Ion Etching Research Articles

Electronic Bond Structure of Carbon Nitride Thin Film Deposited by HiPIMS and dc Magnetron Plasma

We report the difference in electronic bond structure and surface chemical property of amorphous carbon nitride (a-CNx) film as a function of N/C which has been deposited by high power impulse magnetron sputtering (HiPIMS) and DC magnetron (dc-MS) plasma. The spectroscopic analyses suggest that the presence of oxide layer is the major cause for the surface charging in the core level peak. The core electron peaks (C1s, N1s and O1s) in x-ray photoelectron spectroscopy (XPS) show higher surface charging in HiPIMS compare to the film deposited by dc-MS plasma. The core peaks are moved gradually toward its virgin position as the etching duration is increased from 1 min to 80 mins. The films deposited by HiPIMS retain a higher N/C ratio following ion etching as compared to those deposited by DC magnetron sputtering suggesting denser films with a higher degree of cross-linking.

Sb (111) Abnormal Behavior under Ion Etching

Due to a strong spin-orbit interaction (SOI), the surface states of Sb (111) are similar to those for topological insulators (TI) Sugawara et al. (2006). The surface states are protected by time-reversal symmetry and energy dispersion is a linear function of momentum. Defects in crystal structure lead to a local break of the surface translational symmetry and can modify surface states. It is the primary reason to study defects of Sb crystal structure and their effect on the surface states dispersion. Etching of the Sb (111) surface using Ar+ ions is a common way to create defects both in a bulk and on the surface of the crystal. Sb (111) ion etching at room temperature reveals anomalous behavior of surface crystal structure. It results in formation of flat terraces of 2nm in size. Investigation of electronic structure of the etched Sb (111) surface has demonstrated increase of density of states (DOS) at the Fermi level. The results are discussed in terms of local break of conditions of Peierls transition.

Study on electrical properties of ion-beam-etched HgCdTe crystal

In this paper, we study the electrical properties of ion-beam-etched Hg1-xCdxTe (x=0.236) crystal with the help of mobility spectrum analysis technique. In step-by-step chemical etching, it is shown that the p-HgCdTe is completely converted to the n-type one which includes a damaged surface electron layer with a low mobility and a bulk electron layer with a higher mobility after ion etching. The mobility spectra at different temperatures show that the mobility of the surface electrons is independent of temperature in the measurement temperature range while the bulk electrons exhibit a classical behavior of n-HgCdTe with characteristics that are strongly dependent on temperature. Hall data for different thicknesses show that the electrical properties of the bulk layer are uniform. Otherwise, the surface electron layer may be found to consist of a concentration about 2-3 order of magnitude higher than the bulk electron layer.

Gas Sensing Characterisation of CMOS Integrated Nanocrystalline SnO2 – Au Thin Films

Conductometric measurements were performed on a CMOS integrated SnO2 – Au functionalized gas sensor. The sensor material was deposited by spray pyrolysis at 400°C upon a microhotplate (a CMOS integrated structure to adjust the sensor's temperature). The sensing layers were structured by photolithography and ion etching. The functionalization of the SnO2 layers was conducted by evaporation of a 2nm thin gold film. In a subsequent step the sensing layers were tempered at 400°C, which resulted in the formation of Au nanoparticles. The sensor performance is evaluated for ethanol, a hydrocarbon-mix (acetylene, ethane, ethene, and propene) and two relative humidity levels.

Linear variable filters fabricated by ion beam etching with triangle-shaped mask and normal film coating technique

In this Letter, we propose a method of fabricating linear variable filters by ion beam etching with masking mechanisms. A triangle-shaped mask is designed and set between the ion source and sample. During the ion etching, the sample is moved back and forth repeatedly with a constant velocity for the purpose of obtaining the linearly varied thickness of the cavity. Combined with ion beam assistant thermal oxidative electron beam evaporation deposition technology, we finish the fabrication of linear variable filters, whose filtering range is from 500 to 580 nm. The measured results indicate that the transmittance and bandwidth at the peak wavelength are around 40% and 3 nm.

