INTRODUCTION
Thin films are made using transducers on low-cost substrates such as metal, glass, plastics, or polymer bases [1]. The most important characteristic of thin film technologies is that they contributed to a significant reduction in the thickness of semiconductor materials because of the ability of some materials to absorb high of sunlight falling within a few microns compared with several hundred microns needed in silicon thermal technology. In addition, these technologies have enormous potential for cost reduction, primarily by making large areas of interstitial forces compact and fully automated, and thus rapid progress has been achieved with the technologies of Photovoltaic (PV) films, whether in the laboratory or in the industry [2]. Thin films are one of the most suitable means to know many of their physical and chemical properties whose properties are difficult to obtain in their natural form. The term thin films are used to describe one or many layers of material atoms that do not exceed one-micron thickness [3, 4]. Transparent Conductive Oxides (TCOs) are compounds made up of oxygen-containing metal such as CdO, In2O3, ZnO, and SnO2. These substances combine two properties, characterized by high electrical conductivity and optical permeability High (transparent) extensible the permeability spectrum is between 400 - 1500 nm depending on the conditions of the material preparation. Despite the large gap in the energy of these membranes compared to the other conductors, the conduction package is filled with free electrons (shown by the high concentration of charge carriers).
For this reason, modern research has been directed to the field of TCOs because of its technological importance [5]. The cadmium oxide of semiconductors, which has negative connections (n-typs), has a high correlation resulting from the presence of cadmium atoms in compensatory sites or voids due to the oxygen atoms that It operates as a donor center in the crystalline installation with a viscous cubic structure (FCC) and has a direct energy gap of 2.3 eV and has high permeability in the visible area and therefore is classified as transparent conductivity (TCOs) [6].

MATERIALS AND METHODS
It was used the chemical cadmium chloride (CdCl2H2O) purity % 99.9 is a source of ions of cadmium (Cd) for the preparation of thin films pure cadmium oxide concentration (M 0.1) as well as the preparation of the thin films Cadmium oxide doped gallium oxide has attended the addition of (Ga2O3), a white powder added rates (7,5,3,1)% of the total mixture of the solution to the substance of cadmium chloride after dissolved with distilled water, and thus we get the cadmium chloride solution with specific ratios of vaccination component (Ga2O3) and then the mixture blends well stirrer using magnetic stirring while access to a homogeneous solution, clear and colorless and does not contain suspensions . The glass and silicon bases were used for deposition thin films prepared, the glass bases were cleaned by washing them with cleaning fluid and distilled water to remove any oil stains or residue and then placed under the running water to dispose of the cleaning fluid. The bases are then placed in a basin containing distilled water and placed in an ultrasonic device for 15min. The bases are placed in a basin with pure ethanol (96%) in an ultrasonic device for 15min after drying with one direction and placed in an oven for 15 min at 60 ° C and then the bases are ready for use. The rules of silicon by immersing in the ethanol and then placed in the Ultrasonic for 15min and dried in the same way as drying the glass bases. We sprayed the solution in batches to maintain the base temperature during the spraying process where the spraying process is for 5 sec and then stop for 10 sec with a spray rate of (1ml / min). The best vertical area between the end of the spraying device and the bases on the surface of the electric heater is (30 cm). The temperature of 300 ° C was selected in the preparation of the prepared thin films. After the deposited process, the samples were left to cool down to room temperature to complete the crystalline development process. After the deposited process, we measured the thickness of the thin films using Felt metrics F20 at Malaysian University of Science - Malaysia.

