Dual Ion Beam Research Articles

Investigation of Dual-Ion Beam Sputter-Instigated Plasmon Generation in TCOs: A Case Study of GZO.

The use of the high free-electron concentration in heavily doped semiconductor enables the realization of plasmons. We report a novel approach to generate plasmons in Ga:ZnO (GZO) thin films in the wide spectral range of ∼1.87-10.04 eV. In the grown GZO thin films, dual-ion beam sputtering (DIBS) instigated plasmon is observed because of the formation of different metallic nanoclusters are reported. Moreover, formation of the nanoclusters and generation of plasmons are verified by field emission scanning electron microscope, electron energy loss spectra obtained by ultraviolet photoelectron spectroscopy, and spectroscopic ellipsometry analysis. Moreover, the calculation of valence bulk, valence surface, and particle plasmon resonance energies are performed, and indexing of each plasmon peaks with corresponding plasmon energy peak of the different nanoclusters is carried out. Further, the use of DIBS-instigated plasmon-enhanced GZO can be a novel mean to improve the performance of photovoltaic, photodetector, and sensing devices.

Realization of synaptic learning and memory functions in Y2O3 based memristive device fabricated by dual ion beam sputtering

Single synaptic device with inherent learning and memory functions is demonstrated based on a forming-free amorphous Y2O3 (yttria) memristor fabricated by dual ion beam sputtering system. Synaptic functions such as nonlinear transmission characteristics, long-term plasticity, short-term plasticity and ‘learning behavior (LB)’ are achieved using a single synaptic device based on cost-effective metal-insulator-semiconductor (MIS) structure. An ‘LB’ function is demonstrated, for the first time in the literature, for a yttria based memristor, which bears a resemblance to certain memory functions of biological systems. The realization of key synaptic functions in a cost-effective MIS structure would promote much cheaper synapse for artificial neural network.

Mechanical and structural properties of ODS RAF steels submitted to low-energy ions irradiation

The effect of ion implantation on mechanical and structural properties of 12%Cr ODS steel have been investigated. Specimens were submitted to single (He+ or Fe+) and dual ion beam (He+ and Fe+) implantation campaigns. Modification of three mechanical parameters: hardness, Young modulus and yield strength were characterized by means of nanoindentation technique. Structural properties were measured by using Grazing Incidence X-ray Diffraction (GIXRD) method. Correlation between obtained mechanical and structural results have been found. Recorded results show that ion-irradiation causes hardening effect which may be associated with creation of radiation defects and dislocation loops. The weakest effects have been observed for single He-ion implantation, whereas the dual beam irradiation led to significant change of all mechanical parameters. During structural analysis, small shifts of α-Fe peaks have been observed. Reported structural changes can be attributed to the effect of local stress introduced during ion irradiation.

Effects of in situ dual ion beam (He+ and D+) irradiation with simultaneous pulsed heat loading on surface morphology evolution of tungsten–tantalum alloys

The strong thermal and mechanical properties of tungsten (W) are well suited for the harsh fusion environment. However, increasing interest in using tungsten as plasma-facing components (PFCs) has revealed several key issues. These potential roadblocks necessitate more investigation of W and other alternative W based materials exposed to realistic fusion conditions. In this work, W and tungsten–tantalum (W–Ta) alloys were exposed to single (He+) and dual (He+ + D+) ion irradiations with simultaneous pulsed heat loading to elucidate PFCs response under more realistic conditions. Laser only exposer revealed significantly more damage in W–Ta samples as compared to pure W samples. This was due to the difference in the mechanical properties of the two different materials. Further erosion studies were conducted to evaluate the material degradation due to transient heat loading in both the presence and absence of He+ and/or D+ ions. We concluded that erosion of PFC materials was significantly enhanced due to the presence of ion irradiation. This is important as it demonstrates that there are key synergistic effects resulting from more realistic fusion loading conditions that need to be considered when evaluating the response of plasma facing materials.

