Room 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.

Study of the effect of implantation temperature on the migration behaviour of Xe implanted into glassy carbon.

The effect of implantation temperature on the migration behaviour of xenon (Xe) implanted into glassy carbon and the effect of annealing on radiation damage retained by ion implantation were investigated. Glassy carbon substrates were implanted with 320keV Xe+ to a fluence of 2×1016cm-2. The implantation process was performed at room temperature (RT) and 100°C Some of the as-implanted samples were isochronally annealed in vacuum at temperatures ranging from 300°C to 700°C in steps of 100°C for 10h. The as-implanted and annealed samples were characterized using Rutherford backscattering spectrometry (RBS) and Raman spectroscopy. The RT implanted depth profiles indicated that the migration of Xe towards the surface of glassy carbon was accompanied by a loss of Xe ions. The samples implanted at 100°C indicated no diffusion or loss of Xe after annealing at 300°C. However, annealing at temperatures ranging from 400°C to 700°C resulted in a slight shift in the Xe profile tail-end towards the bulk of glassy carbon. The diffusion coefficients (D) in the temperature range of 300°C-700°C for the RT and 100°C implanted samples, activation energies (Ea), and pre-exponential factors (Do), were extracted. The values of D ranged from (9.72±0.48)×10-21 to (1.87±0.09)×10-20m2/s with an activation energy of (6.25±0.31)×10-5eV for RT implanted samples, and the samples implanted at 100°C, D ranged from (3.85±0.19)×10-21 to (6.96±0.34)×10-20m2/s with activation energy of (4.10±0.02)×10-5eV. The Raman analysis revealed that implantation at the RT amorphised the glassy carbon structure while the samples implanted at 100°C showed mild damage compared to RT implantation. Annealing of the RT-implanted sample resulted in some recovery of the damaged region as a function of increasing annealing temperature.

Hot ion implantation to create dense NV center ensembles in diamond

Creating dense and shallow nitrogen-vacancy (NV) ensembles with good spin properties is a prerequisite for developing diamond-based quantum sensors exhibiting better performance. Ion implantation is a key enabling tool for precisely controlling spatial localization and density of NV color centers in diamond. However, it suffers from a low creation yield, while higher ion fluences significantly damage the crystal lattice. In this work, we realize N2+ ion implantation in the 30–40 keV range at high temperatures. At 800 °C, NV's ensemble photoluminescence emission is three to four times higher than room temperature implanted films, while narrow electron spin resonance linewidths of 1.5 MHz, comparable to well-established implantation techniques, are obtained. In addition, we found that ion fluences above 2 × 1014 ions/cm2 can be used without graphitization of the diamond film, in contrast to room temperature implantation. This study opens promising perspectives in optimizing diamond films with implanted NV ensembles that could be integrated into quantum sensing devices.

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

In-situ TEM bubble to cavity evolution due to annealing post helium and dual ion irradiation in Cu-10Ta and Cu-3Ta

Materials have been essential to every major invention in the history of mankind, e.g. satellites, nuclear reactors, or space shuttles would not exist without advancements in materials withstanding temperature and radiation environments. In this work, we investigate room-temperature implantations of helium and concurrent He and Au via in-situ transmission electron microscopy (TEM) followed by isochronal annealing up to 450 °C to understand the microstructural stability and bubble to cavity evolution in advanced nanocrystalline (NC) Cu-3 at.%Ta and Cu-10 at.%Ta alloys. The room temperature irradiation to high helium concentration and displacements per atom (dpa) levels did not lead to significant coarsening of grains in both Cu10Ta and Cu3Ta. Overall grain sizes remained <150 nm indicating extraordinary microstructural stability in both alloys. Post-irradiation, incubation for a few days resulted in the observation of ~1 nm diameter bubbles homogenously distributed in both the alloys and both irradiation conditions. Further evolution of these bubbles to cavities with annealing to 450 °C indicated Brownian motion migration and coalescence to be the dominant coarsening mechanism involved. A comparison of bubble to cavities evolution in Cu3Ta and Cu10Ta under similar conditions showed smaller bubble size and density in Cu3Ta indicating an overall enhanced resistance of Cu3Ta to swelling under both helium and dual-beam irradiation at high temperatures. This is primarily attributed to the high fraction of essential coherent/incoherent precipitates that act as effective defect sinks in Cu3Ta.

