Effect of the Annealing Gas and RF Power Sputtering in the Electrical, Structural and Optical Properties of ITO Thin Films

Abstract

In the paper we propose to investigate the effect of the annealing gas and RF power sputtering on the electrical, structural and optical properties of indium tin oxide thin films for solar cells applications. These thin films were prepared on lightly doped silicon wafer by RF sputtering in Ar environment at room temperature and with a pressure of 8•10-3 mbar. Process parameters such as RF power and post deposition annealing were varied in order to determine their dependence on electrical, structural and optical properties of ITO thin films. Layer morphology and thickness measurements (with cross section) were investigated by scanning electron microscopy, and atomic force microscopy was performed to determine the surface roughness. The dependence of the resistivity, mobility and carrier concentration of these films by varying RF power and thermal annealing were studied by Hall Effect measurement. Spectroscopic ellipsometry was also used to determine the refractive index, thickness, roughness, porosity and optical bandgap of the films. Thus, the optical transmittance in the visible region was found to be above 85 %, the low resistivity and high mobility were found 2.09 10-4 Ω•сm and 35.81 cm 2 /(V•s), respectively, for 200 nm thickness for the sample elaborated with a RF power of 150 W and an annealing at 400 °C for 10 min with rapid thermal annealing under N2. The X-ray diffraction patterns of the thin films indicated a preferred orientation along the (222) plane, which provides a high degree of crystallinity for all N2 annealed samples. The XPS was used to determine oxidation states and identify the elemental content in the films. Obtained results for the surface morphology, electrical and optical properties of the ITO thin film details will be presented.

Properties of ITO thin films rapid thermally annealed in different exposures of nitrogen gas

“…The grain size decrease for exposed RTA sample suggests that the sample experienced a substantial interaction with nitrogen annealing ambient, limiting the sample's reaction with residual air [25], and hence reduced its grains size. A similar decrease in grain size and surface roughness is reported for ITO thin films annealed in a nitrogen gas [28]. On the other hand, the grain size increase with the un-exposed RTA sample is related to the crystallization of this sample in a limited nitrogen gas atmosphere as pointed earlier in XRD analysis.…”

Electrical and optical enhancement of ITO/Mo bilayer thin films via laser annealing

“…Furthermore, enhancing electrical and optical performance at the same time is a critical research topic that has many challenges. Generally, the physical properties of TC materials are essentially affected by many factors, such as the type of substrate [15], the deposition technique [16][17][18], the deposition conditions [19][20][21][22], and the annealing treatment [23]. Among these factors, heat treatment is a significant factor in rearranging the nanostructure, removing defects, and improving the thin film's quality [9].…”

Spectroscopic Ellipsometry Characterization of As-Deposited and Annealed Non-Stoichiometric Indium Zinc Tin Oxide Thin Film

“…Refractive index and extinction coefficient of ITO were intensively studied in the past, including spectroscopic ellipsometry as a tool for the determination of these two physical quantities (e.g., References [ 7 , 8 , 9 , 10 ]). Different model dielectric functions were used for evaluation of data from spectroscopic ellipsometry, including Drude oscillator [ 7 , 8 , 10 ], single oscillator [ 7 ], a combination of Lorentz-type oscillators [ 8 ], and a new amorphous model [ 9 ].…”

“…Refractive index and extinction coefficient of ITO were intensively studied in the past, including spectroscopic ellipsometry as a tool for the determination of these two physical quantities (e.g., References [7][8][9][10]). Different model dielectric functions were used for evaluation of data from spectroscopic ellipsometry, including Drude oscillator [7,8,10], single oscillator [7], a combination of Lorentz-type oscillators [8], and a new amorphous model [9]. Indium-saving oxide, i.e., indium zinc tin oxide (IZTO), thin films have been investigated as possible electrodes for optoelectronic devices, owing to their high optical transparency, low electrical resistivity, and high work function value (e.g., References [11][12][13][14][15]).…”