keV Proton Irradiation Research Articles

Formation of multilayer structure and evolution of shape recovery characteristics in proton irradiated TiNi alloy thin films

TiNi thin films have attracted wide attentions as actuator materials in the micro-electro-mechanical systems (MEMs) for aerospace craft. However, multiple irradiation, such as the proton, was generally considered as an essential expired factor for the materials used in the aerospace. The present paper focused on the microstructure, martensitic transformation and shape recovery property of TiNi thin films after being irradiated by proton. A single layer structure B19′ phase to a dual-phase (B2 and B19′) with multilayer structure after proton irradiation have been revealed through a combination technique of grazing incidence (GI) XRD and TEM. As-formed irradiated films with amorphous layer and B2 austenite phase displayed a two-step martensitic transformation behavior, which occurred in the irradiated and the unirradiated layer. In contrast, the unirradiated counterparts just exhibited a single-step martensitic transformation. In addition, some defects could be seen after the TiNi films being irradiated. Such defects could induce a stress field that produces the R phase in the B2 phase. Furthermore, the synergistic effect of preferential sputtering effect and inverse Kirkendall effect induced the GP zones in the irradiated layer after 120 keV proton irradiation. The existence of amorphous phase and precipitation significantly deteriorated the shape recovery property.

The effect of 500 keV proton irradiation on reduced graphene oxide paper

The extraordinary graphene material has brought about extensive attention in space engineering for outstanding characteristics. The reduced graphene oxide paper (rGOP) was irradiated by 500 keV proton in a ground-based irradiation simulator. The results show that the spacing of layer to layer was increased after irradiation, while the oxygen functional group was decreased. The result of XPS and Raman spectroscopy indicates that the sp3 carbon and defects increased, and the disorder structure in high fluence irradiated materials also increased. Furthermore, the performance degradation for thermal stability and electrical property of rGOP is contributed to the combination of defects and disordered structure.

150 KeV proton irradiation effects on photoluminescence of GaInAsN bulk and quantum well structures

Low-temperature (T = 30 K) photoluminescence (PL) and post thermal annealing effects on 150 KeV proton irradiated GaInAsN bulk, single quantum well and triple quantum well structures (Eg ~1.0 eV) have been investigated. The nitrogen proportion of the samples was confirmed by high-resolution X-ray diffraction (HR-XRD) measurement as 0.26%, 0.30% and 0.20% for GaInAsN bulk, SQW, and MQW samples, respectively. The result shows that the PL intensity of GaInAsN materials degraded seriously by proton irradiation. The PL intensity enhancement were observed for all three types of sample after thermal annealing at 650 °C for 5 min, and MQW sample was recovered by the factor bigger than 100. The irradiation induced red-shift and thermal annealing induced blue-shift phenomena were analyzed by SRIM simulation result and theoretical models of InGaAs band structure.

Effect of 150 keV proton irradiation on the performance of GaAs solar cells

In this paper, the effects of a 150 keV proton radiation on a GaAs sub-cell of GaInP/GaAs/Ge trip junction solar cells and its radiation damage were studied. The degradation behavior of the solar cells was analyzed by theoretical device modeling combined with electro-optical characterization techniques such as external quantum efficiency, IV measurements, and photoluminescence (PL). The degradation of cell output parameters by protons was plotted as a function of the displacement damage dose. The results show that the short-circuit currents degrades less than open-circuit voltages because the base region of GaAs is severely damaged. The PL results indicated that proton irradiation exerted destructive effect on the photoelectric properties of the material. Such destructiveness was due to the numerous defects introduced by proton irradiation, which destroys the integrity of the lattice space, resulting in a decrease in the diffusion length of the minority and an increase in the surface recombination velocity. By COMSOL simulation analysis, it is found that the reason of radiation degradation of GaAs is the decrease of minority carrier time after irradiation and simulation results show that the PL results are in good agreement with the simulation results which can provide a method for the calculation of internal defects and minority carriers in multi-junction solar cells.

Low-energy (40 keV) proton irradiation of YBa2Cu3O7−x thin films: Micro-Raman characterization and electrical transport properties**Project supported by the National Natural Science Foundation of China (Grant No. 61473023), the Aerospace Science and Technology Innovation Fund, CASC and International S & T Cooperation Program of China (ISTCP) (Grant No. 2015DFR80190).

