Nara Institute of Science and Technology

Solution-processed SnO2-based thin-film transistors (TFTs) have attracted significant attention due to their low cost, low toxicity, and the high abundance of SnO2. However, SnO2-TFTs suffer from large negative threshold voltage as well as low on/off ratios because of high residual carrier electrons from oxygen vacancies. It is known that doping elements, such as Si, that form strong chemical bonding with oxygen suppresses oxygen vacancy formation. Here, we fabricated and characterized Si-doped SnO2 (SixSnyO) TFTs. In SixSnyO-TFTs, we found that increasing the Sn molarity leads to an enhancement in field-effect mobility while inducing a negative threshold voltage shift. To clarify the origin of this mechanism, we measured the effective channel thickness of SixSnyO-TFTs by electric field thermopower modulation analyses. The effective mass (m*) of the SixSnyO films slightly decreased with increasing Sn molarity and was approximately 0.15 m0, suggesting that an increase in Sn molarity improves the metal–oxygen network in the film. The effective channel thickness, which corresponds to the accumulation layer thickness, increased with rising sheet carrier concentration at low Sn molarity. On the other hand, it decreased with increasing sheet carrier concentration at high Sn molarity. This suggests that the carrier transport mechanism varies depending on Sn molarity. These findings provide guidance in developing high-mobility and reliable SixSnyO-TFTs through appropriate control of the Sn molarity in SixSnyO.

Stable luminescent multiradicals are photophysically very attractive materials as well as stable luminescent monoradicals due to their complex spin‐multiplicity states or intramolecular electronic and magnetic interactions. This concept article highlights synthetic advances in triarylmethyl‐type stable luminescent radicals, emphasizing methods to construct diradical, triradical, and multiradical systems. These radicals are prepared from triarylmethane precursors via deprotonation, followed by oxidation. The initial synthesis of perchlorinated triphenylmethanes through the BMC methodology (S 2 Cl 2 and AlCl 3 in SO 2 Cl 2 ) chlorination led to perchlorinated Chichibabin diradical. Friedel–Crafts reactions have been widely employed to produce various halogenated triphenylmethanes, which serve as versatile platforms for further functionalization. Incorporation of pyridine rings into the triarylmethyl core enables the formation of coordination systems with multiple radical ligands. Coupling reactions play an important role in expanding these radical frameworks. Direct substitution to the tris(2,4,6‐trichlorophenyl)methyl radical allows for the introduction of N ‐donor groups, creating donor–acceptor luminescent radicals and acceptor–donor–acceptor luminescent diradicals. Pd‐catalyzed couplings enable the functionalization of halogenated triarylmethanes, facilitating their dimerization, trimerization, and other complex architectures. The development of triarylmethane‐based boronic acids and esters has further expanded the synthetic scope, overcoming previous limitations and opening new pathways to stable luminescent diradicals.

Pseudo-haptics techniques are interesting alternatives for inducing haptic perceptions, achieved by manipulating haptic perception through the appropriate alteration of primarily visual feedback in response to body movements. However, the use of pseudo-haptics techniques with a motion-input system can sometimes be limited. This paper investigates a novel approach for extending the potential of pseudo-haptics techniques in virtual reality (VR), focusing on pseudoweight perception as the target case. The proposed approach utilizes a reaction force from force-input as a substitution of haptic cue for the pseudo-haptic perception. The paper introduced a manipulation method in which the vertical acceleration of the virtual hand is controlled by the extent of push-in of a force sensor. Such a force-input manipulation of a virtual body cannot only present pseudo-haptics with smaller physical spaces and be used by various users including physically handicapped people, but can present the reaction force proportional to the user's input to the user. We hypothesized that such a haptic force cue would contribute to the pseudo-haptic, here, the pseudoweight perception. Therefore, the paper endeavors to investigate the force-input pseudo-haptic perception in comparison with the motion-input pseudo-haptics. The paper compared force-input and motion-input manipulation in a point of achievable range and resolution of pseudo-weight. The experimental results suggest that forceinput manipulation successfully extends the range of perceptible pseudo-weight by 80% in comparison to the motion-input manipulation. On the other hand, it is revealed that motion-input manipulation has 1 step larger number of distinguishable weight levels and is easier to operate.

Users are often seated in the real environment, while their virtual avatars either remain standing stationary or move in virtual reality (VR). This creates posture inconsistencies between the real and virtual embodiment representations. The relationship between posture consistency in locomotion techniques and sense of presence in VR is still unclear. This study investigates how visual and somatosensory integration affects the sense of standing (SoSt) and the sense of self-motion (SoSm) when the sitting posture is varied slightly, including highlighting the importance of sitting posture for locomotion design in VR. The degree and occurrence of SoSt and SoSm were assessed by subjective experiments, and it was found that higher sitting and lower sitting postures present higher SoSt and lower SoSm, respectively. Invocation of SoSt also influences postural perception. Perception of travel distance varied according to the posture condition when identical visual flow was presented. The findings suggest that visual and somatosensory integration related to posture enhances SoSt and SoSm, and a sitting posture with a higher seating position is recommended in seated VR locomotion design.