Corrosion resistance and mechanism of CeN, TiN and CeN/TiN bilayer composite film deposited by dual ion beam sputtering

Uranium (U) is an important engineering material in nuclear energy industry. Its environmental instability, however, posed challenges on its applications. Due to the active property and similar electronic configuration, Cerium (Ce) can be used as a reference metal to simulate the protection of uranium from corrosion. In order to improve the corrosion resistance of Ce, ceramic CeN, and ceramic TiN and CeN/TiN bilayer composite film were prepared by dual ion beam sputtering deposition system (DIBD). The crystal structure of films was identified by X-ray diffraction (XRD) and the chemical states of CeN film were characterized by the X-ray photoelectron spectroscopy (XPS). The Surface morphology and structure changes in atmospheric environment were examined by scanning electron microscopy (SEM) and XRD, The corrosion behavior was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The experimental results indicate the single film of CeN or TiN shows poor corrosion resistance, but the CeN/TiN bilayer composite film has better corrosion resistance. Based on the XPS, SEM and impedance analysis, we supposed that the loose of integrity and passivity breakdown on as deposited coating may be the corrosion inducement.

Trap assisted charge multiplication enhanced photoresponse of Li–P codoped p-ZnO/n-Si heterojunction ultraviolet photodetectors

In this work, we report a high-performance p-ZnO/n-Si heterojunction-based ultraviolet (UV) photodetector fabricated by dual ion beam sputter deposition. The lithium–phosphorus (Li–P) codoping route was used to realize low resistive and stable p-type ZnO. The current–voltage characteristics of p-ZnO/n-Si heterojunction photodiode showed good rectifying behavior with a rectification ratio of 170 at ±3 V. The spectral response measurements of the photodiode showed excellent responsivity with a peak observed around ~325 nm and cutoff wavelength around 370 nm. The maximum responsivity achieved was 2.6 A W−1 at an applied reverse bias of −6 V. The external quantum efficiency determined was of the order of ~1000% which is attributed to the trap assisted multiplication of charge carriers.

Damage production in silicon carbide by dual ion beams irradiation

Lattice damage and evolution in single crystalline 6H-SiC under Si + He successively dual ion beams irradiation is studied by using Raman spectroscopy, high resolution X-ray diffraction (HRXRD) and nano-indentation tests. Single Si and He ion irradiations are also performed for the comparison. The results of Raman spectra reveal that the damage level increases with the fluence. A normal strain profile along the ion path is generated due to ion irradiation induced dilation of lattices, contributing mainly by interstitial related defects. Moreover, Si and He ion implantation produced different types of defects. The damage and chemical bonding states are significantly changed after He atoms implanted in Si pre-irradiated samples. Si + He dual ion irradiations increase the damage level further, resulting in changes of the damage states because of complex defects interactions. The nano-hardness of irradiated SiC is combined results of hardening effects of some kinds of defects and the breakdown of covalent-bonds. The mechanical properties present significant differences between single Si, He and Si + He successively dual ion beam irradiations, due to defects evolution during the irradiation process.

Fabrication of broadband antireflection coatings using wavelength-indirect broadband optical monitoring

Multi-layer optical coatings with complex spectrum requirements, such as multi-band pass filters, notch filters, ultra-broadband antireflection coating and etc., whose working wavelength is out of monitoring wavelength range, are difficult to be fabricated using direct broadband optical monitoring (BBOM). In this paper, a broadband antireflection (AR) coating in the wavelength range from 1300nm to 2000nm at 45° incident was designed and deposited by dual ion beam sputtering (DIBS). Ta2O5 and SiO2 were chosen as high and low refractive index coating materials, respectively. The optimized coating structure contains 4 non-quarter-wave (QW) layers. In order to obtain high transmittance, the most important is to realize the thickness accurate control. Due to the limitation of the monitoring wavelength range, which is only from 450nm to 1000nm, a wavelength-indirect broadband optical monitoring strategy was successfully employed to control the layers thickness during the deposition process. At last, a good agreement between theoretical and measured transmittance is obtained. The maximum error (the first layer) is only about 5.3% and the minimum error (the third layer) is about −0.25% base on the results of reverse engineering analysis.

