Scanning tunneling microscopy and scanning tunneling spectroscopy (STM/STS) of a titanium (Ti) amorphous film and titanium oxide dots were investigated at room temperature and in ambient air by scanning tunneling microscope (STM). A smooth amorphous Ti film (3 nm thick) with an area of 1 mum x I mum was chosen and imaged by STM. Tunneling current versus bias spectra for the film are symmetric to the origin in the STS measurements. Ultra thin films were oxidized at different positions by applying different voltage pulses ranging from 3.5 to 5 V for a period of 5 s. The subsequent images of STM show that the higher the bias applied to the film, the larger the dot. The in situ STS measurements were used, for the first time, to study the contaminant-free TiOx dots just as induced by STM. The in situ corresponding tunneling current versus bias spectrum was preceded by formation of a dot and followed by imaging the dot. STS I-V curves exhibit that the formed TiOx dots are n-type semiconductors. A transformation from slight asymmetry to drastic asymmetry of STS curves and increase in band gap indicate that nano-TiOx dots exhibit metallic to semiconducting behaviors with increase in the voltage pulse applied to sample. (C) 2002 Elsevier Science B.V. All rights reserved.