Degradation of the SrRuO3/SrTiO3 interface capacitance induced by mechanical stresses

Trilayer epitaxial heterostructures in which a 700-nm-thick SrTiO3 interlayer is integrated with two SrRuO3 electrodes have been grown by laser ablation. In the top electrode, twenty contact pads (S approximate to 0.1 mm(2)) have been formed using photolithography and ion etching. The bottom SrRuO3 electrode grown on a MgO(001) substrate is common for all film capacitors on the chip. As the temperature decreases in the range of 300-50 K, the capacitance C of the capacitors increases by a factor more than two due to an increase in the permittivity epsilon of the interlayer. At T = 4.2 K, as the bias voltage of +/-2.5 V is applied to the oxide electrodes, the capacitance C decreases by similar to 40%. In the temperature range of 100-300 K, the ratio epsilon(0)/epsilon increases almost linearly with increasing temperature (epsilon(0) is the permittivity in vacuum). At T > 250 K, the dielectric loss tangent of the SrTiO3 interlayer increases exponentially with increasing temperature and substantially depends on the bias voltage applied to the oxide electrodes.

Characterization of the Mixed Oxide Layer Structure of the Ti/SnO2-Sb2O5 Anode by Photoelectron Spectroscopy and Impedance Spectroscopy

The in-depth chemistry of a Ti/SnO2-Sb2O5 anode was investigated by X-ray photoelectron spectroscopy combined with ion etching. The coating was found to be composed of multiple layers of tin and titanium oxides and composition gradients at both the oxide-air and oxide-metal interfaces. The existence of such an extensive titanium oxide layer may be related to the fabrication of the Ti/SnO2-Sb2O5 anode and subsequent inter-diffusion of species. Also, the surface tin oxide layer was found to be non-stoichiometric, which, in relation to the extensive titanium oxide structure, could be explained by a migration of oxygen toward the Ti substrate. Electrochemical tests showed that the film was unstable and continued to grow under anodic polarization. Impedance spectroscopy displayed a continuum in the dielectric relaxation time constants with depth. This variation in relaxation time constants was proposed to be caused by the continuous variation of the composition in the film.

Colloid-facilitated transport of uranium by groundwater at the U–Mo ore field in eastern Transbaikalia

The main objective of the study is field-scale analysis of colloid-facilitated transport of uranium from an underground source to the biosphere as applied to safety assessment of underground repository of spent nuclear fuel (SNF). The uranium deposit (Antei) in eastern Transbaikalia is considered as a natural analog of an underground repository of SNF. Transport of colloid-borne uranium by groundwater from the ore zone to the earth surface is examined. Groundwater at the uranium deposit site was sampled both in the ore zone (at the depth of approximately 750 m) and from the subsurface water. Extraction of the uranium-bearing colloid from the water samples was carried out by subsequent filtration through membranes with decreasing pore size. Uranium concentrations in the filtrate were measured by the methods of light-emitting diode-induced luminescence and inductively coupled plasma mass spectrometry. Chemical composition of the surface of the uranium-bearing colloid particles was determined by the methods of X-ray photoelectron spectroscopy with ionic etching and transmission electron microscopy. It is revealed that uranium-bearing colloid in the ore zone and at the earth surface consists of particles of different types (intrinsic colloid and pseudocolloid).

X-Ray photoelectron spectroscopy investigations of atomic interactions in surface layers of multilayered nanostructures (Co45Fe45Zr10/a-Si)40 and (Co45Fe45Zr10/SiO2)32

The interatomic interaction and chemical state of elements in amorphous multilayered (Co45Fe45Zr10/a-Si)40 and (Co45Fe45Zr10/SiO2)32 nanostructures with different interlayers have been investigated by X-ray photoelectron spectroscopy using synchrotron radiation. The results of X-ray photoelectron spectroscopy investigations have demonstrated that, in surface layers of all the studied multilayered structures, the metallic layer components Co, Fe, and Zr are in the oxidized state. The silicon state is found to be identical and close to the state of nonstoichiometric silicon oxide, regardless of the presumed compositions of SiO2 and a-Si interlayers. After the removal of surface layers of the multilayered structures in the sample preparation chamber by ion etching, the metallic layer components Co, Fe, and Zr are predominantly in the elemental state.

