Effect of low level nozzle height on properties of copper oxide absorption layer prepared by fully computerized spray pyrolysis depositions

The effect of approaching nozzle jet from the deposition surfaceon structural, optical and morphology properties of copper oxide thinfilms was studied. The film was prepared by homemade fullycomputerized CNC spray pyrolysis deposition technique atpreparations speed (3, 4, 5, and 6 mm/sec). The repeated line modewas used at deposition temperature equal 450 °C whereas thespraying time was in the range of (15-30 min) according to thedeposition speed. The film exhibit polycrystalline structure withpreferred orientation along (-111), (022) and (011), (002) at a 2θvalue of (35.63o) and (38.8o) respectively. Optical band gaps wererecorded at these speed shows variance in value from (1.53-2.08 eV).Films thickness were found to be in the range (128-412 nm) whichdepends on preparation speed.


Experimental work
Copper oxide (CuO) layer were deposited by homemade fully computerized CNC spray pyrolysis Deposition (system design, mechanical, electrical, electronic design, controlling program C languages, graphical user interface GUI, under publishing) onto glass substrates from aqueous solutions of copper chloride, dissolved in distilled water, with fixed molar concentration equal to 0.1 M. compressed Air was used as the carrier gas with a constant flow rate equal 4.5 kg/cm 2 .The aqueous solution of copper chloride was sprayed in atmospheric presser onto substrate area (10×10 cm 2 ) which is equal to four microscopic slides in the dimension (75×25×1.2mm 3 ) and substrate temperatures 450°C and variance ± 5 at different preparation speed (3, 4, 5, and 6) mm/sec.While the nozzle -to -substrate distance was kept at the height 20 cm.Films thickness was measured by TFC Thin Film Measurement type (Black CR-25 USA) with resolution 5A o and thicknesses measurement range (50 A o -20 µm).The structural properties of these films were characterized by Xray diffraction using (Shimadzu XRD 6000).the diffraction pattern recorded with continuous scan mode and scanning speed 5deg/min and scan step of 0.1 and Cu Kα radiation (Wavelength (λ) =1.54060A o ).All samples were scanned in the 2θ range of (25-70) deg.The XRD spectra reveal that all obtained films sprayed at substrate temperatures equal to 450 °C have a poly-amorphous with monoclinic structure compared with (JCPDS File №. 05-0661), with preferred orientation along (-111) (002) and (111) (200) plans located at 2θ value of (35.63015 o ) and (38.80148 o ) respectively.Optical properties were monitored by using UV-Visible spectrophotometer type UV Mate SP8001.Transmittances spectra of the CuO layer measured in the range of 300-1100 nm at room temperature and the energy band gap was recorded.

A. Structural properties
CuO layer which are prepared by using fully computerized spray pyrolysis technique (CNC SPD) techniques in different deposition speed, and deposited on glass substrate at 450C, shows enhancement in the crystal structure in higher preparations speed as shown in Fig. 1a, 1b.This is due to density of droplet per unit area deposited on the substrate surface and this lead to the net of thermal energy quite enough to reach the hot substrate surface and results in subsequent decomposition/oxidation, and the opposite behavior occur in lower speed (3, 4 mm/sec).The thermal energy is not sufficient to got decomposition process in correct chemical vapor deposition (CVD).Crystallographic parameter for CuO layer at optimum deposition speed are listed in Table 1.Grain size of the films at different deposition speed was calculated using the Debye-Scherrer formula, and compared with (JCPDS) standard card № (05-0661) and present in Table 1 These results (2θ, lattice parameter d-spacing grain size) are consistent with standard card which previously reported.Fig. 1a, 1b show to as an improvement in the crystal structure, and this was approaching to the practical value (observed value of d, 2θ) from theoretical values form (JCPDS) card.

B. Optical properties
Transmittances spectra of the CuO layer were also measured.Fig. 2A, 2B, 2C, 2D shows the optical transmission T% as a function of the wavelength at two positions (POS) on the sample for the CuO layer at different deposition speed.All the films exhibit high absorbance in the studied UV-Vis range.The energy band gap, Eg, was calculated from the transmission spectra using the following relationship.

(αhυ) 2 = A (hυ -E g ) n
For the photon energy range shown in Fig. 3E, 3F, 3G, 3H, 3α reaches value higher than 10 4 cm −1 .This relatively high absorption coefficient is very important because the spectral dependence of α drastically affects the solar conversion efficiency.The inset shows the representation of (αhν) 2  versus hν used for the calculation of the energy gap Eg.The films exhibit direct transitions corresponding to a band gap Eg in the range of (1.53-2.08)eV.Which is in good agreement with the solar application.

Conclosions
The spray deposition of CuO layer onto glass substrates at different preparation speed and nozzle-tosubstrate distances equal 20 cm shows polycrystalline nature with monoclinic structure.The Transmittance spectra reveal that the transmittance decreasing with increased preparation speed.The higher speed exhibits an improvement on the structural and optical properties over preparation speed.The as-deposited film which changes to smooth and uniform at the speed (5, 6 mm/sec), band gap, thickness, found to be increased in odd number of speed than even number of speed.The band gap energy varies from 1.513 to 2.086 eV with change in preparation speed.