The effect of Pb content and annealing temperature on the electrical properties of PbₓS₁-ₓ films

A polycrystalline lead sulfide PbₓS₁-ₓ alloys with various Pb content (x=0.50, 0.51, 0.52, 0.54, and 0.55) has been prepared successfully. PbₓS₁-ₓ films of thickness 1.5 μm have been deposited onto glass and n-Si subtrates by flash thermal evaporation method at room temperature (R.T) under vacuum 10^-6 torr and deposition rate 0.83x10^-3 μm/sec. These films have been annealed at different temperatures (Ta=R.T, 323, 373, 423, 473, and 523) K. The electrical properties of these films were studied by variation of Pb content and annealing temperature. The d.c conductivity increases with increasing Pb content for all PbₓS₁-ₓ films and decreases with increasing Ta. The electrical activation energy increases at range of temperature and decreases in other range of temperature with increasing annealing temperature and Pb content. From the Hall Effect measurement, the films of (x=0.50, 0.51, and 0.52) are found p-type and the films of compositions (x=0.54 and 0.55) are n-type and change to p-type at 523K. The carriers concentration decreases with increasing annealing temperature and Pb content for p-type, while it increases with increasing annealing temperature and decreases with increasing the Pb content for n-type samples. The Hall mobility increases sharply with increasing Ta and Pb content for p-type films. The drift velocity (vc), carrier life time (τ), and mean free path (l) increase with increasing annealing temperatures for p-type and decrease for n-type, while it increase with increasing Pb content for both p-type n-type filsm. From measurement of the four points probe method, it is found that the silicon is of n-type, whereas PbxS1-x are p-type for (x+0.50, 0.51 and 0.52) and n-type for (x=0.54 and 0.55)