Within the European iMERA-Plus project 'Traceable Characterisation of Nanoparticles' various particle measurement procedures were developed and finally a measurement comparison for particle size was carried out among seven laboratories across six national metrology institutes. Seven high quality particle samples made from three different materials and having nominal sizes in the range from 10 to 200 nm were used. The participants applied five fundamentally different measurement methods, atomic force microscopy, dynamic light scattering (DLS), small-angle x-ray scattering, scanning electron microscopy and scanning electron microscopy in transmission mode, and provided a total of 48 independent, traceable results. The comparison reference values were determined as weighted means based on the estimated measurement uncertainties of the participants. The comparison reference values have combined standard uncertainties smaller than 1.4 nm for particles with sizes up to 100 nm. All methods, except DLS, provided consistent results.

No abstract

One of the major challenges for the reliable use of self-organization phenomena for device applications is to accurately position quantum dots on the surface. A promising way to get ordered dots is to use prepatterned substrates. We show that a combination of focused ion beam (FIB) prepatterned Si(001) substrates and self-assembled Ge quantum dots (QDs) leads to the precise placement of QDs. The technological advantages of this method are to control the Ge dots size and location, and to scale down the interdots distance to ∼20nm. Regarding more fundamental aspects, the accurate control of nanopatterns characteristics allows us to investigate the influence of various experimental parameters on QDs formation. The process proposed consists mainly of three steps: (1) FIB nanopatterning; (2) ex situ cleaning of the FIB-patterned substrate in order to fully remove the Ga contamination before introduction into the molecular beam epitaxy (MBE) chamber; and (3) Ge deposition by solid source MBE. After optimization of the growth parameters, nicely ordered dense arrays of homogeneous QDs are obtained. QDs are organized on the edges of the FIB holes at high temperature or inside the holes at lower temperature. We suggest that two different mechanisms of Ge dots formation are responsible of these results: kinetically limited nucleation at low temperature and stress driven nucleation at higher temperature.

Methods for the fabrication of large areas of nanoscale features with controlled period and intraperiod organization are of interest because of the potential for high-throughput mass production of nanoscale devices. Due to their potential in this regard, much recent attention has been devoted to self-organization processes, [1][2][3][4][5] in which processing causes the spontaneous emergence of a nanoscale pattern. The short-range order can be quite high [2][3][4] but some envisaged applications require long-range order, which is destroyed by uncontrolled topological defects arising spontaneously from the self-organization process. A potentially successful hierarchical fabrication strategy is the fabrication of controlled features at a small, but lithographically tractable, length scale by methods such as conventional mask or optical-standing-wave lithography, in order to guide a self-organization process at the finest length scale. [6][7][8] Topographic patterning has been used for templating the local disorder in two-dimensional (2D) self-assembled monolayers [9] and for templating defect organization or elimination in three-dimensional (3D) colloidal crystallization.[10] Topography has also been used to manipulate semiconductor quantum-dot placement, composition, and strain, through its effect on stress, [11] surface energy, and mobility.[12]3D short-range ordering of grown-in quantum-dot short-period superlattices can result from multilayer growth; [1,4] nanoscale topographic templating of the first layer could dramatically accelerate the development of order and lead to true long-range order. Lithographically and focused ion beam (FIB)-patterned topographies have recently been used to template quantum-dot growth in linear chains, [8] periodic 2D lattices, [7] and in more complex configurations that are promising for novel nanoelectronic architectures, such as quantum cellular automata.[13] The finest features have been templated by serial writing with a FIB, a prohibitively expensive process for mass production that might be circumvented by using a hierarchical fabrication strategy. Here we report the influence of patterned boundaries on the primary material of complementary metal oxide semiconductor (CMOS) technology, i.e., a Si(001) substrate, in guiding self-organized topographic ripples spontaneously appearing during uniform irradiation with low energy Ar + ions. We show that the long-range order of the features can be greatly enhanced by this lateral-templating approach. The emerging pattern can be manipulated by changing the boundary spacing and misorientation with respect to the projected ion-beam direction. We develop a scalar figure of merit, a dimensionless topological defect density, to characterize the degree of order of the pattern. At small boundary separation, greatest order is observed when the separation is near an integer multiple of the spontaneously arising feature size. The defect density is exceedingly low up to a critical misorientation angle, beyond which topological defects develop i...