Tunneling induced decomposition of Mo(CO)6 onto TiO2(110) surface

Tunneling induced decomposition of Mo(CO)6 from the gas phase was studied on TiO2(110) surface by scanning tunneling microscopy (STM) and spectroscopy (STS). The efficiency of the procedure was followed by measuring the dot volume as a proportional indicator of the amount of the decomposed precursor. It was found that below 1 × 10−5 Pa background pressure of Mo(CO)6, there is no measurable effect and above 1 × 10−4 Pa, the nanodot size is too large compared to the curvature of the tip (20–40 nm). A threshold bias of +3.1(±0.1) V on the sample was measured for the decomposition of Mo(CO)6 in gas ambient. In the absence of the precursor, dot formation was observed only above +3.7(±0.2) V, in good agreement with the results reported in our earlier work about nanolithography on clean TiO2(110) substrate (E. Kriván, A. Berkó: J. Vac. Sci. & Tech. B 15(1) (1997)25). By applying voltages in the range of 3.1–3.5 V, a systematic enlargement of the created nanodots was found in the range of 2–20 s of duration and 0.01–1.0 nA of tunneling current. The I–V curves detected on the top of the nanodots have shown that the created features are of insulator character. This observation indicates that the decomposition of Mo(CO)6 is also accompanied by oxidation of the deposited Mo species.