arXiv subjects

Y. González

Publications and source records attributed to Y. González.

8 recordsLinked to original sources

arXiv2025

Structural and optical changes induced by incorporation of antimony into InAs/GaAs(001) quantum dots

We present experimental evidence of Sb incorporation inside InAs/GaA(001) quantum dots exposed to an antimony flux immediately before capping with GaAs. The Sb composition profile inside the nanostructures as measured by cross-sectional scanning tunneling and electron transmission microscopies show two differentiated regions within the quantum dots, with an Sb rich alloy at the tip of the quantum dots. Atomic force microscopy and transmission electron microscopy micrographs show increased quantum-dot height with Sb flux exposure. The evolution of the reflection high-energy electron-diffraction pattern suggests that the increased height is due to changes in the quantum-dot capping process related to the presence of segregated Sb atoms. These structural and compositional changes result in a shift of the room-temperature photoluminescence emission from 1.26 to 1.36 microns accompanied by an order of magnitude increase in the room-temperature quantum-dot luminescence intensity.

cond-mat.mtrl-sci↗

arXiv2025

Ordered InAs quantum dots on pre-patterned GaAs (0 0 1) by local oxidation nanolithography

Ordered InAs quantum dot (QD) arrays have been obtained on pre-patterned GaAs (0 0 1) substrates by atomic force microscopy (AFM) local oxidation nanolithography. Prior to InAs molecular beam epitaxy (MBE) deposition, an ordered square array of nanoholes is formed at the GaAs pre-patterned surface following in situ etching with atomic hydrogen. A low substrate temperature is maintained during the whole process in order to avoid pattern smoothing. Our results show that the density and dimensions of the nanoholes on the GaAs surface determine InAs QD size, nucleation site and InAs dose necessary for their formation. As a function of the geometrical parameters of the nanohole array, we can obtain either ordered 2D arrays of separated QD, closely packed QD or localized areas for QD formation.

cond-mat.mes-hall↗

arXiv2019

Chemically driven isothermal closed space vapor transport of MoO$_2$: thin films, flakes and in-situ tellurization

A novel procedure, based in a closed space vapor transport (CSVT) configuration, has been devised to grow films or flakes of pure MoO2 in a reductive atmosphere, at relatively low temperature and using MoO3 as the source. In contrast with conventional CSVT technique, in the proposed method a temperature gradient is not required for the growth to take place, which occurs through an intermediate volatile transport species that is produced in the complex reduction reaction of MoO3. An added value of this simple method is the possibility of transforming the MoO2 into MoTe2, one of the most interesting members of the transition metal dichalcogenide family. This is achieved in a sequential process that includes the growth of Mo oxide and its (in-situ) tellurization in two consecutive steps.

cond-mat.mtrl-sci↗

arXiv2018

$2\times2$ Hypergeometric operators with diagonal eigenvalues

In this work we classify all the order-two Hypergeometric operators $D$, symmetric with respect to some $2\times 2$ irreducible matrix-weight $W$ such that $DP_n=P_n\left(\begin{smallmatrix} λ_n&0\\0&μ_n \end{smallmatrix} \right)$ with no repetition among the eigenvalues $\{λ_n,μ_n\}_{n\in\mathbb N_0}$, where $\{P_n\}_{n\in\mathbb N_0}$ is the (unique) sequence of monic orthogonal polynomials with respect to $W$. We obtain, in a very explicit way, a three parameter family of such operators and weights. We also give the corresponding monic orthongonal polynomials, their three term recurrence relation and their squared matrix-norms.

math.CA↗

arXiv2013

Strain driven migration of In during the growth of InAs/GaAs quantum posts

Using the mechano-optical stress sensor technique, we observe a counter-intuitive reduction of the compressive stress when InAs is deposited on GaAs (001) during growth of quantum posts. Through modelling of the strain fields, we find that such anomalous behaviour can be related to the strain-driven detachment of In atoms from the crystal and their surface diffusion towards the self-assembled nanostructures.

cond-mat.mtrl-sci↗

arXiv2011

Charge control in laterally coupled double quantum dots

We investigate the electronic and optical properties of InAs double quantum dots grown on GaAs (001) and laterally aligned along the [110] crystal direction. The emission spectrum has been investigated as a function of a lateral electric field applied along the quantum dot pair mutual axis. The number of confined electrons can be controlled with the external bias leading to sharp energy shifts which we use to identify the emission from neutral and charged exciton complexes. Quantum tunnelling of these electrons is proposed to explain the reversed ordering of the trion emission lines as compared to that of excitons in our system.

cond-mat.mes-hall↗

arXiv2011

In-situ accumulated stress measurements: application to strain balanced quantum dots and quantum posts

In this work we use the in-situ accumulated stress monitoring technique to evaluate the evolution of the stress during the strain balancing of InAs/GaAs quantum dots and quantum posts. The comparison of these results with simulations and other strain balanced criteria commonly used indicate that it is necessary to consider the kinematics of the process, not only the nominal values for the deposited materials. We find that the substrate temperature plays a major role on the compensation process and it is necessary to take it into account in order to achieve the optimum compensation conditions. The application of the technique to quantum posts has allowed us to fabricate nanostructures of exceptional length (120 nm). In situ accumulated measurements show that, even in shorter nanostrcutures, relaxation processes can be inhibited with the resulting increase in the material quality.

cond-mat.mtrl-sci↗

arXiv2006

InAs/InP single quantum wire formation and emission at 1.5 microns

Isolated InAs/InP self-assembled quantum wires have been grown using in situ accumulated stress measurements to adjust the optimal InAs thickness. Atomic force microscopy imaging shows highly asymmetric nanostructures with average length exceeding more than ten times their width. High resolution optical investigation of as-grown samples reveals strong photoluminescence from individual quantum wires at 1.5 microns. Additional sharp features are related to monolayer fluctuations of the two dimensional InAs layer present during the early stages of the quantum wire self-assembling process.

cond-mat.mes-hall↗