To investigate the damage profiles of high-fluence low-energy proton irradiation on superconducting materials and related devices, Raman characterization and electrical transport measurement of 40-keV-proton irradiated YBa2Cu3O7−x (YBCO) thin films are carried out. From micro-Raman spectroscopy and x-ray diffraction studies, the main component of proton-radiation-induced defects is found to be the partial transition of superconducting orthorhombic phase to the semiconducting tetragonal phase and non-superconducting secondary phase. The results indicate that the defects induced in the conducting CuO2 planes, such as increased oxygen vacancies and interstitials, can result in an increase in the resistivity but a decrease in the transition temperature TC with the increase in the fluence of proton irradiation, which is confirmed in the electrical transport measurements. Especially, zero-resistance temperature TCO is not observed at a fluence of 1015 p/cm2. Furthermore, the variation of activation energy U0 can be explained by the plastic-flux creep theory, which indicates that the plastic deformation and entanglement of vortices in a weakly pinned vortex liquid are caused by disorders of point-like defects. Point-like disorders are demonstrated to be the main contribution to the low-energy proton radiation damage in YBCO thin films. These disorders are likely to cause flux creep by thermally assisted flux flow, which may increase noise and reduce the precision of superconducting devices.

Impact of 100 keV proton irradiation on electronic and optical properties of AlGaN/GaN high electron mobility transistors (HEMTs)

Proton irradiation-induced effects on AlGaN/GaN high electron mobility transistors (HEMTs) were studied by emulating a certain space radiation environment (upstream of the earth's bow shock) using a relatively low energy (100 keV) proton beam with fluences of 1 × 1010, 1 × 1012, and 1 × 1014 protons/cm2. In order to isolate radiation-induced effects produced by the modification of the epi-layer from the effects produced by the change in the device structure (such as contacts), the epi-layers were irradiated prior to device fabrication, followed by material/device characterization. Proton irradiation-induced sub-gap traps were detected by spectroscopic photo current-voltage measurement. Raman study revealed that the proton irradiation had induced strain relaxation on the AlGaN/GaN HEMTs epi-layer. No substantial change in the crystal quality of the epi-layer was indicated by Raman and PL studies. With increasing proton fluences, increasing charge carrier density was observed, which was estimated via Raman spectroscopy and the charge-control model analysis. The magnitude and direction of the transistor threshold voltage shift were also dependent on proton fluence. Overall, degradation of transistor output characteristics of the fabricated HEMTs was observed with increasing proton fluence. However, based on the observed performance and the level of influence on material/device characteristics by 100 keV protons, it can be suggested that the AlGaN/GaN HEMTs have high endurance for exposure to relatively high fluences of the low-energy proton beam.

Surface modifications and tailoring magnetism in Ni48·4Mn28.8Ga22.8 films by 120 keV proton irradiation

Proton irradiation was performed to investigate the surface modifications and tailoring magnetism of ferromagnetic austenitic Ni48·4Mn28.8Ga22.8 films under different proton fluences. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that seven-layered modulated (7M) martensite can be produced on the surface of austenitic Ni48·4Mn28.8Ga22.8 films at the proton fluence values of 1.0 × 1016 and 2.0 × 1016 p/cm2. The phase transformation temperatures and magnetic properties of the irradiated Ni48·4Mn28.8Ga22.8 films also depend on the proton fluence. Particularly, the magnetism of Ni48·4Mn28.8Ga22.8 films can be tailored by applying proton irradiation under different fluences. When the proton fluence is small as 1.0 × 1015 p/cm2, the saturation magnetization (MS) and the magnetic anisotropy constant (K1) of the irradiated Ni48·4Mn28.8Ga22.8 films can be improved. However, proton irradiation at a fluence as high as 2.0 × 1016 p/cm2 will deteriorate the magnetic performance of the Ni48·4Mn28.8Ga22.8 films. These experimental results are extremely meaningful to improve the magnetic-field-induced strain of Ni-Mn-Ga alloys via irradiation-induced modification or understand the damaged microstructure and magnetic properties of Ni-Mn-Ga alloys under extreme environment.

Lifetime Control in SiC PiN Diodes Using Radiation Defects

Application of radiation defects for lifetime control in contemporary SiC PiN diodes was investigated using the calibrated device simulator ATLAS from Silvaco, Inc. Recombination models accounting for the effect of deep levels introduced by the irradiation were set according to experimental results obtained by C-V and DLTS measurements performed on low-doped n-type SiC epilayers irradiated with 4.5 MeV electrons and 670 keV protons. Global (4.5 MeV electron irradiation) and local (700 keV proton irradiation) lifetime reduction was then applied on the 2A/10kV SiC PiN diode and the ON-state and reverse recovery characteristics were simulated and compared. Results show that the proton irradiation can substantially improve the trade‑off between the diode ON‑state and turn‑OFF losses. Compared to the electron irradiation, the local lifetime killing by protons allows achieving better trade-off and softer recovery curves.

