The influence of the choice of complexing ligand, zinc counter-ion, pH, ionic strength, supersaturation, deposition time and substrate on the nature of ZnO films grown from chemical baths (CBD) are discussed. There are significant differences between CBD and similar routes such as hydrothermal methods for ZnO films. Modelling of speciation and experimental results suggest that acicular ZnO morphologies are best obtained by limiting the concentration of one of either Zn 21 or OH 2 in the presence of a large excess of the other. The presence of a prior ZnO layer can facilitate nucleation at lower levels of supersaturation and enable size tailoring of ZnO columns. The point at which the substrate is introduced into the bath is crucial and can lead to a significant difference in both the width of the rods and optical transparency of the films. HR-TEM has yielded important structural information and a growth mechanism for single crystalline ZnO rods by CBD is described for the first time.

The mean rate of copper loss was 0.25 mumol/day during the first 40 months of use, which is not significantly different from that of similar IUDs without a silver core. The silver core of the copper coil on the Nova-T IUD prevented its fragmentation. Surface deposits containing calcium and sulfur that built up on the IUD did not affect the rate of copper loss.

It has been shown that the direct exposure of the electron image of the microscope to a photographic emulsion is an almost perfect recording system (Valentine and Wrigley 1964). This method of recording, however, has the disadvantage that it is necessary to introduce the photographic emulsions into the vacuum of the microscope. In order to overcome this difficulty the possibilities of photographing a phosphor screen on which the electron image is displayed have been investigated.The apparatus used consisted of a transmission phosphor screen located below the normal plate camera of an EM6G electron microscope. The image produced was then photographed using an 35mm camera fitted with an F/I lens. The density - exposure curve for a number of photographic emulsions was obtained. Some of the results obtained are shown in Fig. 1. It can be seen from these results that exposures comparible with the direct exposure of the electrons to a photographic plate can be obtained.

In a previous paper, the authors have described the engineering requirements needed to detect one atom in the analytical electron microscope (AEM) by using x-ray microanalyis. Whilst the requirements to achieve this goal cannot be specified at present for a particular instrument, the specification for machines being developed by Vacuum Generators have a calculated minimum detection limit (MDL) of fewer than 4 atoms. At these detection limits the usual Gaussian statistics which have applied in AEM give way to Poissonian statistics. This paper will look at some of the interesting consequences of AEM at the atomic level.The energy dispersive x-ray spectrometers (EDS) used in AEM have percentage detection limits usually quoted as about 0.1 wt. %. For this to equal 1 atom as the MDL, the analysed volume, defined by the probe diameter and the specimen thickness, must contain about 1000 atoms. For a field emission gun (FEG) on an AEM, sufficient current (1nA) can be obtained in a small enough probe (1nm FWHM) to allow analysis from a volume containing 1000 atoms (assuming adequate x-ray detection sensitivity) if the sample is about 20 atoms thick.

A major reason for performing microanalysis in the Field-Emission Gun Scanning Transmission Electron Microscope (FEG-STEM) is the very high spatial resolution of the information obtained. It has been estimated that in ideal cases, energy-dispersive x-ray analysis in such an instrument can provide 0.1 wt.% detection sensitivity for an element in a region about 1.5nm in diameter of a foil about 30nm thick. It is obvious that such performance requires that the instrument be properly adjusted, and hence that the probe-forming characteristics be fully understood.There are three fundamental limits on the minimum size of an electron probe, these being i) the geometrical demagnification of the source, ii) diffraction at the beam-limiting aperture, and iii) spherical aberration in the probe-forming lens. In addition, misalignment of the beam-limiting aperture will result in probe aberrations.