Preparation of Cu-W film by ion beam sputtering and characterization

This works aims at exploring the effects of dual ion beam sputtering-assembled W-rich copper-tungsten films. The film characterization was performed by means of X-ray diffraction and magnetic coating thickness testing. Our results indicate a gradual change in the tungsten structure—from approximately metastable and amorphous to crystalline—as the Ar+ ion energy increases during the sputtering process. Due to the reflection effect, an increase in film thickness was also observed with increasing energy. At lower energies, the film deposition become very difficult due to the atomic shot peening effect.

Effect of ion milling on the perceived maturity of shale samples: Implications for organic petrography and SEM analysis

Sample polishing by argon ion beam is a widely used method for examining shale samples for inherent porosity characteristics; the high quality of these surfaces suggests that this technique may also be used for optical reflectance measurements to provide information about the thermal maturity of samples. Yet, the inevitable surface heating that this polishing method engenders has raised concerns that the measured reflectance properties are no longer those of the original sample. To explore the impact of ion milling on the maturity of shale samples as measured by vitrinite and solid bitumen reflectance, five different ion milling configurations were applied to a set of organic-rich New Albany Shale (Late Devonian-Early Mississippian) samples that range in maturity from immature to post-mature. Using two ion mill designs, edge milling vs planar milling, single and dual ion beams, variable acceleration voltages, and milling at room temperature vs samples cooled by liquid nitrogen, provided a wide range of beam heating scenarios. Reflectance of macerals was measured before and after ion milling to investigate whether and to what extent various ion-milling approaches change the reflectance values, and by extension the perceived thermal maturity of organic matter in these samples. Our results demonstrate that more aggressive milling methods, such as the use of multiple beams and higher acceleration voltages elevate reflectance values, and that this effect is most pronounced in immature samples and diminishes for samples of increasing original maturity. Specifically, for the two least mature samples, the most aggressive milling method (configuration D) increased reflectance of vitrinite from 0.48% to 0.58%, and from 0.58% to 0.74%. Increase of reflectance (perceived maturity) can be counteracted by reducing beam intensity (e.g., fewer beams, lower voltage) and cooling of samples with liquid nitrogen. The severity of heating artifacts depends partially on the ion mill design, and non-damaging settings must be determined experimentally for a given ion mill model. Because thermal alteration of organic matter typically involves the expulsion of volatiles, there is also a danger that ion beam heating of immature and oil window samples can skew the porosity characteristics of shale samples. Thus, determining non-damaging ion mill settings has the dual benefit of avoiding measuring false maturity levels and misleading porosity characteristics.

Investigation of formation mechanism of Li-P dual-acceptor doped p-type ZnO

In this work, the dual-acceptor doping method has been used to produce low resistive and stable p-type ZnO thin films. The ZnO:(Li, P) films were deposited on n-type Si substrates by dual ion beam sputtering. The p-type conduction was achieved by thermal annealing at 800 °C for 20 min in N2 ambient. The lowest resistivity of 0.016 Ω cm with a hole concentration and a Hall mobility of 2.31 × 1020 cm−3 and 1.6 cm2/V s, respectively, were obtained at an optimal deposition temperature of 300 °C. X-ray photoelectron spectroscopic analysis confirmed the formation of LiZn and PZn-2VZn acceptor complexes along with a trace of PO defects resulting in a high hole concentration.

Sb-Doped $p$ -MgZnO/ $n$ -Si Heterojunction UV Photodetector Fabricated by Dual Ion Beam Sputtering

Sb-doped p-Mg 0.1 Zn 0.9 O/n-Si-based heterojunction ultraviolet photodetectors were fabricated using dual ion beam sputtering. Current-Voltage measurements showed good rectifying behavior in fabricated devices with rectifying ratio as high as 251.35 at ± 4 V. The detectors exhibited good ultraviolet spectral response having peak responsivity of 0.025 A/W (at 310 nm) and 0.32 A/W (at 320 nm) at -30 V. The values of peak responsivity and external quantum efficiency increased from 1.7 mA/W and 0.75% (at 0 V) to 0.32 A/W and 134.26% (at -30 V), respectively. The value of detectivity of heterojunction devices was calculated to be 3.65 × 10 11 cm · Hz 1/2 ·W -1 at -5 V.