Radiation effects on optical and structural properties of GG17 Glasses induced by 170 keV electrons and protons

The effects of 170 keV electron and proton irradiation are investigated on the optical property and the structure of GG17-type borosilicate glasses for the purpose of assessing the suitability of this material for the rubidium lamp envelope, based on GEANT4 simulating calculation, using electron paramagnetic resonance and Fourier transform infrared spectra and optical-transmittance measurements. The Micro-mechanisms on damage of GG17 Glasses are clarified for electron and proton, respectively. For the electron with the energy of 170 keV, defect creation is due to ionization energy losses and the center is mainly boron oxygen hole center (BOHC) formed by one hole trapped on a bridge oxygen structure with [BO4]−. As a result the number of BOHCs grows as the electron fluence increases. However, for the proton with the energy of 170 keV, the creation of structural defects dominates by means of debonding as a result of an atom having been kicked off the structural chain (displacement effect). This leads to the intensive generation of silicon oxygen hole centers, as well as BOHCs, by the holes trapped on non-bridge oxygen.

Effects of 340 Kev Proton Irradiation on InGaN/GaN Blue Light-Emitting Diodes

The development of GaN-based light-emitting diodes (LEDs) holds promise for various applications such as televisions, mobile phones, traffic signals, automotive lighting and indoor/outdoor lighting. Recently, the application of GaN-based LEDs has been extended to satellite communication systems for weather forecasting or broadband data transmission due to their high radiation hardness. GaN-based devices with small lattice constant (a = 3.189 Å, c = 5.186 Å for wurtzite structure) show superior radiation resistance due to the higher displacement energies compared with other semiconductor systems such as GaAs (a = 5.653 Å). In this work, the low energy (340 keV) proton irradiation effects on optical and electrical performances of InGaN/GaN blue LEDs were investigated. The commercial InGaN/GaN blue LEDs with the emission peak of 441nm were used. The epitaxial structures consisted of p- and n-type GaN layer and InGaN/GaN multi quantum wells grown by metal organic chemical vapor deposition on sapphire substrates. Different proton doses from 5 × 1010 to 1 × 1014 /cm2 were employed to investigate the effects of irradiation doses on the device performances. The irradiated samples were intentionally tilted 7° away from the normal direction of the proton beam to prevent the channeling effect. The Stopping and Range of Ions in Matter (SRIM) simulation was used to estimate the penetration depth of protons and the distribution of vacancies generated by proton irradiations. The L-I-V characteristics of InGaN/GaN blue LEDs were measured with Si photodiode connected to a HP 4156 parameter analyzer. The electroluminescence (EL) spectra were obtained by an optical fiber connected to the Ocean Optics USB 4000 spectrometer. The reverse recovery characteristics were measured with oscilloscope and pulse generator. Figure 1 shows the current-voltage (I-V) of InGaN/GaN blue LEDs before and after proton irradiations with various doses, respectively. The LED diode I-V characteristics of InGaN/GaN blue LEDs were drastically degraded after high dose (1 × 1014 /cm2) proton irradiation. This degradation was caused by the displacement damage, resulting in the reduction of carrier concentration and mobility. However, the degradation of light output was much faster than that of I-V characteristics as shown in Figure 2. This faster degradation of light output indicates that defects generated by energetic protons can act as non-radiative recombination centers. The reduction of light output was also confirmed using EL spectra. In addition, the reverse recovery time, which is related to the minority carrier life time, was also measured by switching the current from 0mA to 50mA. The reverse recovery time before and after 1 × 1013 and 1 × 1014 /cm2 proton irradiations were 80, 79 and 73 ns, respectively. This degradation resulted from the reduction of minority carrier lifetime caused by the introduction of irradiation-induced defects in InGaN/GaN blue LEDs after proton irradiation. In conclusion, the effects of 340 keV proton irradiations on InGaN/GaN blue LEDs were investigated using L-I-V characteristics, EL spectra and reverse recovery characteristics. The optical performances severely degraded compared with the electrical performances due to the radiation-induced defects served as the non-radiative recombination centers. Figure 1

Effect of 170 keV proton irradiation on structure and electrical conductivity of multi-walled carbon nanotubes film

