Book chapter 8

Introduction to Surface and Thin Film Processes

John A. Venables

Cambridge University Press (2000)

Supplementary notes by John A. Venables

© Arizona Board of Regents for Arizona State University and John A. Venables

Chapter 8: Surface processes in thin film devices

Corrections, comments and updates

8.1 Metals and oxides in contact with semiconductors

In section 8.1.3, pages 265-269, some techniques such as SIMS and BEEM are highlighted, as having the necessary sensitivity to detect impurities at the levels responsible for band bending at semiconductor interfaces. This is a fast-moving field, and there are new reviews, e.g. of silicdes and quantum dots, for example by von Känel et al. (2000).

There is however, still a need to develop simple techniques which can be applied in process control situations, and which can distinguish between total impurity levels, as in SIMS, and electrically active impurities. One such technique is based on secondary electron contrast in the SEM, analogous to the techniques described in sections 3.5.1 and 6.2.4 (Janssen et al. 1980, Futamoto et al. 1985); this technique has been shown to have considerable sensitivity when applied to semiconductor layers with different doping levels.

This SEM-based approach has been researched more recently, for application on a more routine basis, and has been shown to monitor the electrically active impurities (Perovic et al. 1995, Castell et al. 1997, Sealy et al. 2000).

New references for section 8.1

8.2 Semiconductor heterojunctions and devices

At the opening of section 8.2.3, page 274, the important role of semiconductor heterostructures in devices was mentioned. This has been recognized in the award of the 2000 Nobel prize for physics to Zhores Alferov and Herbert Kroemer, along with the surviving co-inventor of the integrated circuit, Jack Kilby. Unfortunately for Robert Noyce, Nobel's are not awarded posthumously. This award will stimulate many articles on the early history of the semiconductor industry, including eventually the Nobel prize lectures by the award holders, which are usually published in Rev. Mod. Phys.. The journalists get there first, however, as for example, one in the December issue of Physics Today by Richard Fitzgerald (2000). If you find other snappy short articles on this topic, let me know, as it is useful for students to read about such things in their professional journals.

Almost every issue of the Materials Science Bulletin, it seems, contains major articles on new aspects and applications of heterostructures. For example, the July issue of 2002 has a group of articles on Vertical-Cavity Surface-Emitting Lasers, known as VCSELs, pronounced "Viksells" (Lear and Jones 2002). Within this group, there is an article on the use of Quantum Dots as the active element in VCSELs by Bimberg et al. (2002), but is perhaps not a great idea just to single out this one article, as there are many of interest. The crystal growth of these VCSELs, including the advantageous thin film geometry, both for fabrication and use as components in optical communications, is impressive. I feel that readers who have got some basic principles (from chapters 7 or 8 of this book, for example) will be well placed to profit from such articles, and to appreciate the enormous progress that is being made on integrating optical components with thin film electronics.

New references for section 8.2

8.3 Conduction processes in thin film devices

In section 8.3.3, page 284, mention is made at the top of the page that chaotic effects are to be expected once the 'size' of the device drops below around 30 nm. However, some of the scare stories may be just that; in particular, the device may well be small in one dimension only, and the property of interest may be integrated over the length of the device which is considerably longer than 30 nm. This is an area of active research and development, and it is amazing how far the limits have already been pushed.

On pages 285-7, there is a discussion of magneto-resistance measurements in various geometries, with especial reference to the work of Shinjo et al. in Japan. An update can be obtained from a special issue of J. Phys. D. in honour of Professor T. Shinjo, to mark his retirement from Kyoto University, containing selected papers from the 17th International Colloquium on Magnetic Films and Surfaces (Maekawa & Chapman, 2002).

Another useful review relevant to this section is on the spin-valve transistor (Jansen 2003); here the emphasis is on spin-polarization effects on hot electrons in so-called hybrid devices, involving magnetic multilayers grown epitaxially on silicon. This topic is also included in two articles (by Stuart Parkin, and by Rolf Allenspach and Piere-Olivier Jubert) in a special MRS Bulletin issue on Magnetic materials for magnetic data storage edited by Coufal et al. (2006). These updates include a wide range of topics in magnetic thin films, and techniques sensitive to magnetism, including many of the authors referenced in this section and in section 6.3.

As an icing on the cake of this section, the 2007 Nobel Prize for Physics was awarded to Albert Fert and Peter Grünberg for their work on Giant Magneto-Resistance (GMR). The Nobel lectures are always worth reading for their mix of science and history, understandable by people who are not specialists in the field: a major resource. But I am getting ahead of myself: the Nobel lectures are on December 8, 2007, so watch this space.

New references for section 8.3

8.4 Chemical routes to manufacturing

In section 8.4.2, pages 291-3, I introduce briefly the use of colloidal particles as a route to the production of both optoelectronic materials based on CdSe nanoparticles, and magnetic materials based on coated transition metal nanoparticles. In the time since the publication of the book, these fields have become much better recognized, and references are easier to obtain. A useful introduction to these topics are contained in a special issue of the MRS Bulletin (December 2001) under the title New Aspects of Nanocrystal Research (Liz-Marzán & Norris, 2001) with articles on lasing in CdSe (Klimov & Bawendi, 2001) and transition metal nanoparticles (Murray et al, 2001), amongst others.

In section 8.4.4, pages 294-5, the new methods of combinatorial materials analysis are described in outline with a single example given. Several new firms are operating in this area, and materials science is starting to overlap with biotechnology. Some of these firms can be found on the web using my links to Nanofabrication groups, and via my new page entitled Nanotechnology is everywhere. In addition, an issue of the MRS Bulletin (April 2002) is devoted to Combinatorial Materials Science (Amis et al, 2002).

The whole area of Molecular Electronics is advancing rapidly, with many conferences and review articles appearing over the last few years. An introduction for physicists, and some references, can be obtained from a recent article (Heath & Ratner, 2003) by two of the leading chemists involved, James Heath of CalTech and Mark Ratner of Northwestern University. Heath was one of the winners of the Feynman prize for experimental nanotechnology in 2000, whereas Ratner won the Feynman Theory prize in 2001.

New references for section 8.4

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Latest version 17 November 2007.