E-Journal of Surface Science and Nanotechnology (e-JSSNT) is an electric journal published by the Japan Society of Vacuum and Surface Science since 2003, and this year marks its 20th anniversary. To commemorate this event, a special issue “Progress of Vacuum and Surface Science and Technology in the Early 21st Century” is published with six papers from different research fields reviewing research progress over the past 20 years (or since the beginning of the 21st century). We hope that this issue will give each researcher a hint for future research development by looking back the paths we have taken. The preface and the review papers are also published in English in e-JSSNT, Vol. 21, Issue 2.

In this review, advances in scanning probe microscopy (SPM) from the last two decades are presented. Progress in analyzing C₆₀ molecules is described as an example of molecular imaging quality improvement for each decade. Innovations and progress in SPM imaging techniques are then outlined, especially atomic force microscopy operating in ultrahigh vacuum (UHV) or in aqueous environments, and the widely spread low-temperature and/or high-performance UHV scanning tunneling microscopy.

Living organisms have a hierarchical structure ranging from macro to nano with complex time-evolving dynamics, and there are certain areas where surface science and nanotechnology can contribute. In this review, how soft nanotechnology have been evolved in the field of surface and vacuum society is described with historical background over the last two decades, which includes self-assembled monolayers and supported (and tethered) bilayers as a model of cell membrane. Recent topics in the field of nanobiotechnology are also reported.

Tribology is an interdisciplinary field related to the science and technology of friction, wear, and lubrication, and is expected to contribute to the realization of a carbon-neutral society. Recent advances in tribology are largely due to dramatic advances in nanotechnology and surface science. Recent topics are introduced along with the history of tribology.

Progress of surface and interface science using synchrotron radiation in Japan is reviewed. Investigations for electronic structures, and atomic structures including magnetic, catalytic, and other functional origins with dynamical information have been done. Historical milestones and future prospects are discussed.

This paper describes the recent progress in electron inelastic mean free paths (IMFPs) calculations with the dielectric response function and the optical energy loss function (ELF) as key parameters. As a result, it has been found that for most materials, the IMFP values calculated by the various calculation algorithms agreed well each other in the energy region above 300 eV. However, there is a large difference in the energies under 200 eV. The energy dependence of IMFPs calculated from optical ELFs could be expressed by the modified Bethe equation in the energies between 50 eV and 200 keV. The material dependence of IMFPs could be expressed by the TPP-2M equation. For IMFP calculations, the treatments and evaluations of the electron exchange effect, the effect of energy gap in the energy loss function, and the associated integral region also remain important issues to be addressed in the future.

Electron double-slit experiments, the essence of quantum mechanical “wave/particle duality,” have been extensively and continuously studied because their unrealistic interpretations have attracted many researchers. Here, we discuss recent sophisticated V-shaped double-slit experiments to elucidate electron-path information, i.e., which slit electrons pass through, which path they pursue, and where they arrive and interfere on the image plane. In a transmission electron microscope, an optically zero-propagation distance condition was realized, where the double-slit position was imaged just on the detector plane. Interference fringes composed of dot images were controlled by using two electron biprisms. Using a V-shaped double slit, we confirmed that it is possible to observe interference fringes only when the path information of individual electrons is not available. Furthermore, we studied how the interference fringes would shift their detected positions when electron wave phases were modulated before illumination to the double slit. Phase shifts were generated by tilting electron beams. We confirmed that each single electron as a wave changed its phase even when it traveled alone inside the microscope.