Classical Preparation Techniques Research Articles

Improved preparation techniques for preparing high-performance GaAs photocathodes.

Efficiency and lifetime are always problems raised with photocathodes during operation. With the purpose of obtaining high-performance GaAs photocathodes with high sensitivity and long operational lifetime, it is necessary to investigate the preparation techniques during both the cleaning and the activation procedure. By comparison with the classical preparation techniques, the improved preparation techniques with an optimized chemical etching method and activation procedure are proposed. The experimental results show that the optimized chemical etching solution is more effective in removing oxide and carbon contamination, which can help photocathodes obtain higher sensitivity. On this basis, better long wavelength response and longer operational lifetime can be obtained with the help of the more competitive activation procedure. The proposed preparation techniques will be useful for applications as a source of spin-polarized electrons.

Microstructure Preparation Using Glow Discharge Plasma Taking the Examples of Ni-Ti, Cu-Zn and a Ni-Based Alloy

Abstract The present work investigates the universal applicability of glow discharge plasmas for the microstructure representation of different materials taking the example of Ni-Ti alloys, Cu-Zn alloys, and the Ni based alloy “Hastelloy C 276”. Results are compared with the results provided by classical etching methods. Microstructures became visible for the previously mechanically polished materials within a few seconds, even without detailed optimization of the excitation conditions of the glow discharge plasma. The results partially significantly outperfomed the results of the classical preparation techniques with respect to the detectability of structural details such as grain and phase boundaries. Due to the demonstrated wide and relatively uncomplicated applicability, the per se established glow discharge technology is expected to have a huge potential for application for a rapid and high-contrast microstructure representation.

Low Temperature Scanning Electron Microscopy of Soft Bodied Organisms

Resolving the true fine structure and behavior of soft bodied organisms such as arthropod larvae, acari, nematodes, annelids and pupae by conventional scanning electron microscopy has been difficult. Classical preparation techniques, involving immersion fixation, dehydration and critical point drying, cause significant deleterious changes in specimen structure due to effects of surface tension, osmotic stress and mechanical damage. The intact exoskeleton, cuticle or other limiting membranes of these organisms, creates a formidable obstacle to the penetration of fixatives and solvents, which are only effective after a long period of time (hours). During this time, behavioral postures and much of the structural integrity are lost and most organisms detach from their hosts.In previous studies, our laboratory utilized methods in low temperature freeze stabilization, to preserve and observe the undisturbed fine structure of biological samples. Plunge freezing, although more rapid, resulted in many parasitic organisms dislodging from hosts and being lost.