Electrical and optical properties of point defects in ZnO thin films

Abstract

We show that the deposition of ZnO films under varying oxygen partial pressure and annealing conditions allows for the controllable formation of specific defects. Using x-ray diffraction and photoluminescence, we characterize the defects formed and show that these defects are responsible for changes in film carrier density, carrier type, sheet resistivity and mobility.

Magnetoelectrical properties of W doped ZnO thin films

“…The origin of the NMR could be due to the Anderson-localization [35], carrier concentration change due to energy level splitting in a band [36], mobility change due to energy level variation [36], variable hopping-length hopping probability change [37,38], etc. The observed results assign the point defects, which were proven for pure ZnO thin films in the previous study [39]. In addition to Zn and O dependent point defects, W dependent defects, interstitial W atoms (W_ I ) and substituted W atoms (W Zn ) in W þ 6 , W þ 5 and W þ 4 ionic states, cannot be excluded for W doped ZnO thin films.…”

The effects of postdeposition annealing conditions on structure and created defects in Zn0.90Co0.10O thin films deposited on Si(100) substrate

“…During the depositions, the sample holder temperature was kept at 420 6 1°C. This specific gas concentration was the optimal condition of pure ZnO growth in our earlier work, 26 where we varied the partial pressures from 0:100 to 50:50 percent. Furthermore, this concentration is optimal to eliminate the formation of metallic Zn clusters and obtain large grain sizes with the preferred orientations.…”

“…[18][19][20][21][22] Coey et al 22 emphasized the magnetic formation without magnetic ions in both d 0 systems and other oxides with crystal defects.The point defects also determine the electrical and optical properties of ZnO thin films. [23][24][25][26][27][28] Furthermore, the point defect density of ZnO is studied for the optical performance, 29 photoelectrode application for the solar cells, 30 carrier relaxation dynamics, 31 gas sensing, 32 and fluorescent properties for biomedical applications. 33 The defects are seen as the main control mechanism of physical properties of ZnO.…”

“…39 The annealing temperature and deposition/postdeposition atmosphere are seen as the main parameters to form and control the point defects in the lattice. 23,26,28,40 There have been quite a few systematic analyses on defect formation and relation of these defects with dopant atoms, such as transition metals or nonmagnetic elements, in the lattice. In addition to the effects of transition metals substitution for host anion atoms in lattice, the point defects are also effective on the physical properties, such as ferromagnetic behavior, 41,42 optical transitions, [25][26][27] and electrical properties 26 due to the formation of shallow energy levels.…”

Photocatalytic H2 generation from aqueous ammonia solution using ZnO photocatalysts prepared by different methods

“…Combination of Zn vacancy (V Zn ) (deep acceptor level) with Zn interstitial (Zn i ) (shallow donor level), which also has transition energy in green spectral range, is less probable because these defects would be accompanied also by emission in the blue range (400e450 nm), which is missing in the ZnO(1) spectrum. Red to orange luminescence of samples ZnO(2) and ZnO (3) is probably caused by oxygen vacancy (V O ), which forms very deep donor levels [43]. Oxygen vacancies are more probable on the particle surface and grain boundaries [25,44], that is why higher concentration of these defects in samples ZnO(2) and ZnO(3) with smaller particle size and higher specific surface area was observed.…”