Due to their unusual electrical conductivity, carbon nanotubes as the ideal candidates for making future electronic components have extensive application potentiality. In order to meet the requirements in space electronic components for carbon nanotubes, effect of 170 keV proton irradiation on structure and electrical conductivity of multi-walled carbon nanotubes (MWCNTs) film is investigated in this paper. Surface morphologies and microstructure of the carbon nanotube films are examined by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy, respectively. Electrical conductivities of the carbon nanotube films before and after 170 keV proton irradiation are measured using four-point probe technique. SEM analysis reveals that when proton irradiation fluence is greater than 51015 p/cm2, the surface of the carbon nanotube film becomes rough and loose, and obvious bending, shrinkage, and entanglement of nanotubes are observed. Moreover, the shrinkage phenomenon of MWCNTs caused by proton irradiation is found the first time so far as we know. Based on Raman and XPS analyses, it is confirmed that 170 keV protons can improve the ordered structure of the MWCNTs, and irradiation fluence plays a key role in reducing the disorder in the MWCNTs. Improvement of the irradiated MWCNTs by 170 keV protons can be attributed to restructuring of defect sites induced by knock-on atom displacements. On the other hand, carbon impurities on surface of the MWCNT film are reduced due to the effect of sputtering by the 170 keV proton irradiation, which is also helpful to the improvement of the structure of carbon nanotubes. EPR spectra show that the electrons delocalized over carbon nanotubes decrease with increasing irradiation fluence, implying that the carbon nanotube film is not sensitive to ionizing radiation induced by the 170 keV protons, and the electrical conductivities of the MWCNTs films may be decreased. Four-point probe technical analysis shows that with increasing irradiation fluence, electrical properties of the carbon nanotubes film deteriorate, which can be attributed to the changes in electronic properties and morphology of the MWCNT films induced by 170 keV protons. Acquired results could be beneficial to tailoring of structure and properties for the carbon nanotubes film irradiated by protons to develop nanoelectronics of radiation-resistant systems.

Effect of proton irradiation on mechanical properties of low‐density polyethylene/multiwalled carbon nanotubes composites

The mechanical properties of low‐density polyethylene/multiwalled carbon nanotubes (LDPE/MWCNTs) composites without and with 170 keV proton irradiation were studied by tensile tests. Mechanisms of changes of mechanical properties were examined by means of small angle X‐ray scattering (SAXS), wide angle X‐ray diffraction (WAXD), Raman spectroscopy, and scanning electron microscopy (SEM). The tensile curve of LDPE exhibits three characteristic regions, while those for LDPE/MWCNTs composites only give the first and the second ones. The tensile curves of all samples with 170 keV proton irradiation have no obvious yield phenomenon. The addition of MWCNTs increases the ultimate tensile strength and decreases the elongation at break. Moreover, the ultimate tensile strengths of both LDPE and LDPE/MWCNTs composites with 170 keV proton irradiation are enhanced, and the elongations at break for them are decreased. Based on the analyses of SAXS, WAXD, Raman spectroscopy, and SEM, both the loading of MWCNTs and the proton irradiation can change the mechanical properties of LDPE/MWCNTs composites by a number of factors including the homogeneous distribution of MWCNTs in LDPE matrix, the aberrance zone between MWCNTs, and LDPE matrix, the interaction between MWCNTs and LDPE matrix, and the crystallinities of samples. POLYM. COMPOS., 36:278–286, 2015. © 2014 Society of Plastics Engineers

Effects of roughness and temperature on low-energy hydrogen positive and negative ion reflection from silicon and carbon surfaces

Angle-resolved energy distribution functions of positive and negative hydrogen ions produced from a rough-finished Si surface under 1 keV proton irradiation have been measured. The corresponding distribution from a crystalline surface and a carbon surface are also measured for comparison. Intensities of positive and negative ions from the rough-finished Si are substantially smaller than those from crystalline Si. The angular distributions of these species are broader for rough surface than the crystalline surface. No significant temperature dependence for positive and negative ion intensities is observed for all samples in the temperature range from 300 to 400 K.

Evaluation of 500 keV proton irradiation of bilayer graphene on SiC by the use of SRIM code, a Monte Carlo simulation method for stopping and range of ions in matter

Graphene is experienced its golden age in the world of nanotechnology. Despite the fact that it takes key roles in the very complex areas, it is a simple two-dimensional material which is formed by only carbon atoms with a honeycomb form on especially another material. Graphene monolayer is usually supported by a known SiC substrate. SiC is a valuable material for both electronics and nuclear researches because of the excellent shielding and conduction properties. We simulated 500 keV proton irradiation effects on bilayer graphene on SiC by SRIM code in this paper. SRIM is a very detailed code capable of modeling ranging from very thick materials to single layer structures. This code is based on sending ions with specific energy to a target material. We presented damages and displacements caused by 500 keV protons to bilayer graphene/SiC target in the view of promising face of space and solar cell technology.

