Ar Ion Bombardment Research Articles

Effects of Ar ion bombardment on the structure and properties of β-quartz

β-quartz is an important component that affects the physical and chemical properties of glass-ceramics. The material removal process of ion beam machining is complicated as one of the ultra-precision machining forms. Therefore, it is important to understand the removal mechanism of ion beam machining materials. The methods of molecular dynamics (MD) and first-principles were adopted to investigate the microscopic mechanism of ion beam bombardment of the β-quartz structure. The damage evolution of structures and the evolution of material properties caused by defects respectively from the atomic and electronic levels. Through MD analysis, we find that the random collision between incident ions and matrix atoms can lead to the formation of sputtered atoms. The incidence of ions will increase the disorder degree of the matrix, and the influence on the disorder degree at different depths of the matrix is different. The degree of disorder increases obviously in the range of 50–70 Å from the surface of the matrix. It has a significant impact on the surface topology of the matrix, the number of defects, surface roughness, and matrix density. The results of first-principle calculation show that the refraction, absorption and other characteristics of the system are significantly different with different doping forms, and the energy loss is most affected by substituted doping. And the substituted doping defects have the most significant effects on the structural energy loss. Among, the Ar-substituted O doping structure leads to higher energy loss, and the peak energy loss intensity reaches 5.146. In contrast, the Ar-substituted Si doping structure causes the least energy loss, the intensity is 2.543. This study provides a theoretical basis for the selection of parameters and the realization of ultra-smooth surface in actual ion beam machining.

Effect of Ar-ion irradiation on electrical transport of WS2 monolayer

Two-dimensional transition metal dichalcogenides (2D-TMDs), such as WS2 and MoS2, have attracted exceptional attention as promising materials for future optoelectronic systems due to their unique properties, including a direct band gap, high quantum efficiency, and flexibility. However, exploiting these materials’ potential in their pristine state remains a key challenge because of limited tunability and control over their properties. The introduction of crystal defects, such as vacancies and dopants, induces localized mid-gap states in 2D materials, enhances electrical transport, and creates a platform for tuning and exploiting these materials for practical applications. Our study explores the effect of Ar-ion beam irradiation on monolayer WS2, resulting in enhanced electrical transport compared to the pristine sample. We regulated the Ar-ion bombardment energy to vary the defect concentration from 0.1 to 0.5 keV. Photoluminescence (PL) and Raman investigations, revealed the extent of damage to the material. At the same time, x-ray photoelectron spectroscopy showed changes in the oxidation state with increasing irradiation energy. Our results demonstrated that Ar-ion treatment at low-energy irradiation enhanced electrical transport by ∼12 fold compared to pristine till 0.2 keV of irradiation by incorporating defects. However, higher irradiation energies reduced electrical transport due to increased disorder in the WS2 monolayer. This investigation highlights the potential for controlled defect engineering to optimize the properties of 2D-TMDs for practical applications.

Revealing the controlling mechanisms of atomic layer etching for high-k dielectrics in conventional inductively coupled plasma etching tool

The possibilities of optimization of the two-step atomic layer etching process for HfO2 in conventional plasma etching tools were studied. The surface modification step was realized in Ar/CF4/H2 plasma, and the reaction between the modified layer and the surface was activated by Ar ion bombardment from the plasma in the second step. Investigation of the effects of activation step duration, DC bias during activation, and Ar plasma density was carried out. The mechanism of the etching process has been shown to involve fluorination of oxide during the modification step and subsequent removal of fluorine-containing particles at the activation step. An increase in parasitic sputtering rate and lower process saturation with the growth of DC bias during activation was demonstrated. The advantage of the ALE process in lower surface roughness over the conventional etching process was shown. Similar etching characteristics of HfO2 and ZrO2 suggest a similarity in the etching process for the mixed hafnium-zirconium oxide material.

On the splitting of the surface plasmon resonance band of gold nanopillars developed on rippled Si surface

In this work, we reported split surface plasmon resonance (SPR) bands originated from the Au nanopillars developed on rippled Si substrates. This is the first report of gold SPR splitting on a pre-structured Si surface. The Si surface was subjected to a bombardment of Ar ions to fabricate ripples on the surface. A 5 nm thin layer of Au was then deposited on the rippled surface, and the SPR was studied using UV–visible spectroscopy. Further, X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure spectroscopy (EXAFS) were used to characterize the prepared samples. The AFM confirmed that the deposited gold is in nanopillar form, and the rippled surface governs the growth, shape, and size of gold nanopillars. A large aspect ratio has been observed for the nanopillars, resulting in a red-shifted and split SPR band. The experimental XANES of Au L3-edge were successfully mimicked by simulated XANES, confirming the existence and signature of the nanostructure. For the first time, the local structure information of Au nanopillars constructed on rippled Si substrate has been obtained using the EXAFS approach in different directions and correlated with the plasmonic bands.

