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Methodology for quantitative evaluation of electron radiation damage and calculation of tolerable electron dose was developed to achieve damage-less scanning electron microscope (SEM) observation of beam-sensitive polymer film. The radiation damage is typically evaluated with visual impressions of SEM images; however, this method may be unreliable because observer’s subjectivity may affect the results. Evaluation with quantitative value is crucial to improve reliability. In this study, the radiation damage was evaluated by using normalized correlative coefficient (RNCC) between an initial frame and latter frames of the multiple SEM images that were taken consecutively. Tolerable dose was obtained by defining a threshold point of RNCC where rapid reduction of RNCC started. A SEM image with less damage and acceptable signal-to-noise ratio was obtained by integrating the images from the initial frame to the tolerable frame.

Organic-inorganic lead halide perovskites are promising materials for realization of low-cost and high-efficiency solar cells. Because of the toxicity of lead, Sn-based perovskite materials have been developed as alternatives to enable fabrication of Pb-free perovskite solar cells. However, the solar cell performance of Sn-based perovskite solar cells (Sn-PSCs) remains poor because of their large open-circuit voltage (

Inverse temperature crystallization (ITC) growth of formamidinium tin iodide (FASnI3) is realized using γ-valerolactone (GVL) solvent, which possesses a low Gutmann acceptor number. The high-crysta...

Organic–inorganic halide perovskites (OIHPs) have been intensively studied in recent years for use in solar cells. Many studies have reported the light-induced phenomena of OIHP materials and their solar cells. In this study, we investigated the influence of a hole-transport layer (HTL) on light-induced degradation (LID) of mixed OIHP solar cells, especially at the OIHP/HTL interface, by hard X-ray photoelectron spectroscopy (HAXPES) and impedance spectroscopy. HAXPES shows accumulation of iodine and metallic lead in the vicinity of the OIHP/HTL and electron-transport layer/OIHP interfaces, respectively, after LID. Under light illumination and in the dark after LID, characteristic impedance responses are observed for a sample with a highly damaged OIHP/HTL interface as an intermediate frequency arc and negative capacitance, respectively, because of the electrochemical reaction in the vicinity of the OIHP/HTL interface. Overall, the results indicate that light-induced iodide diffusion to the OIHP/HTL inter...

An area selective doping via ion implantation is a key technology to realize gallium nitride (GaN) based energy-efficient power devices; however, conventional annealing leads to the formation of numerous Mg-enriched defects, which result in inefficient p-type activation. The recent invention of ultra-high-pressure annealing (UHPA) has enabled a significant improvement in p-type activation efficiency. In this study, we investigated the formation of Mg-enriched defects in Mg implanted GaN followed by annealing under either conventional atmospheric pressure or ultra-high-pressure. Unlike the conventional annealing, UHPA leads to a much lower number density of Mg-enriched defects. Correlative scanning transmission electron microscopy, atom probe tomography, cathodoluminescence, and secondary ion mass spectrometry analyses have shown that the number density of Mg-enriched defects is substantially suppressed by the UHPA. The dissolved Mg concentrations in the GaN matrix for both the conventional and the UHPA samples are almost of the same value, approximately 2 × 1018 cm−3; however, the UHPA sample shows over one order of magnitude stronger intensity of donor–acceptor-pair emission than the conventional one. Thus, the implanted Mg is effectively activated as acceptors through the UHPA technique.

Atomic metal wires have great promise for practical applications in devices due to their unique electronic properties. Unfortunately, such atomic wires are extremely unstable. Here we fabricate stable atomic silver wires (ASWs) with appreciably unoccupied states inside the parallel tunnels of α-MnO2 nanorods. These unoccupied Ag 4d orbitals strengthen the Ag–Ag bonds, greatly enhancing the stability of ASWs while the presence of delocalized 5s electrons makes the ASWs conducting. These stable ASWs form a coherently oriented three-dimensional wire array of over 10 nm in width and up to 1 μm in length allowing us to connect it to nano-electrodes. Current-voltage characteristics of ASWs show a temperature-dependent insulator-to-metal transition, suggesting that the atomic wires could be used as thermal electrical devices., One-dimensional atomic metal wires can exhibit useful properties distinct from their bulk equivalents; however they typically suffer from limited stability. Here, Chen et al create atomic silver wires which are stable and exhibit a temperature dependent metal to insulator transition.

