It has recently been demonstrated that the surface atomic structure of materials can be imaged by means of Auger electrons. Angular distribution Auger microscopy (ADAM) produces subatomic resolution images of atomic structure by measuring and displaying the complete angular distribution of Auger electrons emitted from atoms near the surface of a solid material or thin film. Auger angular distributions contain the “silhouettes” of surface atoms “backlit” by emission from atoms located deeper in the solid. The locations and shapes of these silhouettes directly reveal the relative positions of atoms near the surface.

Consequently, ADAM is an exciting new technique for characterizing materials surfaces and epitaxially grown surfaces.

Auger electrons have been employed for surface elemental analysis and depth- profiling for many years. The limited escape-depth of Auger electrons makes Auger spectroscopy inherently sensitive to the surface region. Depth profiling of materials, often performed in combination with ion etching, is widely used. ADAM offers the possibility of nondestructively obtaining profiles and structural information concerning buried interfaces and can also yield images of atomic structure.

For more than 40 years, magnetic recording has been the dominant technology for electronic data storage. During this time, the areal storage density on disks has risen to >108 bits/cm2. On tapes the corresponding figure is 0.2 × 108 bits/cm2. Thus each bit uses about a 1.0 μm2 area. These bits are written and read at data rates that require head-disk relative speeds of tens of meters per second and head-tape relative speeds of several meters per second. All this is accomplished at head-disk spacings of ≈0.2 μm and with contact recording for tapes.

It is truly a wonder that the systems work as well as they do. In fact, for many features in magnetic recording systems it isn't certain why they work as well as they do. However, the demand for storage capacity is estimated to be increasing at about 40% per year. So it is natural to ask whether magnetic recording can maintain its present dominant position in the foreseeable future. The answer is — “Very likely, yes” — but this prediction is based on the assumption that a number of formidable fascinating problems will be solved in order to increase the areal bit density.

The five articles in this special issue present the state-of-the-art in those key areas of magnetic recording that involve materials science, and they define the problems involved in increasing storage density. James U. Lemke discusses the background and outlook for magnetic recording.

There are times when technological or scientific progress is blocked for want of a breakthrough in a key area, just as there appear to be instances of a problem and its solution emerging simultaneously and independently. Upon closer inspection, however, this latter happy state is usually the result of long, hard work by people who had the insight to develop a solution before their peers were aware of the existence of a problem. At the moment, there are a number of convergent events occurring in vacuum technology which in all likelihood will have as profound an effect as the development of ultrahigh vacuum (UHV) technology in the late 1960s and early 1970s. These developments may be viewed as challenges posed by the requirements of certain technologies, or as a series of breakthroughs which will lead to new opportunities. Materials and materials processing or coatings are the key factors in most of these new developments, just as new pump and seal designs, and new vacuum practice were responsible for the development of UHV (10−9–10−11 torr) technology.

In particular, aluminum is emerging as a material which may replace stainless steel for applications where the ultimate in vacuum is required. By suitable treatment, pure aluminum and aluminum alloys can be made to produce static outgassing rates more than 10 times lower than stainless steel. Systems capable of reaching a base pressure in the extremely high vacuum (XHV) range of 10−12–10−13 torr, such as those described in this issue by H. Ishimaru, are now commercially available.