Test beam results of Current Injected Detectors (CID) irradiated up to 5×10 1 MeV neq/cm

Two full size strip detectors were investigated in this study: one with p⁺ strips (p⁺/n⁻/n⁺) and another with n⁺ strips (n⁺/p⁻/p⁺). Both detectors, are made of magnetic Czochralski silicon (MCz-Si) and irradiated to S-LHC fluencies, were tested with 225 GeV muon beam in the CERN H2 area. The Current Injected Detector (CID) sensors were operated in a cooling box capable of providing a −53 °C temperature. Results indicate a relative charge collection efficiency (CCE) at 5×10¹⁵ n_eq/cm² above 30% in irradiated p⁺/n⁻/n⁺ CID detector at 600 V bias voltage. The signal to noise ratio of this CID module was about eight and a forward current of 30 μA was needed for detector biasing. In standard reverse bias, the same detector could not provide a sufficiently large signal for particle tracking purposes. A p-type (n⁺/p⁻/p⁺) sensor was irradiated to a fluence of 2×10¹⁵ n_eq/cm² and measured under the same test beam conditions. According to the theory of CIDs developed by the CERN RD39 Collaboration, this detector module could be biased up to only 230 V due to the low irradiation fluence. The CCE at 230 V was 35% in CID operation and 20% when reverse biased.     

Development of an energy-binned photon-counting detector for X-ray and gamma-ray imaging

The aim of this study is to develop an energy-binned photon-counting (EBPC) detector that enables us to provide energy information of x-rays with a reasonable count statistics. We used Al-pixel/CdTe/Pt semiconductor detectors, which had an active area of 8 mm×144 mm and consisted of 18 modules aligned linearly. The size of a CdTe detector module was 8 mm×8 mm and the thickness of the CdTe crystal was 1 mm. Each module consisted of 40×40 pixels and the pixel size was 200 μm×200 μm. We applied the bias voltage of −500 V to the Pt common electrode. The detector counted the number of x-ray photons with four different energy windows, and output four energy-binned images with pixel depths of 12, 12, 11 and 10 bits at a frame rate of 1200 Hz (300 Hz×4 energy bins). The basic performance of the detector was evaluated in several experiments. The results showed that the detector realized the photon counting rate of 0.4×10⁶ counts/sec/pixel (10⁷ counts/sec/mm²), energy resolution 4.4% FWHM at 122 keV. The integral uniformity of the detector was about 1% and the differential uniformity was about 1%. In addition, the image quality was examined with a resolution chart and step-wedge phantoms made of aluminum and polymethyl methacrylate. And we compared the quality of an acquired image with that acquired with an energy integration detector. The results of these experiments showed that the developed detector had desirable intrinsic characteristics for x-ray photon counting imaging.     

Further studies on the lithium phosphorus oxynitride solid electrolyte

First step in the way to the fabrication of an all-solid microbattery for autonomous wireless sensor node, amorphous thin solid films of lithium phosphorus oxynitride (LiPON) were prepared by radio-frequency sputtering of a mixture target of P₂O₅/Li₂O in ambient nitrogen atmosphere. The morphology, composition, and ionic conductivity were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and A.C. impedance spectroscopy. With a thickness of 1.4 μm, the obtained LiPON amorphous layer provided an ionic conductivity close to 6 × 10⁻⁷ S cm⁻¹ at room temperature. MicroRaman UV spectroscopy study was successfully carried out for the first time on LiPON thin films to complete the characterization and bring further information on LiPON structure.     

Layered δ-MnO2 as positive electrode for lithium intercalation

Layer structured δ-MnO₂ was synthesized by a microwave-assisted hydrothermal method. The morphology of the product consists of flower-like spheres that range from about 200 nm to 3 μm in diameter and are composed of sheets about 5-10 nm in thickness. When tested in the voltage range of 2 to 4.5 V vs. Li⁺/Li in coin cells, the separator is blocked, handicapping Li⁺ conductivity and leading to cell failure. When tested in the voltage range of 2 to 4 V in ethylene carbonate/dimethyl carbonate (EC/DMC), the δ-MnO₂ delivers an initial reversible capacity of 143.7 mAh g⁻¹ and can maintain 120 mAh g⁻¹ at the 60th cycle. The δ-MnO₂ electrode shows good cycling stability at different current densities and delivers a discharge capacity of about 90 mAh g⁻¹ at 1 C, indicating that it is a promising cathode material for lithium ion batteries.     

