Photoluminescence and positron annihilation spectroscopic investigation on a H⁺irradiated ZnO single crystal

Abstract

Low temperature photoluminescence and room temperature positron annihilation spectroscopy have been employed to investigate the defects incorporated by 6 MeV H(+) ions in a hydrothermally grown ZnO single crystal. Prior to irradiation, the emission from donor bound excitons is at 3.378 eV (10 K). The irradiation creates an intense and narrow emission at 3.368 eV (10 K). The intensity of this peak is nearly four times that of the dominant near band edge peak of the pristine crystal. The characteristic features of the 3.368 eV emission indicate its origin as a 'hydrogen at oxygen vacancy' type defect. The positron annihilation lifetime measurement reveals a single component lifetime spectrum for both the unirradiated (164 ± 1 ps) and irradiated crystal (175 ± 1 ps). It reflects the fact that the positron lifetime and intensity of the new irradiation driven defect species are a little higher compared to those in the unirradiated crystal. However, the estimated defect concentration, even considering the high dynamic defect annihilation rate in ZnO, comes out to be ∼4 × 10(17) cm(-3) (using SRIM software). This is a very high defect concentration compared to the defect sensitivity of positron annihilation spectroscopy. A probable reason is the partial filling of the incorporated vacancies (positron traps), which in ZnO are zinc vacancies. The positron lifetime of ∼175 ps (in irradiated ZnO) is consistent with recent theoretical calculations for partially hydrogen-filled zinc vacancies in ZnO. Passivation of oxygen vacancies by hydrogen is also reflected in the photoluminescence results. A possible reason for such vacancy filling (at both Zn and O sites) due to irradiation has also been discussed.

Raman investigation of N‐implanted ZnO: Defects, disorder and recovery

“…Chen et al opined that 183 cm −1 Raman mode in disordered ZnO is due to deformed lattice. Lattice distortion due to native vacancies after N implantation is very much likely in ZnO . As a general trend, the area under this broad mode increases with implantation fluence.…”

Correlation between defect and magnetism of low energy Ar+9 implanted and un-implanted Zn0.95Mn0.05O thin films suitable for electronic application

“…This dynamic recovery of implantation generated defects or defect complexes, in ZnO based systems have been reported. 16,19 Actually this is the reason for the radiation hardness of ZnO and that is happening here also.…”

“…The estimated band gap of ZnO film is 3.25 eV which is less than the reported value 3.37eV. [19][20] The shift in band edge to the lower energy side has been observed for Zn 0.95 Mn 0.05 O films 21 and shown in figure 5. The estimated band gap of Zn 0.95 Mn 0.05 O film is 3.06eV.…”

“…The estimated band gap of ZnO film is 3.25 eV which is less than the reported value 3.37eV. [19][20] The shift in band edge to the lower energy side has been observed for been observed in case of bulk system 6 as well as thin films. 13 It was attributed to the periodic variations in potential within the grain due to trapping of impurities with doping.…”

“…Generally ion implantation generates different types of vacancy/vacancy clusters such as V O , V Zn , Zn antisite (Zn O ), Oxygen antisite (O Zn ) in the system. 16,19 It was reported that presence of vacancy or vacancy clusters in disordered ZnO affects the optical absorption process in two separate ways, close to the band edge. 26 films.…”