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Amorphous _ semiconductor thin films grown by low temperature vapor deposition were annealed at various temperatures from 400 to for 3 minutes in high vaccum chamber. The electrical and magnetotransport properties of as-grown and annealed samples have been studied. X-ray diffraction patterns analysis revealed that the samples still maintain amorphous state after annealling at for 3 minutes and they were crystallized when annealing temperature increase to . Temperature dependence of resistivity measurement implied that as-grown and annealed _ films have semiconductor characteristics, the increase of resistivity with annealling temperature was obseved. The -annealed sample exhibited negative magnetoresistance (MR) at low temperatures and the MR ratio was 8.5% at 10 K. The asymmetry was present in all MR curves. The anomalous Hall Effect was also observed at 250 K.

다결정 Ge 1 ? x Mn x 박막의 자기적 상들에 관한 연구가 이루어졌다. Molecular beam epitaxy(MBE) 장비를 이용해 400 ℃에서 Ge 1 ? x Mn x 박막을 성장시켰다. Ge 1 ? x Mn x 박막의 캐리어 유형은 P타입 이였고, 전기 비저항 값은 4.0 × 10 ?2 ~1.5 × 10 ?4 ohm-㎝이었다. 자기적인 특성과 미세구조의 분석에 기초하여 Ge 1 ? x Mn x /SiO₂/Si(100) 박막에 310 K 이내의 큐리에온도를 지닌 강자성의 Ge₃Mn? 상이 형성되었음을 알 수 있었다. 게다가, Ge₃Mn? 상이 형성된 Ge 1 ? x Mn x 박막은 20 K, 9 T의 자기장에서 약 9 %의 음의 자기저항을 보였다.

We report on the observation of p-type conductivity and ferromagnetism in diluted magnetic semiconductor (Zn 0.97 Mg 0.01 Mn 0.02 )O:P films grown on SiO₂/Si substrates by pulsed laser deposition. The p-type conduction with hole concentration over 1018 ㎝ ?3 is obtained by codoping of Mg and P followed by rapid thermal annealing in an O₂atmosphere. Structural and compositional analyses for the p-type (Zn 0.97 Mg 0.01 Mn 0.02 )O:P films annealed at 800 ℃ indicates that highly c-axis oriented homogeneous films were grown without any detectable formation of secondary phases. The films were found to be transparent in the visible range. The magnetic measurements clearly revealed an enhancement of room temperature ferromagnetism by p-type doping.

Magnetotransport is a prerequisite to realization of electronic operation of spintronic devices and it would be more useful if realized at room temperature. The effects of Be codoping on GaMnAs on magnetotransport were investigated. Mn flux was varied for growth of precipitated GaMnAs layers under a Be flux for degenerate doping via low-temperature molecular beam epitaxy. Magnetotransport as well as ferromagnetism at room temperature were realized in the precipitated GaAs:(Mn,Be) layers. Codoping of Be was shown to promote formation of MnGa clusters, and annealing process further stabilized the cluster phases. The room-temperature magnetic properties of the layers originate from the ferromagnetic clusters of MnGa and MnAs embedded in GaAs. The degenerately doped metallic GaAs matrix allowed the visualization of the magnetotransport through anomalous Hall effect.

We report hole-induced ferromagnetism in diluted magnetic semiconductor Zn_(0.99)Mn_(0.01)O films grown on SiO₂/Si substrates by reactive sputtering. The p-type conduction with hole concentration over 10^(18) ㎝-³ is achieved by P doping followed by rapid thermal annealing at 800 ℃ in a N₂ atmosphere. The p-type Zn_(0.99)Mn_(0.01)O:P is carefully examined by x-ray diffraction and transmission electron microscopy. The magnetic measurements for p-Zn_(0.99)Mn_(0.01)O:P clearly reveal ferromagnetic characteristics with a Curie temperature above room temperature, whereas those for n-Zn_(0.99)Mn_(0.01)O:P show paramagnetic behavior. The anomalous Hall effect at room temperature is observed for the p-type film. This result strongly supports hole-induced room temperature ferromagnetism in p-Zn_(0.99)Mn_(0.01)O:P.

We have investigated the effects of Al codoping on the structural, electrical transport, and magnetic properties of oxide diluted magnetic semiconductor thin films prepared by reactive sputtering. Nondoped thin films show semiconducting transport behavior and weak ferromagnetic characteristic. The Al doping increases the carrier concentration and results in an decrease of resistivity and metal-insulator transition behavior. With increasing carrier concentration, the magnetic properties drastically change, exhibiting a remarkable increase of the saturation magnetization. These results show carrier-enhanced ferromagnetic order in Cr-doped ZnO.

Be-codoped GaMnAs layers were systematically grown via molecular beam epitaxy with varying Mn- and Be-flux. Mn flux was controlled to cover from solid solution type GaMnAs to precipitated GaMnAs. Two Be flux were chosen to exhibit semiconducting and metallic resistivity in the grown layers. The structural, electrical, and magnetic properties of GaAs:(Mn, Be) were investigated. The lightly Be-codoped GaMnAs layers showed ferromagnetism at room temperature, but did not reveal magnetotransport due to small magneto-resistance and high resistance of the matrix. However, room temperature magnetotransport could be observed in the degenerate Be-codoped GaMnAs layers, and which was assisted by the high conductivity of the matrix. The Be-codoping has promoted segregation of new ferromagnetic phase of MnGa as well as MnAs.

