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

Abstract

Understanding defects, disorder and doping due to N implantation in ZnO is one of the most debated issues for the last few years. In the present work, a comprehensive investigation has been carried out using Raman, photoluminescence (PL) spectroscopy and grazing‐incidence X‐ray diffraction on 50 keV N ions implanted granular ZnO with different fluence (approximately up to 6.5% atomic concentration) along with postimplantation annealing. Raman investigation suggests that 275, 510, 643, and 857 cm−1 modes are directly related to nitrogen. Additionally, VZn may have some role in stabilizing 275 cm−1 mode. The broadening (or tailing) of E2low mode is related to vibration of distorted Zn sublattice, which may be a product of ion implantation generated defect cluster like VZn–VO. The distortion starts to reduce with annealing at elevated temperatures. Direct correlation between 555 cm−1 Raman mode and the tailing of E2low mode has been found. More defect clustering is vivid from the reduced PL of the ZnO samples with increasing implantation fluence. So, tailing of E2low Raman mode, increasing intensity of 555 cm−1 mode and nonradiative defect centers are of common origin. Both the ratios E1(2LO)/E1(LO) and E2high/E1(LO) can be used as parameters to measure the defective nature of ZnO after ion implantation/irradiation. Low temperature PL (selected samples) suggests absence of shallow acceptor states, although negative thermal quenching above 175 K has been observed (implantation fluence 1 × 1016 ions/cm2 and annealed at 500°C) which can be a signature of deep acceptors.

In situ backside Raman spectroscopy of zinc oxide nanorods in an atmospheric‐pressure dielectric barrier discharge plasma

“…This roughening most likely caused the symmetry loss at the surface and gave rise to the SO phonon mode. This process induced stress in the lattice due to the creation of interfacial defects in agreement with the results of Mondal et al [41] SO phonon mode, E 2 low , and the E 2 low asymmetric tail were continuously and simultaneously increased over the complete 600-s plasma treatment, showing their direct correlation. After the plasma was turned off, these changes slowly decreased.…”

“…[37] Interestingly, the surface optical (SO) phonon mode (located at 555 cm À1 ) related to defects such as disorderly arranged areas and grain boundaries was observed in the spectra. [34,41,42] Additionally, the positions of the E 2 low and E 2 high are redshifted and broadened (Table S1), indicating a defect-rich structure of the deposited ZnO-NRs. [25] During the plasma treatment using Ar/H 2 O, new narrow peaks appeared at 594, 797, 848, 951, and 1092 cm À1 immediately after the plasma was turned on: the five narrow peaks displayed a high intensity during an additional measurement (not shown here) in which the power of the Raman laser was reduced to zero while focusing on a gap of the net.…”

Raman and Photoluminescence Study of Al,N‐Codoped ZnO Films Deposited at Oxygen‐Rich Conditions by Magnetron Sputtering

“…Some authors assign this mode to native defects such as interstitial zinc or their clusters, others claim that the mode is related to N atoms, mostly Zn i –N O complex defects, and in ref. it is mentioned that this mode is mainly affected by vacancies (presumably V Zn ) in the vicinity of N O sites in ZnO. Furthermore, for nitrogen‐doped ZnO films in the work, this mode also appears and, as in the present study, its intensity linearly correlates with the nitrogen concentration.…”

Fabrication of ZnO Ceramics with Defects by Spark Plasma Sintering Method and Investigations of Their Photoelectrochemical Properties

“…Especially at 1100 • C, the two peaks are strongest in the ZnO(C)-3. The 80~250 cm −1 broad peak (the thick light blue dotted line in Figure 5A) was due to the effect of interstitial zinc (Zn i ) [54,55]. However, the Raman spectrum of ceramics obtained at 700 • C has this peak, which indicates that interstitial zinc (Zn i ) appear in ZnO(C)-1 for the DC pulse current [31], but the concentration of interstitial defects is very low, not the main defects.…”