Size‐controllable fabrication of nano‐to‐microstructures on silicon surface using high‐density ion etching with pulsed bias

A ‘black silicon’ (BS) surface with low reflectance was fabricated by a standard pulsed deep reactive etching technology at room temperature. Aiming for a better understanding, a systematic experiment was conducted by varying the etching window size and bias power duty cycle. The samples were measured and analysed by a scanning electron microscope, the Bruker Optical Profiler and a UV-3400 spectrometer. It was observed that a broad scale range of the surface structures formed on the surface. With the duty cycle at 0.5, only about 100 nanometre scale replicable silicon cones formed on the surface, but as the duty cycle decreased to 0.25, the height of the silicon forest sharply increased to about 10 µm, leading to a low reflectance of 0.9% in the visible range for the surface. To clarify the reason for this trend, the bias effective voltage (BEV) was measured and it was confirmed that the BEV would decrease from 100 to 47 V with the duty cycle adjusted from 1 to 0.25. This suggested that this decrease in BEV leads to a reduction of ion energy and ion flux, and then modifies the fabricated structures. Besides, it was found that the broad etching window area only had a maximum promotion of 20% to the scale of the BS, indicating this method was almost free of loading effect.

Single layer of nickel hydroxide nanoparticles covered on a porous Ni foam and its application for highly sensitive non-enzymatic glucose sensor

A single layer of nickel hydroxide nanoparticles (Ni(OH)2 NPs) was covered on the full surface of a porous Ni foam by simply applying an electrochemical cyclic voltammetric (CV) treatment on a bare Ni foam substrate for 100 cycles in 1.0M NaOH solution. The surface morphology of the obtained Ni(OH)2 NPs/Ni foam electrode was examined by scanning electron microscopy. The thickness of the Ni(OH)2 NPs layer on the electrode was estimated by X-ray photoelectron spectroscopy with Ar+ ion etching. In CV measurement, the Ni(OH)2 NPs/Ni foam electrode exhibited excellent electrocatalytic ability toward glucose in NaOH solution. The Ni(OH)2 NPs/Ni foam electrode was successfully used for the quantification of glucose by an amperometric method. The sensing parameters include a high sensitivity of 1950.3μA/mM-cm2, a linear range from 0.6 to 6.0mM, a detection limit of 0.16μM, and an applied potential of 0.45V (vs. Ag/AgCl/KCl sat’d). The excellent performances obtained in the interference test, the long-term durability test in atmosphere, and the reproducibility test of the Ni(OH)2 NPs/Ni foam sensor indicate the applicability of the proposed electrode as a reliable non-enzymatic glucose sensor.

Ionic liquid assisted chemical strategy to TiO2 hollow nanocube assemblies with surface-fluorination and nitridation and high energy crystal facet exposure for enhanced photocatalysis.

Realization of anionic nonmetal doping and high energy crystal facet exposure in TiO2 photocatalysts has been proven to be an effective approach for significantly improving their photocatalytic performance. A facile strategy of ionic liquid assisted etching chemistry by simply hydrothermally etching hollow TiO2 spheres composed of TiO2 nanoparticles with an ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate without any other additives is developed to create highly active anatase TiO2 nanocubes and TiO2 nanocube assemblies. With this one-pot ionic liquid assisted etching process, the surface-fluorination and nitridation and high energy {001} crystal facets exposure can be readily realized simultaneously. Compared with the benchmark materials of P25 and TiO2 nanostructures with other hierarchical architectures of hollow spheres, flaky spheres, and spindles synthesized by hydrothermally etching hollow TiO2 spheres with nonionic liquid of NH4F, the TiO2 nanocubes and TiO2 nanocube assemblies used as efficient photocatalysts show super high photocatalytic activity for degradation of methylene blue, methyl orange, and rhodamine B, due to their surface-fluorination and nitridation and high energy crystal facet exposure. The ionic liquid assisted etching chemistry is facile and robust and may be a general strategy for synthesizing other metal oxides with high energy crystal facets and surface doping for improving photocatalytic activity.

XPS Investigation of Loss of Antimony in the Thermal Preparation of the Ti/SnO2-Sb2O5 Anode

