High-temperature Implantation Research Articles

Structural formation yield of GeV centers from implanted Ge in diamond

In order to study the structural formation yield of germanium-vacancy (GeV) centers from implanted Ge in diamond, we have investigated its lattice location by using the β − emission channeling technique from the radioactive isotope 75Ge (t 1/2 = 83 min) produced at the ISOLDE/CERN facility. 75Ge was introduced via recoil implantation following 30 keV ion implantation of the precursor isotope 75Ga (126 s) with fluences around 2 × 1012–5 × 1013 cm−2. While for room temperature implantation fractions around 20% were observed in split-vacancy configuration and 45% substitutional Ge, following implantation or annealing up to 900 °C, the split-vacancy fraction dropped to 6%–9% and the substitutional fraction reached 85%–96%. GeV complexes thus show a lower structural formation yield than other impurities, with substitutional Ge being the dominant configuration. Moreover, annealing or high-temperature implantation seem to favor the formation of substitutional Ge over GeV. Our results strongly suggest that GeV complexes are thermally unstable and transformed to substitutional Ge by capture of mobile carbon interstitials, which is likely to contribute to the difficulties in achieving high formation yields of these optically active centers.

Analysis of Basal Plane Dislocation Motion Induced By P+ Ion Implantation Using Synchrotron X-Ray Topography

Silicon Carbide (SiC) is a promising wide bandgap semiconductor for future power devices since it has a wide bandgap, high breakdown voltage and good thermal stability [1]. The most mature method to perform selective area doping in 4H-SiC epiwafers during fabrication is ion implantation [2]. However, such implantation processes employing high energy ions can damage the lattice in the epilayers that can subsequently lead to formation and migration of basal plane dislocations (BPDs) which are known to be detrimental to the performance of the devices [3-4]. Implantation processes are typically conducted under room temperature (RT) conditions, but high temperature (HT) implantation is favorable when the dose level is high [5]. Oxide layer for blocking purpose is inevitable since photoresist can barely remain intact under such high temperature, which will increase the time, cost, and complexity [6-7].Here, we will primarily emphasize the motion of the BPDs under stress from RT implantation. 1.2 kV-rated 4H-SiC PiN diodes with junction termination extension (JTE) annealed with same conditions have been successfully fabricated by implantation with different dose levels and concentration profiles under room temperature and at 600 ˚C. Concentration profiles simulated by Stopping and Range of Ions in Matter (SRIM) are shown in Fig.1(a) [8]. The JTEs were implanted with lower concentrations. Synchrotron monochromatic beam X-ray topography (SMBXT) has been performed to characterize the defects induced by implantation and annealing process. Topographs of PIN diodes are shown in Fig.1 (b)-(h). For the diodes implanted with 1x under RT and HT, there is no evidence of dislocations generated due to implantation and annealing. However, formation of BPD half loops, as highlighted in the red and yellow boxes, can be observed from the edge of the device when the dose level is elevated to 5x and 9x. In addition to that, the basal plane density (BPD) density of 5x RT Box due to implantation and annealing is much more significant than that of 5x RT and 9x RT, indicating that concentration profile can affect the defect generation. Fig.1 (e) shows topograph of PiN diode implanted with 5x under high temperature. The absence of BPDs compared to the RT implanted device to the same concentration profile suggests the generation of BPD is suppressed by the high temperature condition. In 5x RT Box device, opposite sign BPDs are nucleated from opposite edges of device, as indicated in Fig.1 (f)&(g). Here, we will analyze the motion of dislocations generated by ion implantation and annealing.Reference:[1] J. Guo, Y. Yang, B. Raghothamachar, T. Kim, M. Dudley, J. Kim, J. Cryst. Growth[2] F. Roccaforte, P. Fiorenza, M. Vivona, G. Greco, F. Giannazzo, Materials 14(14) (2021) 3923.[3] K. Konishi, R. Fujita, Y. Mori and A. Shima, Semiconductor Science and Technology 2018 Vol. 33 Issue 12[4] M. Nagano, H. Tsuchida, T. Suzuki T. Hatakeyama, J. Senzaki and K. Fukuda, J. Appl. Phys. 108, 013511 (2010)[5] S. Mancini, S. Y. Jang, Z. Chen, D. Kim, Y. Liu, B. Raghothamachar, M. Kang, A. Agarwal, N. Mahadik, R. Stahlbush, M. Dudley, W. Sung, proceeding of 2022 IEEE International Reliability Physics Symposium (IRPS). (accepted)[6] T. Kimoto, J. A. Cooper. John Wiley & Sons Singapore Pte. Ltd. 2014. pp. 197-200[7] D. Kim, N. Yun and W. Sung, 2021 IEEE International Reliability Physics Symposium (IRPS), 2021, pp. 1-4, doi: 10.1109/IRPS46558.2021.9405109[8] J. F. Ziegler, M.D. Ziegler, J.P. Biersack, Nucl Instrum Methods Phys Res B, Volume 268, Issues 11–12, June 2010, Pages 1818-1823 Figure 1