Basic study of single crystal fibers of Pr:Lu3Al5O12 scintillator for gamma-ray imaging applications

Single-crystalline fibers were grown from 0.25, 0.70, and 1.50 mol% Pr-doped Lu₃Al₅O₁₂ (LuAG) melts by the micro-pulling down (μ-PD) method with a diameter of 0.3-0.5 mm and a length of about 200 mm. They were cut to 10 mm long specimens, and their scintillation properties, including light yield and decay time profile, were examined. These results were compared with corresponding properties of the specimens (0.8×0.8×10 mm³) cut from the bulk crystals produced by conventional Czochralski (CZ) growth. The μ-PD-grown fibers demonstrated relatively low light yield and had the same decay time constant when compared with those of the samples cut from the CZ-grown crystals. The fiber crystals were used to assemble scintillating arrays with dimensions of Ø 0.5×10 mm²×20 pixels and Ø 0.3×10 mm²×30 pixels coated by a BaSO₄ reflector. After optical coupling with a position sensitive photomultiplier tube, the fiber-based arrays demonstrated acceptable imaging capability with a spatial resolution of about 0.5 mm.     

Detection of various self-assembled monolayers by AlN-based film bulk acoustic resonator

Various self-assembled monolayers such as carcinoembryonic antigen (CEA), beta actin, and bovine serum albumin (BSA) were detected using an AlN-based film bulk acoustic resonator (FBAR). AlN thin film was deposited by reactive RF magnetron sputtering, on a substrate of Mo (100 nm)/Ti (34 nm)/SiO₂ (480 nm)/Si (300 μm)/Si₃N₄ (300 nm). The film showed a strongly c-axis preferred orientation with a main (0 0 2) peak, as well as a good full width at half maximum (FWHM) of 2.50° in XRD and rocking curve results. The AlN-based FBAR was confirmed to have a resonant frequency of 2.477 GHz and a sensitivity of 3514 Hz cm²/ng. In beta actin, BSA, and CEA, the frequency properties showed variation values of 472.142, 932.573, and 685.421 kHz and mass sensitivities of 3530, 3506, and 3514 Hz-cm²/ng, respectively. The FBAR sensor was confirmed to be very useful for detecting target antigens through the binding of an antigen and an anti-body.     

Performance measurements from LYSO scintillators coupled to a CMOS position sensitive SSPM detector

We have designed a 5×5 mm² position sensitive solid-state photomultiplier (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process that provides imaging capability on the micro-pixel level. The PS-SSPM has 11,664 micro-pixels total, with each having an active area and micro-pixel pitch of 30×30 μm² and 44.3 μm, respectively. The PS-SSPM was then examined for its performance characteristics such as its energy and spatial resolution, and LYSO scintillator array imaging capabilities. When coupled to 5×5×3 mm³ LYSO, the energy resolution at 511 keV (²²Na) was measured as a function of bias, and corrected for the PS-SSPM non-linear output. The resolution is 14% (FWHM) at 511 keV with 30 V bias. The LYSO coincidence timing resolution was 9.4 ns (FWHM) at 511 keV. Spatial resolution studies were conducted using a focused (∼30 μm beam spot diameter) pulsed 635 nm diode laser. Scintillator array imaging studies were conducted at 511 keV using a 6×6 LYSO array, having 500 μm pixels (530 μm pitch) and 5 mm tall.     

