J.C. Anderson

Carrier mobility and field effect in thin indium antimode films

Abstract Thin polycrystalline InSb films in the thickness range 1000–3000 A, have been prepared by the flash evaporation technique. A linear relation is found to exist between the electron mobility and the mean crystallite size. A positive gate field, applied orthogonally to the film, increases the electron mobility by a factor of 30, at 77°K. It is proposed that a potential barrier exists at the grain boundaries, which dominates the scattering process. This model could also explain the temperature dependence of the electron mobility. Typical potential barriers are found to be ∼0.04 eV.

The nucleation and initial growth of gold films deposited onto sodium chloride by ion-beam sputtering

Abstract Data are presented for the initial growth of sputtered films of gold on vacuum-cleaved rocksalt substrates. The films were grown in high vacuum by means of an ion-beam sputtering system, so that no plasma effects were present. The experimental variations of island density with such parameters as deposition time, substrate temperature and deposition rate are reported. These results have been compared with existing data for evaporated films and differences have been found. A simplified treatment of the nucleation and growth kinetics has been used to correlate the results by sputtering to those by evaporation. In the case of sputtering, it has been necessary to postulate a constant density of preferred adsorption sites on the substrate. More detailed theories have been used to confirm the analysis. Apart from the influence of the preferred sites, growth apparently proceeds in the same way for deposition by sputtering and for deposition by evaporation.

The internal stress in evaporated silver and gold films

Abstract The internal stress in the initial stages of growth of evaporated silver and gold films on to glass and mica substrates has been measured using a bending beam method. The thermal stress contribution to the total stress has been calculated. The stresses observed were tensile. Intrinsic stress was found in island structure films. Stress relief immediately after film deposition was observed. The results have been interpreted in terms of a grain boundary annealing mechanism.

Transducers for pressure, temperature and oil film thickness measurement in bearings

Abstract Thin-film manganin pressure transducers have been developed for in situ pressure measurement in lubricated contacts. They are sufficiently small to allow resolution of the pressure spike, predicted by EHL theory. In addition, a resistance transducer for the simultaneous measurement of temperature and a capacitive transducer for the simultaneous measurement of oil film thickness have been developed. We are thus able to present results showing the dependence of position of the EHL pressure spike on load, and the oil film thickness and temperature as a function of pressure, measure by the pressure transducer, in both a laboratory test disc machine and an actual roller bearing.

Barrier-limited mobility in thin semiconductor films

Abstract It is shown that the simple Boltzmann expression for an intercrystalline potential barrier can be applied to low gap non-parabolic band materials, with certain limitations. Experimental results on InSb thin films are presented, in support of this view.

Applications of thin films in microelectronics

Abstract Since the inception of solid circuit technology, thin films have been an essential feature of the integrated circuit, providing interconnections on the silicon chip. The main practical problems associated with them have been lack of adhesion, corrosion and electromigration and these will be reviewed. Thin film circuits are used in hybrid microelectronics and applications and examples will be quoted. The appearance of viable thin-film transistors has opened the way to all- thin-film integrated circuits. These need not be expensive to produce and, in some cases, will be competitive with LSI solid circuits. The TFT is particularly suited to large-area applications such as display panels.

Theory of the thin film transistor

Abstract A theoretical model for a polycrystalline film is proposed which takes account of the potential barriers at the intergrain boundaries and the band bending at the semiconductor/insulator interface. It is shown that a thin film transistor equation based on this model gives an improved fit with experiment compared with a model assuming no band bending at the interface. It is concluded that the device performance is dominated by the semiconductor/insulator interface.

Trapping centres in sputtered SiO2 films

Abstract The traps in SiO 2 insulator films, forming the gate insulators of thin film transistors, were examined by measurement of the time dependence of the threshold voltage. Noise measurements support the premise that electrons tunnel into trapping states from the semiconductor. It is found that the characteristic penetration depth for the tunnelling process is approximately 6 A and the trap density is about 10 24 m −3 . Infrared absorption measurements support the view that the traps are electrically active oxygen vacancies.

Features of the initial growth of gold films deposited on rock-salt substrates by ion beam sputtering☆

Abstract An ion beam sputtering system was used to study the role of the angle of incidence of the sputtered particles on the substrate. It is proposed that differences between these results and those at normal incidence could be due to non-thermal equilibration of some of the incident atoms.

A study of electrical conduction in island structure nickel and 80:20 nickel-chromium films

Abstract The theory of conduction in discontinuous metal films proposed by Neugebauer and Webb has been amplified to take into account electron transfer between charged island species other than charged to neutral island transfers. The effect on the resistivity has been shown to be slight, but the predicted values of temperature coefficient of resistance agree more closely with experiment for films of nickel and nickel-chromium deposited at 2 × 10-5 torr. It has not been possible to test the theory for films deposited at 7 × 10-7 torr, because the large island and gap sizes found in these films either give films that are open circuit or that have near metallic behaviour.