Low leakage current in isolated AlGaN/GaN heterostructure on Si substrate by N ion implantation performed at an elevated temperature

Electrical characterizations of AlGaN/GaN heterojunctions isolated by N implantation at elevated temperatures were investigated. Three-terminal measurements were carried out to characterize leakage paths, and crystal lattice damage due to implantation was monitored by high-resolution x-ray diffraction. Compared with room temperature implantation, the current leakage was reduced by ∼103 times by the implantation at 300 °C. The low leakage was attributed to low acceptor-like energy levels due to low crystal lattice damage by the “dynamic annealing” effect at high-temperature implantation. The post-annealing process increased the current leakage by two orders of magnitude. This indicates that the implantation isolation process should be conducted after higher temperature processes (>450 °C) in the fabrication of GaN devices. These results can provide valuable information for the fabrication, reliability, and mass production of various GaN-based photonics and electronics.

Bonding, retention and thermal stability of shallow nitrogen in diamond (100) by low-energy nitrogen implantation

We investigate the sub-surface bonding, retention, and thermal stability of nitrogen in diamond (100) implanted with 200 and 800 eV N2+ at room temperature (RT) and 600 °C at an ion dose of 3.4×1014 ions/cm2. Upon 200 eV N2+ implantation at RT and 600 °C, nitrogen is incorporated in the diamond lattice mainly in a C-N/C=N bond bonding configuration alongside a small CN(nitrile-like) component. 800 eV N2+ implantation at both RT and 600 °C, the implanted nitrogen can occupy multiple bonding configurations, including C-N/C=N and CN(nitrile-like) bonds. Implantation at 600 °C resulted in higher thermal stability of the implanted nitrogen compared to RT implantation due to dynamic annealing assisted defect curing and desorption of weekly bonded species (possibly nitrogen bonded to defects) during the high temperature implantation. The long-range order of the N2+ implanted diamond surfaces was also investigated using low-energy electron diffraction measurements.

Insights into the effects of Al-ion implantation temperature on material properties of 4H-SiC

In this study, Al implantation in 4H-SiC at the dose of 1 × 1014 cm−2 was investigated. The impacts of implantation temperature on the lattice quality, microstructure, surface composition, and band structure were all studied experimentally and theoretically. Atomic force microscope (AFM) images showed the difference in surface morphology between high-temperature and low-temperature implantation. Transmission electron microscopy (TEM) characterization indicated the lattice damage induced by implantation was recovered after the post-annealing at 1750 °C, except for the samples implanted at room temperature. X-ray photoelectron spectroscopy (XPS) analysis suggested an oxidation effect during and after the implantation process, and it was more serious at lower implantation temperatures. As the implantation temperature incremented, the ratio of Si-C composition with high binding energy increased, the element valence became closer to that of ideal Al-doped 4H-SiC calculated by density functional theory (DFT); and the Fermi level shifted toward the valence band maximum (VBM), demonstrating the formation of efficient p-type doping. A more obvious asymmetric broadening in Raman spectroscopy was observed at higher implantation temperature. The theoretically obtained band structures and bond lengths from DFT calculations corroborated the experimental results, providing physical insights into the possible effect mechanism. In sum, correlations between the implantation process, external material properties, and internal crystal structure were recorded, paving the way for further research and future applications.