Effect of proton irradiation on AlGaN/GaN micro-Hall sensors

The magnetoelectric properties of AlGaN/GaN micro-Hall effect sensors were studied after 380 keV proton irradiation. After irradiation the current-voltage measurements, stability of the magnetic sensitivity of the sensors, and the sheet electron density were degraded with a dramatic decrease of the electron mobility at high temperatures. Raman spectroscopy showed a degradation in the crystalline quality of GaN crystal, but there was no change in the strain.

Microstructures of the interlayer in Mo/Si multilayers induced by proton irradiation

In this work, the microstructure and optical properties of the Mo/Si multilayers mirror for the space extreme-ultraviolet solar telescope before and after 100 keV proton irradiation have been investigated. EUV/soft X-ray reflectometer (EXRR) results showed that, after proton irradiation, the reflectivity of the Mo/Si multilayer decreased from 12.20% to 8.34% and the center wavelength revealed red shift of 0.38 nm, as compared with those before proton irradiation. High-resolution transmission electron microscopy (HRTEM) observations revealed the presence of MoSi2, Mo3Si and Mo5Si3 in Mo-on-Si interlayers before irradiation. The preferred orientation such as MoSi2 with (101) texture and Mo5Si3 with (310) texture was formed in Mo-on-Si interlayers after proton irradiation, which led to the increase of thickness in the interlayers. It is suggested that the changes of microstructures in Mo/Si multilayers under proton irradiation could cause optical properties degradation.

Controlling the doping of single-walled carbon nanotube networks by proton irradiation

We demonstrate the controlled desorption of adventitious dopants on networks of single-walled carbon nanotubes (SWNTs) with 100 keV proton irradiation. Networks of sorted metallic, semiconducting SWNTs, and unsorted SWNTs were investigated. The removal of dopants was indicated by an increase in sheet resistances along with an increase in the absorption of the low energy absorption band of semiconducting SWNTs. Semiconducting and unsorted SWNT networks exhibited the largest change in their sheet resistance, which indicates the conductivity of unsorted SWNT networks is dominated by the tube-tube junctions of semiconducting SWNTs.

Effects of 50 keV and 100 keV Proton Irradiation on GaInP/GaAs/Ge Triple-Junction Solar Cells

GaInP/GaAs/Ge triple-junction solar cells were irradiated with 50 keV and 100 keV protons at fluences of 5 × 1010 cm−2, 1 × 1011 cm−2, 1 × 1012 cm−2, and 1 × 1013 cm−2. Their performance degradation is analyzed using current-voltage characteristics and spectral response measurements, and then the changes in Isc, Voc, Pmax and the spectral response of the cells are observed as functions of proton irradiation fluence and energy. The results show that the spectral response of the top cell degrades more significantly than that of the middle cell, and 100 keV proton-induced degradation rates of Isc, Voc and Pmax are larger compared with 50 keV proton irradiation.

Proton and electron irradiation induced changes in the optical properties of ZnO pigments modified with ZrO2 and Al2O3 nanopowders

The effect of the modification of ZnO powders by ZrO2 and Al2O3 nanoparticles with a concentration of 1–30 wt % is investigated by diffuse reflectance spectra within the wavelength range 0.2 to 2.5 μm before and after 100 keV proton and electron irradiation. It has been established that the introduction of nanoparticles enhances the optical stability of the pigments under proton irradiation, but reduces it under electron irradiation. Samples modified by 5 wt % of ZrO2 nanoparticles have the highest stability of optical properties after proton exposure. The degradation of optical properties under electron irradiation is not high for this concentration of nanoparticles. A decrease in the absorption of pigments modified with nanoparticles after proton exposure is determined by a decrease in the intensity of bands located in the UV and visible regions. After electron exposure the absorption bands have a high intensity in the whole spectrum range.

AMORPHIZATION OF ZnO NANOWIRES BY PROTON BEAM IRRADIATION

We report the effects of 70 keV proton ( H+ ) irradiation on the structure of zinc oxide nanowires (ZnO NWs) for a wide range of irradiation doses at room temperature. It was found that at low dose 5 × 1015 ions/cm2 of protons, few defects were created in ZnO NWs and the defects' density was increased with an increasing proton irradiation dose. After the irradiation dose was increased to 2 × 1017 ions/cm2, the crystal structure of the ZnO NWs was almost completely damaged and the crystalline wurtzite structure of the ZnO NWs could be transformed into a disordered amorphous structure. Structural changes in the ZnO NWs upon bombardment with 70 keV protons were characterized by high resolution transmission electron microscopy (HRTEM).