The effect of thickness on the physico-chemical properties of nanostructured ZnO:Al TCO thin films deposited on flexible PEN substrates by RF-magnetron sputtering from a nanopowder target

International audienceNanostructured aluminum-doped ZnO (ZnO:Al) thin films of various thicknesses were deposited on flexible Poly-Ethylene Naphthalate (PEN) substrates by RF-magnetron sputtering without intentionally heating them to fabricate Transparent Conductive Oxides (TCOs). The compacted ZnO:Al nanopowder with an [Al]/[Zn] ratio of 2%, which was synthesized by the sol-gel method combined with a supercritical drying process, was used as target in the sputtering system. The structural, morphological, optical and electrical properties of the deposited thin films of various thicknesses have been investigated. X-ray diffraction results indicate that all of the deposited thin films have a hexagonal wurtzite structure with c-axis orientation without any secondary phases. The Scanning Electron Microscopy (SEM) cross section images revealed that the films have a dense columnar nanostructure. The atomic percentage of the compositional elements in the films was nearly the same as that in the sputtering nanopowder target. Below a critical thickness of 500 nm, the films exhibit a high transmittance (>77% including the contribution of the PEN substrate) in the visible region. However, the electrical resistivity, Hall mobility and carrier concentration were significantly affected with the increase of film thickness. For thicknesses higher than 500 nm, the thin films exhibit similar electrical properties (resistivity of 3.5×10−4 Ω cm and Hall mobility of 22 cm2 V−1 s−1) but the transmittance decreases in the visible region. The Photoluminescence spectra showed that the Zn interstitial atoms, which enhance the conductivity of the films, are more dominant than the other defects

Modeling and experimental investigation of the close-spaced vapor transport process for the growth of CuIn(S 0,4 Se 0,6 ) 2 thin films

International audienceThis paper reports the prediction of optimal conditions to grow good quality crystalline thin films using the Close-Spaced Vapor Transport process. A new configuration of the horizontal reactor is used and presented. A thermodynamic model is proposed for the Cu-In-S-Se-I system to describe the deposition of CuIn(S0,4Se0,6)2(CISS) compound. The simulation was performed using the SOLGASMIX software which gives the composition of the chemical system at the thermodynamic equilibrium. The model is based on the minimization of the Gibbs energy of the defined chemical system. The present study has allowed us to determine the influence of the source temperature (TS) and iodine pressure (PI2) on the growth of CISS thin films. The different compounds of the solid phase were predicted for various TS and PI2 values. The conditions of stoichiometric and quasi-stoichiometric deposition are 475 ≤ TS ≤ 525 °C and PI2 ≤ 3 kPa. Some deduced conditions from the theoretical prediction were tested experimentally. The CISS samples grown have been analyzed by X-ray diffraction and scanning electron microscope. The thin films, deposited in optimal conditions, are stoichiometric

Modeling and experimental investigation of the close-spaced vapor transport process for the growth of CuIn(S 0,4 Se 0,6 ) 2 thin films

International audienceThis paper reports the prediction of optimal conditions to grow good quality crystalline thin films using the Close-Spaced Vapor Transport process. A new configuration of the horizontal reactor is used and presented. A thermodynamic model is proposed for the Cu-In-S-Se-I system to describe the deposition of CuIn(S0,4Se0,6)2(CISS) compound. The simulation was performed using the SOLGASMIX software which gives the composition of the chemical system at the thermodynamic equilibrium. The model is based on the minimization of the Gibbs energy of the defined chemical system. The present study has allowed us to determine the influence of the source temperature (TS) and iodine pressure (PI2) on the growth of CISS thin films. The different compounds of the solid phase were predicted for various TS and PI2 values. The conditions of stoichiometric and quasi-stoichiometric deposition are 475 ≤ TS ≤ 525 °C and PI2 ≤ 3 kPa. Some deduced conditions from the theoretical prediction were tested experimentally. The CISS samples grown have been analyzed by X-ray diffraction and scanning electron microscope. The thin films, deposited in optimal conditions, are stoichiometric

Characteristics of nanostructured Zn1-xVxO thin films with high vanadium content elaborated by rf-magnetron sputtering

Nanostructured Zn1−xVxO (0 ⩽ x ⩽ 0.50) thin films were synthesized by rf-magnetron sputtering at two different substrate temperatures (room temperature (RT) and 200 °C) and with variable sputtering powers (60, 80 and 100 W). In this method, single targets based on Zn1−xVxO nanopowders prepared by the sol–gel process were used. Characterization of the Zn1−xVxO nanoparticles showed that they crystallize in the hexagonal wurtzite structure. Their size ranged from 20 to 40 nm. The effect of process parameters on the physical and chemical properties of Zn1−xVxO thin films has been studied. For x ⩽ 0.30, the results obtained at 200 °C and 60 W indicate that the films have a high quality of crystallinity. Vegard’s law is respected, indicating that vanadium is incorporated in the ZnO matrix. The chemical compositions of these films were found to be close to the stoichiometry. The films exhibit a columnar structure and a smooth surface. Their average transmission, from the visible to the NIR, was in the range of 75–90%. The values of the band gap of the Zn1−xVxO thin films with x ⩽ 0.30 and elaborated at 200 °C and 60 W, vary from 3.29 to 3.74 eV. This is consistent with blue shifting of near-band edge cathodoluminescence emission. Under particular growth conditions, the investigation shows that the Zn0.80V0.20O sample presents the best properties for potential use in various optoelectronic applications, namely: a single wurtzite phase, low surface roughness (Ra ∼ 0.2 nm), a high transparency of 90% in the UV–Vis–NIR, a wide band gap of 3.74 eV and a resistivity of ∼5 × 10+3 Ω cm