Cu-W thin film structure influenced by Ar+ energy and beam flow during preparation by ion beam sputtering

This article focuses on the effects of Ar+ and beam flow on Cu-W film structure produced using dual ion beam sputtering. The testing method is analysis through XRD. The results show that increasing Ar+ energy and beam flow causes the Cu-W film to crystalize. The Cu-W film deposition speed is primarily determined by Ar+ energy and beam flow.

Forming-free high-endurance Al/ZnO/Al memristor fabricated by dual ion beam sputtering

We report dual ion beam sputtering fabrication of an Al/ZnO/Al memristor displaying forming-free bipolar resistive switching characteristics with memristive behavior without necessitating any post-processing steps. A nearly amorphous ZnO thin film and an appropriate concentration of oxygen vacancies play a significant role in imparting forming-free, stable, and reliable behavior to memory cells. Besides, sufficient non-lattice oxygen ions in the film play a crucial role in the resistive switching process. The AlOx interface layer is observed to strongly affect the switching mechanism in the memory device by altering the barrier at the Al/ZnO interface. The device shows stable switching behavior for >250 cycles with good retention and stable set/reset voltages.

Optoelectronic properties of phosphorus doped p-type ZnO films grown by dual ion beam sputtering

We report highly conductive and stable p-type phosphorus doped ZnO (PZO) thin films fabricated by dual ion beam sputtering and subsequent thermal annealing. Hall measurements established that the annealed PZO films were p-type, which were also confirmed by typical diode-like rectifying current-voltage (I-V) characteristics of the p-PZO/n-Si heterojunction. The maximum hole concentration was evaluated to be 8.62 × 1019 cm−3 with a resistivity of 0.066 Ω cm and a mobility of 1.08 cm2/V s at room temperature. The stability of the p-type conduction was verified by Hall measurement performed again after one year of thin film fabrication resulting in a hole concentration of 3.77 × 1019 cm−3. Spectroscopic ellipsometry was employed to determine the complex dielectric function (ε=ε1+iε2) of p-type PZO films in the 1.2–6.4 eV energy range by a parameterized semiconductor oscillator model. Room temperature excitonic features were identified and the critical point energy was determined by second order derivative of imaginary part of dielectric function. The line shape analysis of ε resulted in a red shift of the energy positions of the critical point with an increase in hole concentration.

Suppression of surface microstructure evolution in W and W–Ta alloys during simultaneous and sequential He and D ion irradiation in fusion relevant conditions

Tungsten (W) has been selected as the divertor material in ITER based on its promising thermal and mechanical properties. Despite these advantages, continued investigation has revealed W to undergo extreme surface morphology evolution in response to relevant fusion operating conditions. These complications spur the need for further exploration of W and other innovative plasma facing components (PFCs) for future fusion devices. Recent literature has shown that alloying of W with other refractory metals, such as tantalum (Ta), results in the enhancement of key PFC properties including, but not limited to, ductility, hydrogen isotope retention, and helium ion (He+) radiation tolerance. In the present study, pure W and W–Ta alloys are exposed to simultaneous and sequential low energy, He+ and deuterium (D+) ion beam irradiations at high (1223 K) and low (523 K) temperatures. The goal of this study is to cultivate a complete understanding of the synergistic effects induced by dual and sequential ion irradiation on W and W–Ta alloy surface morphology evolution. For the dual ion beam experiments, W and W–Ta samples were subjected to four different He+: D+ ion ratios (100% He+, 60% D+ + 40% He+, 90% D+ + 10% He+ and 100% D+) having a total constant He+ fluence of 6 × 1024 ion m−2. The W and W–Ta samples both exhibit the expected damaged surfaces under the 100% He+ irradiation, but as the ratio of D+/He+ ions increases there is a clear suppression of the surface morphology at high temperatures. This observation is supported by the sequential experiments, which show a similar suppression of surface morphology when W and W–Ta samples are first exposed to low energy He+ irradiation and then exposed to subsequent low energy D+ irradiation at high temperatures. Interestingly, this morphology suppression is not observed at low temperatures, implying there is a D–W interaction mechanism which is dependent on temperature that is driving the suppression of the microstructure evolution in both the pure W and W–Ta alloys. Minor irradiation tolerance enhancement in the performance of the W–Ta samples is also observed.

