A metallic alloy is prepared from a gaseous mixture of at least two non-oxide precursor compounds, wherein the non-oxide precursor compounds collectively comprise the metallic constituents. The organic thin film transistor includes a substrate, a gate electrode disposed on the substrate, a p-type organic semiconductor layer insulated from the gate electrode, a source electrode and a drain electrode separated from each other and insulated from the gate electrode, and a hole injection layer interposed between the source and drain electrodes and the p-type organic semiconductor layer. Moreover, the apparatus and method continuously apply the same tracking servo operation to an entire area of the same high-density read-only optical disc or rewritable optical disc.