Abstract
The spectral properties and colour functions of a radio frequency (RF)-based sputtering plasma source was monitored during consecutive sputter deposition of zinc doped indium oxide (IZO) thin films under argon and argon/hydrogen mix. The effect of target exposure to the hydrogen gas on charge density/mobility and spectral transmittance of the deposited films was investigated. We demonstrate that consecutive exposure to the hydrogen gas during the deposition process progressively affects the properties of thin films with a certain degree of continuous improvement in electrical conductivity while demonstrating that reverting to only argon from argon/ hydrogen mix follows a complex pathway, which has not been reported previously in such detail to our knowledge. We then demonstrate that this effect can be used to prepare highly conductive zinc oxide thin films without indium presence and as such eliminating the need for the expensive indium addition. We shall demonstrate that complexity observed in emission spectra can be simply identified by monitoring the colour of the plasma through its colour functions, making this technique a simple real-time monitoring method for the deposition process.
Highlights
Transparent conducting oxide (TCO) thin films are applied in various optoelectronic devices, mobile phone screens, flat panel displays and most importantly in the fabrication of thin film-based solar cell devices, and plasma sputter deposition is one of the main established methods of applying these coatings
The compositions of the thin films obtained at 20 kV show an indium/zinc ratio of 2.3 to 1 to 3.1 to 1, different from the In2 O3 /zinc oxide (ZnO) composition obtained by Sheng et al a closer investigation of the results indicates that the presence of the indium ratio in samples deposited with hydrogen is higher than in those deposited with Ar gas alone and sample S5, which represented the switch from Ar + H to
The compositions of the thin films obtained at 20 kV show an indium/zinc ratio of 2.3 to 1 to 3.1 to 1, different from the In2O3/ZnO composition obtained by Sheng et al a closer investigation of the results indicates that the presence of the indium ratio in samples deposited with hydrogen is higher than in those deposited with Ar gas alone and sample S5, which represented the switch from Ar + H to Ar gas, shows the lowest In/Zn ratio
Summary
Transparent conducting oxide (TCO) thin films are applied in various optoelectronic devices, mobile phone screens, flat panel displays and most importantly in the fabrication of thin film-based solar cell devices, and plasma sputter deposition is one of the main established methods of applying these coatings. The nature of these materials brings about adjustments of dual functionality parameters viz. When sputter deposition of a TCO such as IZO is carried out, one can imagine how vital the sputtering conditions are to the way that the atoms are deposited and laid on the substrate surface, which will define the work function, electron affinity, band-gap and all the discussed parameters. We shall demonstrate that consecutive exposure of pure ZnO target to (Ar + H) will improve the electrical properties of ZnO films without any doping
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