Au/CrSe stacked layers designed as optical absorbers, tunneling barriers and negative capacitance sources

Abstract

Herein thin films of CrSe (500 nm) are deposited onto glass and semitransparent gold nanosheets (100 nm) under a vacuum pressure of 10−5 mbar. Au nanosheets substrates induced the formation of CrSe instead of CrSe2 which grows onto glass substrates. The Au/CrSe stacked layers exhibited enhanced light absorption reaching 25% in the ultraviolet, visible and infrared ranges of light. In addition Au nanosheets successfully redshifted the direct allowed transitions energy band gap from 2.60 eV to 2.40 eV. On the other hand electrical investigations have shown that CrSe2 thin films exhibit a work function of 5.064 eV. The Au/CrSe interfaces displayed tunneling type Schottky barriers of height of 0.56 eV and barrier width of 8 nm. When an ac signal was imposed between the terminals of the Au/CrSe Schottky barriers a negative capacitance (NC) effects was observed in the spectral range of 0.02–1.80 GHz. The NC reached value of − 100 pF at 0.32 GHz. Fitting of the ac conductivity assuming tunneling type of transport indicated a high degree of localization near the Fermi level reaching a density of cm−3 eV−1. The enhanced light absorption and moderate value of work function in addition to the tunneling type of Schottky formation performing as NC source make the Au/CrSe interfaces promising for use in the design of electro-optic system.