Thickness Of Removed Layer Research Articles

Alpha particle energy-range studies by a layer removal method in polycarbonate detectors for determining unknown ion energies

The aim of this study is to apply a “layer removal method” for alpha energy-range determination in polycarbonate detectors (PC) compared with SRIM software. This method is a precise chemical pre-etching process by which a layer of a certain thickness is removed from an exposed or unexposed PC detector surface before applying electrochemical etching (ECE). A group of 500 μm thick PC detectors was exposed to alpha particles of known fluence (∼1.0 × 104 alphas.cm−2) and ∼0.3–∼5.0 MeV energy range, followed by a pre-etching process at 12 different time intervals in 70% ethylenediamine solution. After the ECE process, alpha track density and diameter were determined. Track density versus removed layer thickness for each alpha energy follows a Bragg type peak after which approaching zero at a known removed layer thickness corresponding to the alpha range. The results also show a linear increase of the mean track diameter as the removed layer thickness increases for each energy. On the other hand, this study confirms a shift in the energy range registration by increasing the thickness of the removed layer. Using this precise method, an unknown energy can be determined by step-by-step thickness removal process until the track density approaches zero. In conclusion, the upper energy of ions emitted in a PFD can be determined. This method is a precise and simple method for ion energy-range determination studies for passive ion spectrometry.

Chip experimental analysis approach obtained by micro-end-milling in (Ti-6Al-4 V) titanium alloy and (7075) aluminium alloy

The chip study can be the simile to the biopsy in the machining process, as it exposes physical phenomena that are generated in the machining process (heat transfer, hardening, phase changes, heat treatments, etc.). These physical phenomena are directly influenced by the cutting parameters applied to the process (feed, cutting speed, and depth). A chip analysis procedure is proposed to estimate some of the physical phenomena generated in the micro-end-milling in a conventional CNC machine on 7075 aluminium and Ti-6Al-4 V titanium alloys. The procedure is composed of hardness tests, metallography, scanning electron microscopy (SEM), and infrared thermography. A softened chip is observed in the Ti-6Al-4 V titanium a hardened one in 7075 aluminium alloy. The chip approach evaluation evidences a great variation regarded to thermal characteristics between micro-machining and meso-machining focused on the scale of the removed layer thickness.

МОДЕЛЮВАННЯ ВПЛИВУ АМПЛІТУДНО-ЧАСОВИХ ПАРАМЕТРІВ ЕЛЕКТРИЧНИХ ІМПУЛЬСІВ НА ПРОЦЕСИ АНОДНОГО РОЗЧИНЕННЯ ПРИ ЕЛЕКТРОХІМІЧНІЙ ОБРОБЦІ ДРОТЯНИМ ЕЛЕКТРОДОМ

Combined technology of sequential use of electroerosive and electrochemical machining with wire electrode allows to obtain highquality surface and to form metal components with high accuracy, regardless of material strength and hardness. Pulsed current in electrochemical machining greatly increases process controllability. The paper provides mathematical model of mass transfer in nearanode diffusion layer. This, together with calculation of current density distribution for a scheme with cylindrical cathode and flat anode, gives reasonable choice of amplitude-time parameters of electrical impulses. Such approach provides maximal current efficiency and precise prediction of removed layer thickness of surface obtained by a moving wire electrode. Conducted experimental researches on approbation of calculated method have shown that theoretical calculations are well consistent with experimental data. Proposed method allows to increase efficiency of electrochemical surface finishingafter electroerosive cutting.

Tribological Characteristics of NiAl Matrix Composites with 1.5 wt% Graphene at Elevated Temperatures: An Experimental and Theoretical Study

In this study, the tribological properties of NiAl matrix composites with 1.5 wt% graphene nanoplatelets (NAG) at elevated temperatures were simulated and tested. NAG exhibits excellent characteristics at 100 and 200°C due to the formation of metal oxides and graphene nanoplatelets lubrication film. Furthermore, the removed layer thickness, the stress distributions, and the high stresses of the affected layer have been estimated theoretically. At 400°C, the friction coefficient increased due to the absence of the lubrication layer. In addition, the wear rate increased due to the excessive stresses, the increased layer thickness removal, and the propagation of subsurface cracks.