Surface modification and chemical sputtering of graphite induced by low-energy atomic and molecular deuterium ions

The surface morphology, and chemical/structural modifications induced during chemical sputtering of ATJ graphite by low-energy (<200 eV/D) deuterium atomic and molecular ions are explored by Scanning Electron Microscopy (SEM), Raman and Auger Electron Spectroscopy (AES) diagnostics. At the lowest impact energies, the ion range may become less than the probe depth of Raman and AES spectroscopy diagnostics. We show that such diagnostics are still useful probes at these energies. As demonstration, we used these surface diagnostics to confirm the characteristic changes of surface texture, increased amorphization, enhanced surface reactivity to impurity species, and increased sp³ content that low-energy deuterium ion bombardment to steady-state chemical sputtering conditions produces. To put these studies into proper context, we also present new chemical sputtering yields for methane production of ATJ graphite at room temperature by impact of D₂⁺ in the energy range 10-250 eV/D, and by impact of D⁺ and D₃⁺ at 30 eV/D and 125 eV/D, obtained using a Quadrupole Mass Spectroscopy (QMS) approach. Below 100 eV/D, the methane production in ATJ graphite is larger than that in HOPG by a factor of ∼2. In the energy range 10-60 eV/D, the methane production yield is almost independent of energy and then decreases with increasing ion energies. The results are in good agreement with recent molecular dynamics simulations.     

The effect of In ion on the optical characteristics of Er in Er/Yb:LiNbO3 crystal

The effect of In³⁺ ion on the optical characteristics of Er³⁺ ion in Er/Yb:LiNbO₃ crystal under 980 nm excitation has been investigated. The Er and Yb contents in the crystals were measured by an inductively coupled plasma atomic emission spectrometer (ICP-AES). A significant enhancement of 1.54 μm emission was observed for Er/Yb:LiNbO₃ crystal doped with 1 mol% In₂O₃. The studies on the UV-vis absorption and the OH⁻ absorption spectra indicate that the threshold concentration of In³⁺ ion decreases with the Er/Yb doping in Er/Yb/In:LiNbO₃ crystal. The 1 mol% In₂O₃ doping results in the reduction of absorption cross section in the UV-vis region, meaning the formation of Er³⁺ cluster sites. The enhancement of 1.54 μm emission is attributed to the larger probabilities of the cross relaxation processes ⁴S_3/2 + ⁴I_15/2 → ⁴I_9/2 + ⁴I_13/2 (Er), ⁴S_3/2 + ⁴I_15/2 → ⁴I_13/2 + ⁴I_9/2 (Er) and ⁴I_9/2 + ⁴I_15/2 → ⁴I_13/2 + ⁴I_13/2 (Er) induced by Er³⁺ cluster sites.     

On the effective viscosity of suspensions

This work discusses the classical problem of effective viscosity of a Newtonian fluid with rigid spherical particles. It argues that the simple non-interaction approximation when formulated correctly yields an effective viscosity ratio for the suspension in the form μ/μ₀ = (1 − 2.5?)⁻¹ that remains accurate at much higher volume fractions of particles ? than the usual first-order approximation μ/μ₀ = 1 + 2.5?.     

Dual-cathode method for sputtering magnetoelastic iron-boron films

Magnetoelastic sensors have gained attention in recent years due to their wireless nature and versatility in sensing applications, but there have been issues with fabrication, especially as sensor platform sizes approach the microscale. In this work, a dual-cathode method is presented for the co-deposition of iron and boron to produce magnetoelastic films that serve as the basis for wireless sensors. Deposition rate and film composition experiments were performed to optimize sputtering conditions for obtaining high-quality films with compositions near to the goal of 80/20 at.% iron/boron. The magnetoelasticity of films produced using this method, along with the potential of wireless sensors based upon these films, was confirmed by fabricating small (500 × 100 × 5 μm) sensor platforms and then testing for resonance using a coil and a network analyzer. These sensors were found to have resonance frequencies of around 4 kHz with Q-values, in air, of over 1000. By coating the sensor platforms with gold using a third cathode, and then annealing in a vacuum oven at 220 °C, the environmentally sensitive iron-based alloy that forms the core of the sensor platform may be protected from corrosion.     