Formation of crystalline Si1-xGex top layers by ion implantation in crystalline silicon

Semiconductor nanocrystals incorporated in a dielectric film are widely studied as potential candidates to exceed the Shockley-Queisser theoretical conversion limit of photovoltaic cells. In this context, Ge nanocrystals embedded in SiO2 films seem to be among the best candidates. However, the charges generated in the dielectric film are hard to collect. For this reason, it would be better if the charges were generated in a semiconductor matrix such as silicon, which has better conductivity. However, implanted Ge atoms have poor mobility in a silicon matrix and thus Ge nanocrystals formation is not likely. But even if the formation of Ge nanocrystals seems difficult, it would still be interesting to form crystalline Si1-xGex alloys. This work investigates the formation of the Si1-xGex films by ion implantation and their crystallinity. 36 keV Ge ions were implanted in crystalline Si substrates, with fluences ranging from 5 × 1015 to 1.5 × 1017 Ge/cm2 at temperatures up to 600 °C. Rutherford Backscattering Spectrometry (RBS), Raman Spectroscopy, and Transmission Electron Microscopy (TEM) were used to investigate the microstructure of the Si1-xGex alloys. It is shown that germanium is mostly incorporated in the crystal network in substitutional sites. XRD, Raman spectroscopy, and TEM confirm that the Si1-xGex layer on top of the c-Si substrate is monocrystalline. TEM also indicates the possible presence of nanostructures, extended defects or both. Implantation was also carried out at temperatures up to 600 °C, with the objective of preserving the crystallinity and promoting Ge diffusion into nanoclusters. RBS shows that the Ge profile is more extended in depth for the sample implanted at 600 °C, compared to a room temperature implantation. As the energy of the ions is the same in both samples, this indicates that Ge is able to diffuse in depth during the implantation at 600 °C compared to implantation at ambient temperature. However, RBS/C shows that the minimal yield is higher for the implantation at 600 °C, indicating a high concentration of interstitials or that crystallinity is deteriorated, as confirmed by TEM.

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 (&amp;gt;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.

Entrapment and thermal stability of low energy Argon implanted into diamond studied by in-situ X-ray photoelectron spectroscopy and thermal programmed desorption

The retention and thermal stability of Ar implanted into polycrystalline diamond surfaces with 700 and 5000 eV Ar ions, with high dose (HD) and low dose (LD) of 1016 and 1014 ions/cm2 at room temperature (RT) and 400 °C were investigated. Upon implantation at 400 °C, the thermal stability of the retained Ar is very high and can exceed 1000 °C, whereas, upon RT implantation at the same energy, it is below ∼800 °C. Ar entrapped in a local high crystalline diamond environment possesses a very high thermal stability compared to when it is entrapped in a graphite/amorphous local carbon environment. Ar thermal desorption occurs via diffusion between local defects, greatly enhanced between 600 and 700 °C. Implantation at 400 °C (at HD) results in two distinct regions: graphitic and highly crystalline diamond with low defect density due to dynamic annealing and direct desorption of Ar entrapped within the graphitic/damaged region during the implantation. Ar entrapped in a high crystalline diamond matrix is under higher compressive stress than in graphitic/amorphous carbon.

High conductivity β-Ga2O3 formed by hot Si ion implantation

This work demonstrates the advantage of carrying out silicon ion (Si+) implantation at high temperatures for forming controlled heavily doped regions in gallium oxide. Room temperature (RT, 25 °C) and high temperature (HT, 600 °C) Si implants were carried out into MBE grown (010) β-Ga2O3 films to form ∼350 nm deep Si-doped layers with average concentrations up to ∼1.2 × 1020 cm−3. For such high concentrations, the RT sample was too resistive for measurement, but the HT samples had 82.1% Si dopant activation efficiency with a high sheet electron concentration of 3.3 × 1015 cm−2 and an excellent mobility of 92.8 cm2/V·s at room temperature. X-ray diffraction measurements indicate that HT implantation prevents the formation of other Ga2O3 phases and results in reduced structural defects and lattice damage. These results are highly encouraging for achieving ultra-low resistance heavily doped Ga2O3 layers using ion implantation.

