Copper-oxide Rectifier Research Articles

Penetration of electronics into telephone switching

The invention and development of telephone exchanges were approaching a limit, set by the relay, until electronic devices made a new limit possible. The thermionic valve introduced electronics into telephone speech-transmission systems in the first quarter of the twentieth century, and into data-transmission systems shortly after. Some use was made of copper-oxide rectifiers as switches, but little or none of the valve until the 1930s when operations too fast for relays were required for research apparatus. The breakthrough to large-scale electronic switching and data processing machines was made during the Second World War and was followed after the war by the development of computers, telephone exchanges and other data-processing systems, aided by the rapid development of devices and notably of the transistor and its derivatives. Despite the effort put into electronic telephone systems, their penetration into the networks of the world is relatively slight owing to difficulties of economics and of application to existing networks, a situation which semiconductor large-scale integrated circuits are expected to resolve.

The Solid State

Modern semiconductor physics has developed from the quantum mechanical work on energy band theory of charge carriers in semiconductors associated with the name of A. H. Wilson and his classic papers on the subject, and also with the name of Schottky who pioneered the atomistic approach to disorder phenomena in solids. This work dates from about 1930 and theoretical developments up to the beginning of the War were relatively slow. Semiconductor technology in the same period was represented by a few devices only. These included the copper oxide and selenium rectifiers which were in use in certain equipment and in the process of further development. The silicon whisker detector was being used for the detection and measurement of microwave power. It will be recalled that silicon carbide and galena had been used as detectors of radio waves before the common usage of the thermionic valve. The development of radar during the War, which required semiconductor devices for detecting and mixing microwaves meant that considerable work was carried out on silicon, and parallel work on germanium meant that by the end of the War high‐back voltage rectifiers, using germanium, were available in developmental quantities. Problems of thermal detection meant that photo‐conductive and photo‐voltaic cells were developed for this purpose based on the materials thallium sulphide and lead sulphide. Attention was also focussed on electronic processes in ionic crystals in terms of improving display screens for cathode ray and similar tubes.

Error of rectifier-type milliammeters in low-resistance circuits

Although a bridge-rectifier meter indicates r.m.s. current when the current is sinusoidal, a sinusoidal voltage produces a non-sinusoidal current, and hence an error in the indication, because the resistance of a copper-oxide rectifier is non-linear, varying as the -0.7 power of the current. Series resistance tends to swamp the non-linearity, and the error, calculated by arithmetical integration, is shown on a nomogram relating error, series resistance and meter indication. Experiment confirms the results.

The Temperature Dependence of the Capacity of the Copper Oxide Rectifier

The temperature dependence of the capacity of the space charge layer at a metal semiconductor contact is investigated. The variation in the capacity with temperature has been calculated on the assumption that it should be caused by the temperature variation of the density of free charge carriers in the semiconductor. The results are compared, for an example, with the experimental data of the capacity of copper oxide rectifiers, which are measured by superimposing a small alternating voltage on the d.c. bias voltages, at the several temperatures between -160°C and +60°C, and are analysed on the assumption that there exist some donor impurities in the bulk cuprous oxide layer in addition to the usual acceptor type. The comparison makes it clear that the equation derived theoretically can successfully explain the following facts: (1). At lower temperatures, the magnitude of capacity increases with increasing temperature, and reaches a maximum at a certain temperature and then begins to decrease at higher temperatures. (2). But, the temperature at which the magnitude of capacity reaches a maximum experimentally is slightly higher than that which the theoretical equation predicts. (3). The measurements at -110°C and -160°C show that the values of the capacity at these temperatures may be regarded as those affected by the temperature variation in the electrical resistivity of the bulk Cu 2 O layer rather than the values of the pure barrier capacity. (4). The absolute value in the temperature variation of a barrier capacity expected from the derived equation is about 250µµ farads/cm 2 for copper oxide rectifiers, with -0.5 volt d.c. bias voltage applied between 0°K and 300°K, and this value agrees comparatively well with the experimental results. (5). The variations in capacity are dependent upon the d.c. bias voltage applied and will be smaller when the bias voltage becomes larger.

Method for Determining the Ratio of Planck's Constant to the Charge of the Electron Employing AC Amplification

Filtered pulsating light from a mercury vapor lamp operated on ac is directed upon a commercial high-vacuum phototube, and the photocurrent, which is thereby pulsating dc, is passed by an ac amplifier whose output is fed to a dc milliammeter through a copper oxide rectifier. Using different light filters a retarding potential of increasing magnitude is applied to the phototube until the milliammeter readings reach respective minimum values which are plotted as ordinate against optical frequency as abscissa. The slope of the resulting line is taken as h/e.

