Systematic Variations in Structural and Photoluminescence Properties Produced in Zn Oxide Nanostructures by Cu (0-5)% Substitution

Effects of Cu addition (0-5)% in ZnO are studied for structural and optical properties. The structural, photoluminescence properties and vibrational modes are strongly influenced with the Cu incorporation. Detailed investigations of the structural features of Cu doped ZnO nanostructures are reported. Our results show the systematic decrease in crystallite size (50.40 - 37.56 nm), lattice strain (1.82 - 1.49 micro), lattice stress (216.33 - 177.64 MPa) and energy density (196.78 - 132.69 KJ/m3) in the limit of small dopant concentration (0 < Cu ? 0.02). Decreasing trends are attributed to the smaller ionic size of Cu in comparison of Zn. Beyond Cu= 0.02 an increasing trend was noticed in crystallite size (41.67 - 70.67 nm), lattice strain (1.90 – 3.11 micro), lattice stress (226.32 – 369.35 MPa) and energy density (215.40 – 573.67KJ/m3. This increase in structural parameters is attributed to segregation of secondary phases for Cu content increase beyond 0.02. Two prominent regions in PL spectra were observed and the deconvoulution of these regions show a strong correlation with the structural changes observed within the limit of high and low dopant concentration. The FTIR spectra show shift of Zn-O vibrational mode toward higher frequency with increasing Cu concentration.