Recent progress of cluster ion beam was overviewed. Various applications, such as nano-fabrication and biological material analysis, have been developed by using cluster effects, which are due to high-density and multiple collision between cluster ion and surface. Control of size and energy of cluster beam is essential. High speed etching with high anisotropy is realized with neutral cluster beam, which has very low energy/atom. Both molecular depth profiling of organic multilayer and high resolution molecular imaging were demonstrated by using cluster ions. These new XPS and SIMS techniques provide new opportunities for polymer, molecular electronics, biological materials and life science.

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 Gas cluster ion beam (GCIB) exhibit unique irradiation effects such as dense energy deposition, low-damage irradiation, and surface smoothing effects. Especially, low-damage sputtering of organic materials is one of the hot applications of GCIB. However, it is still necessary to improve beam properties of GCIB. In this paper, we will review characterization of GCIB regarding formation of multiply charged GCIB and effects of collisions with residual gas. As recent applications of GCIB, etching enhancement by introduction of reactive background gas, and a nano-fabrication of magnetic recording device by GCIB are explained.

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 Water cluster ion beam source was developed. Multiply-charged water clusters were generated by ambient or vacuum electrospray. Cluster ions (represented as [(H₂O)_90,000+100H)]¹⁰⁰⁺) impact the solid sample under vacuum with kinetic energy of 10⁶ eV. Supersonic collisions of water droplets with the surface lead to the atomic/molecular level sample desorption, high-efficiency ionization, and non-selective surface etching without sample modification. By this technique, inorganic materials and organic materials can be etched with etching rates of a few and ≥10 nm/min, respectively. This technique was successfully applied to the interface analysis for CuO/Cu.

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 Argon Gas Cluster Ion Beam (Ar-GCIB) is now widely spread in the field of practical surface analysis, such as X-ray photoelectron spectroscopy (XPS) and Time-of-Flight secondary ion mass spectrometry (TOF-SIMS), because of its unique sputtering effect of low chemical degradation for organic materials. GCIB provides the lateral sputtering effect and the high sputtering yield of which are never achieved by monotonic Ar ion beam on organic materials, so that the low chemical degradation of organic materials with high depth resolution and high sputtering rate could be achieved. Of course, a study of the GCIB sputtering phenomena with chemically reactive gasses, instead of Ar gas, for the advanced materials is one of the interesting things from an academic point of view. But the Ar-GCIB technique is expected to use for more practical applications, especially in the industrial field. In this paper, some practical applications of Ar-GCIB with recent XPS and TOF-SIMS instruments will be briefly introduced.

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 We have constructed a simple metal evaporator mounted on a conflat flange with an outer diameter of 70 mm. It consists of a tungsten filament, an alumina tube, two molybdenum electrodes, tantalum foils, and electric feedthroughs. Evaporation rates are measured as a function of electric current. We used it to prepare an Au thin film and a Si (111)-√3 ×√3 R30°-Au surface.

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