The study of surface properties of solids, especially of semiconductor crystals, is of great significance. Each 'real' surface is covered with layers of impurities which influence the surface properties. To eliminate this disturbance the surface must be thoroughly cleaned. This is usually done by heating the probe up to 400ยฐC in ultra high vacuum. This surface cleaning method requires rather costly equipment. Moreover the heating changes the texture of the crystal, which is a disadvantage for many measurements. Another method of obtaining clean surfaces is crystal cleavage which does not change the crystal texture. The cleaving must be done in ultra high vacuum since otherwise the fresh surface would immediately be covered with impurities from the environment. Surface properties are often measured at low temperatures. In these cases it can be an advantage to cleave the crystal immersed in liquid helium and to perform the measurement immediately thereafter in the same cryostat. Liquid helium is not known to have any influence on the properties of the freshly cleaved crystal surfaces. No other substances, except for negligible traces of chemically inactive solid nitrogen, oxygen, hydrogen, etc, are present in a helium bath.