Sol–Gel Derived Al–Ga Co-Doped ZnO Thin Films Embedded with Microrods

Abstract

Aluminium–gallium (Al–Ga) co-doped ZnO (AGZO) thin films with different Al–Ga at.% were spin coated on glass substrates using sol–gel spin coating technique. Morphological images by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) reveal that the granular structures of co-doped films are embedded with microrods, which has never been reported before. The density of the microrods increases with higher co-doping at.%. The Hall Transport measurements reveal that the electrical properties of the co-doped films are comparable with single Ga doped ZnO films, which implies that the co-doping method can be a way forward to reduce the fabrication cost of the doped ZnO films involving expensive raw material. Also, the unique features of the AGZO films embedded with microrods may create new opportunity for these films to be implemented in emerging optoelectronic devices such as solar cells and organic light emitting diodes.

Unique and Excellent Paintable Liquid Metal for Fluorescent Displays

“…The XRD patterns of the samples produced with substrates being undoped, singly doped with Ga, Bi, In, or Sn, and codoped in eGaBiInSn are shown in S1 in the Supporting Information, suggesting that eGaBiInSn probably replaced Al 3+ and Si 4+ settled in the interstitial lattice sites in the Al 2 O 3 or SiO 2 crystals or segregated into an amorphous region. 32,33 The undoped substrates showed ). This proves that the introduction of codoped and singly doped atoms leads to a significant decrease in the crystalline quality (Figure 3d).…”

“…The XRD patterns of the samples produced with substrates being undoped, singly doped with Ga, Bi, In, or Sn, and codoped in eGaBiInSn are shown in Figure . Diffraction peaks due to impurity phases such as Ga 2 O 3 , Bi 2 O 3 , In 2 O 3 , SnO, and SnO 2 were not observed in any of the samples (Figure a,b); the XRD peaks of Ga 2 O 3 , Bi 2 O 3 , In 2 O 3 , SnO 2 , and SnO are shown in Figure S1 in the Supporting Information, suggesting that eGaBiInSn probably replaced Al 3+ and Si 4+ settled in the interstitial lattice sites in the Al 2 O 3 or SiO 2 crystals or segregated into an amorphous region. , The undoped substrates showed multiple highly intense and sharp diffraction peaks, implying well-crystallized structures (Figure b, Substrate). In comparison, fewer and weaker diffraction peaks were observed in the XRD patterns of the singly doped and codoped samples, which can be attributed to the replacement between LM and Al 3+ and Si 4+ .…”

“…This can be explained as an effect of strain due to the substituted impurities. Moreover, following the substitution of impurities of Ga 3+ , Bi 3+ , In 3+ , Sn 2+ , and Sn 4+ ions in the Al 3+ and Si 4+ sites, the larger ionic radii of Ga 3+ (0.62 Å), Bi 3+ (1.03 Å), In 3+ (0.81 Å), and Sn 4+ (0.69 Å) in comparison with those of Al 3+ (0.65 Å) and Si 4+ (0.40 Å) induce lattice expansion. , Even the lattice tensile strain due to the larger In atom may have a more significant influence in comparison to that due to the Ga atom. , The LM diffuses into the substrate and exists as the oxidized ions Ga 3+ , Bi 3+ , In 3+ , and Sn 2+ /Sn 4+ substituted for Al 3+ and Si 4+ . The doped region of the samples produces a large number of excess cations and defects, such as oxygen vacancies, which can be described by eqs –. …”

“…38,39 Even the lattice tensile strain due to the larger In atom may have a more significant influence in comparison to that due to the Ga atom. 33,34 The LM diffuses into the substrate and exists as the oxidized ions Ga 3+ , Bi 3+ , In 3+ , and Sn 2+ /Sn 4+ substituted for Al 3+ and Si 4+ . The doped region of the samples produces a large number of excess cations and defects, such as oxygen vacancies, 40 which can be described by eqs 3−6.…”

Recent Progress in Solution Processed Aluminum and co-Doped ZnO for Transparent Conductive Oxide Applications

“…The film exhibits high crystallinity along (002), >70% transparency, and low resistivity (2.35–4.59 × 10 −3 Ω cm). Furthermore, Zi N. Ng et al [ 73 ] fabricated the Al-Ga co-doped ZnO microrods via the sol-gel spin coating technique. Indeed, the microrod thin film exhibited high transparency (95%), with lowest resistivity, determined by Hall effect, of 23 Ω cm when the doping level was fixed at 1 at%.…”