Ar Ion Bombardment Research Articles

Strong Fermi-level pinning induced by argon inductively coupled plasma treatment and post-metal deposition annealing on 4H-SiC

The effect of pre–metal deposition cleaning on 4H-SiC Schottky barrier diodes (SBDs) by using Ar ion bombardment in an inductively coupled plasma (ICP) chamber was investigated. The ICP treatment produced a thin and Si-depleted amorphous layer on the SiC surface. Partial graphitization was observed in the amorphous layer after post-metal deposition (PMD) annealing. This interfacial layer strongly pinned the Schottky barrier height (SBH). PMD annealing at 500°C resulted in a constant SBH (approximately 1.1eV) and narrow SBH distribution (standard deviation<3meV). However, the amorphous layer was consumed after 600°C PMD annealing due to interfacial reactions. These results suggest that the Ar ion bombardment technique with a suitable thermal budget can be used to form relatively uniform SBDs.

Comparative characterization of graphene grown by chemical vapor deposition, transferred to nonconductive substrate, and subjected to Ar ion bombardment using X-ray photoelectron and Raman spectroscopies

Graphene specimens grown by chemical vapor deposition on copper and graphene transferred to Si/SiO2 substrate were subjected to an Ar+ ion treatment. A combination of X-ray photoelectron spectroscopy and Raman spectroscopy was used for the characterization graphene in as-grown, air exposed, transferred to Si/SiO2, and subjected to Ar+ bombardment states. We paid attention to make the analysis of the same spot of the sample. It is shown, that the bombardment of graphene on Cu substrate leads to edge etching and decrease of graphene crystallites size. The samples on Si/SiO2 appear less susceptible to etching, however, the defect concentrations reach up the value two orders of magnitude higher than that in graphene on Cu. It is explained by an interaction of carbon on the defect sites introduced under the bombardment with carbon-oxygen radicals generated due to decomposition of organic groups adsorbed on graphene surface.

Nanoimprinting of Ti–Cu-based thin-film metallic glasses deposited by unbalanced magnetron sputtering

Abstract Thin-film metallic glasses (TFMGs) are an optimal material for nanoimprint technology. In this study, we prepared Ti–Cu–Zr–Ni–Hf–Si TFMG films by Ar ion bombardment using unbalanced magnetron sputtering (UBMS) and investigated the effect of nanoimprint temperature and deposition bias voltage on the thermal formability during nanoimprinting. The supercooled liquid region of the films increased with increasing Ar ion bombardment intensity. During nanoimprinting of the films deposited at −200 V using a Si mold with a pillar pattern, the hole depth of the nanoimprinted films increased with increasing nanoimprint temperature. During nanoimprinting of the films deposited with different bias voltages using a Si mold with a line and space pattern at 723 K, the line height of the nanoimprinted films increased with increasing bias voltage. This enhancement in the thermal formability was probably due to the decreasing viscosity of the film by Ar ion bombardment. In addition, the surfaces of the nanoimprinted films deposited using intense Ar ion bombardment were very smooth. Thus, Ar ion bombardment by UBMS is an effective method for fabricating TFMGs for nanoimprint technology.

Correlation of H Adsorption Energy and Nanoscale Elastic Surface Strain on Rutile TiO2(110)

Scanning tunneling microscopy (STM) has been used to obtain the aerial distribution of bridge-bonded hydroxyl groups (HOb) on a rutile TiO2(110) surface, modified with a well-defined nanoscale strain field. Our study makes use of earlier findings that 5–30 nm wide locally strained areas of the surface can be formed via low-energy Ar-ion bombardment combined with a thermal treatment. These strained areas appear as protrusions in the STM images, resulting from subsurface argon-filled cavities. Our STM images show that the local surface concentration of OHb groups is lower on the protrusions. This lowering of concentration has been interpreted as a reduction in the local H absorption energy, ΔE, a result similar to that observed on metals. In this paper, analysis of the reduction in this O–H bond energy across the surface shows a strong correlation between ΔEOH and the characteristic surface strain value, S. The ΔEOH values have been calculated through a subtraction of the contribution of the repulsive dipol...

