Non-laminated growth of chlorine-doped zinc oxide films by atomic layer deposition at low temperatures

Abstract

ARTICLE This journal isChlorine doping in a ZnO matrix to a concentration of 0.65±0.05 at.% was accomplished via atomic layer deposition using a home-made chlorine source at a low deposition temperature of 140 o C. Structural and morphological properties were investigated using X-ray diffraction, field emission scanning electron microscopy, and grazing incidence wide-angle X-ray diffraction. The introduction of chlorine into the ZnO matrix resulted in significant grain growth reorientation due to chlorine doping in the oxygen sites of ZnO. Cl − ions preferentially occupied the substitutional O − ion site and O vacancies, and preferential growth in the {100} planes changing to {002} planes along the longitudinal direction of the hexagonal wurtzite structure as a function of Cl doping levels. This important phenomenon was explained by a passivation effect resulting from the chlorine doping mechanism, which was elucidated using transmission electron microscopy. The optical transmittance of undoped ZnO and ZnO:Cl films was approximately the same (88 %), but the optical band gap was increased by the introduction of the Cl dopant in ZnO due to a Burstein-Moss effect. The lowest resistivity of ZnO:Cl was 1.215×10 -2 Ω cm, and the corresponding carrier concentration and mobility were 5.715×10 19 cm -3 and 31.81 cm 2 V -1 s -1 . Finally, the calculated doping efficiency of chlorine in ZnO was as high as 10.8 % when compared with aluminum-doped ZnO, even though the deposition temperature was very low when applied to plastic substrates due to the non-laminated growth of ZnO:Cl films.

Halide‐Modulated Functionality of Wide Band Gap Zinc Oxide Semiconductor Nanoparticle

“…After surface modification with halide ions, halide dopants preferably filled the O related defects (such as oxygen vacancy or substitution of O 2− lattice ions) in the ZnO matrix which results of a reduction of O related surface defects. As the green emission is mainly contributed by deep level defect states, therefore a significant quenching of the visible emission is likely to happen when the halides are attached to the defect states . We found upon attachment of halide ions the defect state emission has been quenched significantly which is shown in Figure a.…”

Development of Inverted Organic Photovoltaics with Anion doped ZnO as an Electron Transporting Layer

“…Another peak in PL spectra shown in the region between 450 nm and 700 nm is giving information about surface defect such as oxygen vacancy and/or point defects of ZnO thin film [22,25,26,30,31]. It is already well known that surface oxygen vacancy of metal oxide film is quite important for the high electrical conductivity of the film.…”

“…Another optical characteristic like photoluminescence (PL) spectroscopy has been widely used to determine the optical band structure, and also PL spectra in the high wavelength represents the status of the surface structure kinds of surface defects of ZnO thin film [22,25,26,30,31]. In conventional PL spectra of ZnO thin film, one can detect two major peaks, one is strong emission peaks in the UV region of 380 nm 400 nm which is related to the property of optical band gap.…”

“…For improving the conductivity and mobility of ZnO thin film, n-type doping process with group III metallic cation elements such as Al [15,17,20,24], Ga [16,20], and In [17,20] is widely used and that substitute the zinc atoms in ZnO lattice [20,24]. Furthermore, it is also well known that group VII non-metallic anion elements doping such as F [18,29], Cl [19][20][21][22][23][24][25][26][27][28][29], Br [29], and I [29] can also improve the conductivity and mobility. These anion elements can substitute the oxygen atoms in ZnO lattice [20,24,28].…”

“…Generally, the oxygen atoms as vacancies can act as an electron-hole recombination sites in I-OPVs [10,30,31], and results in decrease the performance of I-OPV. Among the various methods to reducing the recombination sites of ZnO ETL, anion doping can be one of the ideal concepts, because the atonic radius of group VII anion is almost similar to the oxygen atom as well as their excess electrons can help to achieving the high mobility [23,26] and conductivity [21,24,26] while maintaining high optical transparency [20,21,23,27], compared to group III cation metallic elements. Above all, anion element doping into ZnO ETL has been conducted by various deposition techniques such as electrochemical deposition [19,21,22,24,25], atomic layer deposition [26], radio frequencymagnetron sputtering [29], metalorganic chemical vapor deposition (MOCVD) [20,28], and pulsed laser deposition [23,27].…”