The quantum efficiency of composites containing Europium(II)-doped Ca-α-SiAlON phosphors and sodium borosilicate glasses has been reported to decrease with an increase in the Na 2 O concentration in the glass matrix. To understand the reason for the dependence of this degradation on the glass composition, the reaction between the SiAlON powder and the glass matrix was investigated using a variety of techniques. SEM images of the areas around SiAlON powders showed the formation of a new layer between the SiAlON particles and the glass matrix. EDX images showed that the number of silicon and aluminium atoms decreased while that of boron atoms increased in the new layer. Raman spectra of the composites showed the formation of B N bonds. New layers between the SiAlON phosphor and the glasses were formed owing to exchange between silicon or aluminium and boron; this resulted in the degradation of the composites.

Morphology of single Shockley-type stacking faults (SFs) generated by recombination enhanced dislocation glide (REDG) in 4H–SiC are discussed and analysed. A complete set of the 12 different dissoc...

Recently, organic–inorganic halide perovskites have received attention for applications in solar cells. Measurements of high-quality single crystals reveal lower defect densities and longer carrier lifetimes than those of conventional thin films, which result in improved electrical and optical properties. However, single crystal surfaces are sensitive to exposure to ambient conditions, and degrade under long-term storage in air. The surface also shows differences from the bulk in terms of its optical and electronic characteristics. For a heterojunction device, the interface at the single crystal is important. Understanding the difference between the surface and bulk properties offers insights into device design. Here, we prepared non-sliced and sliced formamidinium lead iodide (FAPbI3; FA+ = HC(NH2)2+) single crystals with a bandgap of 1.4 eV, which matches well with the requirements for solar cell photoabsorption layers. We evaluate the energy level diagrams of the surface and bulk regions, respectively. Our data indicate that the valence band maximum of the surface region is at a higher energy level than that of the bulk region. We also discuss hypotheses for the well-known and unexplained phenomena (multiple bandgaps and bandgap narrowing) seen in the absorption and photoluminescence spectra of single crystals. We conclude that these effects are likely caused by a combination of the degraded surface, Rashba-splitting in bulk, and self-absorption by the single crystal itself.

Group-IV alloy semiconductors have garnered increasing attention as advanced thin-film materials for next-generation electronics. We have demonstrated polycrystalline Ge thin films with the highest recorded crystallinity and carrier mobility using a multistep heating process in solid-phase crystallization. In this study, we apply these recent findings in Ge to Si1-xGex (x: 0–1) and Ge1-ySny (y: 0–0.04) alloys and investigate their crystal and electrical properties. For all compositions, controlling the temperature in each stage increases the grain size to the micrometer order, improving the carrier mobility and reducing the number of defect-induced acceptors. Sb doping further enlarges the grain size (up to 10 µm) in addition to n-type conduction control, whereas the electron concentration varies with the composition. Both hole and electron mobilities significantly depend on the composition owing to the effects of carrier effective mass, grain size, and carrier concentration: the hole and electron mobilities peak at 350 and 150 cm2 V−1s−1, respectively. The relationship between the composition and various physical properties revealed in this study will contribute to the better understanding, control, and device application of polycrystalline thin films based on group-IV alloy semiconductors.

The β-sialon:Eu 2+ phosphor has superior luminescent properties as an excellent green down-conversion material for white light-emitting diodes. To take advantage of its high chromaticity and apply it to field emission displays (FEDs), the drawback of its electron insulation that impedes the electron transmission when excited by e-beam needs to be solved. In this work, a facile method was adopted to coat conductive In 2 O 3 on the surface of β-sialon:Eu 2+ phosphor, and the influence of In 2 O 3 coating on the cathodoluminescent properties was investigated. The results show that the In 2 O 3 coating contributes to charge elimination and significantly improves the cathodoluminescence (CL) of β-sialon:Eu 2+ . Under 19 kV/1.0 nA e-beam excitation, the In 2 O 3 coated sample shows CL intensity about four times higher than that of the uncoated β-sialon:Eu 2+ . Moreover, no luminescence saturation occurs in coated β-sialon:Eu 2+ , indicating that the In 2 O 3 -coated β-sialon:Eu 2+ would be a promising green emissive material for full-color FEDs.