RESULTS AND DISCUSSION 
X-Ray diffraction
Fig. 1 shows the results of x-ray diffraction of pure cadmium oxide thin films and doped to gallium oxide and applied to glass bases. The results showed that all prepared thin films are polycrystalline and have a cubic structure. When the film is pure, it has several levels (220), (200), (111) at (2Ɵ=55.87, 38.96, 33.34) ° preferred orientation (111) of the cadmium oxide and found that all peaks are return to cadmium oxide and this is consistent with the findings of Azhar [7]. when the doping we notice the emergence of a new peak of cadmium oxide at 2Ɵ=66.6 and in the direction (311) with the survival of other peaks and the survival of the preferred direction (111) for cadmium oxide, we also notice a decrease in the intensity of the peaks with very little displacement towards the larger angles, When the rate of doping is increased to 3%, we observe a new peak at 2Ɵ=24.59° and in the direction of (110).
This is Return to Ga2O3 we also note a decrease in the intensity of the other intensity of peaks of cadmium oxide with preferred trend survival (111), and then Increasing the ratio of doping to 5% we note There was no change in the crystalline structure compared with the rate of doping at least and found that there is a slight change in the corners of the peaks of diffraction with the low intensity of all peaks and the survival of the preferred direction of cadmium oxide, and When the rate of doping is increased to7% we notice the emergence of a new peak of (Ga2O3) in direction (222) at 2Ɵ=40.6° with the remaining peaks of the other diffraction (CdO) and gallium oxide (Ga2O3) and the survival of the preferred direction (111) for cadmium oxide. The study showed a decrease in the height of the diffraction peaks of all the prepared thin films when the ratio of doping was increased and there was a very slight change in the angles of the diffraction towards the angles of the largest divergence and the doped did not change the preferred direction of cadmium oxide before and after the doping. This is consistent with the researcher Kesavan [8]. These results were compared with the standard cards (JCPDS) according to card number (6690-900-96). The decrease in the intensities of diffraction peaks after increasing the ratio of doping it is due to the saturation of new nuclei formed material grafting to become random materials on the surfaces of the films and cause high intensity diffraction peaks at the doping rates of less than 7% due to the tendency Crystallization to the formation of centers intend (formation nuclei) new because of the entry of atoms of material grafting into the crystal structure of the reticule resulting from a decrease in the energy barrier nuclei. [9] we account rate particleboard size of all films prepared using the Scherer equation [10].

D = (Kλ/wcosθ)                                                         

When: W= (FWHM (Full Width Half Maximum, D= is the mean size of the ordered (crystalline) domains, K= (Shape factor) = 0.94, Θ= Bragg angle
It is found that the grain size of CdO is reduced when the increases doped by gallium oxide and In this way, it is likely that nanoparticles are present in the preparation of the prepared films, the doping has replaced the Cd atoms, replaced with Ga atoms and merged into the crystalline structure of the film and result reduced on grain size. Table 1 show increases the width of the curve at the middle of the great end (FWHM) when increasing the doping rates. This indicates that the composition is in the direction of nano and this is consistent with the researcher Deokate and his group [11].

Atomic Force Microscopic
Fig. 2 shows three-dimensional images of the Atomic Force Microscope (AFM) showing the surface topography of CdO pure and doped Ga2O3 thin films was deposited on glass substrate, with different ratios (1, 3, 5, 7) % prepared by chemical spry pyrolysis method (300°C) The graph of the distribution of granular aggregates formed on the surface of the films (CdO, CdO: Ga2O3) Which has been deposited. It was found that the average dimeter of the distribution of granular aggregates on the surface of the CdO (105.42 nm) was determined by analytical images that the roughness average was equal to (3.32 nm) for the cadmium oxide film and RMS for cadmium oxide (3.97nm), which represents the square of surface elevations and decreases divided by the total number of their numbers and increasing this value increases the average roughness of the film and vice versa [12]. Table 2 shows the parameters of the atomic force microscope of average dimeter, roughness and root mean square. The table shows that the average dimeter of the (CdO, CdO:Ga2O3, decreases when the gallium doping increasing about (69.07 nm), At the highest rate doping of 7% due to the development of crystalline grains of grain perpendicular to the surface and this is consistent with researcher Yahia [13]. This is evidenced by the increase in crystalline growth due to the increase in the concentration of gallium oxide in the solution and the decrease in the ratio of cadmium oxide where the images show that the atoms of the film have been distributed on all parts of the surface so this membrane is topographically regular. Also, the root mean square of the (CdO: Ga2O3) thin films was decreases when the gallium doping incentives compared to the cadmium oxide pure film to reach (1.05 nm). This is consistent with Ramiz [14]. The table shows that there is a decrease in the average roughness surface of (CdO:Ga2O3)film compared with CdO pure to reach (0.901 nm) at the highest rate of concentration indicating that the deposited atoms on the surface of the membrane have crystallized Nanoparticles [15].
Optical properties
We studied the optical properties of the thin films prepared by measuring the absorbance spectroscopy as a function of the wavelength of the photons falling in the confined area between (300-1100) nm. The optical power gap (Eg), Transmittance (T), absorbance (A) and absorption coefficient Α). The Transmittance (T) of films (CdO, CdO:Ga2O3) was calculated using the following relationship [16].

