Optical, structural and electrical characterization of pure ZnO films grown on p-type Si substrates by radiofrequency magnetron sputtering in different atmospheres

Abstract

ZnO films were grown on p-type Si substrates by radio-frequency magnetron sputtering of ZnO target in pure argon or mixed argon-oxygen plasma and were investigated using atomic force microscopy, spectroscopic ellipsometry, Fourier-transformed infrared spectroscopy and electrical methods. It was observed that the films grown in argon plasma had large surface roughness which increases with the rise of deposition time. The lateral size of ZnO columns showed similar dependence on deposition parameters as the roughness. Contrary to this, the films produced in argon-oxygen plasma were found to be smoother and denser having thinner ZnO columns. These films also demonstrated an abrupt absorption band-gap edge that is the evidence of better crystalline quality of these films (the lower number of native point and elongated defects). Plasmon-phonon interaction in ZnO films as well as the effect of the plasmon system of Si substrate on this interaction was considered. The theoretical approach used for the fitting of specular infrared reflection spectra allowed determining concentration and mobility of free carriers as well as conductivity of ZnO films. It was found that the films grown in pure argon plasma demonstrated a higher concentration and a smaller mobility of free carriers in the comparison with the corresponding parameters of the films grown in argon-oxygen mixed plasma. The direct resistivity measurements show the essentially higher values compared with the values estimated from IR reflection spectra. The possible reasons of this difference are discussed. The utility of infrared reflection spectroscopy for the non-destructive analysis of electro-physical properties of polycrystalline films was shown.

Spectroscopic characterization of phase transformation in Ge-rich Al2O3 films grown by magnetron co-sputtering

“…The simulation of the IRR spectra allows the estimation of the free carrier concentration (n 0 ), the mobility (l) and the film conductivity (r). As an example, the simulation of the spectrum for [Ge] = 20% was performed using the approach developed in [15,16] and the self-consistent parameters for SiO 2 , Al 2 O 3 and Ge, taking the electron effective mass value of 0.16m e . A good agreement was achieved between the experimental and simulated spectra (Fig.…”

Influence of Terbium Doping and Annealing on the Structural and Optical Characteristics of Sputtered Zinc Oxide Thin Films

“…The optical properties of the films were studied using spectroscopic ellipsometry. The experimental spectra were analyzed within the two-layer model, with the upper (near the surface) inhomogeneous rough layer, and the bottom (adjacent to the Si substrate) homogeneous layer [27]. The upper layer was simulated within Bruggeman's model of effective medium, as a mixture of void space and ZnO, with parameters like those of a bottom layer.…”

“…RF magnetron sputtering is also one of the most useful techniques for the fabrication of ZnO thin films with various dopants [21,25]. The diverse content of RE ions can be incorporated easily in a ZnO film, and its structural properties can be controlled by changing the sputtering conditions [26,27]. Specifically, it has been found that, through the varying of the nature of the gases used in the deposition process, the concentration of native point defects can be changed, and both the defect-related emission and the electrical conductivity of the film can be tuned [27,28].…”

“…The diverse content of RE ions can be incorporated easily in a ZnO film, and its structural properties can be controlled by changing the sputtering conditions [26,27]. Specifically, it has been found that, through the varying of the nature of the gases used in the deposition process, the concentration of native point defects can be changed, and both the defect-related emission and the electrical conductivity of the film can be tuned [27,28]. Therefore, it can be expected that the growth ambient can also affect the Tb 3+ emission intensity in ZnO films.…”

Effect of temperature on morphologies and optical study of ZnO thin films deposited by aerosol assisted chemical vapor deposition technique

“…Various deposition techniques for the deposition of ZnO films have been reported in the literature. Methods such as sol-gel [19], nanocluster-beam deposition [20], chemical bath deposition [21], plasma-assisted metal-organic chemical vapor deposition [22], RF-magnetron sputtering [23], successive ionic layer and adsorption reaction [24], spray pyrolysis [25], metal-organic chemical vapor deposition [3], AACVD [26,27] etc have been utilized.…”