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Graphene–oxide–semiconductor (GOS) planar-type electron emission devices with a hexagonal boron nitride (h-BN) protective layer have demonstrated improved oxidation resistance while maintaining their emission performance. The devices with a monolayer or a multilayer (13 nm in thickness) h-BN protective layer can emit electrons even after oxygen plasma exposure (ashing). Remarkably, the device with a monolayer h-BN was able to emit electrons with a maximum efficiency of 11% after a 4-min ashing, showing that a thin h-BN protection layer can provide oxygen tolerance to GOS devices without a significant emission loss. The thicker multilayer h-BN imparted higher oxidation resistance to the device but with decreased emission efficiency compared with the device with monolayer h-BN. Thus, the use of h-BN necessitates a trade-off between the device’s emission performance and its oxidation resistance. In addition, the etching rate of h-BN by the oxygen plasma treatment was found to increase by exposure to air after the first plasma treatment, which indicates that the adherence of H2O to the surface of h-BN is one probable cause of h-BN etching during the ashing process.

A p-type graphene–oxide–semiconductor (GOS) planar-type electron emission device holds promise as a photocathode with a high quantum efficiency (QE) for generating a high-speed modulated electron beam. We report the electron emission properties of a planar-type electron emission device based on a GOS structure using lightly doped p-type silicon as a substrate under laser light irradiation. The electron emission efficiency is 12% with and without laser light irradiation. The emission current shows a four-order of magnitude enhancement in the high field region compared to that in the dark, and a 0.3% QE is obtained without a negative electron affinity surface. This GOS device exhibits advanced photoassisted electron emission characteristics with high photosensitivity on the order of mA/W. The photoemission from the p-type GOS device shows a fast photoresponse with a rise time of less than 0.2 µs, which is the same as that of the current amplifier. By contrast, it shows a slow response of about 2.4 µs at the fall time, which is determined by the diffusion process of the photoexcited electrons in the bulk. The use of a highly doped p-type silicon substrate can be a practical route for further improvement.

Objective Among standard treatments for infantile spasms, adrenocorticotropic hormone (ACTH) is reported as the best treatment, but ACTH is ineffective in one-half of the patients. To establish precision medicine, we examined pharmacoresistance of focal epileptic spasms (ES), generalized ES, and generalized ES combined with focal seizures, diagnosed based on the revised seizure classification of ILAE in 2017. Methods We conducted a retrospective nationwide study in Japan on the long-term seizure outcome of ES. Long-term seizure outcome was evaluated by seizure-free rate, seizure-free period, and Kaplan-Meier curve. Seizure-free was defined as seizure control for longer than two months. Results From the medical history of 501 patients, 325 patients had generalized ES only (GES group) at the start of the first treatment, 125 patients had generalized ES after focal seizure onset (FS-GES group), seven patients had focal ES after focal seizure onset (FS-FES group), and 24 patients had generalized ES combined with focal seizures after focal seizure onset (FS-GES+FS group). Seizure-free period of ES (generalized ES and focal ES) [mean (95% confidence interval)] was 2.7 (0.0-5.4) months in GES group, 1.1 (0.1-2.2) months in FS-GES group, 1.0 (0.2-1.9) months in FS-GES+FS group and 0.1 (-0.2-0.5) months in FS-FES group. Seizure-free rate, seizure-free period and Kaplan-Meier curve of generalized ES were almost the same in GES group and FS-GES group, with characteristics of superior response to ACTH. Mean seizure-free period of generalized ES combined with focal seizures was significantly shorter in FS-GES+FS group than in GES group. Mean seizure-free period of focal ES in FS-FES group was extremely short with exceedingly early relapse. Significance Pharmacoresistance was different in generalized ES, focal ES and generalized ES combined with focal seizures. ES with focal features or with focal seizures may have focal lesions, thus consider surgical options earlier in the course.

Spindt-type emitters were fabricated with cavities made of Al/Mo/SiO2 using the triode high power pulsed magnetron sputtering method. We explored the process parameters (gas pressure and voltage of the additional cap electrode) to optimize the sharpness of the emitter shape. We found that the intermediate pressure and voltage were suited to obtain sharp emitters. Further, we elucidated the crucial effect of the cavity dimensions, such as the cavity depth and hole diameter in the cavity ceiling, on the emitter shape. At a cavity depth of 480 nm, the aspect ratio (AR) of the emitter increased monotonously with an increase in the hole diameter. With a large hole diameter (900 nm) and even shallower cavity (380 nm depth), we attempted to reoptimize the process parameters. Consequently, a very sharp emitter cone structure with an AR exceeding 1.3 was obtained. The cap voltage that produced the optimum AR was found to decrease for the larger-hole and shallower-depth cavities. Finally, the applicability of the process for preparing a working emitter is discussed.