A thin-film multijunction thermal converter was fabricated through the process using 6 inch silicon wafer semiconductor process and bulk micromachining. Evanohm R alloy and chromel-constantan were used as a heater and thermocouple materials, respectively. The temperature coefficient of resistance of Evanohm R heater was about 75.12 ppm/ and the voltage sensitivity of the thermal converter indicated about 5.75 mV/mW in air. The transfer differences, measured by FRDC-DC method in the frequency range from 20 Hz to 10 kHz, showed the value under about 1.36 ppm, 0.83 ppm for the film thickness of 500, 200 nm, respectively. And in case of a 200 nm-thick thermal converter, the AC-DC transfer differences seems to be stabilized below the value of 1 ppm in the frequency range from 1 kHz to 500 kHz.

We have measured the DC permeability of feebly magnetic materials by a special waveform of magnetizing field. As the signal is processed in AC mode, the drift and input impedance loading effects of an analog integrator can be avoided. The rapid magnetization change enhances the induced signal. The measured permeability of stainless steels shows no dependence on the frequency of special waveform.

【In this study, an HP-mod. type(KHR-45A), which is used as a heater tube material in the pyrolysis process, was evaluated for its carburizing properties. It was confirmed from the microstructural observation of the tubes that the volume fraction of carbide increased and that the coarsening of Cr-carbide generated as a degree of carburization increased. The depth of the hardened layer, which is similar to the thickness of the carburized region of each specimen, due to carburization is confirmed by measurement of the micro-Vickers hardness of the cross section tube, which thickness is similar to that of the carburized region of each specimen. Two types of chromium carbides were identified from the EBSD (electron back-scattered diffraction) image and the EDS (energy-dispersive spectroscopy) analysis: Cr-rich $M_{23}C_6$ in the outer region and Cr-rich $M_7C_3$ in the inner region of tubes. The EDS analysis revealed a correlation between the ferromagnetic behavior of the tubes and the chromium depletion in the matrix. The chromium depletion in the austenite matrix is the main cause of the magnetization of the carburized tube. The method used currently for the measurement of the carburization of the tubes is confirmed; carburizing evaluation is useful for magnetic flux density measurement. The volume fraction of the carbide increased as the measuring point moved into the carburized side; this was determined from the calculation of the volume fraction in the cross-section image of the tubes. These results are similar to the trends of carburization measurement when those trends were evaluated by measurement of the magnetic flux density.】

)Abstract Samples of GaMnAs, GaMnAs codoped with Be, and GaMnAs simultaneously codoped with Be andMg were grown via low-temperature molecular beam epitaxy (LT-MBE). Be codoping is shown to take the Gasites into the lattice efficiently and to increase the conductivity of GaMnAs. Additionally, it shifts thesemiconducting behavior of GaMnAs to metallic while the Mn concentration in the GaMnAs solid solution isreduced. However, with simultaneous codoping of GaMnAs with Be and Mg, the Mn concentration increasesdramatically several times over that in a GaMnAs sample alone. Mg and Be are shown to eject Mn from theGa sites to form MnAs and MnGa precipitates.Key wordsGaMnAs, Be codoping, Mg codoping, MBE, Magnetic semiconductor PACS: 75.50Pp, 75.70Ak, 81.15.Hi

A study of GaN and p-GaN growths with doping of Mg, Be and Mn was undertaken using a single GaN precursor source via molecular beam epitaxy. Measurements of the changes in surface morphology and film resistivity with growth temperature and doping were carried out. Mg or Be acceptors were shown to improve the surface roughness of the films through forming of acceptornitrogen-hydrogen complexes. Thermal annealing for acceptor activation was performed in vacuum, Ar, and N2 by using rapid thermal annealing. The environment of the activation annealing process was shown to affect the activation kinetics and the activation behaviors. A nitrogen ambient delayed the activation of the acceptors, but higher temperature promoted the activation process. The behaviors of the acceptor-nitrogen-hydrogen complexes were systematically examined through experimental set-ups and comparison with the behaviors in GaN:Mn film.

We report the synthesis of cubic spinel thin films and the tunability of the conduction type by control of the oxygen partial pressure ratio. Zinc cobalt oxide films were grown on(200 nm)/Si substrates by reactive magnetron sputtering method using Zn and Co metal targets in a mixed Ar/atmosphere. We found from X-ray diffraction measurements that the crystal structure of the zinc cobalt oxide films grown under an oxygen-rich condition (the /Ar partial pressure ratio of 9/1) changes from wurtzite-type O to spinel-type with the increase of the Co/Zn sputtering ratio, . We noted that the above structural change accompanied by the variation of the majority electrical conduction type from n-type (electrons) to p-type (holes). For a fixed / of 2.0 yielding homogeneous spinel-type Ofilms, the type of the majority carriers also varied, depending on the/Ar partial pressure ratio: p-type for an -rich and n-type for an Ar-rich atmosphere. The maximum electron and hole concentrations for the Zn films were found to be 1.3710 c and 2.4110 c , respectively, with a mobility of about 0.2 /Vs and a high conductivity of about 1.8 Ω/ /.

A low temperature anode-supported tubular solid oxide fuel cell was developed. The anode-supported tube was fabricated using extrusion process. Then the electrolyte layer and the cathode layer were coated onto the anode tube by slurry dipping process, subsequently. The anode tube and electrolyte were co-fired at , and the cathode was sintered at . The thickness and gas permeability of the electrolyte depended on the number of coating and the slurry concentration. Anode-supported tube was satisfied with SOFC requirements, related to electrical conductivity, pore structure, and gas diffusion limitations. At operating temperature of , open circuit voltage of the cell with gastight and dense electrolyte layer was 1.1 V and the cell showed a good performance of 450 mW/.