Topographically-selective atomic layer etching of SiO2 using radical fluorination of the surface followed by Ar ion bombardment

The chemical nature of surface fluorination followed by ion bombardment has been explored to achieve a topographically selective atomic layer etching of silicon dioxide at RT. In this work, a two-step low-pressure sulfur hexafluoride (SF6) remote plasma modification (without any ion bombardment) followed by argon (Ar) ion bombardment is presented. In situ investigations of the surface bonding confirmed the modification during the half-reaction steps and spectroscopic ellipsometry data reveal the thickness change while suggesting an incubation period prior to obtaining a uniform etch per cycle of 0.14 nm with a synergistic 30 s fluorination of the surface followed by a 60 s Ar bombardment. The etch profile of the trenched structured sample displays the isotropic etch for the two-step process, as well as the feasibility of a topo-selective top-and-bottom etch by bias application in the Ar bombardment step.

Surface stress release in AlCrN coatings determined by synchrotron radiation multi-reflection grazing-incidence X-ray diffraction

In this work, the residual stress distribution of c. 3.8 μm arc-evaporated AlCrN coatings was investigated by the synchrotron radiation multi-reflection grazing-incidence X-ray diffraction method. Ar ion bombardment post-treatment was also used to tune the stresses in the AlCrN coating to elucidate the evolution of stress therein. The result showed that the as-deposited AlCrN coating showed large surface stress of −1500 MPa, this sharply decreased in magnitude to −800 MPa in the internal coating. Ar ion bombardment (post-treatment) could significantly reduce the surface stresses by around −1000 MPa and the interior stresses by around −400 MPa for an AlCrN coating, the “shot peening” effect arising therefrom could promote migration and diffusion of the adatoms, which contributed to the reduction of the micro-strain and interior stress. Furthermore, Ar ion bombardment also promoted the growth of surface grains, which also contributed to the stress reduction in the near-surface region of the AlCrN coating. In addition, Ar ion bombardment could increase the substrate stresses from −32 MPa to −210 MPa. The results suggested that internal stress reduction could be achieved by promoting the migration and diffusion of adatoms.

Direct diffusion bonding of 1060Al processed by surface activation with various doses of Ar ion bombardment

In this work, the microstructure and properties of the 1060Al surface after bombardment with different doses of Ar ion and the evolution rule of the quality of the subsequent solid-state diffusion bonded joints have been investigated in detail. The results showed that the oxide layer could be removed completely at an appropriate ion bombardment dose (2 × 1018ion/cm, while kept the same energy of 1 keV), the roughness of the surface was also reduced, crystal defects such as dislocation loops formed near the surface, all of the above factors were beneficial for diffusion bonding. Well-bonded joints with a bonding ratio of ∼97.7% and a shear strength of ∼45.9 MPa could be obtained even at lower process parameters (450 °C/90 min, 5 MPa). When the bombardment dose was too low, the residual oxide film and the rough surface were not conducive to atomic diffusion at the interface, resulting in the unbonded defects in the joint. While the irradiated expansion of the 1060Al surface occurred when the bombardment dose was too high, and the bulges would crack under pressure. In both cases, it could not obtain a well-bonded interface, the joints showed a lower shear strength.

Amorphous carbon interlayer modulated interfacial thermal conductance between Cu and diamond

Introducing an interlayer is an effective method to improve the interfacial thermal conductance (G) of highly mismatched Cu/diamond interface. However, the relative role of interfacial bonding effect and vibrational bridging effect of the interlayer is still not clear. Herein, we introduce amorphous carbon (a-C) layer by Ar ion bombardment, oxygenated a-C layer by Ar/O2 mixture ion bombardment, and C-O bond by acid treatment at the Cu/diamond interface to regulate the interfacial bonding effect and vibrational bridging effect. The G of Cu/diamond is increased by 44% with increasing interfacial bonding strength from 12 mN to 17 mN and then is independent on interfacial bonding strength above 17 mN, which mainly comes from the interfacial bonding effect. Compared with the as-cleaned Cu/diamond interface, a 35% increase of G is obtained by inserting a 4.5 nm-thick a-C interlayer between Cu and diamond, which mainly comes from the vibrational bridging effect. The vibrational bridging effect overwhelms the interfacial bonding effect in improving the G of Cu/diamond interface when the interfacial bonding strength is relatively high. The findings give insights into the mechanisms dictating heat transfer of highly mismatched metal/non-metal interface and provide a new avenue for improving the G of Cu/diamond interface.

