On improving the track development properties of soda glass detectors

A detailed study of track development properties of soda glass detectors is carried out by varying the etching parameters, i.e. etching time, etchant temperature and the composition of the etching solution. The etch product layer (EPL) which mainly limits the sensitivity of these detectors is dissolved chemically as soon as it is formed. The largest observable etch pit diameter by the use of this method is almost double the one obtained using HF. Room temperature (39 ± 1)°C appears to be the optimum temperature for etching of soda glasses in this solution. The spectrometric response of soda glasses to fission fragments of ²⁵²Cf has also been studied, using this solution. The energy resolution of soda glass detectors is seen to improve and become comparable with the energy resolution of phosphate glass detectors.     

Study of 132Xe ion tracks in a soda glass detector

Soda glass track detectors have been exposed to ¹³²Xe ion cyclotron beams at the Joint Institute for Nuclear Research, Dubna (USSR). The etch pit diameters are measured for different etching times after etching the detectors in a ‘new etchant’ free of the adverse effect of the etch product layer. The computed values of energy loss, $\text{d}\text{E}\text{d}\text{x}$, in soda glass have been correlated with the track diameter. The energy resolution of soda glass and the critical angle for etching of ¹³²Xe ion tracks in glass detectors have also been determined. The maximum etched track length of Xe ions in soda glass has been compared with the theoretical range. The effects of different annealing conditions on the bulk etch rate, the track etch rate, the etching efficiency, the track diameter and on the range of Xe ions in soda glass have been studied.     

Etude de la conduction ionique de verres a base de ZrF4

The electrical and dielectric properties of new ZrF₄ based glasses have been studied in the frequency and temperature ranges 5Hz-500kHz and 130–280°C. Transport number measurements following Tubant's method showed that the glasses investigated are F^? conductors. The conductivities and activation energies for conduction are about 10^?6(Ωcm)^?1 at 200°C and 18 kcal.mole^?1 respectively. Preliminary interpretation of the change of conductivity with composition is given.     

Controlling the Length of Conical Pores Etched in Ion‐Tracked Poly(ethylene terephthalate) Membranes

An etching procedure that allows for reproducible control of the length of conically shaped pores etched into poly(ethylene terephthalate) (PET) membranes is developed. At the lower etch temperature used (20 °C), the length of the pore is found to be linearly related to etch time. At the higher etch temperature (30 °C) the etch rate is five times faster and the pores quickly propagate through the entire thickness of the PET membrane. Hence, the lower etch temperature is best for controlling the pore length. Pores etched at this temperature are used to prepare arrays of gold cones where the length of the cones is controlled from 1 to 10 µm. The track‐etch rates and the radial‐etch rates at both of the etch temperatures used are also reported.     

Dry Etching with Nanoparticles: Formation of High Aspect‐Ratio Pores and Channels Using Magnetic Gold Nanoclusters

Methods for generating nanopores in substrates typically involve one or more wet‐etching steps. Here a fundamentally different approach to produce nanopores in sheet substrates under dry, ambient conditions, using nanosecond‐pulsed laser irradiation and magnetic gold nanoclusters (MGNCs) as the etching agents is described. Thermoplastic films (50–75 µm thickness) are coated with MGNCs then exposed to laser pulses with a coaxial magnetic field gradient, resulting in high‐aspect ratio channels with tapered cross sections as characterized by confocal fluorescence tomography. The dry‐etching process is applicable to a wide variety of substrates ranging from fluoropolymers to borosilicate glass, with etch rates in excess of 1 µm s^–1. Finite‐element modeling suggests that the absorption of laser pulses by MGNCs can produce temperature spikes of nearly 1000 °C, which is sufficient for generating photoacoustic responses that can drive particles into the medium, guided by magnetomotive force.     

Dislocation etch pits and growth of arsenic-antimony single crystals

Single crystals of an arsenic-antimony solid solution have been grown at the minimum melting point (612‡C) composition (25.5 at.% arsenic) where the solidus and liquidus touch. Pyramidal etch pits produced on (111) cleavage faces mark the sites of emergence of dislocations; dislocation densities are low, ranging between 10³ and 10⁵ per cm². The relationship between an unambiguous, right handed axial set and etch pit orientation on the (111) surface is established. The permissible Burgers vectors and dislocation reactions are detailed and are related to the observed etch pit types. In general, the results obtained also apply to the A7 structure elements themselves and amend previous findings of the crystallographic relationships between dislocation directions and etch pits.     

