Secondary Emission Mode Research Articles

Investigation of silicon doped by zinc ions with a large dose

The formation of nanoparticles in СZn-Si(100) implanted with 64Zn+ ions using a dose of 5 × 1016 cm–2 and an energy of 50 keV at room temperature with subsequent thermal processing in oxygen at temperatures ranging from 400 to 900°C is studied. The surface topology is investigated with scanning electron (in the secondary emission mode) and atomic force microscopes. The structure and composition of the near-surface silicon layer are examined using a high-resolution transmission electronic microscope fitted with a device for energy dispersive microanalysis. An amorphized near-surface Si layer up to 130 nm thick forms when zinc is implanted. Amorphous zinc nanoparticles with an average size of 4 nm are observed in this layer. A damaged silicon layer 50 nm thick also forms due to radiation defects. The metallic zinc phase is found in the sample after low-temperature annealing in the range of 400–600°C. When the annealing temperature is raised to 700°C, zinc oxide ZnO phase can form in the near-surface layer. The complex ZnO · Zn2SiO4 phase presumably emerges at temperatures of 800°C or higher, and zinc-containing nanoparticles with lateral sizes of 20–50 nm form on the sample’s surface.

Characterization of photomultiplier tubes in a novel operation mode for Secondary Emission Ionization Calorimetry

Hamamatsu single anode R7761 and multi-anode R5900-00-M16 Photomultiplier Tubes have been characterized for use in a Secondary Emission (SE) Ionization Calorimetry study. SE Ionization Calorimetry is a novel technique to measure electromagnetic shower particles in extreme radiation environments. The different operation modes used in these tests were developed by modifying the conventional PMT bias circuit. These modifications were simple changes to the arrangement of the voltage dividers of the baseboard circuits. The PMTs with modified bases, referred to as operating in SE mode, are used as an SE detector module in an SE calorimeter prototype, and placed between absorber materials (Fe, Cu, Pb, W, etc.). Here, the technical design of different operation modes, as well as the characterization measurements of both SE modes and the conventional PMT mode are reported.

ZnO Nanoparticle Formation in <sup>64</sup>Zn<sup>+</sup> Ion Implanted Al<sub>2</sub>O<sub>3</sub>

ZnO nanoparticles (NPs) formed in (-1012) sapphire substrates have been studied. The NPs were formed by implantation of 64Zn+ ions followed by furnace annealing in oxygen atmosphere for 1h at elevated temperatures. The radiation defects and Zn implant profiles were investigated by Rutherford backscattering spectroscopy of He+ ions with energy of 1.7MeV with scattering angle of 160o at Van de Graff accelerator using the ion channeling technique (RBS/CT). The surface morphology was studied by atomic force microscopy (AFM) and scan electron microscopy in secondary emission mode (SEM-SE). The distribution of Zn implant profiles was analyzed by secondary ion mass-spectrometry (SIMS). Identification of the phase content of the materials was carried out by X-ray photoelectron spectroscopy (XPS). In as implanted samples, a near-surface amorphization layer was formed, and in this layer the surface voids were created. After annealing in temperature range of 600-900°C the ZnO phase was synthesized in sapphire substrate. After annealing at 900°C one can see the phase variation from ZnO/Zn phases at sample surface to metal Zn phase in sample body at a depth of 40nm. Annealing at temperatures above 900°C leads to disappearing of ZnO phase and creating of ZnAl2O4 phase.

SEM observations in the back-scattered mode of the soil–root zone of Brassica napus (cv. Rafal) plants grown at a range of soil pH values

In the study of the root–soil interface, scanning electron microscopy (SEM) in secondary emission mode and transmission electron microscopy are commonly used techniques. As these methods have some limitations, there is a need to explore other techniques which may be suitable for the observation of the root–soil zone. One of the most promising methods is the application of SEM in the back-scattered electron (BSE) emission mode. The root zone of plants of winter oilseed rape ( Brassica napus cv. Rafal) grown at a range of soil pH and soil phosphorus (P) concentrations was examined by SEM in BSE mode. The method for the preparation of transverse sections of the root–soil contact zone is presented. The BSE scanning images of the root–soil interface obtained allowed investigation of the flow paths of plant nutrients from the soil towards roots and their distribution in the roots. Concentration of aluminium in the cell walls of immature roots and at the soil–root interface was observed in the most acid soils. Potassium, calcium and phosphorus were found in differentiated roots associated with the external tissues of the central cylinder. The intimate contact of root surface with soil mineral particles could also be observed.

