publications

References 26 publications

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

Temperature effect on (2 + 1) experimental Kardar-Parisi-Zhang growth

Epitaxial growth of CdMnTe quantum dots directly on Si(111)

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