T = IT / Io                                                                       

IT: Radiation intensity passing, Io: Radiation intensity on the surface.
The relation between the Transmittance (T) and the wavelength (λ) was plotted as in Fig. 3. It was observed that the Transmittance of the pure cadmium oxide (35.45%) and transmittance increases when the gallium doping increasing to 84.4% at the highest doping rate (7%), this is consistent with the researcher [7, 11]. The difference in transmittance values may be due to the thickness factor, The transmittance is inversely proportional to the thickness of the films, since the higher thickness allows greater chance for different optical absorption processes in the film and thus attenuation of a larger part of the beam falling on the film, as well as the presence of surface defects and the high roughness of the surface cause increased dispersion of falling radiation [17]. The optical absorption coefficient (α) of the pure CdO and the CdO: Ga2O3 thin films were measured with different concentrations [16].
It was found to be more valuable than (104 cm-1) and thus the films have a direct energy gap. The correlation between the absorption coefficients was drawn of cm-1 (α) as a function of the wavelength as shown in Fig. 4 Within the restricted spectral range (300 - 1100) nm is observed from the figure the absorption coefficient decreases when the gallium doping increasing, the optical absorption edge is oriented towards the wavelengths while the wavelength gain is observed within the range of (300-1100) nm. This is due to the increase of spectral transmittance within this spectral range and the absorption coefficient is reduced at the high wavelengths of almost all the films, That mean the probability of electronic transitions is low within this spectral region But its value is Increased at the edge of absorption and depends on the composition of the film and its components and this is consistent with researcher Kumaravel [18, 19].
The optical energy gap was determined by drawing the photonic relationship between the photon energy (hυ) and (αhυ) 2. Fig. 5 shows the optical energy gap values of pure CdO and CdO:Ga2O3 with a with different ratios 1, 3, 5, 7 %, It was found that the values of the energy gap that increases with the increase in gallium oxide concentration.
This is consistent with the previous study [11, 20] where the value of Eg equals (2.3 eV) for pure cadmium oxide thin films and the value of (Eg) equals 4 eV for CdO: Ga2O3 thin films at the highest ratio concentration (7%). This is due to increased material crystallization and reduction of defects, thus reducing the local levels near the edge of the valance and conduction band, which led to an increase in the energy gap, and thus we conclude that the optical energy gap can be controlled by controlling the added impurities.
Fig. 6 shows the relationship between the optical energy gap and the grain size of the pure cadmium oxide and doped with the gallium oxide thin films, where the optical energy gap is found to increase when the grain size decrease of the prepared thin films.

sensitivity measurements
This section includes an analytical presentation of allergy characteristics including measures of sensitivity change with doped rates as well as temperature, response time and  recovery time for pure cadmium oxide doped with gallium oxide thin films in percentages (1,7)%, prepared by chemical spray pyrolysis technique and deposited on silicon substrate (CdO, CdO:Ga2O3/ Si). ). Fig. 7 shows the change in resistance as a function of time at temperatures of (100, 200 and 300) °C for pure CdO and CdO: Ga2O3 thin films with adopting rate of (1.7%) using to nitrogen dioxide gas (NO2) with concentration ratio of 3%.
The resistance of the CdO and CdO: Ga2O3 thin films increased when the film was exposed to gas and after the resistance returned to the first level before the NO2 reaction. This was the result of NO2 reaction with the surface of CdO [21]. As well as the result of the integration of gallium atoms in the CdO film, which give the levels of scalable and thus snaps electrons from the conduction band and the interaction of NO2 gas with the sensor gets oxidized and thus increase the resistance of the film because NO2 gas snake’s electrons from oxygen O2- As follows [22]:

NO2 (gas) + e- → NO2- (ads)                                     

NO2(ads) + O- (ads) + 2e- → NO (gas) + 2O2- (ads)            

Sensitivity values were calculated according to the following equation [23]:

S = |( Rg - Ra ) / Ra| × 100%                                           

Rg: The electrical resistance of sensing film with the gas.
Ra: The electrical resistance of the film to the sensor in the air.
Fig. 8 shows the sensitivity change as a function of the doping rates for pure CdO and CdO:Ga2O3thin films at a rate of (1.7)% at (100,200,300) ° C, It was found that the sensitivity of the pure films at the temperature of 100°C is (12.5%) and that this value increases with increasing the temperature up to (22.2%) at the temperature of 200°C and when the temperature increase to 300°C, The sensitivity of the surface of the metal oxide is increased due to the interaction between the oxygen and the surface. In the case of vaccination with the lowest ratio of 1%, it is found that the sensitivity is greater than in the pure membranes. At the temperature of C100, the sensitivity value is 13.3% , When the temperature increases, the sensitivity increases to 27.3% at C200 and increases when the temperature rises to reach the highest sensitivity value of membranes prepared on silicone bases (40%) at C300 ° C and the reason for increased susceptibility to vaccination with this behavior can be explained by the fact that vaccination in general gives a larger surface area of the grafted membranes and more porous ,As well as different interaction between gas and the vaccination particles , So all these processes increase the interaction of gas with the oxide, which increases the value of sensitivity and this is consistent with what the researcher found Shaath [24], and when the vaccination rate is increased to 7%, we note that the sensitivity values are lower than those in the membranes with 1% pure membranes and also decrease in temperature. The reason may be due to the inclusion of this sample on a large amount of impurities so we note the lack of stability, The reason may be that the surface will not be able to oxidize the gas too intensely and NO2 may be burned before reaching the surface of the membrane and thus the sensitivity decreases with increasing temperature [25].
We also calculated response time and latency according to the following equations [26]:

Response time = (tgas(on) – tgas(off)) × 0.9   (6)

Recovery time = (tgas(off) – tgas(recovery)) × 0.9   (7)

Figs. 9 and 10 shows the relationship between response time and recovery time as a function of the vaccination rates at temperatures of (100, 200, 300) C ° For pure CdO membranes and gallium oxide CdO: Ga2O3 with percentages of inoculation% (1,7) and the precipitation on the silicon bases the direction of NO2 gas by 3%. Its shown that The response time and recovery time were reduced by 1% with vaccination and increased by 7% for all membranes, The best sensitivity was obtained at 40% at the response time (s12) and the retrieval time (45s) at 300 ° C, and that this rapid response of the sensor may be due to the small particle size, which leads to the large granular boundaries where the interaction occurs between gas and oxygen absorption and thus occur rapid oxidation of gas [27]. 

CONCLUSION
The X-ray diffraction results showed that the pure cadmium oxide atoms were vaccination with gallium oxide that Prepared, all of which have a polycrystalline and cube-type structure, and the vaccination has led to the emergence of new peaks of calcium oxide, as well as reduced granular size. The results of AFM images showed that granular particle size decreased when calcium oxide was used for all vaccination rates as well as surface roughness. The study of optical properties showed that the thin Cdo: Ga2O3 membranes have a straight gradient energy gap whose values vary between 2.3-4 eV depending on the vaccine. The optical energy gap can be controlled by vaccination. This is used to obtain better quality membranes for applications the operation. The permeability of membranes also increased when the vaccination rate increased. We found CdO membranes that vaccination with gallium oxide that deposition on silicon bases it has a greater sensitivity than the inorganic membranes That is, vaccination has improved the protective properties of CdO membranes Gallium oxide was not altered by the type of conductivity and remained n-type.

ACKNOWLEDGEMENTS
The thin film laboratory at the College of Science, University of Anbar.

CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.