Effects of Ar ion bombardment by unbalanced magnetron sputtering on mechanical and thermal properties of Ti-Cu-Zr-Ni-Hf-Si thin film metallic glass

This study investigated the effects of Ar ion bombardment during deposition by unbalanced magnetron sputtering (UBMS) on the structure and mechanical and thermal properties of Ti–Cu–Zr–Ni–Hf–Si thin film metallic glass. It was found that Ar was incorporated into the amorphous structure of the deposited films because of the Ar ion bombardment and that the Ar content in the films could be changed from 0.2at% to 14.7at% by controlling the intensity of Ar ion bombardment. The thermal stability of the films was improved by the bombardment process. Further, the surface and cross-sectional morphologies of the films became very smooth and highly dense with an increase in the bombardment intensity. On the other hand, the density of the amorphous structure decreased with the increase in the Ar content. The hardness and Young's modulus also changed with the intensity of Ar ion bombardment. The change in the film hardness was due to the change in the residual stress in the films. Thus, Ar ion bombardment during deposition by UBMS is a useful method for improving the structure and mechanical and thermal properties of thin film metallic glasses.

Influence of surface topography on the secondary electron yield of clean copper samples

Secondary electron yield (SEY) due to electron impact depends strongly on surface topography. The SEY of copper samples after Ar-ion bombardment is measured in situ in a multifunctional ultrahigh vacuum system. Increasing the ion energy or duration of ion bombardment can even enlarge the SEY, though it is relatively low under moderate bombardment intensity. The results obtained with scanning electron microscopy and atomic force microscopy images demonstrate that many valley structures of original sample surfaces can be smoothed due to ion bombardment, but more hill structures are generated with stronger bombardment intensity. With increasing the surface roughness in the observed range, the maximum SEY decreases from 1.2 to 1.07 at a surface characterized by valleys, while it again increases to 1.33 at a surface spread with hills. This phenomenon indicates that hill and valley structures are respectively effective in increasing and decreasing the SEY. These obtained results thus provide a comprehensive insight into the surface topography influence on the secondary electron emission characteristics in scanning electron microscopy.

Controllable preparation of 1-D and dendritic ZnO nanowires and their large area field-emission properties

Large-scale one-dimensional (1-D) and dendritic ZnO nanowires were synthesized on Si substrates using a catalyst-free thermal oxidation technique. By adjusting the stress of the starting Zn thin film for the growth using an Ar ion bombardment process, controllable syntheses of samples composed of only one or a mixture of these two morphologies were achieved. Different nucleation mechanisms were proposed by detailed observations of nucleation and growth process of 1-D and dendritic ZnO nanowires. The strain-induced mass diffusion model and self-catalytic gas-liquid-solid model were used to explain the growth of 1-D and dendritic ZnO nanowires, respectively. In addition, the field-emission characteristics of ZnO nanowires were measured, which showed that dendritic ZnO nanowires have stable emission current.

The study of FTO surface texturing fabrication using Argon plasma etching technique for DSSC applications

This paper is aimed to investigate the fabrication of the fluorine-doped tin oxide (FTO) texturing by using Argon (Ar) plasma etching. The pressure and temperature of Ar gas during plasma etching were 1.6 mbar and 240-285oC, respectively. The plasma etching time was varied from 3 and 10 min. We also prepared without etching samples as reference. UV-Vis spectrophotometer showed that the transmittances of etching samples are higher than the without etching samples. The root mean square roughness (Rq) of etching samples are lower than the without etching samples. It is considered that the Ar ions bombardment can modify the FTO surfaces. However, the etching time does not significantly affect the FTO surfaces for 3 min and 10 min. The Rq of the without etching sample, the etching sample for 3 min, and the etching sample for 10 min are 11.697 nm, 9.859 nm, and 9.777 nm, respectively. These results are good agreement with the four point probe measurement that indicated that the sheet resistance (RS) for each the without sample, the etching sample for 3 min, and the etching sample for 10 min are 16.817 Ωsq, 16.067 Ω/sq, and 15.990 Ω/sq. In addition, the optical transmittance of the etching sample for 3 min and the etching sample for 10 min at wavelengths of 350 - 850 nm are almost similar. This is evidence that the etching time below 10 min cannot significantly change the morphology, optical and electrical properties.

