Electrical conductivity in quantum dot solids is crucial for application in devices. In addition to the well-known ligand exchange strategies for enhanced conductivity, the current study examined the optical, structural, and electrical properties of ethanedithiol-treated layer-by-layer (LbL) assembled quantum dot solid (QDS) films following low-temperature annealing (room temperature to 170 °C). As the annealing temperature increased, it was induced that the average separation between nanocrystal quantum dots is decreased, and accordingly, the overall conductivity of the QDS increased exponentially. From a simplified percolation model, the activation energy of temperature-dependent quantum dot attachment was estimated to be around 0.26−0.27 eV both for PbS and PbSe quantum dot solids. Furthermore, the results of this study indicated that device applications requiring higher conductivity, attainable through high-temperature annealing, may also require repassivation after annealing.

We have previously proposed a piezoelectric sensor configuration determined using an optical-access method and reported the simulation results. Two issues have to be resolved for fabricating such a sensor; one is to develop a suitable optical-to-electrical conversion technique, and the other is to develop an optical measurement method for piezoelectric resonance. We examined the use of a Schottky-barrier photodiode (SBPD) for photoelectric conversion to excite piezoelectric vibration in the very high frequency (VHF) region. We found that the photoelectric output of SBPD corresponds to the intensity of the modulated light. The excitation power of piezoelectric vibration is between 10 µW (at 70 MHz) and 32 µW (at 50 MHz). However, optical detection of piezoelectric vibration is difficult. In this paper, we propose a waveguide-type light circuit using a pair of Y-branch elements based on the Mach-Zender interferometer. An analysis on the sensitivity of the circuit for vibration detection was carried out and relatively higher sensitivity was predicted. Furthermore, the photoelastic constant p 66 for AT-cut quartz was measured.

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Although a cubic phase of Mn3Ga with an antiferromagnetic order has been theoretically predicted, it has not been experimentally verified in a bulk or film form. Here, we report the structural, magnetic, and electrical properties of antiferromagnetic cubic Mn3Ga (C-Mn3Ga) thin films, in comparison with ferrimagnetic tetragonal Mn3Ga (T-Mn3Ga). The structural analyses reveal that C-Mn3Ga is heteroepitaxially grown on MgO substrate with the Cu3Au-type cubic structure, which transforms to T-Mn3Ga as the RF sputtering power increases. The magnetic and magnetotransport data show the antiferromagnetic transition at TN = 400 K for C-Mn3Ga and the ferrimagnetic transition at TC = 820 K for T-Mn3Ga. Furthermore, we find that the antiferromagnetic C-Mn3Ga exhibits a higher electrical resistivity than the ferrimagnetic T-Mn3Ga, which can be understood by spin-dependent scattering mechanism.