U-shaped distribution of interface states in metal-(Langmuir-Blodgett) Si structures with phthalocyanine Langmuir-Blodgett films

Abstract

A considerable part of the effort aimed at practical applications of Langmuir-Blodgett (LB) films is based on metal-insulator-semiconductor structures with an incorporated LB layer as the insulator. In accordance with this trend the present communication deals with a study of the metal-LB-Si structures with thin copper tetra-4- t-butylphthalocyanine films deposited by the conventional LB technique onto silicon substrates (ϱ ≈ 5 Ω cm). The experimental methods used were deep-level transient spectroscopy in a charge-modification mode and a feedback charge C-U method. The analysis of the results indicates the existence of energy states at the LB-Si interface. The states form a continuous U-shaped spectrum in the gap of the semiconductor. The high density of the states (about 10 12eV −1 cm −2) is typical of the “wet” technologies to which LB deposition belongs.