Boron ion implantation on femtosecond-laser-irradiated diamond surface

We investigated the effect of femtosecond-laser-induced surface modifications on ion incorporation into diamond crystals. The (001) surface of a diamond crystal was irradiated with femtosecond laser pulses. Boron ions were implanted on the laser-irradiated surface of two crystals: one at 600 °C and the other at room temperature. The ion concentration along the depth of the crystal was measured with secondary ion mass spectroscopy. The concentration profile was parabolic, and in the deeper region after the peak, the ion concentration was higher in the irradiated area than in the nonirradiated area in both crystals. That is, the introduction of laser-induced surface modifications enhanced the ion migration along the depth direction. Transmission electron microscopy showed that the crystallinity of diamond was better in the crystal subjected to high-temperature implantation. These results support the idea that femtosecond-laser-induced surface modifications can enhance dopant incorporation into diamond while preserving the diamond’s crystallinity.

Microstructural Evolution and the Irradiation Sensitivity of Different Phases of a High Nb-Containing TiAl Alloy under He Ions Implantation at Room- and Elevated Temperatures

A high Nb-containing TiAl alloy Ti-45Al-8.5Nb-(W, B, Y) with nearly lamellar microstructure has been irradiated by 200 kV He2+ to a fluence of 1 × 1021 ions/m2 with a dose of about 1.1 dpa at 298 K and 773 K in this work. It is found that an amorphous layer formed on the surface, and no helium bubbles can be observed in the alloy after room temperature ion implantation. The surface roughness of the alloy increases significantly with the bombardment of helium ions, indicating that the ion implantation increases the surface defects. The high-temperature ion implantation leads to the phenomenon of blistering on the alloy surface, and helium bubbles are observed in both α2 and γ phases of the alloy irradiated at 773 K. The average size of the helium bubbles in the α2 (15~20nm) is larger than that in the γ (3~5 nm) phase, while the helium bubble density is opposite. Moreover, the growth mechanism of helium bubble is also investigated. By means of nanoindentation, an obvious irradiation hardening phenomenon is measured after the room temperature ion implantation. In addition, the irradiation sensitivity of different phases is also discussed in this work. The results show that the γ phase has the highest irradiation sensitivity, α2 phase second, β phase minimum. The results of this work, especially microstructure evolution and the evaluation of phase-related irradiation sensitivity during ion implantation, can be expected to provide experimental evidence for the applications of TiAl intermetallic compounds in the nuclear industries.

Effect of beam current on defect formation by high-temperature implantation of Mg ions into GaN

We evaluated the beam current dependence of defect formation during Mg ion implantation into GaN at a high temperature of 1100 °C with two beam currents. Photoluminescence spectra suggest that low-beam-current implantation reduced the vacancy concentration and activated Mg to a greater extent. Moreover, scanning transmission electron microscopy analysis showed that low-beam-current implantation reduced the density of Mg segregation defects with inactive Mg and increased the density of intrinsic dislocation loops, suggesting decreases in the densities of Ga and N vacancies. The formation of these defects depended on beam current, which is an important parameter for defect suppression.

The Impact of Process Conditions on Surge Current Capability of 1.2 kV SiC JBS and MPS Diodes.

This paper demonstrated the impact of process conditions on the surge current capability of 1.2 kV SiC junction barrier Schottky diode (JBS) and merged PiN Schottky diode (MPS). The influence of ohmic contact and defect density produced by implantation was studied in the simulation. The device fabricated with high temperature implantation had less defect density in the implant region compared with room temperature implantation, which contributed to higher hole injection in surge current mode and 20% surge capability improvement. In addition, with lower P+ ohmic contact resistance, the device had higher surge capability. When compared to device fabrication with a single Schottky metal layer in the device active area, adding additional P+ ohmic contact on top of the P+ regions in the device active area resulted in the pn junctions sharing a greater portion of surge current, and improved the devices’ surge capability by ~10%.

Lattice Defects and Exfoliation Efficiency of 6H-SiC via H2+ Implantation at Elevated Temperature.

Silicon carbide (SiC) is an important material used in semiconductor industries and nuclear power plants. SiC wafer implanted with H ions can be cleaved inside the damaged layer after annealing, in order to facilitate the transfer of a thin SiC slice to a handling wafer. This process is known as “ion-cut” or “Smart-Cut”. It is worth investigating the exfoliation efficiency and residual lattice defects in H-implanted SiC before and after annealing. In the present paper, lattice damage in the 6H-SiC implanted by H2+ to a fluence of 5 × 1016 H2+/cm2 at 450 and 900 °C was investigated by a combination of Raman spectroscopy and transmission electron microscopy. Different levels of damage caused by dynamic annealing were observed by Raman spectroscopy and transmission electron microscopy in the as-implanted sample. Atomic force microscopy and scanning white-light interferometry were used to observe the sample surface morphology. Surface blisters and exfoliations were observed in the sample implanted at 450 °C and then annealed at 1100 °C for 15 min, whereas surface blisters and exfoliation occurred in the sample implanted at 900 °C without further thermal treatment. This finding can be attributed to the increase in the internal pressure of platelets during high temperature implantation. The exfoliation efficiency, location, and roughness after exfoliation were investigated and possible reasons were discussed. This work provides a basis for further understanding and improving the high-efficiency “ion-cut” technology.

