Abstract Statistical evaluation of two-level fluctuators (TLFs) in quantum dots is essential for improving the coherence of silicon spin qubits. However, conventional methods detect TLFs only under high-sensitivity conditions, which limits the accessible voltage range for characterization. Here we introduce a method that detects individual switching of TLFs in a silicon quantum dot even at low-sensitivity conditions. This method can extract the voltage dependence near the conditions activating the TLF switching, which provides insight into TLF switching mechanisms. Our approach facilitates routine statistical characterization of noise caused by TLFs in silicon spin qubits.

Abstract Mathematical order such as the golden ratio, Fibonacci sequences, and other quasiperiodic or aperiodic patterns provide a compact design language for functional matter. This review traces their role from describing non-periodic order in quasicrystals, fractals, and optical systems to actively engineering wave and energy transport, with particular emphasis on phononic and thermal phenomena. We highlight periodic superlattices as phononic crystals that control coherent–incoherent crossover, Golomb ruler-based architectures as paradigms of controlled disorder enabling broadband suppression of transport channels, and quasiperiodic sequences such as Fibonacci, Thue–Morse, and Double-Period designs that generate hierarchical scattering and partial localization. Taken together, these advances show how mathematically encoded order can sculpt phonon and photon landscapes in a highly structured way, suggesting mathematics-guided routes toward cross-scale control of heat, light, and related excitations.

Abstract A low contact resistivity (ρc ) of 3.2×10−5 Ωcm2, which is comparable to that of Ti/Al-based contacts with high-temperature annealing (≈1000°C), is obtained for Pt contacts formed on heavily Al+-implanted p-type SiC followed by 600°C-annealing. A small barrier height at the Pt/p-type SiC interface is confirmed by the capacitance–voltage measurements of vertical Schottky barrier diodes, which should be the origin of the low ρc . The structural analyses revealed that a reacted layer consisting of Pt silicides and C atoms is formed at the Pt/SiC interface by 600°C-annealing.

Abstract The Mg concentration ([Mg]), acceptor concentration (Na), and compensating donor concentration (Nd) of Mg-ion implanted (Mg-I/I) and Mg+N-ion-implanted (Mg+N-I/I) GaN with various ultra-high-pressure annealing (UHPA) durations were analyzed in-depth. Sequential N-ion implantation (N-I/I) suppressed Mg diffusion after 30 min of UHPA. The net acceptor concentration of Mg+N-I/I GaN after 30 min of UHPA was more than twice that of Mg-I/I GaN. Sequential N-I/I followed by 30 min of UHPA enhances Mg substitution at Ga sites (Na/[Mg] ≅ 70%) and reduces compensating donors (Nd/Na ≅ 18 % ) while maintaining the initial Mg depth profile, thereby enabling precise Mg doping control.

Abstract We report on the study of high-field performance of Si-doped n-AlN layers that were grown using a pulsed metalorganic chemical vapor deposition (PMOCVD) process. In the past we showed this pulsed doping approach to lead to doping efficiency superior to that in the conventional MOCVD process. Here using them as the drift layer for a quasi-vertical conduction Schottky barrier, we show their ability to withstand high reverse bias voltages and sustain an electrical field as high as 9.9 MV cm−1. Our study thus demonstrates the viability of the PMOCVD growth and doping approach to yield n-AlN layers suitable for high current-high voltage devices.

Abstract A rutile germanium dioxide (r-GeO2) vertical Schottky barrier diode (SBD) was fabricated. An unintentionally doped n-type single-phase r-GeO2 epitaxial layer and Sb-doped n+-type graded Ge y Sn1−y O2 buffer layers were grown on an Nb-doped n+-type (001) TiO2 substrate via mist chemical vapor deposition. A Ni Schottky electrode and a Ti/Al Ohmic contact were formed on the surface and the backside, respectively. Capacitance–voltage and current–voltage characteristics of the Ni/r-GeO2 vertical SBD revealed clear rectification behavior and a significantly low on-resistance. These findings contribute to the advancement of r-GeO2-based electronic devices.

Abstract Nonvolatile and reversible control of perpendicular magnetic properties of thin Co0.2Fe0.6B0.2 layers formed on a MgO layer was demonstrated by ferroelectric switching of the stacked Al0.88Sc0.12N and Ta2O5 layers. A change in the coercivity (H c) of the 1.3-nm-thick Co0.2Fe0.6B0.2 layer from 30 to 141 Oe was confirmed by depleting electrons at the interface, modifying the magnetic domain wall energy. Saturation magnetization showed a slight decrease toward depletion condition, presumably presenting a dead layer at the interface. The ferroelectric polarization-induced control of magnetism has high potential for magnetic memory applications.

Abstract Perovskite solar cells (PSCs) have attracted much attention due to their high-power conversion efficiency and solution processability. Establishing a method to easily evaluate the defects present in PSCs is a key factor in achieving efficient large area PSCs. In this work, we have established a simple method to identify the defects in PSCs by combining several imaging methods. We revealed that the scratches in PSCs can be identified by combining electroluminescence, photoluminescence, and thermal imaging methods. We believe that the proposed methodology will provide important insights into the strategy for establishing efficient large-scale PSCs.

Abstract A biological spectral imaging system based on photoacoustic spectroscopy is proposed for real-time in vivo measurements of biological samples. The system irradiates biological samples with mid-infrared laser light modulated at several hundred kilohertz and detects ultrasonic waves generated within the sample using a piezoelectric transducer. Spectral imaging results obtained using a bovine meat sample demonstrated that muscle and fat could be distinguished based on signal intensity at only two wavelengths, identified through support vector machine optimization. These findings enabled the imaging of porcine brain samples containing d-2-hydroxyglutarate, a tumor marker.