Observation of sputtering of yttrium from Y2O3 ceramics by low-energy Ar, Kr, and Xe ion bombardment in microwave-excited plasma

Y2O3 ceramics were immersed in microwave-excited Ar, Kr, and Xe plasmas, and the sputtering of yttrium atoms from Y2O3 ceramics as a result of low-energy (range of approximately 10 eV) Ar, Kr, and Xe ion bombardment was observed. The amount of sputtered yttrium atoms well correlated with the ion bombardment energy estimated by Langmuir probe measurement. The estimated sputtering yield was 10−5 or less for such a low ion bombardment condition.

Effect of reactive gas additives on surface morphology evolution of stainless steel substrate undergoing low energy Ar ion bombardment

In many cases surface ion bombardment results in roughening of metal's and alloy's surfaces. In the present study, a phenomenon of surface roughening inhibition during the ion bombardment is presented. The phenomenon occurred during the plasma extracted ion sputter etching at normal incidence with 400 eV positive ions, when 1% of dried air was added into the plasma forming Ar gas. Two 18%Cr–10%Ni mechanically polished to about 2 nm average roughness (Ra) stainless steel test pieces were sputter etched with and without the air additive. The roughening was inhibited to Ra ≈ 4 nm, which was about 9.5 times lower than that of the sputtered without air additive (Ra ≈ 38 nm). The phenomenon is discussed in terms of chemisorption of active plasma species introduced by the air additive and competing roughening/smoothening mechanisms.

Effect of O2 on etch characteristics of Co2MnSi thin films in CH4/O2/Ar gas mixture

Co2MnSi thin films masked with TiN films were etched in CH4/Ar and CH4/O2/Ar plasmas by inductively coupled plasma reactive ion etching. The etch rates decreased with increasing CH4 concentration in CH4/Ar gas, whereas the etch selectivity increased. The addition of O2 to CH4/Ar gas resulted in significant improvement in the etch profile but a decrease in the etch rates. Optical emission spectroscopy showed that a variety of COx, OH, and H2O species were formed in the CH4/O2/Ar plasma, acting a role as a passivation layer to protect the pattern sidewalls. X-ray photoelectron spectroscopy also confirmed the formation of metal oxides on the film surface, which could be sputtered off easily by Ar ion bombardment. A high degree of anisotropy of Co2MnSi films was obtained in the CH4/O2/Ar etch gas.

Effect of Surface Morphology of Catalysts Nickel Coatings Obtained by Cathodic Arc in the Synthesis of Carbon Nanostructures

In this work carbon nanostructures were synthesized by CVD using nickel films deposited onto silicon substrates by cathodic arc technique. In order to modify the surface morphology of the catalyst, the silicon substrate and the nickel coating were exposed to an Ar ion bombardment generated in a dc glow discharge at room temperature. The surface morphology was examined by atomic force microscopy (AFM). The morphology of the nanotubes and other carbon structures was observed by scanning electron microscopy (FE-SEM) and Transmission Electron Microscopy (TEM).It was found that nanofibers with helical geometry grew on the nickel catalyst deposited onto the silicon substrate without the glow treatment, and carbon nanofiber with a linear geometry grew on the nickel catalyst deposited onto the silicon substrate with the glow treatment. Carbon nanotubes (CNTs) were obtained when the Si substrate and the Ni film were treated with the glow discharge.The CNTs obtained are mostly very thin with an average diameter between 8 and 15nm, with only a few CNTs with external diameters of up to 60nm.

Non-crystallization and enhancement of field emission of cupric oxide nanowires induced by low-energy Ar ion bombardment

The effect of low energy Ar ion bombardment on the structure and field emission properties of CuO nanowires was studied. The morphology and structure were characterized by scanning electron microscopy and high resolution transmission electron microscopy. Non-crystallization of the nanowire was found after bombardment, which was due to the diffusion of the defects induced by knock-on ions. The work function of nanowires decreased after bombardment which was attributed to the preferential sputtering of oxygen. Field emission measurements showed that after bombardment with different energy the turn-on field decreased first and then increased with increasing ion energy. The lowest turn-on field was obtained with the optimal ion energy of 215eV. The typical turn-on fields of the as-grown samples and samples after Ar ion bombardment with energy of 215eV were about 6.5V/μm and 5.25V/μm, respectively. The lowered field emission turn-on field was attributed to the increase of field enhancement factor and decrease of work function.

