A two-dimensional crystal of the copper boride was grown on the well-known Cu(111) surface by boron deposition. The atomic structure and the electronic state were analyzed by a concerting usage of positron diffraction and photoemission spectroscopy. The surface layer is composed of the B and Cu atomic chains that are alternately arranged. It has been known that the B and Cu phases are completely separated in three-dimensional (3D) materials. The present study intriguingly revealed that a compound is formed in two-dimension (2D) at the surface. In addition, the Cu(111) substrate was found to affect a relative height between the B and Cu chains. The 2D Cu-B compound on Cu(111) likely becomes an ideal B/Cu interface to develop surface science and boron chemistry.

AlGaN/GaN high electron mobility transistors (HEMTs) possess favorable material properties and are compatible with large-scale manufacturing, making them promising as a next-generation power device. However, there is a lack of information available on the effect of an insulator dielectric passivation layer on the breakdown voltage (V_br) of AlGaN/GaN HEMTs. This study utilizes technology computer aided design to investigate the impact of different insulator dielectric passivation layers, such as SiO₂, SiN, Al₂O₃, and HfO₂, on V_br of AlGaN/GaN HEMTs. Furthermore, the study optimizes the parameters of the field plate length (L_FP) and insulator thickness to maximize V_br of AlGaN/GaN HEMTs. Results indicate that HEMTs with a field plate (FP-HEMTs) have greater V_br than HEMTs without a field plate (N-HEMTs). With the optimized conditions of a 1.8 µm L_FP and a 0.95 µm insulator thickness with HfO₂ passivation, V_br of 1120 V is achieved. The findings suggest that the field plate (FP) and passivation layer can significantly improve the efficiency and reliability of AlGaN/GaN HEMTs while the impact of AlGaN/GaN heterostructure parameters on V_br is minimal.

A report of nano-scale interaction of chloromethane (methyl chloride) (CH₃Cl) with the Fe(110) surface; van der Waals density functional theory (DFT) study. Physisorption of a CH₃Cl molecule via changing the site and orientation of the molecule was studied on the Fe(100) surface using DFT. All reasonable molecular and dissociative adsorption routes of the CH₃Cl molecule on the Fe(100) surface have been systematically investigated. Molecular adsorption was considered on four different surface sites with different orientations with Cl, C, and H atoms toward and away from the surface. Chemisorption was considered by decomposition of CH₃Cl into a methyl (CH₃) group and a Cl atom via a cleavage of the C–Cl bond and by decomposition into a CH₂Cl group and a H atom via a cleavage one of the C–H bonds. Chemisorption produces a greater degree of bonding than physisorption.

Atomic structures of an insulating and hydrophobic zeolite sample of mordenite were measured by high-energy X-ray diffraction, and a pair distribution function analysis was carried out. Valence- and conduction-band O 2p partial densities of states (DOSs) in a mordenite were measured by soft X-ray emission and absorption spectroscopies (SXES and SXAS), respectively. The SXAS spectrum for the conduction band O 2p orbital has characteristic structures like that of crystalline SiO₂, while pre-shoulders are observed in mordenite. By choosing characteristic energies in the SXAS spectrum for the incident photon energies, SXES spectra were obtained, in which a large peak and three small peaks or shoulders can be assigned by a lone pair orbital and bonding (σ) ones, respectively. A density functional theory was applied to determine the exact atomic structures and electronic states, and they are in good agreement with the corresponding experiments. It is concluded that the O 2p partial DOS is mainly O-Si covalent bonds, and the Al and Na atoms have minor contributions for them. From this study, it was found that the fundamental properties of complex zeolites can only be obtained in combination of experimental and theoretical investigations as mentioned above, which can open feasibilities to uncover the origin of active sites in functional zeolites.

The modification of a polyimide surface containing a 30% fraction of steroidal structure was studied as a function of storage time by vibrational sum frequency generation (SFG) spectroscopy and optical second-harmonic generation (SHG). The variation of the symmetric and anti-symmetric stretching modes of the CH₃ isopropyl group at the end of the side chain of the rubbed polyimide was detected in the SFG spectra after a 3-month storage time in a practical environment. It suggests that the isopropyl group might be reoriented. On the other hand, the SHG response of the same sample showed an insignificant storage-time dependence. As a result, the phenyl rings of the polyimide are judged to be unmodified after long-term storage time. The change is suggested to occur for two main reasons. One is the interaction between the polyimide polymers and the ambient water molecules. The other is the adsorption of unknown organic molecules on the polyimide surface.

We have performed first principles calculation study based on density functional theory on the adsorption of iodine and astatine on Au(111) and Au(211), including spin-orbit coupling (SOC) effects in some calculations. These surfaces are the dominant surface termination to represent a face-centered cubic nanoparticle. We found that both iodine and astatine adsorb stronger on the edge-bridge site of the Au(211) surface than on the flat Au(111) surface by about 0.2 eV. This result also makes the adsorbate less likely to diffuse after adsorption on the (211) surface as compared to the (111) surface. Additionally, we found that SOC effects, usually a necessity when considering heavy elements, are not significant in these cases, as can be seen by the energy and geometric data. Finally, we found the difference in adsorption energy between iodine and astatine on gold surface can be expected due to the presence of 4f electrons in astatine, which is not present in iodine. The 4f electrons offer less shielding of the nucleus, making the valence electrons of astatine closer to the nucleus, and therefore a smaller atomic radius. This information is useful both for experimental verification and future developments of gold nanoparticles for radiotherapy.

