Study the Influence of Antimony Dopant and Annealing on Structural, Optical and Hall Parameters of AgInSe2 Thin Film

Sb-dopedAgInSe2 (AIS: 3%Sb)thin films were synthesized by thermal evaporation with a vacuum of 7*10 -6 torr on glass with (400+20) nm thickness. X-ray diffraction was used to show that Sb atoms were successfully incorporated into the AgInSe2 lattice. Then the thin films are annealed in air at 573 K. XRD shows that thin films AIS pure, AIS: 3%Sb and annealing at 573 K are polycrystalline with tetragonal structure with preferential orientation (112).raise the crystallinity degree. The Absorption spectra revealed that the average Absorption was more than 60% at the wavelength range of 400–700 nm. UV/Visible measure shows the lowering in energy gap to 1.4 eV forAIS: 3%Sb at 573 Kt his energy gap making these samples suitable for photovoltaic application, The electric property was better when AgInSe2: 3%Sb at 573 K , thin films were of donor type and the concentration of electrons in them increased with increasing Sb doped and annealing temperature.


Introduction
The chalcopyrite thin films likeAgInSe2 which have tetragonal crystallizes and is a crystal structure for AIBIIIC2VI where (A= Ag, Cu, B= Ga, Al, In and C= Se, S, Te). These compounds are analogs to binary zinc blend II-VI. Silver-based chalcopyrite semiconductor has as better candidates for solar cell fabrication [1]. Ternary Silver Indium Diselenide (AIS)is a typical ntype semiconductor [2,3] that possesses direct gap energy [4] lies between 0.8 and 2.0 eV [5] high optical absorption (_10 −5 cm −1 ), (AgInSe2) is the best-promised absorber materials for photovoltaic cell [6]. In many works doping AIS with different elements such as boron (B)doping on AgInSe2 by ion implantation and heat-treatment technique desired behaviors for photoconductive of the B-AgInSe2 thin film when 473K [7]. The influence of germanium(Ge) doping on the AgInSe2 thin film properties has been studied with good optical transmittance spectra and the conductivity from type [2]. The electrical conductivity enhancements about IHJPAS. 5 3 (3)2022 17 three orders by doping Tin (Sn) in the Ag sites in n-type, the increased conductivity for the films shows the Sn in AgInSe2 film as better applicants for fabrication of p−n junction in PV [8]. Found that the effects of Zinc (Zn) doping in AgInSe2 the Fermi level tend to shift toward the conduction band when Zn is a substitute for the Ag and forms the active donor defects, increasing the carrier concentration ND and decreasing the lattice thermal conductivity by modifying the crystal structure [9]. Several techniques used to fabrication AIS, such as spray pyrolysis technique [10,11], reactive evaporation [8],pulsed electrodeposition technique [12]. co-evaporation [13], sol-gel spincoating technique [14]. hybrid sputtering/evaporation process [15]. DC magnetron sputtering [16], chemical bath deposition [17]. hot-press method [18]. thermal evaporation with different ion uences [19]. thermal evaporation with annealing [20].electrodeposition process [21].Bridgman technique [22]. Simple Chemical Method [23]. the crystal structure of AIS is tetragonal structure chalcopyrite with the lattice constant a =b= 6.102 A° and c = 11.69 A° [11]. AgInSe2 blended organic-inorganic solar cells were fabricated and obtained was efficiency of 0.2% [24] Doping ofAntimony (Sb) in AIS occupies the cation (Ag or In) site, rather than the anion (Se) site since the relative electronegativity of Sb (2.05) compared to those of Ag (1.93) or In (1.78) or Se (2.55), the ionic radii is a major factor uses for choosing applicable contribution materials [23]. Structural, optical and electrical properties of AIS film could be controlled for example the ionic radius of Antimony is close to the ionic radius of Ag, In and Se ions. Sbis suitable dopant for AIS because theSb ionic radii (0.9 Å ) while Ag +1 (1.29Å) , In +3 (0.94Å), Se -4 (0.56Å) [25,26]. This study aims to concentrate on the effect of (Sb) doped on the optical structural properties and all Effects of AgInSe2 film and the interconnection between these parameters.