Effect of thermal annealing on SHI irradiated indium implanted glassy carbon

The effects of swift heavy ion irradiation on implanted glassy carbon, the modification and migration of indium after vacuum annealing have been investigated. Radiation damage was introduced to the glassy carbon substrates after room temperature implantation by 360 keV indium ions to a fluence of 2.0 × 1016 ions/cm 2. The implanted samples were subsequently irradiated at room temperature by swift heavy ions (167 MeV Xe 26+ ions). Isochronal annealing of both sets of samples from 200 to 600 °C for 1 h was performed in vacuum. TheSHI irradiation, induced some restructuring in the damaged glassy carbon substrates. Vacuum annealing of the SHI irradiated samples gave rise to recovery and the diffusion of implanted In which was different from that of the as-implanted sample. Higher retention was observed at each temperature for SHI irradiated samples compared to as-implanted samples. The diffusion coefficients of the SHI irradiated samples were lower than for un-irradiated sample.

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%.

Effect of heat treatment on the migration behaviour of selenium implanted into polycrystalline SiC

This study reviews the migration behaviour of selenium in polycrystalline SiC, which acts as the main diffusion barrier in the coated fuel particles for Very High Temperature Reactors. Se ions of 200 keV were implanted into polycrystalline SiC wafers to a fluence of 1 × 1016 cm−2 at three temperatures, which were room temperature, 350 °C and 600 °C. The implanted samples were annealed at temperatures ranging from 1000 to 1500 °C in steps of 100 °C for 10 h. The migration of implanted Se was monitored by Rutherford backscattering spectrometry (RBS) while structural and morphological changes were monitored by Raman spectroscopy and scanning electron microscopy (SEM). Implantation of Se at room temperature amorphized the near surface region of the SiC substrates, while in samples implanted above the critical amorphization temperature the crystal structure was retained with some radiation damage. Annealing at 1000 °C resulted in the recrystallization of the amorphized SiC layer. In the case of room temperature implantation, the broadening of the implanted Se profile in RBS spectra was observed to occur after annealing at 1300 °C and became significant with an increase in annealing temperature. This broadening was accompanied by a peak shift towards the surface and loss of implanted Se. No broadening was observed in samples implanted above the critical amorphization temperature, but the peak shift towards the surface began after annealing at 1300 °C in samples implanted at 350 °C and 600 °C.

Mono-Versus Poly-Crystalline SiC for Nuclear Applications

3C-SiC layers of different microstructures (monocrystalline (100) and (111) oriented and polycrystalline) were implanted with high energy (800 keV) 129Xe++ ions. Implantations were performed at room temperature (RT) and at 500 °C using two different fluences of Φ1 = 1x1016 and Φ2 = 1x1017 at/cm2. Surface blistering was only observed for RT and Φ2 implantations into poly-SiC material while mono-SiC kept rather smooth surface. This was due to more homogeneous Xe bubbles distribution (200 nm deep) in the mono-SiC than in the poly-SiC. Xe retention was found to be almost complete for all samples. Some Xe enhanced diffusion was detected in the poly-SiC material which was attributed to grain boundaries. Some irradiation-induced oxidation effect was evidenced, O element being located at the depth where Xe bubbles are accumulating. This was more pronounced for poly than for mono-SiC. These results demonstrate that SiC microstructure affects many aspects of its behavior upon Xe irradiation.

Exploring conductivity in ex-situ doped Si thin films as thickness approaches 5 nm

Silicon (Si) has been scaled below 10 nm in multigate and silicon-on-insulator (SOI) device technologies, but clearly Si thickness cannot be reduced indefinitely, as we will run out of atoms eventually. As thickness approaches 5 nm, surfaces and interfaces will significantly impact the electrical behavior of Si, and surface physics cannot be discounted. Below that, bulk material properties will be altered considerably in the few-monolayer limit. One of the most basic defining properties of a semiconductor is its conductivity. To improve conductivity, while inducing a channel by appropriate biasing, it is necessary to define an accurate impurity doping strategy to reduce parasitic resistance. In this paper, we investigated the changing electrical conductivity of SOI films as a function of the Si thickness, in the range of 3–66 nm. SOI films were ex situ doped using three different approaches: liquid/vapor phase monolayer doping of phosphorus using allyldiphenylphosphine, gas-phase doping of arsenic using arsine (AsH3), and room-temperature beam-line ion implantation of phosphorus. The circular transfer length method and micro-four-point probe measurements were used to determine the resistivity of the Si films, mitigating the contribution from contact resistance. The resistivity of the Si films was observed to increase with decreasing Si film thickness below 20 nm, with a dramatic increase observed for a Si thickness at 4.5 nm. This may drastically impact the number of parallel conduction paths (i.e., nanowires) required in gate-all-around devices. Density functional theory modeling indicates that the surface of the Si film with a thickness of 4.5 nm is energetically more favorable for the dopant atom compared to the core of the film.

