Physical investigations on pulsed laser deposited nanocrystalline ZnO thin films

Abstract

The nanocrystalline ZnO thin films were deposited by pulsed laser deposition on quartz and i-Si (100) substrates at different substrate temperatures (473 K-873 K) and at different mixed partial pressures (0.05, 0.01, and 0.5 mbar) of Ar + O 2 . The structural studies from XRD spectra reveals that the films deposited at 0.05 mbar and at lower substrate temperatures were c-axis oriented with predominant (002) crystallographic orientation. At 873 K along with (002) orientation, additional crystallographic orientations were also observed in case of films deposited at 0.01 and 0.5 mbar pressures. The composition of Zinc and Oxygen in ZnO films from EDAX reveals that the films deposited at lower partial pressures were have high at.% of O 2 whereas higher partial pressures and substrate temperatures had high at.% Zn. The surface microstructure of the films show that the films deposited at lower partial pressures (0.05 mbar ) and at lower substrate temperatures (473 K) were found to have nanoparticles of size 15 nm where as films deposited at 873 K have nanorods. The length of these nanorods increases with increasing Ar + O 2 partial pressure to 0.5 mbar. The optical energy gap of the film deposited at lower partial pressure and substrate temperature was 3.3 eV and decrease with the increase of substrate temperatures. The films deposited at 0.5 mbar and at 873 K emitted an intense luminescence at a wavelength of 390 nm. The mea-K. Srinivasarao ( ) · K. Pandurangarao Post graduate department of Physics, P.G. Centre, P.B. Siddartha

Influence of the Zn plasma kinetics on the structural and optical properties of ZnO thin films grown by PLD

“…Intrinsic defects lead to stress in the material, which results in a less homogeneous lattice that can induce a reduction in crystallinity; at the same time, the intrinsic defects introduce localized states that modify E g values. In samples grown at energies between 60 and 100 eV, it is probable that an oxygen deficiency allowed the introduction of localized defect states, possibly related to Zn excesses like Zn i , which causes a band gap narrowing [18].…”

“…These energy conditions, along with directionality in the plasma, give to PLD advantages for deposition using background reactive gasses, since the reactions required to achieve the desired oxide stoichiometry are more effective [17]. The physical properties of ZnO thin films grown by PLD have been widely studied, regarding the influence of substrate [18][19][20][21] and annealing temperature [5,6,22], oxygen pressure [6,7,15,23], substrate type (quartz [24], silicon [25], diamond-like carbon [26], sapphire [9] or glass [27]) and targets [28]. Furthermore, experimental parameters, as well as the deposition techniques, have been optimized to achieve materials with high crystalline quality [29,30].…”

Sputtering pressure influenced structural, electrical and optical properties of RF magnetron sputtered MoO3 films

“…The films formed at low sputtering pressure of 2 Pa exhibit weak absorption bands at 985 cm −1 , 805 cm −1 , 663 cm −1 and 560 cm −1 . The absorption bands seen at 985 cm −1 are related to the stretching vibration mode of Mo=O [46,47], at 805 cm −1 are related to the stretching vibrations of Mo=O and at 663 cm −1 correspond to the…”

ZnO thin films grown at different plasma energies by the laser ablation of metallic Zn with a 532 nm wavelength

“…While emissions in the visible region are associated with defect carrier concentrations: donor (zinc interstitial Zn i and oxygen vacancies V O ) and acceptors (Zinc vacancies V Zn and oxygen interstitial O i ) [7]. However, intensities of photoluminescence emissions, are also related to other physical characteristics such as crystalline quality and microstructure [8]. On the other hand, the natural electrical conductivity in ZnO is n-type and is associated to a majority concentration of oxygen vacancies, V O , and zinc interstitials, Zn i [7].…”

“…Deposits at room temperature can present advantages as in the fabrication of films for flexible electronics applications [19]. The crystallinity of the ZnO thin films, obtained by plasma methods, such as PLD, are related to collisions of the species contained in the plasma (ions and particles) and it is usually tuned by the use of different oxygen work pressure [8,20,21]. The crystallinity of the deposited films can also be modified by the use of the different photon energies of the laser.…”