Heat treatment of diamond grains for bonding strength improvement

The heat treatment of synthetic cubo-octahedral diamond grains to produce tight bonding by making their surface rough is reported. In order to obtain a rough surface, a thermal etching technique at atmospheric pressure in air at 700 to 1100°C is applied. The shape, surface features and surface area are investigated, then in order to examine the effect of the roughened diamond surface on bonding strength, peeling and bending tests were carried out. The results obtained showed that: rough surfaces may be obtained by thermal etching at atmospheric pressure in air; on etching at 700 to 1000°C, the etch rate of the {111} face is higher than that of the {100} face, and in particular, diamonds etched at 700 to 1000°C have a hollow {111} face; the surface area of one grain can be increased by etching — on etching at 900°C for 15 min, surfaces become fully covered with clear etch pits and the surface area shows maximum value; the surface area seems to have an influence on bonding strength, and when diamond grains are bonded with phenol resin or electroless plating nickel, bonding strength improves by about 10%.     

Wet etching of GaN,AlN, and SiC: a review

The wet etching of GaN, AlN, and SiC is reviewed including conventional etching in aqueous solutions, electrochemical etching in electrolytes and defect-selective chemical etching in molten salts. The mechanism of each etching process is discussed. Etching parameters leading to highly anisotropic etching, dopant-type/bandgap selective etching, defect-selective etching, as well as isotropic etching are discussed. The etch pit shapes and their origins are discussed. The applications of wet etching techniques to characterize crystal polarity and defect density/distribution are reviewed. Additional applications of wet etching for device fabrication, such as producing crystallographic etch profiles, are also reviewed.     

Preparation and characterization of dense sodium superionic conducting Na5YSi4O12 (NYS)

Na₅YSi₄O₁₂ has been prepared from spray-frozen/freeze-dried precursor powders calcined at 620°C for three hours. Sintering at 1140°C for 30 minutes gave a ceramic of 97.7% theoretical density. The material was single phase NYS with a 300°C resistivity of 6.5 Ωcm, an activation energy for Na⁺ ion conduction of 20.1 kJ/mol, a flexural strength of 75 MPa, a duplex fine grain structure of (0.1–3μm) and a constant linear thermal expansion coefficient (25–470°C) of 13.1 × 10^?6/°C ±5%. The properties of the NYS ceramics are especially sensitive to small soda deficiencies.     

Dielectric properties of lead zirconate titanate thin films seeded with barium strontium titanate nanoparticles

A low temperature synthetic method recently proposed by the authors was applied to the fabrication of lead zirconate titanate (PZT) thin films containing crystalline seeds of barium strontium titanate (BST) nanoparticles. PZT precursor and the BST particles were prepared with complex alkoxide methods. Precursor solution suspending the BST particles was spin-coated on Pt/Ti/SiO₂/Si substrate to film thickness of 500–800 nm at particle concentrations of 0–25.1 mol%, and annealed at various temperatures. Seeding of BST particles prevented the formation of pyrochlore phases, which appeared at temperatures above 400 °C in unseeded PZT films, and induced crystallization of PZT into perovskite structures at 420 °C, which was more than 100 °C below the crystallization temperature of the unseeded PZT films. Measurement of dielectric properties at 1 kHz showed that the 25.1 mol% BST-seeded PZT films annealed at 450 °C had a dielectric constant as high as 300 with a dissipation factor of 0.05. Leakage current density of the film was less than 1×10⁻⁶ A/cm² at applied electric field from 0 to 64 kV/cm.     

Annealing temperature dependence of effective piezoelectric coefficients for Bi3.15Eu0.85Ti3O12 thin films

The effects of annealing temperatures 600, 650, 700, and 750 °C on microstructure, chemical composition, leakage current, ferroelectric, dielectric, and piezoelectric properties of Bi_3.15Eu_0.85Ti₃O₁₂ (BET) thin films prepared by metal–organic decomposition were studied in detail. The largest spontaneous polarization 2P _s (98.7 μC/cm² under 300 kV/cm), remnant polarization 2P _r (81.7 μC/cm² under 300 kV/cm), dielectric constant ε_r (889.4 at 100 kHz), effective piezoelectric coefficient d ₃₃ (46.7 pm/V under 260 kV/cm), and lowest leakage current (1.3 × 10⁻⁶ A/cm² under 125 kV/cm) of BET thin film were obtained with annealing at 700 °C. The mechanisms concerning the dependence of the enhancement d ₃₃ are discussed according to the phenomenological equation, and the improved piezoelectric performance could make BET thin film a promising candidate for piezoelectric thin film devices.     