Ion bombardment induced surface microstructural modification of aluminum alloy

Surface microstructural modifications of 2A12 aluminum alloy exposed to 60 keV Ar ion bombardment with the dose of 1 × 1017 ions/cm2 under vacuum were studied in detail. The amorphous layer with the thickness of ∼130 nm accompanied with polycrystalline aluminum was formed at the surface after Ar ion bombardment. Beneath the amorphous layer, Al2CuMg precipitates were observed. Dynamic recrystallization(DRX)and grain growth were observed with the increment of texture intensity. Surface residual compressive stress and strain were enhanced characterized by electron back-scattered diffraction. After ion bombardment, the contact angles of diiodomethane and DI water on aluminum alloy were increased, and a notable decrement of surface energy of aluminum alloy was measured from 32.5 mJ/m2 to 23.4 mJ/m2. The diffusion experiments indicated that the mutual diffusion of Cu and Al was inhibited due to the bombardment-induced amorphous layer at aluminum alloy surface, which is beneficial to its application as a structure material in aerospace field.

Stress‐Free Detachment of Flexible Substrate from Glass Carrier Using CO2 Point Laser for Large‐Area Applications

AbstractA novel detachment method is presented for flexible substrates from glass carrier wafers using a CO2 point laser. In a conventional laser lift‐off process, laser‐induced illumination and thermal stress degrade device performance. In this approach, a point laser is applied on the edge of the flexible substrate, where electrical components do not exist, and thus, no performance degradation occurs during the laser process. In addition, the carrier surface properties are modified to control the adhesion force between the flexible substrate and the glass carrier. A spin‐on‐dielectric layer (SOD) is utilized, and Ar ion bombardment is performed on SOD. The point laser detachment method is demonstrated in flexible thin‐film transistors, and no change is observed in the electrical characteristics before and after detachment from the carrier wafer.

Toward Perfect Surfaces of Transition Metal Dichalcogenides with Ion Bombardment and Annealing Treatment.

Layered transition metal dichalcogenides (TMDs) are two-dimensional materials exhibiting a variety of unique features with great potential for electronic and optoelectronic applications. The performance of devices fabricated with mono or few-layer TMD materials, nevertheless, is significantly affected by surface defects in the TMD materials. Recent efforts have been focused on delicate control of growth conditions to reduce the defect density, whereas the preparation of a defect-free surface remains challenging. Here, we show a counterintuitive approach to decrease surface defects on layered TMDs: a two-step process including Ar ion bombardment and subsequent annealing. With this approach, the defects, mainly Te vacancies, on the as-cleaved PtTe2 and PdTe2 surfaces were decreased by more than 99%, giving a defect density <1.0 × 1010 cm-2, which cannot be achieved solely with annealing. We also attempt to propose a mechanism behind the processes.

Effect of H, He and Ar irradiation on β-Ga2O3 material

In this work, the projected range, the nuclear stopping power(Sn), electronic stopping power (Se), vacancies, replacement collisions, and total target damage of β-Ga2O3 by H, He and Ar ion bombardment are investigated by the Monte Carlo SRIM software. The ions were vertically incident on a 1-um β-Ga2O3 material, and their energies varied from 100 keV to 1 MeV. The results showed that the projected range increased for all three ions with increasing incident energies, with H ions having the largest projected range. The Sn for Se with incident energy of 0-1MeV in β-Ga2O3 is much greater than the Sn for H and He, while the Sn for Ar decreases gradually with the increase of incident ion energy, and the Se shows a gradual increasing trend. Compared with H and He, the number of vacancies induced by Ar were the largest at the same incident energy and thickness of β-Ga2O3. In addition, it is obvious that the total target damage of Ar on β-Ga2O3 material were much more serious than H and He.

