Structural, optical and electrical properties of heavy ion irradiated CdZnO thin films

• CdZnO is an efficient TCO material for photovoltaic applications.
• Band gap decreased from 3.10 eV (pristine) to 2.79 eV (fluence: 5 × 1012 ions/cm2).
• It exhibits hexagonal wurtzite with (002) orientation in pristine and ion irradiations.
• Minimum resistivity and high carrier mobility at fluence of 5 × 1012 ions/cm2.

The thin films of CdZnO were deposited on glass substrates using dc magnetron sputtering technique and investigated after heavy ion-irradiations of 100 MeV Au ions with the fluences ranging from 1 × 1011 ions/cm2 to 1 × 1013 ions/cm2. The structural, optical and electrical properties of the irradiated and pristine films were studied by glancing angle X-ray diffraction (GAXRD), UV–vis–NIR spectroscopy and Hall effect measurement. The structural characterization using GAXRD pattern shows an enhancement of crystallinity up to the ion fluence of 5 × 1012 ions/cm2, and the crystallinity decreases at the highest fluence of 1 × 1013 ions/cm2 and these films exhibit hexagonal wurtzite crystal structure (002) with a c-axis orientation. The optical transmittance spectra reveals a red shift and the optical band gap decreases upon ion-irradiation with the minimum band gap at the ion fluence of 5 × 1012 ions/cm2. The average transmittance of the thin film of CdZnO increases from 75% to 85% after irradiation (up to 5 × 1012 ions/cm2). The atomic force microscopy image of the films reveals that roughness decreases up to the fluence of 5 × 1012 ions/cm2 and increases at higher fluences. The films irradiated with a fluence of 5 × 1012 ions/cm2 would show better electrical properties like low resistivity, high carrier concentration and mobility compared to other irradiated films.