The effect of operating a vacuum ion gauge on carbonaceous (C) contamination of a hydrogen (H)-passivated Si surface before epitaxial growth was investigated. The dependence of C contamination on the residence time in the loading chamber, t(lc), was determined with or without operating a vacuum ion gauge. The results showed that C contamination of a H-passivated surface was greatly increased by use of the ion gauge. With ion gauge operation in a vacuum of 1X10(-6)-1x10(-7) Torr in the loading chamber, the configuration of the ion gauge and upside down-stacked wafers is shown to be a dominant factor of C contamination of the Si surface. The presence of C contaminants could be determined by observing SiC diffraction patterns using in situ reflection high energy electron diffraction (RHEED), since the C contaminants reacted with Si to produce single crystalline SiC at a temperature as high as 850 degrees C. The RHEED patterns demonstrated that the single crystalline SiC had a zinc-blende structure. Single crystalline SiC islands with an ellipsoidal cross section were observed by high resolution transmission electron microscopy. In the subsequent epitaxial growth of Si, a well oriented single crystalline Si layer could be grown over the SiC islands although the effect of C contamination on the electrical characteristics of the interface was not clarified. Longer t(lc) with the ion gauge also required a higher temperature to achieve a 2X1 reconstructed surface structure from the H-passivated Si surface.