Defect generation and recovery in polycrystalline ZnO during annealing below 300 °C as studied by in situ positron annihilation spectroscopy

Luitel, Homnath; Sanyal, Dirtha; Gogurla, Narendar; Sarkar, A.

doi:10.1007/s10853-017-0993-x

Cited by 18 publications

(24 citation statements)

References 43 publications

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“…In our view, it is most probably a signature of isolated N O in ZnO. The other peaks at 2.42 and 2.70 eV have been associated with V O and ~2.10 with V Zn s . Intense 2.42 eV PL is due to N‐activated subband gap state that has been reported by several authors .…”

Section: Resultssupporting

confidence: 76%

“…However, there are other opinions also regarding the origin of this transition . Typical defect species associating both V Zn and V O s near the grain boundary region contribute to this PL emission even at room temperature . In case of O or Ar ion irradiation, always a decrease of the I 3.313 /I 3.366 has been observed .…”

Section: Resultsmentioning

confidence: 99%

“…An increase in open volume defects due to 200°C annealing along with a decrease of the same above 400°C in granular ZnO has been previously observed, and positron annihilation spectroscopy identifies such defects as V Zn or V Zn -V O types. [4,40] So, the nonmonotonic variation of the intensity of 275 cm −1 Raman mode renders its involvement with V Zn alongwith doped N atoms. [41] Regarding the E 2 high Raman mode at 439 cm −1 , the reduction of intensity can be found only above 10 14 ions/cm 2 irradiation fluence.…”

Section: Resultsmentioning

confidence: 99%

“…[56,57] Typical defect species associating both V Zn and V O s near the grain boundary region contribute to this PL emission even at room temperature. [40,58] In case of O or Ar ion irradiation, always a decrease of the I 3.313 /I 3.366 has been observed. [15] N implantation causes just the opposite effect.…”

Section: Resultsmentioning

confidence: 99%

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

Mondal

Pal

Sarkar³

et al. 2019

J Raman Spectroscopy

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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.

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Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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

Mondal

Pal

Sarkar³

et al. 2019

J Raman Spectroscopy

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“…Such pairs dissociate when the crystal is annealed above 250 o C 20 . In fact, it has been shown that during growth, VZn (zinc vacancy)and VO (oxygen vacancy) simultaneously appear in the system 21 VO defects (in general (VZn)m (VO)n type with m ≈ n) during annealing (at relatively lower temperature 23 ) or by multiple collision cascades of energetic ions may lead to nano-voids in the system 24,25 . From surface energy consideration, if two open volume defects with similar radii coalesce to a form larger one, energy is lowered roughly by 20%.…”

Section: Introductionmentioning

confidence: 99%

Clustered vacancies in ZnO: chemical aspects and consequences on physical properties

Pal¹,

Gogurla²,

Das³

et al. 2018

J. Phys. D: Appl. Phys.

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Chemical nature of point defects, their segregation, cluster or complex formation in ZnO is an important area of investigation. In this report, 1.2 MeV Ar ion beam is used to incorporate defects in granular ZnO. Evolution of defective state with irradiation fluence 1 × 10 14 and 1 × 10 16 ions/cm 2 has been monitored using x-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopic study. Choice of such fluence regime ensures spatial overlapping of successive ion-target collision cascades so that reorganization of point defects can take place in the form of more stable clusters or in the direction of possible recovery. XPS study shows presence of oxygen vacancies (VO) in the Ar ion irradiated ZnO. Zn(LMM) Auger spectra clearly identifies transition involving metallic zinc in the irradiated samples. Intense PL emission from interstitial Zn (IZn) related shallow donor bound excitons (DBX) is visible in the 10 K spectra for all samples. Although overall PL is largely reduced with irradiation disorder, DBX intensity is increased for the highest fluence irradiated sample. Raman study indicates damage in both zinc and oxygen sub-lattice by energetic ion beam. Representative Raman modes from defect complexes involving VO, IZn and IO are visible after irradiation with intermediate fluence. Further increase of fluence shows, to some extent, a homogenization of disorder. Huge reduction of resistance is also noted for this sample. Certainly, high irradiation fluence induces a qualitative modification of the conventional (and highly resistive) grain boundary (GB) structure of granular ZnO. Low resistive path, involving IZn related shallow donors, across the GB can be presumed to explain resistance reduction. Open volumes (VZn and VO) agglomerate more and more with increasing irradiation fluence and finally get transformed to voids. Results as a whole have been elucidated with a model which emphasizes possible evolution of new defect microstructure that is distinctively different from the GB related disorder. Based on the model, qualitative explanations of commonly observed radiation hardness, colouration and 3 ferromagnetism in disordered ZnO have been put forward. A coherent scenario on disorderaccumulation in ZnO has been presented, which we believe, will guide further discussion on this topic.

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Investigation of Nonlinearity in ZnO Varistor Ceramics Based on Defect Characterization

Roy,

Sanyal

2023

Trans. Electr. Electron. Mater.

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Defect generation and recovery in polycrystalline ZnO during annealing below 300 °C as studied by in situ positron annihilation spectroscopy

Cited by 18 publications

References 43 publications

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

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

Clustered vacancies in ZnO: chemical aspects and consequences on physical properties

Investigation of Nonlinearity in ZnO Varistor Ceramics Based on Defect Characterization

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