Localisation and identification of recombination‐active extended defects in crystalline silicon by means of focused ion‐beam preparation and transmission electron microscopy

Abstract

A series of four new complexes bearing N‐heterocyclic carbene ligands (NHCs) as well as four compounds bearing N‐heterocyclic carbene ligands with remote heteroatoms (rNHCs) of the general types [(NHC)(PPh3)2PdCl]+BF4− and [(rNHC)(PPh3)2PdCl]+BF4−, respectively, have been prepared in high yields. Crystal and molecular structures have been determined for four representative examples. These compounds proved to be efficient catalysts for aryl coupling reactions of the Heck and Suzuki types (reaching TONs of as high as 6,200,000). Both aryl bromides and aryl chlorides can be used as substrates. Like the well known mixed, standard (NHC)(phosphine) compounds, the new six‐numbered, one‐N‐heterocyclic carbene complexes (and in particular certain rNHC‐containing ones) also combine the advantageous stability of bis(carbene) and the high activity of bis(phosphine) complexes. Furthermore, their good catalytic performance and, especially, their easy synthesis based on cheap and commercially available starting materials, make them by far superior when compared to the mixed (NHC)(phosphine) catalysts known thus far.

Localization and preparation of recombination-active extended defects for transmission electron microscopy analysis

“…While the former approach has to rely on the existence of surface features, the latter suffers from partly or totally damaging the defects to be studied. 16 In this paper, we report in situ EBIC in a dual beam FIB system for localization of recombination-active extended defects and subsequent on-site preparation of TEM lamella by FIB techniques. We will show that this approach opens the route for investigating the atomic structure and chemistry of such defects at high resolution even for low defect densities typical for numerous problems.…”

“…A straightforward approach is to detect defects by recombination-sensitive imaging techniques such as EBIC or LBIC and use pre-existing surface features 15 or preferential etching 16 to locate defects by means of scanning electron microscopy ͑SEM͒ in a dual beam FIB. While the former approach has to rely on the existence of surface features, the latter suffers from partly or totally damaging the defects to be studied.…”

Recombination and Charge Collection at Nickel Silicide Precipitates in Silicon Studied by Electron Beam‐Induced Current

“…It should be noted that the latter was prepared by thermal evaporation on the polished and thoroughly cleaned surface without any etching step or HF dip to 1) minimize H incorporation [ 48 ] and 2) avoid preferential chemical etching of the metal silicide precipitates. [ 49 ] The latter is essential to study precipitates in the contact geometry, as described in Section 2.3 and 2.4.…”

Structure, chemistry and electrical properties of extended defects in crystalline silicon for photovoltaics

“…The rather small defect density in this case made a traditional TEM sample preparation rather difficult so that the focused-ion beam (FIB) technique in combination with defect delineation by preferential chemical or ion-beam etching was applied [34]. The result of a successful preparation using very short preferential etching is shown in Fig.…”

“…Briefly, particle colonies are observed which simultaneously contain copper-rich silicide precipitates containing a few at% of nickel and nickel-rich silicide precipitates that contain some copper. As an example obtained from investigations of a TEM lamella prepared as described in [34], Fig. 3(a) provides a high-resolution electron (HRTEM) micrograph taken from the interior of a colony.…”