Effect of UV Irradiation on the Growth of ZnO:Er Nanorods and Their Intrinsic Defects

Abstract

Nanorods of erbium-doped zinc oxide (ZnO:Er) were fabricated using a hydrothermal method. One batch was prepared with and another one without constant ultraviolet (UV) irradiation applied during the growth. The nanorods were free-standing (FS) as well as deposited onto a fused silica glass substrate (GS). The goal was to study the atomistic aspects influencing the charge transport of ZnO nanoparticles, especially considering the differences between the FS and GS samples. We focused on the excitons; the intrinsic defects, such as zinc interstitials, zinc vacancies, and related shallow donors; and the conduction electrons. UV irradiation was applied for the first time during the ZnO:Er nanorod growth. This led to almost total exciton and zinc vacancy luminescence reduction, and the number of shallow donors was strongly suppressed in the GS samples. The effect was much less pronounced in the FS rods. Moreover, the exciton emission remained unchanged there. At the same time, the Er3+ content was decreased in the FS particles grown under constant UV irradiation while Er3+ was not detected in the GS particles at all. These phenomena are explained.

X-ray assisted point defects creation in micron-size Zn, Mo oxide particles at liquid nitrogen temperature

“…In order to follow the trend with the increased Mo content, the doping level of Mo was increased to 30 %. The ZnO:Mo(30 %) sample, however, appeared to be not ZnO but the mix of complex molybdates as it was also reported in [27,28]. Even in this case the knowledge of charge trapping processes is important for bonding peculiarities understanding as they are critical for phase purity of the material and charge/energy transfer there.…”

“…(i) Ultrafast excitonic luminescence with the decay time of hundreds of ps as mentioned in the recent reports on the ZnO:Mo [6,18,19]. The maximum of the excitonic band appears at about 380 nm, however, it is changing depending on the type of nanostructure: in the free-standing nanorods/nanocolumns it is redshifted as compared to the deposited films of aligned nanorods [20]. (ii) Excitonic emission can be moderated by different treatments as reported in many works [8,[21][22][23].…”

“…They should originate from the Mo 5+ occupying different positions. Taking into account that according to XRD, the ZnO:Mo(30 %) is the mix of at least two material phases Zn3MoO9•H2O and Zn5Mo2O11•5H2O as reported in [28], the There is another group of signals appearing centered at the free electron g factor (corresponds to the resonance magnetic field 3342.5 G) and spreading almost symmetrically with respect to this data point covering the resonance magnetic field range from 3260 to 3425 G range (figure 2A). The character of the localization of these spectral features and the same reaction to the different microwave power led to conclusion that they should originate from d 5 shell.…”

Peculiarities Related to Er Doping of ZnO Nanorods Simultaneously Grown as Particles and Vertically Arranged Arrays

“…By analogy with PL, the CL spectra were composed of excitonic (3.25 eV in NRA and 3.19 eV in NRF) and red bands (1.91 eV in NRA and NRF). The difference in the spectral positions of the excitonic emission is typical for the hydrothermally grown ZnO nanorods …”

“…The difference in the spectral positions of the excitonic emission is typical for the hydrothermally grown ZnO nanorods. 52 According to the CL image obtained for the 3.25 eV emission, larger rods emit brighter. There must be nonradiative transitions on the surface of smaller rods, stronger than in the case of the larger ones, degrading the excitonic luminescence there.…”