Theoretical feasibility study on neutron spectrometry with the polyallyldiglycol carbonate (PADC) solid-state nuclear track detector

Neutron spectrometry with the polyallyldiglycol carbonate (PADC) film detector was analyzed in detail. The computer codes TRACK_TEST and TRACK_VISION, which were originally developed for studies on alpha-particle tracks, were modified to compute parameters of etched proton tracks developed in the PADC film detector and to simulate their appearance under an optical microscope in the transmission mode. It was shown that protons with same energy and recoil angle could produce different etched tracks with various size and shape, depending on the point of their creation. As such, it was necessary to employ multiple etching, and to measure the removed layer thickness and to record the track appearance after each etching step. A new variable, namely, the effective removed layer heff, was introduced as the difference between the total removed layer and the depth where the proton was created in the detector. A program modified from the TRACK_VISION code was used to plot the appearance of a number of representative etched proton tracks. For proton energies larger than 2MeV, the V function for protons in PADC was found to be almost constant, so the simple formulas for major and minor axes of proton track openings could be used to determine the proton energy, recoiled angle as well as the energy of the neutron which caused the proton recoil. For lower proton energies, a databank of various proton tracks showing the track opening appearances and the track profiles should be created for comparison to facilitate the determination of the proton energy.

Achievement of high planarization efficiency in CMP of copper at a reduced down pressure

We report improved planarization efficiency (ratio of step height reduction and removed layer thickness) in chemical–mechanical planarization (CMP) of copper lines at a down pressure of 2 psi. The CMP slurry used to achieve these results contains fumed silica particles (abrasive), β-alanine (surface complexing agent) and H 2O 2 (oxidizer), combined with dissolution inhibiting ammonium dodecyl sulfate (ADS) and/or low concentrations (≤1 mM) of benzotriazole (BTAH) at a solution pH of 4.0. When only ADS or BTAH is used, Cu dissolution rate is reduced, but at the cost of somewhat low planarization efficiency. Combination of ADS (typically 3 mM) and BTAH (≤1 mM) in the slurry significantly improves both the surface polish rates and the planarization efficiency. The processed surface (examined by optical profilometry) is noticeably defect-free for this particular system. The mechanisms of surface dissolution and passivation are discussed, and contact angle data are used to elucidate the surface passivating nature of the inhibitor films. The results presented here are relevant for further developments in the area of low pressure CMP of Cu lines overlying fragile low-k dielectrics in the new interconnect structures.

Ion mixing at 20 keV: A comparison of the effects of Ga +, Ar + and CF 4+ ion irradiation

Medium-energy (some tens of keV) ion irradiation is frequently used in various technologies. It is well known that during this irradiation serious alterations are introduced to the material, changing its structure, composition, etc. While there are studies on the amorphization, no results have been reported on the medium-energy ion beam-induced mixing, however. In this work, we present Auger electron spectroscopy (AES) depth profiling measurements of Si/Cr multilayer samples, which were irradiated by various ions (Ga +, Ar +, CF 4 +) of 20 keV applying angles of incidence of 5° (Ga +), 65° (Ga +) and 75° (Ar +, CF 4 +). The ion beam-induced mixing at the Si/Cr interface (the broadening of the interface) was measured as a function of the removed layer thickness. The weakest and strongest ion mixing (for a given removed layer thickness) were found for CF 4 + and Ga + 5° irradiations, respectively. In the case of Ga + irradiation, the larger the angle of incidence the weaker the ion mixing. The extent of mixing does not correlate with the corresponding projected range. Comparison of the experimentally measured ion mixed profiles with those given by dynamic TRIM simulations gave poor agreement for Ar + and fails for Ga + irradiations, respectively.

