# Recent Advances in the Growth and Characterizations of SILAR-Deposited Thin Films
## 5 Metal Oxide Thin Films
### Copper Oxide and Cuprous Oxide Films  
The p-type Cu\({}_{2}\)O (cuprous oxide or copper (I) oxide) films were deposited on the substrates at 70 \({}^{\circ}\)C, and then annealed under various temperatures (100 to 500 \({}^{\circ}\)C) for  
Figure 9: FESEM images of the SILAR-deposited Bi\({}_{2}\)O\({}_{3}\) films under two different magnifications (**a**,**b**). The TEM image (**c**) and the HRTEM image (**d**) of the Bi\({}_{2}\)O\({}_{3}\) scratch powder sample reproduced with permission from [179], [PERSON], 2017.  
60 min [180]. The phase transition could be observed (Cu\({}_{2}\)O to CuO) at 300 \({}^{\circ}\)C. The resistivity values were calculated to be 6.12 \(\times\) 10\({}^{4}\)\(\Omega\)-cm and 8.23 \(\times\) 10\({}^{3}\)\(\Omega\)-cm, respectively. [PERSON] and co-workers [181] revealed that the copper (II) oxide or cupric oxide (CuO) thin films were monoclinic structures, as well as the formation of nanorod morphology. The photoluminescence spectra and photoelectrochemical cell indicated strong peaks (465 and 516 nm) and power conversion efficiency of 0.26% for 100 deposition cycles. The cuprous oxide nanorods were prepared on soda lime glass substrates in the presence of sodium chloride (NaCl) [182]; the chemical reactions could be explained in Equations (55) and (56).  
\[\mathrm{Cu}(\mathrm{S}_{2}\mathrm{O}_{3})^{-}\rightarrow\mathrm{Cu}^{+}+ \mathrm{S}_{2}\mathrm{O}_{3}^{2-} \tag{55}\]  
\[2\mathrm{Cu}^{+}+2\mathrm{OH}^{-}\rightarrow\mathrm{H}_{2}\mathrm{O}+\mathrm{ Cu}_{2}\mathrm{O} \tag{56}\]  
Raman spectroscopy confirmed the characteristic peaks (143, 214, 280, 332, and 620 cm\({}^{-1}\)) corresponding to the Cu\({}_{2}\)O phase. The XRD and SEM analyses indicated polycrystalline (in nature) with the (111) plane and spherical grains, respectively. The crystallite sizes (15.94 to 14.14 nm) and resistivity (15,142 to 685 \(\Omega\)-cm) reduced, but the dislocation density (3.94 \(\times\) 10\({}^{-3}\) to 5 \(\times\) 10\({}^{-3}\)) and strain (2.17 to 2.45 \(\times\) 10\({}^{-3}\)) increased with the increasing concentration of NaCl (0 to 6 mmol). The electrical properties of the as-deposited films, such as sheet resistance (1.27 to 33.46 M\(\Omega\))/square), surface resistivity (685 to 15,142 \(\Omega\)-cm), activation energy (0.14 to 0.21 eV), and band gap energy (1.96 to 2.36 eV) were reported under different contents of the NaCl electrolyte (0 to 8 mmol). [PERSON] and co-workers [183] suggested that amorphous films were annealed up to 823 K. The nano-spherical grain sizes (SEM) and crystalline sizes (XRD) were 50-100 nm and 14-21 nm, respectively. The band gap values in the as-deposited films and annealed films (373 K) were observed at about 2.3 and 2.4 eV. The lower band gaps for the films annealed were at 373-673 K (1.85 eV) and 673-823 K (1.7 eV). [PERSON] and co-workers [184] described the growth of Cu\({}_{2}\)O films on glass slides by using copper thiosulfate and NaOH. Anneal films were produced under different temperatures and times. The summaries of the band gap, resistivity, carrier concentration, mobility, and crystalline structure (Table 3) were highlighted by researchers. The fluorine-doped tin oxide glass was used as the substrate during the formation of Cu\({}_{2}\)O thin films [185]. The XRD and SEM results showed the most intense peak corresponding to the (111) plane and micro-crack morphology, respectively. Experimental findings showed that electrical resistivity and the band gap were reduced when the pH of the cationic solution was reduced.