We have developed a three dimensional Haasen-Alexander-Sumino model to investigate the distribution of dislocation density and residual strain in Si crystals and compared the calculation results with experimental data performed in mono-like and multicrystalline silicon ingots. The results show that the residual strain in a multicrystal is lower than in a mono-like crystal, whereas the dislocation density in the multicrystal is higher than that in the mono-like crystal. This phenomenon is due to the relation between dislocation density and residual strain caused by the difference of activated slip systems in a mono-like crystal and a multicrystal.

We investigated two types of V-shaped extended defects on the basal plane in epitaxial 4H-SiC by synchrotron X-ray topography, photoluminescence imaging/spectroscopy and transmission electron microscopy (TEM). One is the (2, 5) stacking fault (in Zhdanov notation) bounded by two partial dislocations with the Burgers vector b ± 1/4[0 0 0 1]; the other is the (2, 3, 3, 5) stacking fault bounded by partial dislocations with b = ±1/4[0 0 0 1]. The core of the partial dislocations associated with the (2, 3, 3, 5) fault has an out-of-plane component (Frank component) and three in-plane components (Shockley components); the three Shockley components are cancelled out in total. The electronic structures of the (2, 5) and (2, 3, 3, 5) stacking faults were further examined by photoluminescence spectroscopy and first-principles calculations. It is suggested that the (2, 5) and (2, 3, 3, 5) stacking faults both have an interband state at a similar energy level, although they differ structurally.

When we observe a p-n junction in a certain semiconductors using scanning electron microscope, it is known that the p-type region is brighter than n-type region in secondary electron (SE) image. To clarify this origin, the p-n junctions in 4H-SiC was observed using fountain secondary electron detector (FSED). The original FSED image shows brighter p-region than n-region, which is similar to the SE image taken by Everhart-Thonley detector, mainly due to the background component of SE signal. By subtracting the background, the line profiles of FSED signal across p-n junction have been recorded according to the SE energies. These profiles may include the detailed information of p-n junction.

To clarify the bright contrast of insulating ceramics in secondary electron (SE) image taken using scanning electron microscopy (SEM), the low-pass secondary electron signals and images of conductive AlN and insulating β-SiAlON powders taken by fountain detector (FD) were inspected. It was found that the background component of β-SiAlON is originally strong. This component may come from the SE acceleration according to the charging. The low energy SEs of 5–20 eV were strong in AlN particles. According to the wide acceptance angle of FSED, we could not detect clear energy shift in SE spectra. These observations suggest that the bright contrast of insulating materials is not an intrinsic character of insulators but the SE3 contribution.

The threading dislocations in GaN provide diffusion routes for impurity incorporation, which substantially influences GaN based optoelectronic devices. Here, we investigated the characteristics of the impurity incorporation at threading dislocations by HCl vapor phase etching and cathodoluminescence (CL) measurements. The distinctive etch pits induced by HCl vapor phase etching correspond definitely to different types of dislocations, and the etching process causes simultaneously H incorporation at a high temperature. CL spectra of the etch pits were analyzed, and the observed difference in the redshift of near band emission peak indicates that mix dislocations are more favorable for impurity incorporations than that of edge dislocations. The understanding on the impurity incorporation behavior at threading dislocations helps to obtain high quality GaN nanostructures.

Nb-doped SrTiO 3 showed interesting resistive switching phenomena, which could be modulated by either thermal treatment or doping level. The impacts of oxygen vacancies and dislocations on resistive switching were investigated by comparing the switching behaviors of as-prepared and air-annealed crystals with a variety of doping levels. It was found that both oxygen vacancies and dislocations may have effects on the switching depending on the doping level. It was dominated by oxygen vacancies for low doping and dislocations for high doping.

The effect of Σ3 generation on random grain boundaries (R-GBs) were investigated using multicrystalline Si (mc-Si) grown from the microcrystalline template with random orientation. There existed three cases for the contrast variation of electron-beam-induced current (EBIC) on R-GBs after Σ3 generation from them, namely decrease, increase and constant cases. No clear tendency of EBIC contrast variation was found at the initial growth stage. On the other hand, the constant case became dominant at the steady state. This result indicates that Σ3 generation does not affect the electrical activity of R-GBs.

Thermal stability of perovskite solar cells is crucial for their practical use. In this report, we show good 74% stability retention after a thermal stress test at 85 °C for 350 h) with high efficiency (>18%) using Rb modified perovskite absorber layers. It is posited that the mechanism of the thermal stability improvement is due to the formation of RbPbl3 which suppresses Pbl2 growth. This facile way for improving thermal stability is promising for realizing solar cells with high efficiency and stability.