Magnetic Amplifier controls for Rectifier Protecting Underground Metallic Structures Cathodically

Abstract This paper covers the initial attempt on the part of the Ohio Bell Telephone Company to use a magnetic amplifier to give continuous control of the output of a copper-oxide rectifier used f...

Measurement of the DC Resistance of Selenium and Copper Oxide Rectifiers below Room Temperature

Values of the steady-state dc resistance of copper oxide and selenium rectifiers as a function of temperature from 79°K to 300°K have been obtained. The maximum potentials used were 2.5 volts in the forward direction and 6.0 volts in the backward direction. It was found that a plot of the logarithm of the resistance against the reciprocal of the temperature was nearly linear for all except the reverse direction of the selenium rectifier. For the latter case at 6.0 volts the resistance went through a minimum below 200°K.

Modulators, frequency changers and detectors using rectifiers with frequency-dependent characteristics

In the calculation of the performance of modulators, frequency changers, and detectors it is found difficult to allow for any frequency dependence of the resistance characteristic of the rectifier, although when copper-oxide rectifiers are used, such dependence is very severe. An approximate method of allowing for such an effect is described in the paper, and it can be applied easily to the analysis of circuits where the terminating impedances are finite only at a finite number of modulation-product frequencies and zero at all other such frequencies. In particular, the case where either the input or the output frequency is low, the carrier frequency is high and only one sideband is accepted is considered in some detail, and the results are illustrated by numerical examples based on copper-oxide modulators working at frequencies up to 6 Mc/s. It is also shown how the conversion insertion-loss can be stabilized against temperature variation by a suitable choice of terminating resistance. The working and results are the same for shunt, series and ring modulators, for conditions of low input frequency with high output frequency and vice versa.

The theory of direct-current characteristics of rectifiers

It is shown how the image force can be taken into account very simply by making a minor improvement in the current theory of rectification. The equations obtained have been compared with experimental d. c. reverse characteristics of the copper oxide, selenium and germanium rectifiers, assuming in each case, first, that a Mott barrier is present, and, secondly, that a Schottky barrier is present. Agreement is satisfactory, the hypothesis of a Schottky barrier leading to a slightly better fit in all cases. As regards the numerical constants calculated from a fit of the experimental results, satisfactory values can be obtained if a Mott barrier is assumed. If a Schottky barrier is presupposed, the results for the copper oxide and selenium rectifier lead to very low values for the mobilities and high values for the impurity centre densities in the barrier region. This is discussed. The effect of the image force on the current carrier distribution is illustrated, and a general relation between the diffusion and diode theory established.

Image Force in Rectifiers

THEORETICAI current-voltage characteristics of copper oxide and selenium rectifiers have been obtained by integrating the so-called diffusion equation1. The result so obtained involves the distribution of the potential of the current carriers in the semiconductor. In general, this rises to a maximum near the interface between the semi-conductor and the rectifying electrode, and then decreases towards the metal in virtue of the image force e2/4kx2 (k is dielectric constant of the semi-conductor), which acts on a current carrier in the semi-conductor when it is close to the metal electrode. With increasing applied reverse potentials this maximum is lowered, thus producing the increase in reverse current density which is familiar from known experimental characteristics. The potential due to the image force is additional to a potential distribution which arises from the physical nature of the barrier region. The case of an insulating barrier2, the case of a barrier containing a uniform distribution of spontaneously ionized impurity centres3, and a combination of the two14,5 have been treated neglecting the space charge due to the current carriers; the insulating barrier has also been studied6 with proper allowance for the space charge due to the current carriers. Only in ref. 2, however, has a theoretical characteristic been given which incorporates the effect of the image force. A general method of taking into account the image force is proposed here, and the results are applied to the copper oxide rectifier.

Theory of Rectification of an Insulating Layer

The problem treated is the rectification by a blocking layer of low inherent conductivity. The potential distribution is determined by the space charge due to free, current-carrying charge instead of by that due to fixed charge. The difference between this case and that treated by previous theories is pointed out. The theory is applied to copper oxide rectifiers. The result is found to agree with experimental results better than the previous theories. The applicability of the theory to other cases is also discussed.

