Electrical Behaviour of Langmuir Films: A Review, Part I

Abstract

The electrical behaviour of thin films obtained by a variety of processes, e.g. thermal evaporation in vacuum, have been extensively studied. However, the study of organic mono- and multilayer films obtained by the Blodgett–Langmuir technique (commonly referred to as Langmuir films) has gained considerable momentum only during the past decades. Unlike evaporated films, the striking features of these organic films are their controllable thicknesses down to one monolayer (~ 25 Å) and the possibility of obtaining them free from holes and conducting imperfections. The aim of this paper is to describe the film deposition techniques, some of the properties of the films so obtained and to review their electrical behaviour. It is also intended to make this review a comprehensive and up-to-date source of information for those who are either already engaged in this field or are planning to make Langmuir films the subject for future investigations.In this survey, emphasis is put on problems worth further study to obtain greater insight into the basic properties of these films. Further, since they possess some interesting electrical properties, this paper may prove useful in the assessment of our depth of knowledge about them and in reducing the existing gap between basic research and technological applications. Thus their potential usefulness in the development of devices is also discussed.The survey is divided into two parts. Part I is concerned with deposition techniques, the physical properties of Langmuir films and certain electrical properties, namely dielectric behaviour and electrical conduction phenomena. Part II, which will appear in the next issue, will be concerned with electrical breakdown behaviour, voltage induced changes in electrical behaviour (forming) and ionic transport phenomena in the films and will finish with suggestions as to future trends in work with such films together with a summary of possible applications.To assist the reader, the two parts have been numbered consecutively with regard to sections of the text, figures and references.