Rotating compensator sampling for spectroscopic imaging ellipsometry

In this work, a rotating compensator sampling for spectroscopic imaging ellipsometry (SIE) is presented and demonstrated by characterization of a SiO₂ nanofilm pattern on Si substrate. Experiment results within spectrum of 400-700 nm show that the rotating compensator sampling is valid for SIE to obtain the ellipsometric angle distributions ψ (x, y, λ) and Δ (x, y, λ) over the thin film pattern, the sampling times of ψ (x, y) and Δ (x, y) with 576 × 768 pixels under each wavelength is less than 8 s, the precision of fitting thickness of SiO₂ is about 0.2 nm and the lateral resolution is 60.9 μm × 24.6 μm in the parallel and perpendicular direction with respect to the incident plane.     

Amorphous structure and electrical performance of low-temperature annealed amorphous indium zinc oxide transparent thin film transistors

The effect of low-temperature (200 °C) annealing on the threshold voltage, carrier density, and interface defect density of amorphous indium zinc oxide (a-IZO) thin film transistors (TFTs) is reported. Transmission electron microscopy and x-ray diffraction analysis show that the amorphous structure is retained after 1 h at 200 °C. The TFTs fabricated from as-deposited IZO operate in the depletion mode with on-off ratio of > 10⁶, sub-threshold slope (S) of ~ 1.5 V/decade, field effect mobility (μ_FE) of 18 ± 1.6 cm²/Vs, and threshold voltage (V_Th) of − 3 ± 0.7 V. Low-temperature annealing at 200 °C in air improves the on-current, decreases the sub-threshold slope (1.56 vs. 1.18 V/decade), and increases the field effect mobility (μ_FE) from 18.2 to 23.3 cm²/Vs but also results in a V_Th shift of − 15 ± 1.1 V. The carrier density in the channel of the as-deposited (4.3 × 10¹⁶ /cm³) and annealed at 200 °C (8.1 × 10¹⁷ /cm³) devices were estimated from test-TFT structures using the transmission line measurement methods to find channel resistivity at zero gate voltage and the TFT structures to estimate carrier mobility.     

Nanostructured Cu2O thin film electrodes prepared by electrodeposition for rechargeable lithium batteries

Uniform films of Cu₂O with thickness below 1 μm were prepared from a Cu(II) lactate solution. The deposits were compact and of high purity with the particle size varying from 60 to 400 nm. They were tested as electrodes in lithium batteries and their electrochemical response was consistent with the Cu₂O + 2e⁻ + 2Li⁺ ↔ 2Cu + Li₂O reaction. Nevertheless, the reversibility of this reaction was dependent on thickness. Kinetic factors associated with the poor electronic conductivity of Cu₂O could account for the relevance of the influence of film thickness. The thinnest film, about 300 nm thick, exhibited the best electrochemical performance by sustaining a specific capacity as high as 350 Ah kg^− 1.     

High sensitivity and wide bandwidth image sensor using CuIn1 − xGaxSe2 thin films

We have fabricated a novel image sensor using Cu(In,Ga)Se₂ (CIGS). A combined process of dry etching using HBr and Ar gasses and wet etching using dilute HCl solution was developed as isolation process of CIGS photodiode deposited at 400 °C. Etchant residues of the dry etching, which consist of Cu complex, were almost completely cleaned using the wet etching process and favorable vertical side wall of CIGS films was obtained without mechanical damages. As a result, high performance image sensors with low leakage current of ~ 10^− 8 A/cm² and wide wavelength range up to ~ 1240 nm were achieved. The developed image sensor consisted of 352 × 288 pixels with 10 µm × 10 µm pixel sizes, was able to capture clear images of night scenes.     

