Thickness dependence of dielectric properties of TlGaS2 thin films

Abstract

Bulk TlGaS2 single crystals were produced by the Bridgman method. TlGaS2 thin film samples were deposited from bulk crystals by the thermal evaporation technique under a high vacuum. TlGaS2 thin films were deposited in the 100-750 nm thickness range. Dielectric spectroscopy measurements were operated in the frequency range of 1-105 Hz and temperature range of 273-373 K under the voltage of 1 V (rms). TlGaS2 thin films have amorphous. Bulk TlGaS2 has a crystalline structure based on X-Ray diffraction patterns. Three polarization mechanisms were detected from the analysis of Cole-Cole plots. At low frequencies, the effect of interfacial polarization was observed. Toward higher frequencies, two dipolar polarization mechanisms were detected. In comparison to the bulk TlGaS2 single crystal, the dielectric constant of the thin films has 100-1000 times larger values at frequencies lower than 100 Hz. The thickness limit at which bulk physical properties started has been investigated. The transition thickness between bulk/thin film properties was detected at around 700 nm. The low dielectric constant and the good conductivity around 10-8 S/cm at105 Hz can give opportunities to use these thin films in technological applications.