Modeling of plasma-controlled evaporation and surface condensation of Al induced by 1.06 and 0.248μm laser radiations

Phase transition on the surface of an aluminum target and vapor plasma induced by laser irradiation in the nanosecond regime at the wavelengths of 1.06μm in the infrared range and 0.248μm in the ultraviolet range with an intensity of 108–109W∕cm2 in vacuum are analyzed. Special attention is paid to the wavelength dependence of the observed phenomena and the non-one-dimensional effects caused by the nonuniform (Gaussian) laser intensity distribution and the lateral expansion of the plasma plume. A transient two-dimensional model is used which includes conductive heat transfer in the condensed phase, radiative gas dynamics, and laser radiation transfer in the plasma as well as surface evaporation and back condensation at the phase interface. It was shown that distinctions in phase transition dynamics for the 1.06 and 0.248μm radiations result from essentially different characteristics of the laser-induced plasmas. For the 1.06μm radiation, evaporation stops after the formation of hot optically thick plasma, can occasionally resume at a later stage of the pulse, and proceeds nonuniformly in the spot area, and the major contribution to the mass removal occurs in the outer part of the irradiated region. Plasma induced by the 0.248μm laser is colder and partially transparent since it transmits 30%–70% of the incident radiation; therefore evaporation does not stop but continues in the subsonic regime with the Mach number of about 0.1. The amount of evaporated matter that condenses back to the surface is as high as 15%–20% and less than 10% for the 1.06 and 0.248μm radiations, respectively. For a beam radius smaller than ∼100μm, the screening and retarding effect of the plasma weakens because of the lateral expansion, thickness of the removed layer increases, and condensation after the end of the pulse is not observed. Comparison of the numerical and experimental results on the removed layer thickness has shown, in particular, the importance of accounting for the plasma effect to predict the correct trends for radiation intensity and beam radius.

Experimental study of low energy ion mixing

We have measured the energy dependence of the depth resolution in AES depth profiling experiments using glancing ion incidence angle and specimen rotation during ion sputtering. It was found that under these conditions the depth resolution did not depend on the removed layer thickness, but rather on the ion energy. An ion energy change was immediately followed by a change in the depth resolution. Based on this observation we concluded that, in the cases of TaNi and MoSi multilayer systems, ion mixing is the most important contribution to depth resolution in the energy range of 4–10 and 3–10 keV, respectively. Hence, by measuring depth resolution, we can obtain data on ion mixing.

Characterization of subsurface damage in GaAs processed by Ga+ focused ion-beam-assisted Cl2 etching using photoluminescence

Subsurface damage in GaAs processed by a Ga+ focused ion-beam-assisted Cl2 etching is studied by photoluminescence (PL) measurement. The PL intensity of the processed sample decreased to (1)/(30) – (1)/(40) compared to that of the unprocessed sample. The recovery of PL intensity by a step removal of the damaged layer is observed as a function of the removed layer thickness. The removal of a 0.7-μm-thick surface layer enables the PL intensity to be recovered perfectly, which leads to the postulate that the damaged layer thickness is 0.7 μm at least, which is much larger than the ion range (about 0.01 μm). The recovery of PL intensity is analyzed on a one-dimensional model in the direction normal to the sample surface. Computer simulations of PL intensity are carried out. The calculated result fully explains the experimental PL intensity recovery as a function of the removed layer thickness, which gives the profile of subsurface damage in the sample.

Chemical preparation of GaSb(001) substrates prior to MBE

The chemical preparation of GaSb(001) substrates was performed by Br2-HCl-HNO3-CH3COOH solution. The removed layer thickness was evaluated as a function of the constituent concentrations and the etching time. The surface quality was controlled by SEM, RHEED and AES. With this treatment, excellent surface morphology of substrates and growth film is obtained.

Etching behaviour of light particle tracks in CA SSNTD

Abstract The recording energy range and efficiency of CA SSNTD made in China to proton and deuteron registration were determined, and the recording energy range to alpha particle registration was determined too. The highest energies of alpha particle, proton and deuteron registrated are 11.7, 0.8 and 1.35 MeV respectively. At a certain removed layer thickness range, the efficiencies of vertical incident protons with energy 400–900 keV and deuterons with energy 450–1350keV registrated are all 100%. The restricted energy loss rate criterion proposed by Benton was tested for the sensitive CA SSNTD using protons, deuterons and alpha particles. It is shown that the model may be applied to light particle registrations. For these light particle registrations by the detector, there is a functional relation between the etching rate ratios and ranges, therefore, it may be used to identify light particles.

