Book Review: (2) High Resolution Electron Microscopy

J.C.H. Spence is well known to be an original and innovative physicist and a prolific publisher, not only in premier scientific journals, but also of highly regarded texts. Spence was one of the key figures in the translation of the capabilities of High Resolution Electron Microscopy (HREM) from the domain of experimental and theoretical physics into the hands of materials, biological and other scientists investigating the nanoscale universe. His first edition of this book in 1980 accompanied a period of rapid advances in instrumentation and of HREM applications. Since activity in this field has slowed little, if at all, since 1980, the significantly updated 2002 edition is eagerly anticipated.

In reviewing this new edition, I decided to make comments in the framework of three somewhat different perspectives:-

Firstly, what does this new book offer the scientist contemplating HREM for the first time? Be warned - this book certainly takes nothing of an "HREM for Dummies" approach. While it is skilfully written throughout and is clear, concise and engaging, the book is uncompromising in its rigour and allows the reader little room for taking short cuts in their understanding of the physics involved. It will clearly be of highest value to those with the need to go deeply into HREM. Of the several alternative texts available for the HREM student, this is the most comprehensive in its co-ordinated and thorough discussion of the fundamentals of optics, of image formation and interpretation, and of practical limitations. In my opinion, it is the reference book for practical, fundamental HREM and will be the text preferred for extended graduate courses in the field. In contrast, it is unlikely to be favoured by those seeking a short course in HREM, that is unless they already have a very firm grounding in the physics of optics, interaction of waves with matter, etc.

Secondly, what does this 2002 edition offer the microscopist familiar with the 1980 edition? (I make no comparisons to the second, 1988 edition). Spence does not comment about removing the word "Experimental" from the title but his extensive revision deals with many practical issues, including scanning transmission (STEM) advances, technical developments in electron sources, in aberration and astigmatism corrections, and in signal detection, and selected examples of recent successes in imaging defects. These are all valuable additions to the book, with Spence adroitly matching important information about fundamental, technical and applications perspectives. Fundamental and self-contained material from the first edition, with minor updates, has been transferred to and makes up about half of the new edition. The remainder of the book is largely new. Spence understandably points to the literature in HREM having become so vast that it represents a serious challenge even to refer to and to summarise other excellent reviews. As a result, the newest material is different in style, being much less self-contained and requiring the student to consult many other sources. While this is perhaps unfortunate, it is impossible to do better in four hundred, already concisely written, pages. I selected one of the new topics, HREM in biology, for closer inspection as a non-specialist and came away with a much improved general knowledge about developments in the field (even though I read none of the many references made to other literature). Nevertheless, I doubt that this material alone would convince many life scientists to rush out to buy the new, improved edition. However, if my overall impression as a practising electron microscopist is any guide, most readers will be impressed favourably by the 2002 edition, will gain new insight into a remarkable range of HREM-related topics, and will be stimulated by the sense of vitality and excitement embedded in the book.

Thirdly, what does this book offer the reader of Crystallography News? Two state-of-the-art topics, reviewed by Spence in some detail, will attract attention - namely super-resolution schemes, and the value of the electron microscope for extracting information about atoms in crystals. Spence emerges, unsurprisingly, as an enthusiast for application of modern electron techniques. At the same time, he is adamant that HREM images in isolation, appealing as they are, and notwithstanding the sub-angstrom resolution that is now achievable, cannot yet be interrogated to yield unknown structures. Even in combination with image simulations and electron-diffraction-intensity measurements, insufficient knowledge of basic specimen parameters like thickness continues to stand in the way of unconstrained structure solution using electrons. Perhaps not everyone will agree with Spence about this, but his arguments are well made.

I am impressed by the user-friendliness of this book. The variety of information is logically and excellently laid out. Material is cross referenced carefully and extensively, and is indexed reasonably thoroughly. I searched particularly carefully through material which has been transported from the first edition and found very few errors in the renumbered cross references and the new index - an impressive achievement in itself. Illustrations in general clearly bring home the messages from the text. If I can be critical about presentation, the quality of reproduction of black-and-white images has deteriorated since 1980 - line diagrams are fine but some of the images appear muddy and with inappropriate contrast. For example, the 2002 reproduction of the pair of images in the book's Figure 6.16, intended to illustrate graininess, is now worthless since reproduction has obliterated its intended message. How ironic, considering this is a text directed at maximising image information!

Finally, like thousands of other scientists around the world, today I am able to carry my specimen off to a modern TEM and be confident of returning to my office carrying some high magnification images of lattices and nanostructures. But are they high resolution images, and are they interpretable? John Spence's new book is one that I will repeatedly consult in my search for the answers, not only in analysing the image detail, but also in better planning how my next experiment can be improved.

John Fitz Gerald
Australian National University