Germanium “quantum dots” embedded in silicon: Quantitative study of self-alignment and coarsening

Abstract

We report on experiments aiming to produce Ge quantum dots embedded in Si. Employing cross-sectional transmission electron microscopy, we have studied the misfit stress-induced self-alignment of islands belonging to consecutive Stranski–Krastanov layers of Ge buried in Si by molecular beam epitaxy. Quantitative evaluation of the micrographs has revealed the critical Si interlayer thickness below which the island positions in successive Ge layers begin to correlate. Moreover, we have quantitatively analyzed the influence of the Si interlayer thickness on the coarsening of the Ge islands from one buried Ge layer to the next.

Microstructure of quantum dots ensembles by EXAFS spectroscopy

“…Experimental k 2 -weighted GaK EXAFS spectra of samples 1-14 and bulk GaN (see Table 2) Table 2) -solid line, and theoretical fit resultdashed line First shell Ga-N coordination numbers N N =4, sum of second shell Ga-Ga and Ga-Al coordination numbers N Ga +N Al =12 and threshold energy E 0 = -7 have been fixed in the fitting procedure. As can be seen in Table 2, (N Ga ) -coordination numbers increase with an increase of GaN layers effective thickness from 1 to 6 (samples [1][2][3][4]. Values of N Ga make it clear that at the first steps of growth (1 ≤ m ≤ 4) the two-dimensional GaN layers can arise in some cases (at growing procedure above 600 °C) in accordance with our model estimation [9].…”

“…So the Ge/Si and GaN/AlN quantum dots vertical alignment have been recently demonstrated [1][2][3][4][5]. The aim of this paper is quantitatively determination by EXAFS spectroscopy an influence of the thickness of the principal (Ge, GaN) and blocking layers (Si, AlN), number of QDs layers in "sandwich heterostructure" and some of the preparation conditions on the microstructure characteristics of system with QDs.…”

“…It has been shown by AFM (atomic force microscope) that islands undergo a transition from a broad size distribution in a single layer to intraplanar size equalization and rapid coarsening of the islands for systems with low enough layers' thickness of barrier material [4], i.e. the average island's size increases with the number of deposited layers in such multi-layered structures [4,5]. However, the coarsening effect only occurs in the first several periods and is not evident afterwards.…”

Исследование структурных и излучательных свойств Ge(Si) квантовых точек, упорядоченных на поверхности Si(001)

“…Для исследования структур методами микроспектро-скопии комбинационного рассеяния света (КРС) и мик-рофотолюминесценции (ФЛ) были выращены образцы, содержащие 4 слоя вертикально и латерально упорядо-ченных одиночных КТ Ge. Толщина прослойки Si меж-ду слоями с наноостровками составляла ∼ 15 нм, что обеспечивало вертикальное совмещение островков [16]. Температура формирования КТ в многослойных струк-турах, так же как и однослойных, составляла 700…”

Dipole Emission to Surface Plasmon-Coupled Enhanced Transmission in Diamond Substrates with Nitrogen Vacancy Center- Near the Surface

“…With NV-'s symmetry axis being one of the <111> crystallography directions [26,27], it is possible to identify such planes in which the energy transfer efficiency from NV-to the antenna is maximized. Such a platform may also be realized by other substrates with near surface emitters such as a SiC with defects [28] or a silicon with embedded quantum dots [29]. A review on quantum dots and ways to enhance its emission is given by Xu et al [30].…”