Corroded exines from Havinga's leaf mold experiment. SEM

Abstract Representative types of exine corrosion, seen on scanning electron micrographs, are illustrated from a leaf mold sample from the corrosion experiment of Havinga (1964). This work complements earlier transmission electron microscopy of the same sample (Rowley et al., 1990). Corroded areas are among the most dramatic indicators and products of exine destruction in samples of pollen and spores from Havinga's leaf mold material. Severely corroded regions, as seen using the secondary emission mode of the SEM, were most often found on exines with a continuous tectum (Myrica, Betulaceae, Corylaceae, Ulmus), but they also occurred to some degree in Fagus and on spores of Lycopodium. In taxa having pollen with a more or less continuous tectum the surface of the tectum was not destroyed but instead became depressed to the level of the floor of corroded areas. This “sunken tectum”; aspect of corrosion results from tunneling within the tectum without destruction of the surface. Muri of reticulated exines showed little indication of corrosion. Muri of Lycopodium, considered by Havinga as the most resistant exine in his experiment, were, however, often seen to be somewhat corroded and in some spores severely so. Fractures or tears, common to exines of many of the 19 taxa in Havinga's material, are illustrated for Fraxinus, Fagus, Quercus, Tilia, Pinus, and Lycopodium. Isolated sectors fractured from some taxa, e.g., Pinus and Tilia, are identifiable, but others are difficult to identify. In Pinus, where a portion of a sacculus was broken off, the surface of the foot layer showed hemispheroidal unit‐structures. Examples of folding and collapse were especially prominent in Taxus, Juniperus, Salix and Acer. Exines of these taxa were extremely difficult to recognize as pollen grain exines under oil immersion or with moderate SEM magnifications, although at higher magnifications exine structural details were seen to be intact. Small pit‐like circular holes were frequent on exines of Myrica and other betuloid grains, Fagus, Acer, Polypodium, and Lycopodium. These small holes may be of special interest since in Lycopodium they have been reported following abiological experiments.

Fractal Aspects of Lamellar Ferroelectric Domain Structures Formed under the Influence of Depolarization Fields in CsH2PO4and (NH2CH2COOH)3·H2SO4

Ferroelectric 180° domain structures of CsH 2 PO 4 (CDP) and (NH 2 CH 2 COOH) 3 ·H 2 SO 4 (TGS) have been observed in unelectroded b plates using the secondary emission mode of a scanning electron microscope (SEM). It is found that a lamellar domain structure is formed in CDP. The lamellar structure shows the fine periodicity along the normal to the walls nearly parallel either to the (100) plane or to the (801) plane. The periodic pattern corresponds to the first prefractal domain pattern that is characterized by the first prefractal of the pentad Cantor set. It is also revealed that the lamellar domain structure of TGS is observed to be the first prefractal domain pattern. The SEM observations establish that the prefractal domain patterns first dis- covered in KDP are common to the lamellar 180° domain structures which are formed in proper ferroelectrics under the influence of depolarization fields. CDP, TGS, ferroelectric domain, SEM, fractal, Cantor set, depolarization field, surface energy density

Application of back‐scattered electron imaging to the study of the lichen‐rock interface

SummaryIn the study of the lichen‐rock interface, light microscopy, scanning electron microscopy (SEM) in secondary emission mode and transmission electron microscopy are the most commonly used techniques. As these methods have some limitations, there is a need to explore other techniques for observation of the lichen‐substrate interface. One of the most promising methods is the application of SEM in the back‐scattered electron (BSE) emission mode.The thallus ofAspicilia intermutans(Nyl.) Arn. growing on granitic rock was examined by SEM in BSE mode. The detailed preparation of transverse sections of the lichen‐rock contact zone is presented. The BSE scanning images of the lichen‐rock interface obtained present new insights into the ultrastructural features of the biological components, providing more information about the biogeophysical and biogeochemical weathering of rock.

The use of backscattered electrons for imaging purposes in a scanning electron microscope

It is shown that the use of a very large detector for backscattered electrons can provide a signal comparable to that obtained in the secondary emission mode and that the resolution available is also comparable. A technique is described whereby the difference is taken between these two signals, and the use of this difference signal can significantly enhance surface details. It is believed that the use of such a signal should ultimately prove advantageous in increasing resolution.

Scanning Electron Microscopy of Final-instar Larval Mouthparts of the Black Cutworm, Agrotis ipsilon13

Surface features of mouthparts of mature larvae of the black cutworm, Agrotis ipsilon (Hufnagel), were examined using the secondary emission mode of a scanning electron microscope. Particularly visible were 8 small sensilla basiconica at the distal extremity of the maxillary palp, 3 sensilla campaniformia on this palp and 2 sensilla styloconica on the galea. Additional features of the labrum, mandibles, hypopharynx and labial palps were displayed and discussed. A description is presented of coordinated mouth part function based on present structural findings and literature reports.