Langmuir-Blodgett films in amorphous silicon MIS structures

In this paper we describe the properties of MIS structures based on hydrogenated amorphous silicon (a-Si:H) and organic films deposited using the Langmuir-Blodgett technique. Results are reported for undoped a-Si:H passivated with an insulating film of cadmium stearate 80 nm thick. The deposition of the monolayers was found to be critically dependent on the surface condition of the semiconductor.The capacitance data display well-defined accumulation and depletion regions and suggest that inversion is obtained when the device is reverse biased. The conductance data are similar in shape to those observed for conventional MOS structures on crystalline silicon. However, hysteresis and frequency dispersion effects complicate their interpretation in terms of surface state densities.From this preliminary investigation we conclude that useful MOS devices incorporating both thick and thin insulating layers can be based on the a-Si:H/Langmuir-Blodgett film system.