Nanoscale strain engineering on the surface of a bulk TiO2 crystal.

Arrays of highly strained 5-25 nm-wide regions have been prepared on rutile TiO2(110) surface through a low energy Ar ion bombardment technique. Using scanning tunneling microscopy (STM) and an innovative STM tip-triggered nanoexplosion approach we show experimentally that the protrusions arise from subsurface Ar-filled pockets. Continuum mechanics modeling gives good estimates of the corresponding elastic deformation. Surface strain values of up to 4% have been deduced.

Enhanced bioactivity of polyvinylidene chloride films using argon ion bombardment for guided bone regeneration.

Polyvinylidene chloride (PVDC) is a long chain carbon synthetic polymer. The objective of this study was to improve the bioactivity of PVDC films through surface modification using argon (Ar) ion bombardment to create Ar-modified PVDC films (Ar-PVDC) to address the clinical problems of guided bone regeneration (GBR), which is technique-sensitive, and low bone regenerative ability. First, the effects of Ar ion bombardment, a low temperature plasma etching technique widely used in industry, on PVDC film wettability, surface chemistry, and morphology were confirmed. Next, fibroblast-like and osteoblast-like cell attachment and proliferation on Ar-PVDC were assessed. As a preclinical in vivo study, Ar-PVDC was used to cover a critical-sized bone defect on rat calvaria and osteoconductivity was evaluated by micro-computed tomography analysis and histological examinations. We found that the contact angle of PVDC film decreased by 50° because of the production of -OH groups on the PVDC film surface, though surface morphological was unchanged at 30 min after Ar ion bombardment. We demonstrated that cell attachment increased by about 40% and proliferation by more than 140% because of increased wettability, and 2.4 times greater bone regeneration was observed at week 3 with Ar-PVDC compared with untreated PVDC films. These results suggest that Ar ion bombardment modification of PVDC surfaces improves osteoconductivity, indicating its potential to increase bone deposition during GBR.

Enhancing the stability of microplasma device utilizing diamond coated carbon nanotubes as cathode materials

This paper reports the enhanced stability of a microplasma device by using hybrid-granular-structured diamond (HiD) film coated carbon nanotubes (CNTs) as cathode, which overcomes the drawback of short life time in the CNTs-based one. The microplasma device can be operated more than 210 min without showing any sign of degradation, whereas the CNTs-based one can last only 50 min. Besides the high robustness against the Ar-ion bombardment, the HiD/CNTs material also possesses superior electron field emission properties with low turn-on field of 3.2 V/μm, which is considered as the prime factor for the improved plasma illumination performance of the devices.

Ion-Beam Irradiation Effect in the Growth Process of Graphene on Silicon Carbide-on-Insulator Substrates

We investigated the effect of ion-beam irradiation of the 3C-SiC(111) surface on the growth of graphene by the SiC surface-decomposition method. When a 3C-SiC(111) surface was irradiated by 1 keV Ar+ ions at a dose of 4.5 × 1015 cm2 in an ultra-high-vacuum chamber and then annealed at 1200 °C for 1 min, the formation of graphene layers was promoted in comparison with that in the absence of ion-beam irradiation. X-ray photoelectron spectroscopy studies showed that Ar ion bombardment of the 3C-SiC(111) caused breakage of surface bonds and helped Si atoms to desorb from the surface.

Influence of the surface chemistry on TiO2 – TiO2 nanocontact forces as measured by an UHV–AFM

Particle-wall contact forces between a TiO2 film coated AFM tip and TiO2(110) single crystal surfaces were analyzed by means of UHV–AFM. As a reference system an octadecylphosphonic acid monolayer covered TiO2(110) surface was studied. The defect chemistry of the TiO2 substrate was modified by Ar ion bombardment, water dosing at 3×10−6Pa and an annealing step at 473K which resulted in a varying density of Ti(III) states. The observed contact forces are correlated to the surface defect density and are discussed in terms of the change in the electronic structure and its influence on the Hamaker constant.

