Structural and morphological studies of (NiO) 1-x (CuO) x Thin Films Prepared by Chemical Spray Paralysis Technique

. (NiO) 1-x (CuO) x Thin Films have been deposited on glass substrates by chemical spray paralysis technique for with different ratios at temperature (375±10) °C with spray rate 4s./1min. The structural properties of thin films have been investigated by the study of X-Ray diffraction analysis and morphological by study atomic forces microscope (AFM) . From the XRD result showed all simples are polycrystalline and various structural parameters were calculated. all the films show most preferred orientation along (111), (200) and (220) planes. The (AFM) results shows that the roughness decreases with mixing ratios.


INTRODUCTION
There are various techniques for the preparation of thin films but chemical spray paralysis technique has been largely used for the preparation of thin films. This method is summarized by spraying the solution of the chosen chemical material on hot substrate to form thin film on it [1]. This is the easiest method comparing with the others, this method was used by Chamberlain and Skarman in 1966 [2]. The advantages of the chemical spray pyrolysis technique are summarized by Low cost comparing with the other methods, Easy and fast in preparing thin film, The possibility of getting wide area thin film with a suitable thickness and high stability in time with its physical property [3].
Nickel oxide NiO of semiconductor compounds and the group is (II-VI) of the periodic Table [4]. And has a crystalline structure of the rock salt kind of structure of sodium chloride salt (NaCl) [5]. These nickel oxide NiO has cubic (NaCl-like FCC) structure and pale green color. The FCC structure is having lattice parameter of 0.4195 nm with slight triangular distortions at low temperatures. The stoichiometry of NiO is roughly indicated by the color of the sample . The color of the NiO is highly sensitive to the presence of higher valence states of nickel even in traces. It exhibits widely varying magnetic, optical, electronic and electrochemical properties depending on synthesis process and resultant defect structure [6]. The unit cell of a centralized faceted type (FCC) and the bond that connects between the nickel oxide ions are covalent bond resulting from the participation of two electrons between the nickel atoms and oxygen atoms [7]. The material nickel oxide from the transparent conductive oxides (TCO) which have high conductivity and lighting gap energy directly ,the width of energy gap 3.5 eV at 300K so that the cutter wavelength of 354 nm in the violet end of the spectrum region [8], we can deduce from this that film absorbency be at the wavelength of violet, while the long-wavelength be window.
NiO is one of these oxides and last years, a growing interest has been devoted to nickel oxide thin films. Due to its high chemical stability, as well as optical magnetic and electrical properties, NiO has a wide range of applications such as films for electro chromic devices, organic light emitting diodes, chemical sensors, n-p junction electrodes in dye sensitized solar cells and ptype large band gap oxide [9]. In recent years, cupric oxide (CuO) has attracted increasing interest for its prospective applications in many fields. As an important low cost and non-toxic transition metal oxide with a narrow band gap of ~1.2 eV at room temperature [10]. CuO is a p-type semiconductor with monoclinic crystalline structure and cell parameters a= 0.4684 nm, b= 0.3423 nm, c= 0.5128 nm and β= 99.54°. Its energy gap is in the range 1.21-1.51 eV. This is an attractive system for many researchers due to its photoconductive and photo-thermal applications and for studies of the transport mechanism in cuprates with high-TC superconductivity. copper oxide films have received much attention for its various applications some of which are in catalysis, semiconductors, batteries, gas sensors, biosensors , magnetic storage media , solar cells , electronics , varistors, capacitors and field transistors. Because the chemical and physical properties of CuO are strictly dependant of its morphology, in recent years considerable efforts have been made to synthesize various types of CuO nanostructures. Copper oxide has been dark brown inclined to the black odorless [11] .

2-EXPERIMENTAL DETAILS
(NiO) 1-x (CuO) x consists of mixing two compounds nickel oxide and copper oxide with different ratios, at first prepare NiO and CuO compounds severally. NiO solution was prepared by dissolving of (NiCl 2 .6H 2 O) [which is a powder of green color, it's molecular weight 237.69 g/mol] in 50 ml distilled water at room temperature , a magnetic stirrer is incorporated for this purpose for about (30) minutes to facilitate the complete dissolution of the solute in the solvent as shown in equation (1) [12]: (1) Also CuO can preparing of Cu(CH 3 COO) 2 .H 2 O [which is a powder of green color it's molecular weight 199.65 g/mol] in 100 ml distilled water and using magnetic stirrer too according to the following reaction in equation (2) [13]: (2) When preparing NiO and CuO solvents mixing the solutions with different ratios as shown in Table  (1) according the following relation:

X-Ray Diffraction (XRD)
XRD pattern of (NiO) 1-x (CuO) x thin film prepared by spray pyrolysis technique at substrate temperature of (375°C) have been shown in figurs (4-1 a,b,c,d,e,f) . The peaks of the XRD were observed between 2θ= 0° and 2θ =70°. These films showed a crystal structure of the films was identified to be polycrystalline, and this is agreement with [14,15,16].
The results showed there is obvious effect on the crystal structure at mixing, thus there is a shifted slightly in peaks position and the Table (1) shows peaks position for all pure and mixing films. Also can be calculate the following values :  International Letters of Chemistry, Physics and Astronomy Vol. 58

1-Interlayer spacing between the crystalline planes (d)
It calculated for all preparing films by using Bragg's law .We found that the results are approach for the standard values [17] . nλ = 2d sinθ (4) where λ = 0.154 nm and θ is Bragg's angle of XRD peak.

2-The Grain Size (G.S)
The grain size of the films was calculated for all peaks using the Scherrer's formula [18].
where ß = full width at half maximum (FWHM) measuring by radian angels.From the Table (2) found the average grain size for (NiO) pure and (CuO) pure equal to 40.61 nm and 36.76 nm respectively, while its observed the average grain size of the mixing films for all ratios is decreased with increasing the mixing ratios, this is a reason of the radios of Cu +2 is (0.69 Å) less than of ionic radii of Ni +2 (0.78Å) each Cu ion could substitute one host cation. However, assuming that copper oxide exists in the form of CuO, the substitution process should not be accompanied by any change in the oxidation state of NiO [19].

3-Micro strain (ε)
Its calculated by the equation (3), from the Table (2) can be seen the average micro strain for NiO pure and CuO pure equle to 0.086 % and 0.094% respectively.
Also can be observed that the average micro strain for mixing films is increase with decrease the average grain size, the strain is increased in NiO when its formed mixture with CuO. This may be due to the accumulation of CuO on the grain boundary of NiO which inhibit the crystal growth and leads to strain generation in NiO grains [20].

Atomic Force Microscope (AFM)
The topography study of the surface to the prepared films and the effect of mixing ratio used Atomic Force Microscope (AFM) with the ability to depiction and analysis of these surfaces and give the statistical values with high accuracy about surface roughness values depending on the Root Mean Square (RMS) of the average roughness. Through microscopic analysis (AFM) we can study the effect of (thickness, concentration, temperature, method of preparation ..... etc.) on the properties of the deposited film material to the fact that the study of the surfaces of film materials important to recognize how the distribution and arrangement of atoms on surfaces, and to identify the differences or homogeneity properties or attributes relating to each atom separately and illustrative image about the distribution rate of the crystalline size onto surfaces [21]. Figures (2-1,2,3) shows the AFM images within the scanning area (1800×1800nm) and analytical ability (pixels = 612,612) of all samples deposited at substrate from glass with temperatures of T s =375 o C . Figure (2-1 a,b,c,d,e,f) shows a diagram of distribution of growth granular gropes on the surfaces of the deposited films, Table  shows that the average diameters (grain size) of (NiO) pure and (CuO) pure thin films are (83.54 and 80.78 nm) respectively that agreement with [12,22] and the average diameters (grain size) for (NiO) 1 respectively, the first three results decreases in roughness rate and the root mean square RMS with increases the mixing ratios it obvious that surface is smooth, the increase of root mean square in last result lead to increase crystalline growth in vertical direction more than horizontal direction [21]. Figure (2-3 a,b,c,d,e,f) shows image in 3-Dimension of prepared thin film. This image was found that the surface thickness of the thin films value in figure (2-3 a,b,c,d) observed decreases in thickness which mean getting homogeneous crystalline growth along horizontal direction lead to uniform granular surface morphology thin film, while figure (2-3e) the crystalline defects have led to get un uniform granular surface morphology thin film.

4.CONCLUSIONS
The (XRD) measuring of (NiO) 1-x (CuO) x thin films showed its polycrystalline cubic type and decreasing the peak intensity in preferred direction (111) and deviation (2θ) with in obvious decreased in the average grain size reach to (31nm).AFM image showed the RMS, roughness and average grain size decreases with increases the mixing ratio.