Effects on graphene of electron irradiation at 25 keV and dosages up to 1018 electrons/cm2

We report on the properties of defects in exfoliated graphene on SiO2 produced by electron irradiation at 25 keV and dosages from 4.96 × 1015 to 9.56 × 1017 electrons/cm2. With increasing dosage, graphene exhibits the two-stage amorphization trajectory reported for the Ar ion bombardment of graphene. Initially, the ratio of the D-peak height, ID, to the G peak height, IG, increases as new defects are formed. In the second stage, ID/IG decreases as defects cover most of the sample. In the second stage, we find that the full width at half maximum of the Raman 2D, D, and G peaks increases by 3, 3, and 6 cm−1, respectively. These values are less by factors of about 10, 5, and 10, respectively, than those reported for amorphous graphene produced by Ar ion bombardment. We find that ID/IG monotonically decreases in the second stage as the annealing temperature increases from 80 to 220 °C. Assuming that ID/IG is proportional to the defect density, we find an activation energy for defect healing, Ea = 0.48 eV, which is significantly less than Ea = 0.95 eV reported for vacancies and closer to Ea = 0.29 and 0.58 eV reported for hydrogen and hydroxyl group adsorbates, respectively. We propose that, in the second stage, graphene does not become amorphous, and the defects responsible for the D peak are adsorbates.

Effect of charge-up of surfaces of sintered Y2O3 and yttrium oxyfluoride on their erosion rates due to ion bombardment

The erosion rate of sintered Y2O3 and yttrium oxyfluoride (Y-O-F) due to Ar ion bombardment was investigated for use in the plasma process chamber. The Ar ion bombardment was performed by irradiations of Ar plasma and Ar ion beam. In addition, charge-up behavior of these ceramics was investigated by two methods. One was the measurement of the surface voltage during the plasma irradiation (the so-called self-bias voltage), and the other was the measurement of the surface voltage generated due to the accumulation of static electricity in the clean room air. It was found that the negative self-bias voltage of the Y2O3 surface was smaller than that of Y-O-F. It was also found that Y2O3 was easily positively charged by the accumulation of the static electricity compared to Y-O-F, which was consistent with the observed relationship of the self-bias voltages between Y2O3 and Y-O-F. For the evaluation of the erosion rate due to Ar ion bombardment, it was found that the material and setting of masks to make the erosion step for evaluating the rate greatly affected the results. When electrically conductive masks with electrically connecting to a substrate were used, the erosion rate of Y-O-F was smaller than that of Y2O3. The results suggested that the intrinsic ion-bombardment-induced erosion rate of Y-O-F was smaller than that of Y2O3, because the ion bombardment energy was expected to be almost the same due to the existence of the conductive masks. On the other hand, when insulating masks were used, the rates of Y2O3 and Y-O-F were almost the same level. Considering the aforementioned charge-up behavior, the results suggested that a relatively larger positive charge-up of the Y2O3 surface during the ion bombardment decelerated injecting ions, resulting in the decrease in ion bombardment energy and, thus, the erosion rate.

Crystalline Phase Segregation of Quantum-Dots-Passivated CH3NH3PbI3 Film via Argon Plasma Treatment

In this study, a composite perovskite film composed of lead cesium triiodide (CsPbI3) quantum dots (QDs) and methylammonium lead iodide (CH3NH3PbI3; MAPbI3) was proposed. The CsPbI3 QDs prepared by hot-injecting were used as an anti-solvent in precursors to passivate the surface of this composite perovskite film. The further argon (Ar) plasma treatment improves the surface of the film. The effects of the powers from 100 to 200 W on the composite perovskite film structure, chemical element composition, and optical properties were studied. The experimental results demonstrate that the CsPbI3 QDs passivation boosts the ultraviolet light absorption (350–450 nm) and inhibits the formation of the PbI2 phase. Furthermore, Ar plasma treatment effectively improved CsPbI3 QDs passivation on MAPbI3 film. The powers lower than 140 W cause C=O bonds to dissolve and coordination bonds to form between OA carboxyl moieties and undercoordinated Pb2+ ions. At 160 and 140 W, the obvious crystal phase segregation and a decrease in light absorption are observed, respectively. Meanwhile, the strong bombardment of Ar ions at higher than 160 W causes the severe degradation of MAPbI3 film.

Selective atomic layer etching of Al2O3, AlNx and HfO2 in conventional ICP etching tool

The atomic layer etching process of Al2O3, AlNx and HfO2 in conventional plasma etching tool was investigated. The etching process is based on surface modification by fluorocarbon film deposition from Ar/CF4/H2 plasma and subsequent activation of etching by Ar ion bombardment from plasma. The study of deposition process showed that varying plasma composition surface kinetics significantly change from deposition to etching. This is associated with the rise of fluorine concentration both in plasma and in deposited fluorocarbon film. Plasma mixture with low CF4 fraction was chosen for modification step of ALE process because it provides low fluorinated film which does not etch SiO2 and TiN improving selectivity to the potential mask material in etch process. The ALE process shows self-limiting characteristics providing the ALE process window at duration of modification step. The etch rate is 0.16 nm/cycle for Al2O3, 0.20 nm/cycle for AlNx and 0.11 nm/cycle for HfO2, which is close to monolayer mode. Relatively short cycle duration provides feasible etch rate in terms of time consumption. The significant selectivity over TiN (more than 20) was achieved allowing employing TiN as mask material for high resolution selective etching.

