High resolution measurements of spectrally resolved cathodoluminescence (CL) decay have been made in several commercial and experimental phosphors doped with Eu and Tb at beam energies ranging from 0.8 to 4 keV. CL emission from the lowest two excited states of both rare earth activators was compared to the decay of photoh.nninescence (PL) after pulsed laser excitation. We find that, at long times after the cessation of electron excitation, the CL decay rates are comparable to those measured in PL, at short times, the decay process is considerably faster and has a noticeable dependence on the energy of the electron beam. These beam energy effects are largest for the higher excited states and for phosphors with larger activator concen~ations.Measurements of the experimental phosphors over a range of activator fractions from 0.1 to 0.002 show that the beam energy dependence of the steady-state CL efficiency is larger for higher excited states and weakens as the activator concentration is reduced; The latter effect is strongest for YzSi05:Tb, but also quite evident in Y203:Eu. We suggest that the electron beam dependence of both the decay lifetimes and the steady state CL Recent demonstration of prototype flat panel field emission displays has emphasized the need for phosphors which are efficient at low electron beam energiesl-3. DISCLAIMERExcept for ZnO, which has poor chromaticity, essentially all conventional phosphors have efficiencies which decline monotonically as the electron excitation energy drops below 5 keV. Consequently most manufacturers have utilized conventional cathode ray tube phosphors excited by 4-6 keV electrons in prototype FED displays; these devices have high internal electric fields, a feature that raises device cost and complexity and introduces problems with charging of dielectric standoffs.Conventional explanations for reduced low voltage CL efficiency usually begin with the assumption that to achieve excitation of the luminescent activators, beamexcited electrons and holes must recombine near to, or at these impurities, and that: 1. the near surface region of phosphors is highly defective, reducing the local electron-hole lifetime, or 2. Most of the excited electrons and holes actually diffuse to the surface, where they combine non-radiatively. Both 1. and 2. would be increasingly important if the primary exciting electrons have low energy and, hence, reduced range. In these scenarios, most of the crucial energy loss occurs before excitation of the activators. In this letter we will present both steady state and pulsed CL data which seem to show that non-radiative energy losses after activator excitation may be important for the phosphors that are studied here. This data also emphasizes the increasingly important role of activator interactions in quenching CL at low beam energies. 3All of the CL phosphor samples with decay measurements reported a conventional Kimba114 electron here were made on screened gun by pulsing the grid to turn the electron beam on and off. Extensive si...

We have investigated the deposition of size-selected metal clusters (Ag400) onto a stepped graphite surface. The clusters were produced with an inert gas condensation cluster source and were imaged on the surface with a high-resolution scanning electron microscope. For modest cluster deposition energies, cluster aggregation is much more limited at the steps than on the flat terrace regions of the surface, suggesting the possibility of the fabrication of structured arrays (e.g., chains) of size-selected particles. A theoretical analysis of the particle-particle gap size distribution along the step probes the 1D mobility of the particles trapped at the step.

We report the fabrication of ordered arrays of silicon nanopillars via reactive ion etching (RIE). Self-assembled polymer spheres are used as masks for the deposition of hexagonal arrays of Ag islands on a silicon substrate. Following the removal of the polymer spheres, the sample is etched with SF6 and CF4 at 100 W leading to hexagonal arrays of silicon nanopillars. The aspect ratio of the pillars can be influenced by the etching time; maximum aspect ratios of 15:1 have been produced.

The formation of 10 nm scale Si pillars using deposited metal clusters of various kinds (Au, Ag etc) as nuclei for the creation of etch masks has been investigated via microwave plasma etching at about . Experiments using size-selected Ag clusters indicate that the cluster size affects the efficiency of pillar formation but has little effect on the diameter of the fabricated pillars. The average diameter of pillars fabricated with Au clusters is 9 nm, while that with Ag clusters is 19 nm. This is attributed to the difference in chemical reactivity of the clusters with S or F, the components of the etching gas, which results in a different ability to form etch masks by condensation of species.

We have studied the formation of Cu clusters from Cu atoms deposited onto a Si (111) surface patterned with (2–5 μm width) lines of photoresist. In addition to a thin Cu layer on the exposed Si surface, large (∼150 nm) clusters nucleate at the boundary between the Si and the resist strips, which remain after removal of the resist by dissolution. The results show how it is possible, using the resist to collect deposited atoms, to assemble nanoscale cluster structures with a precision (∼150 nm feature size) which is much better than the resolution of conventional optical lithography (∼μm linewidth).