Coexistence of optically active radial and axial CdTe insertions in single ZnTe nanowire

Abstract

We report on the growth, cathodoluminescence and micro-photoluminescence of individual radial and axial CdTe insertions in ZnTe nanowires. In particular, the cathodoluminescence technique is used to determine the position of each emitting object inside the nanowire. It is demonstrated that depending on the CdTe deposition temperature, one can obtain an emission either from axial CdTe insertions only, or from both, radial and axial heterostructures, simultaneously. At 350 °C CdTe grows only axially, whereas at 310 °C and 290 °C, there is also significant deposition on the nanowire sidewalls resulting in radial core/shell heterostructures. The presence of Cd atoms on the sidewalls is confirmed by energy dispersive X-ray spectroscopy. Micro-photoluminescence study reveals a strong linear polarization of the emission from both types of heterostructures in the direction along the nanowire axis.

Probing the light hole/heavy hole switching with correlated magneto-optical spectroscopy and chemical analysis on a single quantum dot

“…In addition, a low-energy tail is observed in figure 3(b), that we ascribe to the presence of the shallow (Zn,Cd)Te internal shell. Such a tail, and structures at even lower energy, are observed in other NWs with CdTe insertions, and similar features have been identified as due to lateral QDs [27]. They can be efficiently eliminated by using adapted growth conditions [24].…”

Light-hole exciton in a nanowire quantum dot

“…32 CL spectroscopy on similar structures confirms that the well-isolated emission line at 1.96 eV, which is also well spatially confined, is related to a single longitudinal QD, while eventual radial (Cd,Mn)Te structures would emit at a higher energy, above 2.1 eV. 33 Finally, antibunching experiment on similar emitters without magnetic doping revealed a single photon emission with g 2 (0) = 0.35, confirming the 3D confinement of the carriers inside the dot. 34 Such experiment could not be performed on our magnetically-doped dots yet because of the line broadening resulting from the large magnetic doping of the dot.…”

Controlling the shape of a tapered nanowire: lessons from the Burton-Cabrera-Frank model

“…In a microscopic approach, the two relevant parameters are the sticking probability / hopping probability ratio, pinc p hop , and the desorption probability / hopping probability ratio, p des p hop . We identify two extreme domains: (1) if the sticking efficiency βτ /λ des , although non-zero, is below a threshold ∼ a ⊥ /R, the sidewall steps remain in the vicinity of the NW basis, and the axial growth is determined by λ des ; this is the domain of cylinder-shaped NWs, and the conditions to choose in order to insert a quantum dot without the formation of parasitic dots on the sidewalls [26,27,41] (2); for a sticking efficiency above this threshold, two segments coexist along the NW, an array of equidistant steps (which govern the radial growth and the cone angle) and a longer tip terrace (which governs the axial growth rate). The NW shape then resembles that calculated for a specific case and described in figure 3 (d) of reference [23].…”