Nitrogen ion implantation into pure iron for formation of surface nitride layer

Low energy N ion implantation into pure Fe was performed to study Fe1−xNx formation under various ion irradiation conditions. It was shown that after the room-temperature implantation the amount of N introduction reaches a saturation at about 42% atomic density. Increasing N fluences further does not increase N levels. For the N saturated layer, adding post-irradiation annealing causes N out-diffusion at 300 °C and higher temperatures. On the other hand, N implantation at elevated temperatures does not provide extra thermal stability. Transmission electron microscopy and localized diffraction analysis show that the metastable N saturated layer contains a mixture of Fe3N and FeN2.

Observation of multiple magnetic phases and complex nanostructures in Co implanted amorphous carbon films

Room temperature implantation of 30 keV Co ions into an amorphous carbon film with a high fluence of 1.2 × 1017 Co/cm2 results in formation of magnetic nanostructures displaying multiple magnetic phases. Cross-sectional TEM images show formation of Co containing nanoparticles at the surface and near-surface regions of the implanted films. EDXS measurements suggest the nanoparticles to be composed primarily of Co and O at the surface and Co and C in deeper regions. These nanoparticles with differing compositions were observed to be segregated by a thin layer devoid of Co. Magnetic measurements reveal the presence of superparamagnetic behavior from small CoxC nanoclusters with a blocking temperature of 5 K. There is a small fraction of larger CoxC nanoclusters that show magnetic hysteresis even at room temperature. The saturation magnetic moment is as high as 0.51 μB/Co at 2 K and 0.32 μB/Co at room temperature. Spin-disorder is seen with a range of spin glass temperatures below ∼70 K. Our high fluence Co implantation into amorphous carbon has resulted in the formation of complex magnetic nanostructures composed of cobalt, oxygen, and carbon. These nanostructures give rise to multiple magnetic phases such as superparamagnetism, spin glass, ferromagnetism, and possibly antiferromagnetism.

Quantification of germanium-induced suppression of interstitial injection during oxidation of silicon

The oxidation of silicon is known to inject interstitials, and the presence of silicon–germanium (SiGe) alloys at the Si/SiO2 interface during oxidation is known to suppress the injection of silicon self-interstitials. This study uses a layer of implantation-induced dislocation loops to measure interstitial injection as a function of SiGe layer thickness. The loops were introduced by a 50 keV 2 × 1014 cm−2 P+ room-temperature implantation and thermal annealing. Germanium was subsequently introduced via a second implant at 3 keV Ge+ over a range of doses between 1.7 × 1014 cm−2 and 1.4 × 1015 cm−2. Results show that upon oxidizing at 850 °C for 3 h or 900 °C for 70 min to condense the germanium at the Si/SiO2 interface, where if forms a Si0.5Ge0.5 alloy. Upon subsequent oxidations of 850 °C for 6 h or 900 °C for 2 h, partial suppression of interstitial injection can be observed for sub-monolayer doses of germanium, and more than three monolayers of Si0.5Ge0.5 (1.4 × 1015 cm−2) are necessary to suppress interstitial injection below the detection limit during oxidation. These results show that low-energy implantation of germanium can be used to eliminate or modulate injection of oxidation-induced interstitials.

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.

Effect of buried extended defects on the radiation tolerance of ZnO

Interaction between defects of different types often determines their evolution in semiconductors under ion irradiation. Here, we investigate the role of buried pre-existing extended defects in the damage accumulation in ZnO single crystals implanted at room temperature and at 15 K with 80 keV N ions. For the room temperature implants but not for the 15 K ones, the defect accumulation around the projected range is strongly suppressed while a pronounced build-up occurs in the region of the pre-existing defects. This is attributed to thermally activated migration of point defects from the implanted volume and subsequent trapping/annihilation by the pre-existing defects. The obtained results imply that a defect engineering scheme involving formation of a high density of extended defects outside the active volume of a ZnO-based device could be beneficial to enhance the radiation tolerance.