Introduction The Ti/SnO2-Sb2O5 anode was found to be suitable for the electro-oxidation of organics in municipal wastewater, due to its low cost, high efficiency and strong oxidation power1. Similar to other anodes of metal-oxides on titanium, it can be prepared by the thermal decomposition of metal chlorides on a titanium substrate, but this method suffers the loss of oxides by the evaporation of the chloride salts2, which is particularly serious with the Ti/SnO2-Sb2O5 anode.The present work focused on investigating this problem, using XPS to explore the surface and in-depth profiles of the coating film. Experimental Methods The Ti/SnO2-Sb2O5 anodes were prepared by methods modified from literature1,3. An isopropanol solution of SbCl3 and SnCl4·5H2O mixed at a target composition (Sb:Sn) was brush coated onto a polished Ti surface. The coated anodes were then heated slowly to 500°C in 2 hours to finish the conversion from chlorides to oxides.XPS analysis was conducted on the fabricated anodes. The spectra were analyzed and quantified, using powdered SnO2, Sb2O3 and Sb2O5 as external standards. The Sn3d5/2, Sb3d3/2 and O1s peaks were used for quantification. The O1s peak was processed by subtracting the overlapping Sb3d5/2 signal and then deconvoluting into 3 sub-peaks. Oxygen in the metallic oxide lattice had the lowest binding energy and also the highest intensity, and it was used for quantification. In-depth profiling was performed with angle resolved XPS and with XPS under simultaneous Ar+ ion etching. Results and Discussions Fig 1(a) summarizes the measured composition from XPS versus the target composition expected from the coating solution in some samples, with black dots representing the electrodes prepared by the present method. Fig 1(b) shows that the majority of the Sb was in the 5+ state.The measured Sb/Sn ratio was much lower than the target and was randomly distributed. The loss of Sb was suspected to be caused by the vaporization of SbCl3 from the coated anodes. Unlike SnCl4·5H2O which only decomposes under the temperatures used, SbCl3 can vaporize at 220°C. Therefore during the heating, the element of Sb may undergo both evaporation and oxidation. Evaporation potentially can occur at a lower temperature than oxidation and result in significant loss of Sb prior to the oxide film formation. To test this hypothesis, another piece of Ti/SnO2-Sb2O5 was prepared and heated rapidly to 500°C. Rapid heating should reduce evaporation, and indeed the resulting film was found to retain more Sb (Fig 1(a) red square marker).In-depth profiles of Sb/Sn were analyzed investigate the distribution of Sb in the film. Angle-resolved XPS (Fig1(c)) showed an increase in the Sb/Sn ratio with tilted viewing angle towards the surface. XPS with Ar+ ion etching also showed that Sb was detected only within the top 5nm of the material. It can be deduced that the antimony was concentrated at the surface. This could be of concern as the Sb may not effectively dope the SnO2 to lower its conductivity. Conclusions and Future Work XPS revealed the loss and surface concentration of Sb in Ti/SnO2-Sb2O5 anodes. These were probably associated with the vaporization of SbCl3 during the electrode fabrication which is undesirable in the pyrolytic preparation of this electrode. Future work will be on the electro-deposition method as a substitute to produce adhering films of controllable Sb/Sn compositions. References L. Lipp and D. Pletcher, Electrochim. Act. 42 1091 (1997)Ch.Comninellis and G.P.Vercesi, J. App. Electrochem. 21 136 (1991)Q. Ni, D. W. Kirk, S. J. Thorpe, ECS Trans. 50(19) 87 (2013)

Adhesion and structural stability enhancement for Ag layers deposited on steel in selective solar coatings technology

Improvement of structural and morphological stability of Ag layers has to be pursued for effective employment in solar coating technology for “parabolic trough” thermal plants. Starting from the consideration that stainless steel surface of a receiver tube does not behave as an excellent substrate for fabricating appropriate Ag layers in terms of adhesion strength and thermal stability, both substrate pre-treatments and adaptive layer deposition have been taken into account. Beneficial effect of substrate ionic etching pre-treatment on adhesion coupled with utilization of “α phase” tungsten film as adaptive layer gave evidence for large improvement both on adhesion strength and on morphological stability of Ag layers subjected to thermal cycles at 400°C under vacuum. Using Ag as infrared reflector and Wα as adaptive layer, an optimized cermet-based selective coating suitable for receiver tube operating at 400°C has been fabricated. This coating, subjected to annealing processes at 400°C under vacuum up to 29days, showed excellent thermal and optical stability.

The structure of fossil fungal spores based on the results of ion etching

New data on the structure of fossil fungal spores in coal beds were obtained with the use of the previously developed method of ionic etching (sputtering). The multilayer structure of spore shells was found for the first time, and considerations of the biochemical composition of layers were presented. The morphology of spores and their internal cytochemical elements was characterized. The reasonability of a further petrographic study of the spores of fungi in the coal beds is discussed.