Effect of Bending on Selenium Rectifier Disks

Bending a selenium rectifier disk causes a temporary increase of the current flowing through it in both directions. The effect (discovered in December 1942) is especially pronounced in the reverse direction, where a momentary increase of the current intensity up to 300 per cent and more can be produced through bending by hand, while in the forward direction values exceeding 5–10 per cent have not been observed. With copper oxide rectifiers no trace of a similar effect could be detected. The following, mostly qualitative, observations were made on our own disks, in the reverse direction: (1) The bending causes an increase of the current, whether the selenium layer lies on the convex or on the concave side of the disk. (2) In general, the stronger the bending the greater the effect. (3) The increase of current is, at its maximum, a temporary one. After bending a disk with a constant force, the momentary increased current intensity diminishes in the first few seconds rapidly, then slowly, and reaches its end value after some minutes. The behaviour of the disk is then, within certain narrow limits, that of a biased system: an increase of the bending increases also the current and vice versa. (4) Temperature has a pronounced influence; at 40–50° C., the effect is essentially smaller, and it seems to disappear more rapidly than at room temperature. (5) The effect depends upon the applied voltage. While at small voltages (1–2 volts) no effect is observable, with increasing voltages it increases also rapidly and reaches a maximal value as high as 350 per cent 15–20 volts with some disks.

A theory of flicker noise in valves and impurity semi-conductors

A theory of contact noise at low frequencies is described It is assumed that this noise is due to diffusion of clusters of mobile impurity centres on to the contact surface, as in Schottky's theory of flicker effect in valves. A cluster disappears in time due to ionization and consequent ionic conduction away from the contact surface. This diffusion-conduction process is used to derive a formula for the flicker noise which is applicable to emission from oxide-coated filaments of valves and to contacts between particles of impurity semi-conductors, as in lead sulphide photo-conductive cells and rectifiers. The spectral power density of the noise is found to depend on current j and frequency f as jx+1/fx, where 1<x<2. Experimental results for PbS cells, oxide emitters and copper-oxide rectifiers are found to be in good agreement with this law. Carbon resistors are also found to obey this law, and it is suggested that the same mechanism of diffusion of clusters of impurity atoms on to the contact surface between crystals is responsible for the effect.

Some Notes on the Copper-Oxide Rectifier and the Thermionic Tube in the Voltage-Doubling Circuit

The voltage-doubling circuit is again investigated in this paper. The employment of this circuit and the copper-oxide rectifier is due to a consideration of the demands imposed on the unit described. The tube and the copper-oxide rectifier are thus compared in this circuit. Expressions are derived in as simple a manner as possible. Graphs of performance are presented. The application of this circuit to radio transmitters and receivers is discussed. It is realized that some of the facts are well known, but the comparisons are found to be somewhat easier if they are quoted.

Construction and Ratings of Copper-Oxide Rectifiers for Cathodic Protection of Pipelines

Construction and Ratings of Copper-Oxide Rectifiers for Cathodic Protection of Pipelines

Automatically Controlled Copper-Oxide Rectifiers for Electroplating and Anodizing Applications

Automatically Controlled Copper-Oxide Rectifiers for Electroplating and Anodizing Applications

The copper-oxide rectifier in electrochemical work

The copper-oxide rectifier in electrochemical work

The copper-oxide rectifier in electrochemical work

MUCH has been written about the copper-oxide rectifier during the 23 years of its existence, yet the subject is far from exhausted. It still remains one of the most interesting developments of recent years. A brief résumé of its history may be of interest.

The Copper-Oxide Rectifier in Electrochemical Work

MUCH has been written about the copper-oxide rectifier during the 23 years of its existence, yet the subject is far from exhausted. It still remains one of the most interesting developments of recent years. A brief resume of its history may be of interest.

Characteristics and Applications of Selenium-Rectifier Cells

The rectification properties of selenium cells were first discovered in the year 1883. C. T. Fritts described them in the American Journal of Science. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11,12</sup> However, they were never used to any extent, except possibly as photocells. After the introduction of the copperoxide rectifier, research activities were stimulated, and selenium cells were again rediscovered. The first commercial cells were made in Germany in the early '30's, and, as the technique of manufacture improved, better cells were made with better life expectancy. The General Electric Company, after a period of developmental activity, started to make cells in 1938, first in its research laboratories, and subsequently a manufacturing plant was set up which permits producing cells in large quantities within relatively close electrical tolerances. This paper contains data pertaining to these cells particularly, and the information may not apply in detail to cells manufactured by other methods without some correction factors.