Optical design of Cu/Zr0.2AlN0.8/ZrN/AlN/ZrN/AlN/Al34O62N4 solar selective absorbing coatings

A novel metal–dielectric stacks coating of Cu/Zr0.2Al0.8N/ZrN/AlN/ZrN/AlN/Al34O62N4 as the solar selective absorbing coating was designed. Thin films of Zr0.2AlN0.8, ZrN, AlN and Al34O62N4 deposited by the dual ion beam assisted deposition (DIBAD) were investigated by X-ray diffraction and spectroscopic ellipsometry. XRD results indicate the deposited films of Zr0.2Al0.8N, AlN, and Al34O62N4 are poorly crystallized, whereas, the ZrN film is polycrystalline. The Drude-type dispersion model and Tauc–Lorentz dispersion model are used for determining the complex refractive indices of ZrN and Zr0.2Al0.8N, respectively. For Al34O62N4 and AlN films, Cauchy’s dispersion formula is employed to determine their optical constants. A seven-layer stack with alternating ZrN and AlN layers is optimized by optical simulation programme of TFCalc. The optimized coating obtains the solar absorptance of 0.942 and the emittance of 0.12 at 100°C.

Analysis of sub-bandgap losses in TiO2 coating deposited via single and dual ion beam deposition

We present a detailed study of sub-bandgap losses in TiO2 optical coatings prepared by using a single and a dual ion beam deposition. By extracting high-precision spectra of the losses in the TiO2 layers deposited under varied parameters we were able to study the losses in great detail. We were able to identify several spectral features and discuss their origin. Additional experiments allowed us to determine the contribution of absorption and scattering to the losses, as well as to discern whether the observed losses have volume or interface character. The results reveal that the dominant source of absorption in the high-quality samples is volume absorption originating from the so-called Urbach tail. We discuss the limitations imposed by the Urbach tail.

Technical Aspects of Delivering Simultaneous Dual and Triple Ion Beams to a Target at the Michigan Ion Beam Laboratory

The Michigan Ion Beam Laboratory (MIBL) at the University of Michigan in Ann Arbor, Michigan, USA, plays a significant role in supporting the mission of the U.S. DOE Office of Nuclear Energy. MIBL is a charter laboratory of the NSUF (National Scientific User Facility – US DoE) and hosts users worldwide. The laboratory has evolved from a single accelerator laboratory to a highly versatile facility with three accelerators (3 MV Tandem, a 400kV Ion Implanter and a 1.7 MV Tandem), seven beam lines and five target chambers that together, provide unique capabilities to capture the extreme environment experienced by materials in reactor systems. This capability now includes simultaneous multiple (dual, triple) ion irradiations, an irradiation accelerated corrosion cell, and soon, in-situ dual beam irradiation in a transmission electron microscope (TEM) for the study of radiation damage coupled with injection of transmutation elements. The two beam lines that will connect to the 300kV FEI Tecnai G2 F30 microscope are expected to be operational by the end of 2017. Multiple simultaneous ion beam experiments involving light and heavy ions are already in progress. This paper will outline the current equipment and will focus on the new capability of running dual and triple ion beam experiments.

双离子束溅射中红外SiO2薄膜热稳定性研究

SiO2films are deposited on Si and sapphire (α-Al2O3) substrates by Dual Ion beam sputtering method. The microstructure, surface morphology, residual stress and optical stability of SiO2coating in the wavelength of 0.4~1.2 μm and 3~5 μm are investigated, systematically. The results indicate that the residual stress goes through a local minimum value at ~400. There is a close relationship between the optical constant and the surface conditions, residual stress, microstructure of SiO2film. As the temperature increases up to 1 000, SiO2film can keep well thermal stability without notable damage morphology. The result can give some guidance for designing the optical coatings used in harsh environments. © 2017, Science Press. All right reserved.