The Influence of High-Temperature Nitrogen Plasma-Based Ion Implantation on Niobium Creep Behavior

Niobium has been considered for applications in the aerospace sector, but its use at high temperatures is restricted, due to the great affinity of refractory metals with oxygen, which results in the formation of oxide layers and a decrease in their mechanical resistances. In the present work, Nb samples were submitted to High-Temperature Nitrogen Plasma-Based Ion Implantation (HT-NPBII). The process runs at a working pressure between 3 and 4 mbar and negative high voltage pulses of 7 kV/30 μs/300 Hz were applied to samples heated to 1000°C, at treatment times of 1 h, 4 h, and 8 h, respectively. Microstructural and mechanical characterizations of the treated samples revealed the formation of a layer of Nb2N, with 3.0 μm thickness and increase in the surface hardness from 225 HV for the untreated material up to about 2498 HV, for samples treated during 8 h. Creep tests were performed at 500°C and with loads varying from 25 to 40 MPa. Results indicated a decrease in the secondary creep rate for treated specimens when compared to the untreated ones. This behavior can be attributed to the formation of a nitride layer on the surface of Nb that acts as barrier to avoid the oxygen diffusion into the material under high temperature conditions.

Photoluminescence properties of implanted Praseodymium into Gallium Nitride at elevated temperatures

Since Rare-Earth (RE) doped Gallium Nitride (GaN) is expected to be used as electrically driven single photon source at room temperature, low dose RE-ion implantation and their activation as luminescent centers are of interest. This paper reports photoluminescence (PL) properties of Praseodymium (Pr) implanted GaN at different temperatures ranging from room temperature to 1200 °C. All the Pr-implanted GaN samples are thermally annealed after implantation and show strong PL emissions at 650.2 nm and 652.0 nm, originated from 3P0→3F2 transition in 4f-shell of Pr3+ ions. It is shown that the PL intensity originating from Pr3+ ions is reduced as the implantation temperature increases for the Pr-implanted samples annealed at 1200 °C. This result suggests that Pr3+ ions quench due to the formation of complex defects and defect clusters. The effect of high temperature implantation on the recovery of GaN crystallinity is discussed in terms of critical dose and displacement damage.

Impact of high-temperature implantation of Mg ions into GaN

Magnesium (Mg) ion implantation into gallium nitride (GaN) at 1000 °C is proposed. Since ion implantation and annealing occur simultaneously in high-temperature implantation, it is considered that Mg ions can be introduced at an appropriate position upon their implantation. GaN vertical diodes implanted with Mg ions were fabricated and current–voltage measurements were performed. As a result, clear rectifying properties were confirmed in a sample that was implanted with Mg ions at 1000 °C and annealed after implantation. However, the sample subjected to Mg ion implantation at RT and annealed after implantation showed no clear rectification. These results show that high-temperature implantation of Mg ions at 1000 °C reduces Mg ion implantation-induced damage and simultaneously activates Mg ions upon their implantation.

Effect of ion-implantation-induced defects and Mg dopants on the thermoelectric properties of ScN

For applications in energy harvesting, environmentally friendly cooling, and as power sources in remote or portable applications, it is desired to enhance the efficiency of thermoelectric materials. One strategy consists of reducing the thermal conductivity while increasing or retaining the thermoelectric power factor. An approach to achieve this is doping to enhance the Seebeck coefficient and electrical conductivity, while simultaneously introducing defects in the materials to increase phonon scattering. Here, we use Mg ion implantation to induce defects in epitaxial ScN (111) films. The films were implanted with Mg+ ions with different concentration profiles along the thickness of the film, incorporating 0.35 to 2.2 at.% of Mg in ScN. Implantation at high temperature (600 C), with few defects due to the temperature, does not substantially affect the thermal conductivity compared to a reference ScN. Samples implanted at room temperature, in contrast, exhibited a reduction of the thermal conductivity by a factor of three. The sample doped with 2.2 at.% Mg also showed an increased power factor after implantation. This study thus shows the effect of ion-induced defects on thermal conductivity of ScN films. High-temperature implantation allows the defects to be annealed out during implantation, while the defects are retained for room-temperature implanted samples, allowing for a drastic reduction in thermal conductivity.