Plasma damage mechanisms in low k organosilicate glass and their inhibition by Ar ion bombardment

In-situ x-ray photoelectron spectroscopy and ex-situ Fourier transform infrared spectroscopy studies of vacuum ultraviolet (VUV) photons with or without O2, and O radicals point to distinct mechanisms of carbon abstraction in nanoporous organosilicate glass (OSG) films. VUV alone in the absence of O2 results in Si-CH3 bond scission and recombination preferentially at silicon monomethyl sites, obeying diffusion kinetics. In contrast, the presence of O2 interferes with recombination, resulting in diffusion-dominated carbon loss kinetics, enhanced Si oxidation, and greatly accelerating the rate of carbon loss in both the near surface and bulk regions of the OSG, at both monomethyl and dimethyl sites. Carbon abstraction due to exposure to (O(3P)) does not follow diffusion kinetics, and such interactions yield a SiO2-like surface layer inhibiting further O diffusion. Results indicate that diffusion-dominated carbon abstraction kinetics previously observed for OSG exposure to O2 plasma damage is primarily attributable to the diffusion of O2 down OSG nanopores, reacting at photoactivated sites, rather than the diffusion of O radicals. OSG pretreatment by 900 eV Ar+ bombardment effectively inhibits both VUV + O2 and O damage mechanisms by formation of ∼1 nm thick SiO2-like surface region that inhibits both O and O2 diffusion.

Bosch 공정에서 Si 식각속도와 식각프로파일에 대한 Ar 첨가의 영향

Bosch 공정의 식각 단계에서 Ar을 첨가하였을 때 Si의 식각특성을 관찰하기 위하여 식각 단계에서 <TEX>$SF_6$</TEX> 플라즈마만 사용한 경우와 Ar 유속비율이 20%인 <TEX>$SF_6$</TEX>/Ar 플라즈마를 각각 사용하여 Si을 Bosch 공정으로 식각하였다. Bosch 공정의 식각 단계에서 <TEX>$SF_6$</TEX> 플라즈마에 Ar 가스를 첨가하면 <TEX>$Ar^+$</TEX> 이온에 의한 이온포격이 증가하였고 이는 Si 입자의 스퍼터링을 초래할 뿐 아니라 F 라디칼과 Si의 화학반응을 가속하였다. 그 결과 식각 단계에서 20%의 Ar이 첨가되어 Bosch 공정으로 수행된 Si의 식각속도는 Ar이 첨가되지 않은 경우보다 10% 이상 빨라졌고 식각프로파일도 더욱 비등방적이었다. 이 연구의 결과는 Bosch 공정으로 Si을 식각할 때 식각속도와 식각프로파일의 비등방성을 개선하는데 필요한 기초자료로 사용될 수 있을 것으로 판단된다. The etch rate and etch profile of Si was investigated when Ar was added to an <TEX>$SF_6$</TEX> plasma in the etch step of the Bosch process. A Si substrate was etched with the Bosch process using <TEX>$SF_6$</TEX> and <TEX>$SF_6$</TEX>/Ar plasmas, respectively, in the etch step to analyze the effects of Ar addition on the etch characteristics of Si. When the Ar flow rate in the <TEX>$SF_6$</TEX> plasma was increased, the etch rate of the Si substrate increased, had a maximum at 20% of the Ar flow rate, and then decreased. This was because the addition of Ar to the <TEX>$SF_6$</TEX> plasma in the etch step of the Bosch process resulted in the bombardment of Ar ions on the Si substrate. This enhanced the chemical reactions (thus etch rates) between F radicals and Si as well as led to sputtering of Si particles. Consequently, the etch rate was higher more than 10% and the etch profile was more anisotropic when the Si substrate was etched with the Bosch process using a <TEX>$SF_6$</TEX>/Ar (20% of Ar flow rate) plasma during the etch step. This work revealed a feasibility to improve the etch rate and anisotropic etch profile of Si performed with the Bosch process.