Effect of temperature and frequency on the dielectric properties of cellulose nanofibers from cotton

The present work has been carried out to evaluate the dielectric properties and ac-electrical conductivity of cellulose nanofibers. The cellulose nanofibers (CNF) described in this work are the ones extracted from cotton via a simple acid hydrolysis method and are characterized with X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV–Visible diffuse reflectance spectroscopy. The optical band gap of CNF found out using the Kubelka–Munk plot is 3.30 eV. The dielectric constant, dielectric loss, and ac-electrical conductivity of the prepared CNF have been investigated in the temperature range from 30 °C to 300 °C and in the frequency range from 50 Hz to 5 MHz. The synthesized system exhibits a higher dielectric constant value for all temperatures in the low-frequency (0.1 kHz) region and a frequency-independent behavior above 10 kHz. In the high-frequency region, the dielectric constant is independent of temperature. Also, the study shows that the conductivity increases with increasing frequency and temperature. The maximum values of ac-conductivity at room temperature (30 °C) and high temperature (300 °C) are found to be 4.58?×?10^–5 S/cm and 2.26?×?10^–4 S/cm, respectively. In brief, the studies point to the application potential of CNF for future flexible electronics.

     

A new single-component low-cost emitter etch-back process for silicon wafer solar cells

A way of achieving lightly doped emitter is a combination of a heavy emitter diffusion and emitter etch back, which has an added advantage of phosphorous diffusion gettering. However, this chemical emitter etch-back process must fulfil some critical requirements, e.g. cost-effectiveness, near-conformal Si etching even after deep emitter etch back, controlled Si etch rate, post-etch clean Si surface and lowest safety issues in chemical handling and drainage. In this work, we report a new low-cost (less than 1 US Cents/wafer), single-chemical, non-acidic, high-throughput emitter etch-back process for tube-diffused emitters for crystalline Si wafers. This process uses only sodium hypochlorite solution at 80 °C as the Si etchant. This process is versatile with its applications on phosphorous and boron tube-diffused monocrystalline Si and phosphorous tube-diffused multicrystalline Si wafers. The preparation, usage and drainage of this highly diluted solution are easy and safe. The Si etching process leads to excellent spatial uniformity over large-area Si wafers (243 cm²). With deep etch back resulting in a change of sheet resistance by ~60 Ω/sq, the standard deviation value changes by only 2.7%. High surface conformity in the etch-back surface is evident from reflectance studies. Quasi-steady-state photoconductance and photoluminescence imaging are used to demonstrate improved electrical parameters of the etch-back wafers.     

Extremely high dose neutron dosimetry using CR-39 and atomic force microscopy

Atomic force microscopy (AFM) has been applied to the analysis of CR-39 nuclear track detectors for high dose neutron dosimetry. As a feasible study to extract the neutron dose, we have employed a (239)Pu-Be neutron source with the traditional track density measurement of recoil proton etch pits from a high density polyethylene (CH(2)) radiator. After very short etching ( approximately 1 microm), etch pit densities were measured as a function of neutron fluence (neutron dose) up to 1.4 x 10(10) cm(-2) (6.6 Sv). Neutron sensitivity was also measured to be 6.6 x 10(-4). Maximum measurable neutron dose was estimated to be approximately 200 Sv by measuring the fraction of the total image area occupied by the etch pits.     

