ZnO a multifunctional material: Physical properties, spectroscopic ellipsometry and surface examination

The investigation reports on the transparent and conducting pure and metal doped zinc oxide (ZnO) thin layer. The layers are ultrasonic sprayed onto microscope glass substrates at 350 degrees C. The effect of Sn doping level (from 0% to 3%) is discussed in one hand and metal (Al, Cu and Sn) doping effect on the properties in other hand. Spectroscopic ellipsometry, optical, structural and electrical analyses of the as-grown films have been achieved. The (002)-oriented hexagonal wurtzite crystal structure is revealed by X-ray pattern having a grain size of 4.5-15 nm which confirms the nanosized aspect. The UV-VIS-IR spectrophotometer measurements reveal that the as-grown films are highly transparent in the visible and IR ranges (T similar to 90%). A slight influence of dopants on the band gap energy which ranges between 2.24 and 2.29 eV is emphasized. The electrical parameters such as bulk density, resistivity and mobility are measured by Hall measurement system (HMS). The films thickness is estimated by spectroscopic ellipsometry values and found to be of 178-330 nm. The electrical properties confirm an enhancement of bulk density and conductivity within the range - 1.06 x 1012-5.09 x 10(13) (cm(-3)) and 3.2 x 10(-5)-1.05 x 10(-3)(1/Omega cm) due to dopants incorporation as predicted. Inversion to p-type is demonstrated in Sn-doped ZnO sample. The nanostructures are observed in 2D scanned AFM views, size are of micro/nanometer and roughness is of 3.39-15 nm.