Search

This paper introduces a new artificial intelligence software which is capable of controlling devices using fingers in the air. With Ubimouse, touch-panels, restaurant ordering systems, ATM systems, and etc., which are commonly used by various people in public, can be contact-less devices. These touch-less devices, especially under the harsh conditions of COVID-19, are desired to prevent infections mediated by touch devices. Also, these devices cannot be used while wearing gloves due to their touch sensing fault. Thus, in fields using gloves, there is a demand for non-contact device operation. To satisfy these demands, we have developed “UbiMouse”. This is an AI software that allows you to operate the device by moving your fingers toward the device. In the AIs in UbiMouse, a convolution model and a regression model are used to identify fingers’ features from camera footage and to estimates the position of a detected finger, respectively. We demonstrate an operation of UbiMouse without contact. Along with this operation in the air, a mouse cursor is guided to the specified location with high accuracy.

The development of efficient electrically driven color-tunable solid-state light sources will enable new capabilities in lighting and display technologies. Although alternative light sources such a...

Eu ions were doped into InGaN by organometallic vapor phase epitaxy. The influence of In composition on the optical properties of Eu-doped InGaN (InGaN:Eu) was investigated using photoluminescence (PL), and combined excitation-emission spectroscopy (CEES). The PL spectra of InGaN:Eu showed a new series of emission lines, which became dominant with increasing In content. CEES measurements confirmed that these emission lines originated from a new Eu luminescent center, with In as a second nearest neighbor. Thus, it is possible to distinguish the typical Eu-N related luminescent sites from the new Eu-N-In related luminescent site. Based upon our findings, we propose that Eu 3+ ions doped in InGaN could be used as a microscopic probe for the detection of In segregation.

We report on the growth and optical properties of Tm-doped AlGaN layers by organometallic vapor phase epitaxy (OMVPE). The morphological and optical properties of Tm-doped GaN (GaN:Tm) and Tm-doped AlGaN (AlGaN:Tm) were investigated by Nomarski differential interference contrast microscopy and photoluminescence (PL) characterization. Nomarski images reveal an increase of surface roughness upon doping Tm into both GaN and AlGaN layers. The PL characterization of GaN:Tm shows emission in the near-infrared range originating from intra-4f shell transitions of Tm3+ ions. In contrast, AlGaN:Tm also exhibits blue light emission from Tm3+ ions. In that case, the wider band gap of the AlGaN host allows energy transfer to higher states of the Tm3+ ions. With time-resolved PL measurements, we could distinguish three types of luminescent sites of Tm3+ in the AlGaN:Tm layer, having different decay times. Our results confirm that Tm ions can be doped into GaN and AlGaN by OMVPE, and show potential for the fabrication of novel high-color-purity blue light emitting diodes.

The detrimental influence of oxygen on the performance and reliability of V/III nitride based devices is well known. However, the influence of oxygen on the nature of the incorporation of other co-dopants, such as rare earth ions, has been largely overlooked in GaN. Here, we report the first comprehensive study of the critical role that oxygen has on Eu in GaN, as well as atomic scale observation of diffusion and local concentration of both atoms in the crystal lattice. We find that oxygen plays an integral role in the location, stability and local defect structure around the Eu ions that were doped into the GaN host. Although the availability of oxygen is essential for these properties, it renders the material incompatible with GaN-based devices. However, the utilization of the normally occurring oxygen in GaN is promoted through structural manipulation, reducing its concentration by 2 orders of magnitude, while maintaining both the material quality and the favorable optical properties of the Eu ions. These findings open the way for full integration of RE dopants for optoelectronic functionalities in the existing GaN platform.

We report on the epitaxial growth and the optical properties of Tm,Yb-codoped ZnO (ZnO:Tm,Yb) thin films by sputtering-assisted metalorganic chemical vapor deposition. The characteristic light emission due to the intra-4f shell transitions of Tm3+ and Yb3+ ions in the ZnO host is observed at 4 K by using photoluminescence (PL) characterization. The time-resolved PL measurements on the Tm3+ and Yb3+ emission reveals that the carrier decay time of each ion can vary by changing the concentration of both Tm3+ and Yb3+ ions, which depends on a mixing ratio of Tm2O3 and Yb2O3 in a sputtering target. The energy transfer from Tm3+ to Yb3+ ions occurs in the sample with the high mixing ratio, and the reversed energy transfer process occurs with the lower mixing ratio. These results indicate that the concentration, and thus the carrier dynamics of Tm3+ and Yb3+ ions in the ZnO:Tm,Yb host, can be controlled by altering the mixing ratio of the sputter target and the frequency power.