G.G.P. van Gorkom

Characteristic infrared luminescence in GaP due to Mn

Abstract The observation at low temperatures of a structured characteristic luminescence in Mn-doped GaP is reported. This luminescence, centred at ≈ 1.34 eV, is attributed to the 4 T 1 → 6 A 1 internal transition of Mn 2+ (3d 5 ) on a Ga site. Some aspects of the fine structure are discussed, notably the observation of a localized vibration of Mn and the possible presence of a dynamic Jahn-Teller effect.

Modes in electron-hopping transport over insulators sustained by secondary electron emission

A general formalism for hopping electron transport over insulators sustained by secondary electron emission is presented. Steady-state electron transport takes place when the charging of the insulator, which turns out to be self-stabilizing, is such that the average secondary electron yield becomes equal to unity. The steady-state potential distribution for the electron transport is determined for various insulating geometries with the aid of Monte Carlo calculations and compared with the low-hopping approximation. The Monte Carlo results show that the steady-state potential distribution can exhibit several interesting features such as spontaneous symmetry breaking of statistical origin and the occurrence of local repulsive parts in the geometry. In several cases the numerical results, including the above two features, are found to agree well with the results of experiments.

Basics of electron transport over insulators

Abstract The basic mechanism of electron transport in vacuum through insulating structures is discussed. The transport is based on a self-regulating secondary electron emission process. A general description of the transport process is presented. Three methods to model steady-state transport are briefly reviewed. The features are discussed in the light of application in displays. Also, non-steady-state effects and the role of space charge are addressed.

Introduction to Zeus displays

Abstract This article describes why and how a research program to realize the ‘picture on the wall’ was started in the Philips Research Laboratories some seven years ago. The objective was to maintain the performance advantages of the cathode ray tube (CRT) while realizing a small depth and a low weight of the display. This is accomplished by using electrons in vacuum impinging at high energy on cathodoluminescent phosphors. Insulating internal supports to withstand the atmospheric pressure are required to make the display thin and light. A radical solution was discovered which led to a display with a thickness of about 1 cm for any display size and which is capable of producing CRT quality TV pictures.

A new Mn2+ centre in CaF2

Abstract An EPR, ENDOR and optical study of manganese in CaF 2 has been made. It was found that two different Mn 2+ centres were present, both having cubic symmetry without axial components. One of these is well known in the literature and its EPR spectrum is characterized by a very small cubic field splitting and a well resolved fluor hyperfine structure. The other centre shows no resolved superhyperfine structure and a larger cubic field splitting. The spin hamiltonian parameters of both centres have been determined accurately at three temperatures, 4.2, 77 and 295°K. This temperature dependence is discussed briefly. The ENDOR measurements have shown that the second Mn 2+ centre is Mn 2+ at a Ca 2+ site with no fluorine first neighbours. Analysing the results of the EPR, ENDOR and optical measurements we have reached the conclusion that, most probably, centre II is Mn 2+ at a Ca 2+ site and surrounded by six or eight oxygen ions.

Construction and physical processing of Zeus panels

Abstract The construction of a Zeus panel is discussed. This type of panel has a relatively simple self-aligned construction with a limited number of different components. Due to the low number of connections, rather robust connectors can be used. The complete physical processing cycle, very important for this type of panel, can be as short as 3 h which is shorter than the processing of a standard CRT.

Monte Carlo calculations of the electron hop transport in various parts of a Zeus display

Abstract Electron transport over insulators sustained by secondary electron emission is studied using Monte Carlo calculations. With the aid of these Monte Carlo calculations, the steady-state potential distribution and the properties of the electron trajectories in various insulating structures are determined. Each of these structures represents a part of the Zeus display and together the results show how electrons, generated by the cathode, enter the transport channels and are transported through the Zeus display until they reach the phosphor screen. In the various cases, the results according to the Monte Carlo calculations agree well with the results of experiments.

ESR of a Mn-S nearest neighbour complex in GaP

Abstract ESR measurements on a manganese-sulphur nearest neighbour complex having axial symmetry along 〈111〉 axes are reported. The spin Hamiltonian parameters are found to be g = 2.002 ± 0.001, A = (-57 ±1) × 10 -4 cm -1 , D = (-306 ± 2) × 10 -4 cm -1 and ( a − F ) = (+12 ±2) × 10 -4 cm -1 . The formation of these complexes is discussed. briefly.

Performance of Zeus displays

Abstract It is shown that the overall performance of Zeus displays is quite good, as illustrated by photographs of operating panels displaying ‘CRT-quality’ TV pictures. Results of measurements of all relevant performance parameters are presented, as well as an analysis of these data in relation to the design and operation of the displays. Measurements of the luminance as a function of the screen current density and of the screen voltage of Zeus displays are reported. A white D65 luminance of 1000 Cd/m2 is obtained at a screen voltage of 4.5 kV and a screen current density of about 9 μA/cm2. The luminous efficacy of the phosphor screen in the panels is found to be 12 lm/W (in the absence of saturation) for white D65. The efficacy of a 17″ Zeus panel (including transport power dissipation, cathode heating power and addressing power) is about 4 lm/W. The factors determining the internal contrast and colour purity of Zeus panels are discussed. Experiments to determine the relevant contrast parameters are described as well as the results of direct measurements of the internal contrast, colour purity and colour selectivity. Internal contrast values of more than 1000 have been obtained, and a colour selectivity better than 700. The available colour gamut is close to that of CRTs. Preliminary measurements of the external contrast of 17″ panels with a black matrix and front glass with 50% optical transmission yield a contrast value of 60 at an ambient light level of 100 lux. The factors determining the picture uniformity in Zeus displays are discussed. Several panels with good uniformity have been realized. No artefacts associated with moving pictures occur, the only significant artefact is caused by charge transfer effects. The visibility of this effect can be sufficiently reduced by using suitable ‘flush’ pulses and by optimizing the geometry. The displays used for the performance measurements have a quincunx dot arrangement and dot pitches 0.5 × 0.6mm, giving PAL resolution on 28″ panels. Small experimental panels with pitches of 0.3 × 0.5 mm and 0.25 × 0.30 mm have been realized and operate satisfactorily. The viewing angle of Zeus displays is close to 180 degrees. Preliminary tests show that lifetimes well over 10,000 h are possible if the glass surfaces hit by electrons are covered with an MgO coating and if the blue phosphor is coated with a very thin calcium polyphosphate layer.

Transport and extraction in Zeus displays

Abstract In a Zeus display hopping electrons are transported through channels with extraction holes. If a sufficient transport field is applied, the electrons hop low and leakage through the holes is negligible. The electrons can be extracted from the channel by applying a positive voltage pulse to an extraction electrode. With sufficient pulse amplitude the extraction efficiency is 100 %, independent of small variations in material properties, which enables the creation of uniform images. Experiments on a model transport channel confirm the mechanisms behind transport and extraction.