We report on a photoemission microscopy apparatus using a 10.9-eV laser developed at the National Institute for Materials Science (NIMS). Our spectrometer realizes photoemission spectroscopy with a high spatial resolution by combining an imaging double energy analyzer with the electronic lens system of photoelectron emission microscopy. Energy-filtered photoelectron imaging is available in both real and momentum spaces. The spatial resolution in the real space mode is ∼30 nm. We show energy-filtered photoelectron images of a silver grid-patterned sample in real space and the band mapping of Au(111) in momentum space to demonstrate the performance of our spectrometer.

In this study, we evaluated the hydrophilicity of low-refractive-index SiO₂ optical thin films deposited using a combination coating method of electron beam (EB) deposition and direct current pulse sputtering. In this deposition method, the introduction of process gas during deposition deteriorates the vacuum level, shortens the mean free path of deposited particles, and produces low-refractive-index films due to the low density associated with the columnar structure. Furthermore, the refractive index of the thin film deposited by using the combination coating method was 1.28. The low density of the thin film increases the surface roughness of the thin film, resulting in hydrophilic properties (contact angle, θ ≤ 10°). Although conventional EB deposition also exhibited hydrophilicity (contact angle, θ ≤ 10°) immediately after film deposition, the contact angle increased about 1 week after film deposition and lost its hydrophilicity after 1 year (contact angle, θ = 47°). The cause of this factor is the deposition of hydrocarbons in the air. However, the combination coating method obtained high hydrophilicity (contact angle, θ ≤ 10°) even after 1 year of deposition. The possible reason is the chemical termination by sputtering plasma besides the structural factor of the surface roughness, which is sufficient to sustain the hydrophilicity for 1 year.

This paper describes a new version of the mass filtered ion gauge (MFIG) sensor [D. Maas et al., Proc. SPIE 10145, 101452I (2017)]. By changing the entire design of the sensor its sensitivity could be improved, its mass filter function could be improved and last but not least its electronics was made far more robust. MFIG (shown in Graphical Abstract) is a metrology tool for detecting low levels of contamination (volatile organic compounds) with a high time resolution. As such it detects bursts, but also transients and continuous contamination in high vacuum systems. The high time resolution for an extended mass range discriminates this sensor from a residual gas analyzer (RGA). MFIG is also more sensitive than a state-of-the-art RGA as a result you can also detect contamination earlier. As such the MFIG sensor can be used as a traffic light and it can alert the system or operator in an early state when the system is out-of-spec. With these two unique characteristics the MFIG can prevent additional contamination to the system or additional yield loss. The development of this sensor was done within the European program MadeIn4. The development started with a use case and requirement analysis. The design process was supported by COMSOL^TM modeling. After realization of MFIG sensor it was evaluated in a laboratory environment in which we could insert controlled gas mixture into a high vacuum system. In this paper we will show that MFIG is both more sensitive and faster than a state-of-the-art RGA in detecting contaminations.

The density functional theory (DFT) is used to analyze the fundamental electronic properties, electronic states of bowtie shaped nanographene (C₃₈H₁₈ Clar's Goblet, CG), which is expected to be applied to such as spintronic devices. We also analyze triangulene, which is similar to CG and easier to make larger structures by increasing connections than CG. We investigate up to the trimer for CG and up to the tetramer for triangulene. In addition, we calculate the electronic structure of nanographene doped with boron and nitrogen. CG and triangulene have smaller bandgaps with BN dopants at the ferromagnetic state. We find that in ferromagnetic states, nitrogen and boron doping brings the up-spin and down-spin levels closer to the Fermi level, especially in triangulene, both levels are almost equal to the Fermi level, and the wavefunctions are localized at both ends of the triangulene.

We have developed the beam windows for the COherent Muon to Electron Transition (COMET) project. The COMET project is under construction at the proton beam accelerator facility J-PARC in Japan. Windows are one of key components on the beam line. The beam window should pass the beam of proton or other particles effectively, with robustly separating sections of the beam line. After research and developments for the beam windows especially focused on the shape and structure, we employed a dome shape which has radius curvature(s) on to the beam passing area, instead of a conventional thin and flat shape. Additionally, we employed a thicker structure on the circumference part to give higher mechanical strength. To manufacture cost consciously, the beam windows are fabricated by a three-dimensional printer, additive manufacturing (AM) to realize a hard to cut and machine shape. The detailed dimensions were designed through numerical analysis. There are requirements of high transmission efficiency of the beam, such as the material density must be low, and the thickness must be as thin as possible, while minimizing the nuclear heat generation by beam energy loss. Thus, the material was chosen as titanium alloy, Ti-6Al-4V. After the window shape was formed by AM, the voids inside the window were killed by hot isostatic pressing. Finally the window was polished to be smoothen the surface and tailored its thickness. As the first step to be used for the COMET project, for Phase-α we fabricated domes of 270 and 220 mm to mate with the rotatable flanges. The target values of the dome were the thickness tailored below 0.5 mm, and the pressure withstanding performance over 0.8 MPa for each diameter model. Throughout the tests we confirmed that the windows satisfied the target values, and the windows could withstand 0.9 MPa when pressurized from concave side of the dome.