Improved photoelectrochemical detection of mercury (II) with a TiO2-modified composite photoelectrode

The spectrophotometric change of a mercury (II) (Hg²⁺) selective small molecule chemosensor has been successfully converted into a photovoltaic response upon ligating Hg²⁺. The photon excitation was followed by charge separation facilitated by TiO₂ and polyaniline (PANI), resulting in an electron transfer to an electrical back contact. The photoresponse of the Hg²⁺ selective chromophore was converted to an electron current equivalent to the amount of Hg²⁺ in solution. The favourable properties of a Hg²⁺ sensitive chemosensor was combined with the semiconductor capabilities of TiO₂ to construct a sensor that is capable of generating a current in the presence of Hg²⁺ under illumination. A composite of the fluorescent chemosensor rhodamine 6G hydrozone derivative (RS) and PANI was immobilized on indium tin oxide (ITO) plates coated with TiO₂ and subjected to photovoltammetric measurements. The photovoltammetric responses of the coated layers were investigated to determine the sensitivity and selectivity of the immobilized sensor to Hg²⁺ in the presence of background ions. The photo-response increased linearly with increasing Hg²⁺ concentration from 10 to 200 μg L⁻¹ with a limit of quantification (LOQ) of 4 μg L⁻¹. The pH independence for the photoresponse was limited by the TiO₂ layer and was optimal between pH 6 and 7.     

Development of integrated ΔE-E silicon detector telescope using silicon planar technology

An integrated ΔE-E silicon detector telescope using silicon planar technology has been developed. The technology developed is based on standard integrated circuit technology and involves double sided wafer processing. The ΔE and E detectors have been realized in a PIN configuration with a common buried N⁺ layer. Detectors with ΔE thicknesses of 10, 15 and 25 μm, and E detector with thickness of 300 μm have been fabricated and tested with alpha particles using ²³⁸Pu-²³⁹Pu dual alpha source. The performance of the detector with ΔE detector of thickness 10 μm and E detector of thickness 300 μm has been studied for identification of charged particles using 12 MeV ⁷Li⁺ ion beam on carbon target. The results of these tests demonstrate that the integrated detector telescope clearly separates the charged particles, such as alpha particles, protons and ⁷Li. Due to good energy resolution of the E detector, discrete alpha groups corresponding to well known states of ¹⁵N populated during the reaction could be clearly identified.     

Stability,electrochemical behaviors and electronic structures of iron hydroxyl-phosphate

Iron hydroxyl-phosphate with a uniform spherical particle size of around 1 μm, a compound of the type Fe_2−y□_y(PO₄)(OH)_3−3y(H₂O)_3y−2 (where □ represents a vacancy), has been synthesized by hydrothermal methods. The particles are composed of spheres of diameter <100 nm. The compound exhibits good electrochemical performance, with reversible capacities of around 150 mAh g⁻¹ and 120 mAh g⁻¹ at current densities of 170 mA g⁻¹ and 680 mA g⁻¹, respectively. The stability of crystal structure of this material was studied by TGA and XRD which show that the material remains stable at least up to the temperature 200 °C. Investigation of the electronic structure of the iron hydroxyl-phosphate by GGA + U calculation has indicated that it has a better electronic conductivity than LiFePO₄.     

SIMS and GDMS depth profile analysis of hard coatings

Rapid development in hard coating technology calls for simple construction depth profile analysers. Here we present results of depth profile analysis of a set of Ar arc plasma deposited TiN, CrN layers. The results are obtained with the use of recently constructed simple glow discharge mass spectrometer (GDMS) and compared with secondary ion mass spectrometer (SIMS). In SIMS (SAJW-05 model) we apply 5 keV Ar⁺ ion beam of about 100 μm in diameter. Digitally controlled spiral scanning of primary ion beam is performed over 1.6 mm² area. Secondary ions are extracted from the central part due to an “electronic gate” and analysed by quadrupole mass spectrometer QMA-410 Balzers (16 mm rods).GDMS analyses are performed on SMWJ-01 glow discharge prototype spectrometer. To supply discharge in 1 hPa argon we use 1.5 kV DC voltage. The analysed sample works as a cathode in a discharge cell. Area of the analysis is ∼4 mm² due to the use of secondary cathode—high purity tantalum diaphragm. Sputtered atoms are ionised, next extracted into the analytical chamber and finally analysed by the quadrupole mass analyser SRS-200 (6 mm rods).The results show that the use of simple construction GDMS analyser allows obtaining similar or even slightly better depth resolution than it can be obtained in the SIMS spectrometer. Application of glow discharge analysis opens new possibilities in direct quantitative depth profile analysis of hard coatings.