Experimental
From highly purity (99.99%) of Silver (Ag) Indium (In) and Diselenide (Se) elements with stoichiometric proportions (1:1:2) to prepare: 3%Sb thin films, these elements were put in a quartz tube with a vacuum (4.5×10 -4 mbar), these three elements heated up to (1100K)was higher than the melting temperature of AgInSe2 (1050 K) [19]. In an electric furnace for six hours in the end the alloy is left to cool to room temperature.AIS: 3%Sb thin films(pure and doped at 573K) were deposited by the thermal evaporation method(6×10 -6 torr) on glass substrates with 400 nm thickness.3%Sbdoping methods were carried out by using the thermal diffusion at 473 K in an electric furnace for 60 minutes. X-ray diffraction has been used to study the structure of these films by detailed 2Ө from 20° to 80 °with intervals of 0.05°, Scherer's Formula was used to calculate the crystalline size of the films [27,28]: where 0.9 is the shape factor and B(FWHM). is the width of the diffraction peak at half maximum intensity.
The optical interferometer method was used to determine the thickness of AgInSe2: 3%Sb samples. Optical properties of thin film preparation, transmission and absorption spectrums in the range between (400 to 1000) nm have been noted, and lambert law and Tauc equation have been used to determine the absorption coefficientsαand the energy gap (Eg opt ) respectively from the absorption spectrum [27,29]: where D is a constant depending on the temperature and the properties of the valence & conduction bands and α: the absorption coefficient, h the incident photon energy,r: is a parameter for the type of the optical transition. A: absorbance, t: thickness.
Optical Constants such as k: extinction coefficient, n refractive index, real part εr& imaginary part εi of dielectric constant can be considered by the relations below: [30,31,32]: The Hall Effectresults showed the type of thin film of AgInSe2: 3%Sb has been calculated by the relations below [31]: When The Hall coefficient (RH), electric current (Ix) and Hall voltage (VH), magnetic field (Bz).  Table (1) show our study, the comparison with the ICDD 00-038-0952 card standard value very good matched, the degree of crystalline increasing when AgInSe2: 3%Sb dopant and annealing at 573 K.Peak main intensity of (112) was increased with the addition of 3%Sbcomparison with that for AgInSe2 and shifts approximately 3° to lower 2θ angle in comparison with that for AgInSe2 because that the Sb atomic "radius" (0.9 Å)smaller than that for In (0.94 Å) and Ag (1.29Å). The increase of intensity refers to include of Sb atom in the progress to the growth of crystallinity. No diffraction peak related to Sb was observed from the XRD patterns. It was illustrated that Sb ion replaces or enters the interstitials of AIS as shown in the same Table. The FWHM decreases with Sb content added so subsequently the crystallite size is increased as calculated by equation (1). The effect of annealing at 573 K& 1h is similar to that of as-deposited thin films. However, annealed thin films show higher crystalline quality compared to as-deposited thin films this may be attributed to the nucleation formation.   Table (2) show the optical properties and the effect of 3% (Sb)and annealing 573K on transmittance and absorbance spectra of thin AIS films in the range 400-1000 nm. It is observed that the absorbance of all thin films increases with decreasing the wavelength. This may be due to decreasing the corresponding transmittance with decreasing the wavelength. The type and value of optical energy gap (Eg opt ) for AIS, 3% (Sb)and annealing at 573K thin films are determined using Tauce Equation (2), the allowed direct transitions occur in a thin film. This result agrees with R. Panda et. al. [19]. The absorption coefficients (α) which were of order 10 4 in these films were calculated from the absorbance spectra. It is obvious from Figure (3) that the energy gap decreased to 1.4(eV) which has significant for optoelectronic device applications. This behavior may be attributed to the advance in the film's crystallite size. The calculated energy gaps are listed in Table (2). The value of the refractive index (n), the extinction coefficient (k) and the real and imaginary parts of the dielectric constant (εr, εi) for AIS thin film are calculated from equations (3)(4)(5)(6)(7). The calculated values of optical constant at the wavelength (λ) equal to 500nm are listed in Table (2). The refractive index n is a significant parameter for optical material and application. The values of n decrease with doping 3% (Sb)and annealing temperature (in the visible region) due to a decrease in the corresponding reflection and attributed to an increase in the carrier concentrations in AIS thin film, this result agrees with Suresh Pal1et. al. [32].The extinction coefficient increases as seen in Table (2) takes the same behavior as the absorption coefficient because the extinction coefficient is directly related to the absorption of the light as in equation (4). The fundamental electron excitation spectrum of the film was termed using the frequency dependency of the complex dielectric constant. The real (εr) and imaginary (εi) parts of the dielectric constant are related to the n and k values and the value of εr and εi at λ=500nm

IHJPAS. 5 3 (3)2022
20 decreases because the behavior of εr is similar to that of the n equation (6), while the behavior of εi is similar to that of k because it mainly depends on the k value equation (7). The effect of doping3% (Sb) and annealing on the value of εi were smaller than that of the pure thin film, which indicates a small dielectric loss.

IHJPAS. 5 3 (3)2022
22 The type concentration of the charge carrier, resistivity and Hall mobility for pure, 3%Sb doped and AgInSe2: 3%Sb doped after annealing to T=573 K thin films have been estimated from Hall effect measurements, the calculated values are shown in Table (3). From  this Table, one can be noticed that the value of the Hall coefficient for all examined AgInSe2 and 3%Sb doped thin films are negative which means that all the prepared samples exhibit ntype conductivity, i.e. the conduction is dominated by electrons. This is due to the donor centers formed during the deposition. This result agrees with previous investigations [2,3].
Moreover, it is seen that the carrier concentration increases with increasing annealing temperature due to an increase in the film grain size which leads to a decrease in the density of grain boundaries and thus reduces the electron trapping probability. As a result, the number of collisions between carriers will increase, which leads to a decrease in their mobility with increasing the annealing temperature.

4.Conclusions
Pure tetragonal AgInSe2: 3%Sb doped and AgInSe2: 3%Sb doped after annealing to T=573 K films were well synthesized by a thermal evaporation method. The grown AIS thin films were then doped with Sb at temperature 473 K by a thermal diffusion process. After doping, the crystallinity of the thin film was improved. Our findings show that the polycrystalline of tetragonal with (112) orientation crystal structure AgInSe2thin film from XRD. The grain size rose from XRD with 3%Sb doping. From the optical studies the3%Sb doping into AgInSe2 promoted a decreased band gap in comparison with the undoped AgInSe2chalcopyrite, the absorption coefficients increasing. The ability to improve the growth and quality of the grains structure, the Hall effect shows the conductivity type of the grown films remained n-type and the enhancement in the optical properties highlights 3%Sb doped AgInSe2 to be applied as an absorber layer in films making these films suitable for photovoltaic application.