High Voltage SiC JBS Diodes with Multiple Zone Junction Termination Extension Using Single Etching Step

A novel variation of lateral etching junction termination extension (VLE-JTE) for Silicon carbide (SiC) power junction barrier Schottky rectifier (JBS) using a single mask is proposed and investigated. Simulation results shows that the breakdown voltage of JBS terminated with VLE-JTE can achieve 6500V, reaching up to more than 95% of parallel-plane junction bulk breakdown. Moreover, it implements a single mask with window areas varying laterally away from the main junction instead of extra ion implantation or etching steps to achieve multiple-zone JTE, making it easier to be implemented in applications.

X-ray photoelectron spectroscopy of the effects of Ar+ ion sputtering on the nature of some standard compounds of Zn, Cr, and Fe

X-ray photoelectron spectroscopy combined with Ar+ ion etching is a powerful technique for identifying the different chemical states of compounds in depth profiles to obtain information about buried regions beneath surfaces. The possibility of sputter damage is known but has been insufficiently investigated in the case of corrosion products of Zn-based steel coatings such as ZnCr. Thus, in this work, reference materials were studied according to their stability against ion sputtering. Indeed, some of the investigated compounds exhibited a highly unstable chemical nature. On the basis of these findings, the reliability of depth profiles of real samples can be rated.

Aerosynthesis: Growth of Vertically-Aligned Carbon Nanofibres with Air DC Plasma

Vertically-aligned carbon nanofibres (VACNFs) have been synthesized in a mixture of acetone and air using catalytic DC plasma-enhanced chemical vapour deposition. Typically, ammonia or hydrogen is used as an etchant gas in the mixture to remove carbon that otherwise passivates the catalyst surface and impedes growth. Our demonstration of the use of air as the etchant gas opens up the possibility that ion etching could be sufficient to maintain the catalytic activity state during synthesis. It also demonstrates a path toward growing VACNFs in the open atmosphere.

Effect of coating and plasma treatments on the induced coupled plasma-reactive ionic etching of boron-doped diamond for microelectromechanical systems (MEMS) applications

Induced coupled plasma etching was performed on poly-crystalline boron-doped diamond (BDD) films synthesized by microwave assisted chemical vapor deposition (MWCVD). Effects of the input power and of the gas composition and pressure on etching performances have been investigated. A basic aluminium layer and a new hybrid material have been studied as protecting film for the patterning. Best conditions to get high etch rates were a gas ratio Ar/O2 of 27% (vol.) under 10 mTorr at 200 W (input power). Aluminium (Al) masking induced un-intentional whiskers formation which was removable using CHF3 as a reactive gas with the drawback to lower the process selectivity. In order to get both a high etching rate and a high selectivity, a hybrid material based on an organic/mineral resin was then used as the masking material. This performing photoresist film allowed etching a 3.6-μm-thick BDD film at 200 nm min−1.

Enhanced Cell Affinity of Chitosan Membranes Mediated by Superficial Cross-Linking: A Straightforward Method Attainable by Standard Laboratory Procedures

It is well accepted that the surface modification of biomaterials can improve their biocompatibility. In this context, techniques like ion etching, plasma-mediated chemical functionalization, electrospinning, and contact microprinting have successfully been employed to promote the cell adhesion and proliferation of chitosan (CH) substrates. However, they prove to be time-consuming, highly dependent on environmental conditions, and/or limited to the use of expensive materials and sophisticated instruments not accessible to standard laboratories, hindering to a high extent their straightforward application. Filling this gap, this paper proposes the superficial cross-linking of CH as a much simpler and accessible means to modify its superficial properties in order to enhance its cellular affinity. CH membranes were prepared by solvent casting followed by a cross-linking step mediated by the chemical vapor deposition (CVD) of glutaraldehyde (GA). The membranes were characterized against non- and solution cross-linked membranes in terms of their mechanical/surface properties and biological performance. Among others, the CVD membranes proved (i) to be more mechanically stable against cell culture and sterilization than membranes cross-linked in solution and (ii) to prompt the adherence and sustained proliferation of healthy cells to levels even superior to commercial tissue culture plates (TCPs). Accordingly, the CVD cross-linking approach was demonstrated to be a simple and cost-effective alternative to the aforementioned conventional methods. Interestingly, this concept can also be applied to other biomaterials as long as GA (or other volatile components alike) can be employed as a cross-linker, making possible the cross-linking reaction at mild experimental conditions, neither requiring sophisticated lab implements nor using any potentially harmful procedure.