The possibility of growing multicomponent oxides by spatial atmospheric atomic layer deposition has been investigated. To this end, Al(x)Zn(1-x)O films have been deposited using diethyl zinc (DEZ), trimethyl aluminum (TMA), and water as Zn, Al, and O precursors, respectively. When the metal precursors (i.e., TMA and DEZ) are coinjected in the deposition region, the Al/(Al + Zn) ratio can be accurately controlled by either varying the TMA flow to the reactor or the exposure time of the substrate to the precursors. A high doping efficiency level (up to 70%) is achieved in Al-doped ZnO, resulting in films with a high carrier density (5 × 10(20) cm(-3)), low resistivity (2 × 10(-3) Ω cm), and good optical transparency (>85%) in the visible range. The morphology of the films changes from polycrystalline, in conductive i-ZnO and Al-doped ZnO, to amorphous, in highly resistive Al-rich films. The unique combination of the fine tuning of the composition, morphology, and electrical properties of the films with high deposition rates (>0.2 nm/s) paves the way for spatial ALD as an emerging disruptive technique for the growth of multicomponent oxides over large areas.
Indium-doped zinc oxide (ZnO:In) has been grown by spatial atomic layer deposition at atmospheric pressure (spatial-ALD). Trimethyl indium (TMIn), diethyl zinc (DEZ) and deionized water have been used as In, Zn and O precursor, respectively. The metal content of the films is controlled in the range from In/[In+Zn] = 0 to 23% by co-injecting the vaporized metal precursors (i.e. DEZ and TMIn) in the deposition region and varying their flows. A high doping efficiency (up to 95%) is achieved, resulting in films with very high carrier density (6·1020 cm−3), low resistivity (3 mΩ·cm) and high transparency in the visible range (> 85%). The morphology of the films changes from polycrystalline to amorphous with increasing indium content above 15%, while maintaining a low resistivity value (< 7 mΩ·cm). Spatial-ALD combines a fine tuning of the composition, morphology and electrical properties of ZnO:In films with high deposition rates (> 0.1 nm/s).
Undoped and indium-doped ZnO films have been deposited by atmospheric spatial atomic-layer-deposition (spatial-ALD). The stability of their electrical, optical, and structural properties has been investigated by a damp-heat test in an environment with 85% relative humidity at 85 °C. The resistivity of the ZnO films increased during damp-heat exposure mainly due to a sharp decrease in the carrier mobility, while the carrier density and transparency degraded only partially. The increase in resistivity can be ascribed to a degradation of the structural properties of ZnO films, resulting in a higher level of tensile stress, as indicated by x-ray diffraction analysis, and in a reduced near-ultravoilet emission level in their photoluminescence spectra. Al2O3 thin (25–75 nm) films grown by spatial-ALD at 0.2 nm/s are used as moisture barrier to effectively enhance the stability of the electrical and structural properties of the films.
Undoped and indium doped ZnO films have been grown by Spatial Atomic Layer Deposition at atmospheric pressure. The electrical properties of ZnO films are controlled by varying the indium content in the range from 0 to 15 %. A minimum resistivity value of 3 mΩ·cm is measured in 180 nm thick films for In/(In+Zn) ratio equal to 6 %, corresponding to a majority carrier density of 6·1020 cm-3 and a mobility of 3 cm2/Vs. All the films are highly transparent (> 80 %) in the visible range.
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