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To expand and utilize the potential of intermetallic compounds, the importance of quaternary half-Heusler (HH) compounds has attracted attention in the field of thermoelectrics and other inorganic materials research. In this study, triple half-Heusler (THH) Mg2VNi3Sb3 was successfully synthesized by following an unconventional valence balance strategy. X-ray diffraction (XRD) and scanning electron microscope energy dispersive spectroscopy (SEM-EDS) showed the pure and homogeneous nature of samples. Even though both ternary components of Mg2VNi3Sb3, i.e., MgNiSb and VNiSb are expected to be unstable with the metallic transport properties, Mg2VNi3Sb3 possesses semiconducting behavior with Seebeck coefficient peak larger than 115 μV K−1 around 500 K with the small bandgap of 0.12 eV. The lattice thermal conductivity (κL = 2.0 W m−1 K−1) of Mg2VNi3Sb3 is much smaller than κL of conventional half-Heusler and double half-Heusler materials. Since high thermal conductivity has been always a problem for HH materials, the synthesis of THH with low lattice thermal conductivity can be a new direction for developing high-performance HH compounds. Through the synthesis of THH Mg2VNi3Sb3, a new strategy to explore the huge compositional space for further improvement of thermoelectric performance and extended tunability of intermetallic compounds was demonstrated. [ABSTRACT FROM AUTHOR]

This paper describes a 77-GHz three-stage driver amplifier integrated with a very compact 4-dB digital attenuator. The attenuator can provide successful suppression in the gain variation of the amplifier according to ambient temperature in practical use. In addition, the amplifier matching fashion using short stubs and series transmission lines helps suppress unwanted transducer gain and return gain in the out-of band of lower than 77 GHz. The amplifier fabricated in pseudomorphic high electron-mobility technology can deliver a gain of 17.9 dB with an input return loss of 21.0 dB and an output return loss of 22.7 dB in the 77-GHz band, while keeping lower than -16.5 dB of gain in the out-of band. Over the temperature range from -20[degrees]C to 100[degrees]C, the measured results show that a gain variation of less than 2.0 dB is achieved by using the attenuator, while the gain variation without the attenuator is as large as 6.0 dB. The die size is as small as 2.3 x 1.4 [mm.sup.2] due to the very compact attenuator of a 0.2 x 0.6 [mm.sup.2] occupied area. Index Terms--Amplifiers, attenuators, millimeter-wave amplifiers, minimization methods, radar applications, temperature.

Carbon nanotube probe and a highly sensitive dynamic measurement scheme has enabled us to use atomic force microscopy to measure oscillatory forces in water on approaching a surface that is laterally characterized on a nanometer scale. The study suggested that the action of a dehydrating agent or water-structure breaker might be chiefly on the nearby surface rather than on water.

Scanning tunneling microscopy and self-assembled techniques were used in measuring the electrical conductivity of organic molecules. The synthesized molecule (1,1':4,' 1'-terphenyl)-4 -methanethiol (TP) with three phenyl rings were used in the study. Results indicated that the TP molecules have protruding domains with heights that increase as the lateral size of the domain grows from 1 to 10 nm. This suggested that there was an increase in the vertical conductance due to the lateral, intermolecular interaction.

This paper reports on the excellent performance of V-band monolithic high electron-mobility transistor (HEMT) oscillators, and discusses oscillation characteristics on drain bias. With regard to output characteristics, double-hetero (DH) HEMT (especially with a high-density Si-planar doped layer) are superior to single-hetero (SH) HEMT's. A monolithic microwave integrated circuit (MMIC) oscillator has been developed with a planar doped DH HEMT and has achieved the peak output power of 11.1 dBm at a 55.9-GHz oscillation frequency. Phase noise of -85 dBc/Hz at 100-kHz offset and -103 dBc/Hz at 1-MHz offset have been achieved at a drain voltage of 5.5 V and a gate voltage of 0 V. These characteristics have been achieved without any buffer amplifiers or dielectric resonators. This study has revealed that the phase noise decreases as drain voltage increases. This phenomenon is caused by lower pushing figure and lower noise level at a low-frequency range obtained under a high drain voltage. It is because the depletion layer in the channel is extended to the drain electrode with increase of drain voltage, resulting in the small fluctuation of the gate-to-source capacitance. We also investigate low-frequency noise spectra of AlGaAs/InGaAs/GaAs DH HEMT's with different bias conditions. The low-frequency noise decreases for more than 3 V of the drain voltage. A unique mechanism is proposed to explain this phase noise reduction at high drain voltage. Index Terms - Drain bias, HEMT, MMIC's, phase noise.

A novel technique of low-energy N2 neutral beam (NB) (<10 eV) irradiation was investigated as a means of controlling the surface nitridation of self-assembled monolayers (SAMs). This low-energy process without UV photons was able to nitride the surfaces of terphenyl SAMs. Furthermore, by varying the on/off period for irradiation, a pulse-time modulated NB process could be used to control the atomic ratio of nitrogen in terphenyl molecules. Time-of-flight secondary ion mass spectra revealed that one H in the terphenyl group was substituted by a NH2 group because of irradiation by the N2 beam. The data suggested that the low-energy NB technique caused less damage to modified surfaces than the conventional plasma process did. Therefore, we believe that it is a potential damage-free process for modifying the surfaces of soft organic materials and films. [ABSTRACT FROM AUTHOR]