Synthesis and characterization of new glasses based on Li<Subscript>2</Subscript>S-P<Subscript>2</Subscript>S<Subscript>5</Subscript>-Sb<Subscript>2</Subscript>S<Subscript>3</Subscript> system

There is great interest in sulfide glasses because of their high lithium ion conductivity. New sulfide glasses based on Li₂S-P₂S₅-Sb₂S₃ system have been synthesized by a classical quenching technique. A summary of thermal and structural characterization is presented. Electrical conductivities of the samples have been determined by Impedance Spectroscopy. The compositions of low lithium content (below 20% mol) have presented low electronic conductivities close to 10⁻⁸ S/cm at room temperature. The compositions of medium lithium content (30–50% mol) have presented mixed ionic-electronic behavior with predominant on ionic conductivity with a maximum values around 10⁻⁶ S/cm for samples up to 50% Li₂S at room temperature. Arrhenius behavior is verified between 25°C and T_g for all glasses with activation energies about 0.55–0.64 eV. A comparative study of conductivities with glasses belonging to the other chalcogenide systems has been undertaken.     

Preparation and ionic conductivity of new B2S3-Li2S-LiI glasses

Glasses obtained in the B₂S₃-Li₂S-LiI system have been investigated. Ionic conductivity is higher than 10^?3Ω^?1cm^?1 at 25°C for LiI-rich glasses. The electrochemical stability range and chemical stability allow their use as solid electrolytes in solid state batteries.     

A study of the surface reaction on the etched ITO thin films by using inductively coupled plasma

In this study, we investigated the etching characteristics of indium tin oxide (ITO) thin films at CF₄/Ar plasma. The maximum etch rate of 29.8 nm/min for the ITO thin films was obtained at CF₄/Ar (=80/20) gas mixing ratio. The standard conditions were the RF power of 800 W, the DC-bias voltage of −150 V, the process pressure of 2 Pa, and the substrate temperature of 40 °C. Corresponding to these etching conditions, chemical reaction of the etched ITO surface has been studied by X-ray photoelectron spectroscopy measurement to investigate the chemical reactions between the surfaces of ITO thin film and etch species. The preferential losses on the etched surfaces were investigated using atomic force microscopy.     

Hydrogen plasma etching of silicon dioxide in a hollow cathode system

Chemical etching of various materials has been observed when hydrogen plasmas are used in material processing. In the case of the deposition of diamond films the preferential etching of sp² bonded carbon is considered to be of fundamental importance. A few papers have been published which have indicated that etching by hydrogen ions is different to that by hydrogen atoms. In this paper we describe the etching of silicon dioxide by hydrogen which was plasma-activated in a molybdenum-lined RF hollow cathode. The etch rate was seen to be thermally activated but decreased with increasing plasma power. The addition of a few percentage of helium increased the etch rate. The application of a − 50 V bias to the sample holder almost doubled the etch rate indicating the importance of ion bombardment for the chemical reaction. At high plasma powers and substrate temperatures in excess of 450 °C a thin molybdenum deposit was formed on the quartz samples.     

Dissolution kinetics of MgO crystals in aqueous acidic salt solutions

The revelation and morphology of dislocation etch pits as well as the rates of macroscopic dissolution and selective etching on the {1 0 0} plane of MgO crystals in aqueous solutions of various inorganic salts are investigated in relation to the nature and concentration of salt in solution and the etching temperature. It is found that addition of a salt generally facilitates etch pit formation and that the rates of surface dissolution and selective etching increase with additive concentration, etchant temperature and character and ageing of dislocations, while the etch pit morphology depends on the concentration and chemical nature of an impurity, etching temperature and the ageing of the dislocations. It is also observed that some fast etching solutions produce very shallow etch pits at screw dislocations. The results are discussed from a consideration of solution pH, standard electrode potentials of metals and stability of complexes present in solution. The importance of the surface entropy factor in revealing etch pits at screw dislocations is pointed out.     

Etch pits in flux-grown corundum

Procedures have been developed for chemically polishing and etching {0001}, {10¯11}, {10¯12}, {11¯20}, and {1¯100} planes in crystals of ruby and sapphire grown from a PbF₂ flux. The shape and the orientation of the etch pits were found to be characteristic for each plane and the density of the pits was 10² to 10⁴/cm². Similar pits were produced in flame-fusion material, but the density was 10⁶ to 10⁸/cm². Ruby and sapphire crystals grown by the same process behaved similarly. There is evidence that etch pits reveal dislocations which emerge normally to the basal or to the prismatic planes, since similar patterns of pits were produced after the removal of successive layers of material parallel to these planes, and a correlation was found between the pit patterns on opposite {0001} faces. Inconclusive evidence on this point was obtained for the rhombohedral planes.