Effects of substrate bias on the sputtering of high density (111)-nanotwinned Cu films on SiC chips

This article presents a study of the influence of the substrate bias on the microstructure, preferred orientation, and mechanical and electrical properties of nanotwinned Cu film. The formation of a nanotwinned structure and (111) surface orientation can be properly controlled by applied substrate bias. High density nanotwinned structures were introduced into Cu films sputtered on SiC substrates with over 90% of (111)-orientation at − 150 V. Densely packed Cu nanotwins were observed within the columnar grains stacked up on each other along the film growth direction, with an average twin spacing of 19.4 nm. The Cu films deposited on SiC substrate via bias sputtering had surface roughness of 8.6 to 15.8 nm. The resistivity of the copper nanotwinned films sputtered with various substrate biases varied. The optimal indentation, 2.3 GPa, was found in the nanotwinned Cu film sputtered with a bias voltage of − 150 V. The effects of Ar ion bombardment on microstructure, surface morphology and properties are further discussed.

Ion bombardment-induced defect reduction at a-Si:H/c-Si interfaces: possible microstructural changes and mobile hydrogen roles

A beneficial effect of argon (Ar) ion bombardment for crystalline silicon (c-Si) surface passivation has been studied. Experiments of an Ar plasma treatment over an hydrogenated amorphous silicon (a-Si:H) layer grown on c-Si are performed, where an a-Si:H layer is prepared at different levels of defect density. Interestingly, the c-Si surface passivation is improved by an Ar plasma treatment for a defect-rich, i.e. low-quality, a-Si:H layer, while it is deteriorated by the treatment for a low-defect, i.e. high-quality, a-Si:H layer. The improvement of passivation is discussed in terms of microstructural changes of a-Si:H, associated with redistribution of hydrogen, where mobile hydrogens play an important role.

Surface modification of pure aluminum via Ar ion bombardment for Al/Al solid-state diffusion bonding

Ar ion bombardment was applied to modify the aluminum surface and a subsequent solid-state diffusion bonding was performed. The effect of Ar ion bombardment on surface conditions and properties was studied to analyze the relationship between surface modification and joint performance. With increase of the Ar ion energy, the surface oxide film was removed and its surface roughness tended to decreased first and then increased. The oxide-free aluminum surface with minimal roughness of 0.61 nm was obtained by 1 keV bombardment while the numerous small dislocation loops uniformly distributed in the aluminum surface structure enhanced the surface hardness. Under high-energy bombardment (>5 keV), the surface became swollen or even porous due to the growth of dislocation loops and Ar bubbles that made the surface rough and embrittled, which deteriorated the microstructure and strength of bonded joints. The well-bonded joint with shear strength of 45.9 MPa was obtained at 1 keV bombardment and diffusion bonding temperature of 450 °C. The specific shear strength of ~60% was higher than that of conventional Al diffusion bonded joints. This work is of significance for the manufacture of well-bonded aluminum microchannel heat exchangers. • Bombardment-induced modification is studied in terms of morphology and structure. • The relationship among bombardment, modification and bonding behavior is discussed. • The evolution of bombarded defects affects the surface hardening and embrittlement. • Well-bonded Al joints are obtained at low temperatures by Ar ion bombardment.

Surface microstructure and wetting of SiC ceramic modified by ion bombardment

Ion bombardment is one of the powerful methods to modify the surface characteristics of materials. In this study, SiC ceramic is bombarded under different fluences by 60 keV Ar-ion beam. The effects of Ar ion bombardment on the surface microstructure and subsequent wetting of SiC ceramic using AgCu-Ti filler metal are investigated. Ar ion bombardment can break the SiC bond of SiC cell, thus, SiCx(x < 1), SiCx(x < 1) twins and the amorphous layer are generated in the SiC surface with the increase of fluence from 1×1014/cm2 to 1×1017/cm2. With the increase of fluences, the contact angle decreases by the acceleration of interfacial reaction rate as a result of the break of SiC bond in SiC surface in the rapid spreading stage. The amorphous layer is gradually formed in the SiC surface, requiring more time to reach the equilibrium stage for droplets, while the bonding quality of the SiC/AgCu-Ti wetting interface is obviously improved. Significant modification in the microstructural and excellent wetting behavior are obtained by leveraging the ion bombardment technique.