Inducing defects in 3.3 kV SiC MOSFETs by annealing after ion implantation and evaluating their effect on bipolar degradation of the MOSFETs

Process-induced basal plane dislocations (BPDs) formed by annealing after aluminum ion implantation were investigated, and their effect on the bipolar degradation of body diodes in 3.3 kV SiC MOSFETs was evaluated. Contact resistance in the p+ region decreases with ion dose but increases with implantation temperature due to the formation of the recrystallized layer at SiC surface and difference of acceptor activation rates in high and low temperature implantation. In the case of high ion dose implantation at room temperature, contact resistance was of 1.3 × 10−3 Ωcm2. However, process-induced BPDs formed with high ion dose implantation at room temperature, and could be suppressed with low ion dose or high implantation temperature. They were formed after activation annealing, and expanded to form stacking faults (SFs) under both continuous irradiation from a Hg lamp and current stress. Bipolar degradation occurred in the case of MOSFETs fabricated using high ion dose implantation at room temperature, but was not observed in the case of either low ion dose or high implantation temperature. The activation energy for SF expansion velocity in the 〈1–100〉 direction was estimated to be 0.20 eV at a forward current density of 125 A cm−2. Moreover, the results of a long duration current stress test with high current density and high junction temperature indicate that low ion dose or high implantation temperature can suppress the formation of process-induced BPDs. MOSFETs fabricated using optimized ion implantation conditions show high reliability under bipolar operation.

SIESTA: A high current ion source for erosion and retention studies.

Second ion experiment for sputtering and TDS analysis is a high-current ion source for erosion and retention studies with focus on wall materials for fusion devices. The system is composed of a DuoPIGatron type ion source, three consecutive grids for ion extraction, acceleration and beam focusing, a differential pumping stage, a dipole magnet for mass filtering, a quadrupole doublet lens, a target chamber, a load-lock, and a chamber for thermal desorption spectrometry. The acceleration potential of the source can be varied between 500 V and 10 kV. The target chamber has a base pressure of 10-8 mbar and an operating pressure of 5 × 10-7 mbar. The target can be rotated to study angle-dependent effects and can be heated via electron-impact heating up to 1300 K for high temperature erosion and implantation studies. The target chamber is equipped with an in situ magnetic suspension balance. The operating parameters of the ion source were mapped to achieve the maximum ion current at the target for various gas species and accelerating potentials. The beam emittance for a D3 + ion beam was measured after deflection in the dipole magnet. This was used for ion beam simulations, which were instrumental for the design of the quadrupole lenses. If the quadrupole doublet is used, the ion flux to the target is increased by up to a factor of 4. Additionally, the relative population of neutral particles present in the beam at the target was quantified and is equal to 0.8% when averaged over the measurement positions. The typical beam footprint at the target under normal incidence has an area of 0.5 cm2. The ion current reaching the target increases with the accelerating potential. Due to this effect, the ion flux density at the target in the low-ion-impact-energy range can be increased by operating the source at a higher extraction potential and by applying a (decelerating) potential to the target. Ion impact energies as low as 200 eV/D are achieved this way with a D3 + current of 100 μA when focusing the beam with the quadrupole doublet lens, equating to a D particle flux density of 3.7 × 1019 m-2 s-1. At ion impact energies of 2 keV/D, the maximum achievable flux density with D3 + is 6 × 1019 D m-2 s-1. Experimental determination of sputter yields was performed via ex situ weight loss measurement for bulk Au samples, showing reasonably good agreement with simulations and experimental data from the literature.