Neutron radiographic characteristics of MA-ND type (allyl-diglycol-carbonate) nuclear track detectors

Abstract Neutron radiographic properties of recently developed new nuclear track detectors (MA-ND/α, MA-ND/p and MA-ND/p1), manufactured from allyl diglycol carbonate, were studied. It was found that the quality of radiographic image has an optimum at a removed layer thickness of about 0.8μm. The image obtained under this condition is characterized by high detection sensitivity to neutrons (∼8·10 -3 tracks/n th when using B converter) and by excellent inherent unsharpness (∼5μm) as well as high image contrast (maximum value of net optical density is ∼1.4).

Fast neutron spectrometry based on proton detection in CR-39 detector

Abstract We have developed a home-made proton-sensitive CR-39 track detector called MA-ND/p. Using this and the n-p scattering process the performance of a fast neutron spectrometer has been studied by applying two different methods. These are based on track density determinations by using varying radiator thicknesses at constant etching time and by using varying etching times at fixed radiator thickness, respectively. For both methods studied a computer programme is made to calculate the theoretically expected neutron sensitivity as a function of neutron energy. In these calculations, by using the conditions given by the theory of etch-track formation, the requirements for having observable proton tracks under different irradiation conditions are taken into consideration. For both methods the neutron sensitivities, expressed in terms of observable etched proton tracks per neutron, are determined experimentally too for 3.3 and 14.7 MeV neutron energies. The neutron sensitivity is measured as a function of both the radiator thickness and the removed layer thickness of CR-39 type track detector. The theoretical and experimental data obtained are compared.

Neutron sensitivity measurements of LR115 track detector with some (n, α) converters

The neutron sensitivity of an LR115 track etch detector with several commercially available (n, α) converters was experimentally investigated, and the results were compared with the calculated ones. For the irradiations, the filtered beams of the reactor at the National Bureau of Standards (NBS, Washington D.C.) with neutron energies of 2,24 and 144 keV were used. Detectors were irradiated also in the NBS thermal column; and at a zero power reactor of the Central Research Institute for Physics (CRIP), Budapest, where the neutron energy spectra were of 1/ E type and of average energies (weighted by the reaction cross-sections) of 10 eV and 10 keV. Apart from the determination of sensitivity values, the following points represent the essential part of the experimental results: 1. 1. The sensitivity varies exponentially with the removed layer thickness; and the slope of that function depends on the composition of the radiator, being less for materials containing only Li. 2. 2. The net track density and removed layer thickness, as random variables, have normal distributions with variances depending on the value of the removed layer thickness and on the composition of the radiator. In general, for a given layer removal, the variance of the track density is the smallest for radiators containing Li only.

Neutron sensitivity of LR 115 SSNTD using different (n, α) radiators

The neutron sensitivity of Kodak-Pathé LR 115 II type cellulose nitrate track detectors with different (n, α) radiators was investigated by calculations and measurements. The α counting efficiency using an optical microscope is 95% and 92% for α particles with maximum energies of 2 and 1.5 MeV, respectively. When using an image analyser the etched through-tracks (holes) with diameter greater than 2 μm are counted. The efficiency then depends only on the original and removed layer thickness but not on the etching temperature within the range of 40 to 65°C and 2.5 to 6 N normality of the NaOH etchant. Efficiency varies from about 3 to 20% for alphas from the 6Li(n, α)T reaction if the removed layer lies in the range of ∼7 to 10 μm, and varies from ∼2 to 10% for 10B(n, α) 7Li reaction alphas when the layer removal is ∼8 to 10 μm.

Cr gettering by Ne ion implantation and the correlation with the electrical activation of implanted Si in semi-insulating GaAs

Electrical activation of implanted Si in gettered semi-insulating GaAs has been studied. The gettering was performed by Ne implantation and heat treatment. Then, Si ion implantations were performed after removing the surface layer of the gettered substrate to various thicknesses. Higher activation than the native value has been observed when the removed layer thickness is about 1 μm. According to the measurements of Cr concentration profile and the estimation of Cr concentration from the Si activations, the cause of the increased activation has been found to be the Cr decrease in a region deeper than the Ne-implanted region.