Electron sensitivity, photosensitivity and thermoplasticity of copper-doped Ge25Se75 thin films prepared via spin-coating

Abstract

Copper-doped Ge25Se75 thin films were deposited via spin-coating using anhydrous copper(I) or copper(II) chloride precursors to examine the effects of Cu oxidation states on film properties. The solution processing offered a cost-effective route with a mass production potential of perspective Cu-doped chalcogenide materials. The Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) techniques confirmed the Cu incorporation at its targeted concentration (5 at.%). The XPS also revealed a reduction of Cu2+ to Cu+ oxidation form, presumably already in the solution phase. Optical characterisation revealed a redshift in the bandgap due to Cu-Se bond formation while annealing at 210 degrees C led to partial crystallisation, forming CuGeSex-like phases. The combination of wet etching with electron beam lithography and optical holography showed a significant increase in the stability of copper-doped material. Similarly, the thermoplasticity of copper-doped samples was affected as the hot embossing temperature dramatically shifted towards higher temperatures. However, despite having the same Cu+ oxidation state, the selected copper precursor still significantly influenced the majority of studied phenomena. These findings prove that Cu doping in the solution phase modifies the optical, mechanical and potentially electrical properties of Ge25Se75 thin films, making them viable for resistive memory or high-temperature photonic applications.