Retraction Note to: Investigation of Co-Doped ZnO Nanowires by X-ray Absorption Spectroscopy and Ab Initio Simulation

The local structure of single room- and high-temperature Co-implanted ZnO nanowires with subsequent thermal annealing has been studied using hard-x-ray techniques in combination with ab initio Zn K-edge x-ray absorption near-edge structure (XANES) simulations. X-ray fluorescence data reveal a homogeneous distribution of Co atoms/ions with concentration of about 0.1 at.% to 0.3 at.% in the nanowires. XANES data indicate substitutional incorporation of Co2+ ions at Zn sites in both types of nanowire. Improved structural order around Co atoms is obtained in nanowires with high-temperature ion implantation followed by thermal annealing. The ab initio Zn K-edge simulations not only confirm recovery of implantation-induced damage in the ZnO host lattice by the thermal annealing process, but also assist in studying the effect of oxygen vacancies in the Zn K-edge XANES spectra. Microphotoluminescence data certify that high-temperature ion implantation with subsequent thermal annealing is an effective approach to achieve the strongest optical activation of Co ions and good energy transfer to Co ions from the ZnO host matrix.

An Electrical and Physical Study of Crystal Damage in High-Dose Al- and N-Implanted 4H-SiC

In this paper, an investigation into the crystal structure of Al-and N-implanted 4H-SiC is presented, encompassing a range of physical and electrical analysis techniques, with the aim of better understanding the material properties after high-dose implantation and activation annealing. Scanning spreading resistance microscopy showed that the use of high temperature implantation yields more uniform resistivity profiles in the implanted layer; this correlates with KOH defect decoration and TEM observations, which show that the crystal damage is much more severe in room temperature implanted samples, regardless of anneal temperature. Finally, stress determination by means of μRaman spectroscopy showed that the high temperature implantation results in lower tensile stress in the implanted layers with respect to the room temperature implantation samples.

Annealing effects on the migration of ion-implanted cadmium in glassy carbon

The migration behaviour of cadmium (Cd) implanted into glassy carbon and the effects of annealing on radiation damage introduced by ion implantation were investigated. The glassy carbon substrates were implanted with Cd at a dose of 2×1016ions/cm2 and energy of 360keV. The implantation was performed at room temperature (RT), 430°C and 600°C. The RT implanted samples were isochronally annealed in vacuum at 350, 500 and 600°C for 1h and isothermally annealed at 350°C up to 4h. The as-implanted and annealed samples were characterized by Raman spectroscopy and Rutherford backscattering spectrometry (RBS). Raman results revealed that implantation at room temperature amorphized the glassy carbon structure while high temperature implantations resulted in slightly less radiation damage. Isochronal annealing of the RT implanted samples resulted in some recrystallization as a function of increasing temperature. The original glassy carbon structure was not achieved at the highest annealing temperature of 600°C. Diffusion of Cd in glassy carbon was already taking place during implantation at 430°C. This diffusion of Cd was accompanied by significant loss from the surface during implantation at 600°C. Isochronal annealing of the room temperature implanted samples at 350°C for 1h caused Cd to diffuse towards the bulk while isothermal annealing at 500 and 600°C resulted in the migration of implanted Cd toward the surface accompanied by a loss of Cd from the surface. Isothermal annealing at 350°C for 1h caused Cd to diffuse towards the bulk while for annealing time >1h Cd diffused towards the surface. These results were interpreted in terms of trapping and de-trapping of implanted Cd by radiation damage.

RETRACTED ARTICLE: Investigation of Co-Doped ZnO Nanowires by X-ray Absorption Spectroscopy and Ab Initio Simulation

The local structure of single room- and high-temperature Co-implanted ZnO nanowires with subsequent thermal annealing has been studied using hard-x-ray techniques in combination with ab initio Zn K-edge x-ray absorption near-edge structure (XANES) simulations. X-ray fluorescence data reveal a homogeneous distribution of Co atoms/ions with concentration of about 0.1 at.% to 0.3 at.% in the nanowires. XANES data indicate substitutional incorporation of Co2+ ions at Zn sites in both types of nanowire. Improved structural order around Co atoms is obtained in nanowires with high-temperature ion implantation followed by thermal annealing. The ab initio Zn K-edge simulations not only confirm recovery of implantation-induced damage in the ZnO host lattice by the thermal annealing process, but also assist in studying the effect of oxygen vacancies in the Zn K-edge XANES spectra. Microphotoluminescence data certify that high-temperature ion implantation with subsequent thermal annealing is an effective approach to achieve the strongest optical activation of Co ions and good energy transfer to Co ions from the ZnO host matrix.