I-V and C-V characteristics of ferroelectric SbSI (film)-Si-metal

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Abstract
Antimony sulphoiodide (SbSI) films (0·1 to 0·5 μm) have been prepared by flash evaporation on silicon substrates and field effect studies have been made in SbSI(film)-Si-Metal structure over a wide temperature range to cover both ferro- and paraelectric phases. Crystalline films could be obtained by keeping the substrate at 120°C. Post fabrication annealing at 100°C in Argon gas atmosphere considerably improved the quality of the films, as evinced by the increase in its dielectric constant. The current-voltage (I-V) characteristics show a rapid increase of current with applied voltage for low voltages and then show a tendency towards saturation at high voltages. The non-linear I-V characteristics at low voltages are due to the heterojunction formation at (n)Si-(p)SbSI films interface. The built in potential 0·23V estimated from I-V characteristics is supported by the photovoltage observed in this structure. At high voltages the current is controlled by the resistance of the films, and the room temperature resistivity of the film ≈107 ohm cm is in good agreement with reported values. The C-V characteristics have been studied by an automatic C-V plotter and resemble that of MIS structure. The overall C-V curve is not affected markedly by the heterojunction, indicating the breakdown of heterojunction at high voltages. The capacitance in the accumulation region shows a broad peak (e1 = 64) at about 20°C, confirming the ferroelectric nature of the film. The memory behaviour observed in C-V was noticed even up to 15°C above the transition temperature. However, the area of the loop was decreased in the paraelectric phase. This suggests that the interface effects giving rise to space charge build up play a dominant role in the hysteresis behaviour and the ferroelectric polarization of the film plays a secondary role.

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