We observed Ga focused-ion-beam (FIB) irradiation effect onto diamond-like carbon (DLC) free-space nanowiring (FSW) fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD). A bended FIB-CVD FSW completely strained after Ga-FIB irradiation with raster scanning. This is probably caused by generation of compression stresses onto the surface of FSW, because the surface state of the nanowire changed with Ga-FIB irradiation. Transmission electron microscope (TEM) study indicates that Ga of FSW core part disappeared after Ga-FIB irradiation and a near-edge X-ray absorption fine structure (NEXAFS) analysis revealed C-Ga bond formation onto the surface. This is attributed to a movement of Ga from the core region to the surface, and/or an adsorption of Ga onto the surface by Ga-FIB scanned irradiation. The transformation of FSW is not only fascinating as physical phenomenon, but also effective for fabricating various 3-dimensional nanodevices equipped with nanowires utilized as electric wiring.

We propose a novel technique to grow the single-walled carbon nanotubes (SWNTs) with specific chirality at the desired position using free electron laser (FEL) irradiation during growth and surface treatment. As a result, only the semiconducting SWNTs grew at the area between triangle electrodes, where the ozone treatment was done to be hydrophilic when an alcohol chemical vapor deposition (ACCVD) process was carried out with the 800 nm FEL irradiation. Although the number of possible chiral index is 22 in the SWNTs grown without the FEL irradiation, the number is much reduced to be 8 by the FEL.

In this paper, we report the fabrication and device characteristics of InP/InGaAs double heterojunction bipolar transistors (DHBTs) with buried SiO2 wires. The SiO2 wires were buried in the collector and subcollector layers by metalorganic chemical vapor deposition toward reduction of the base-collector capacitance under the base electrode. A current gain of 22 was obtained at an emitter current density of 1.25 MA/cm2 for a DHBT with an emitter width of 400 nm. The DC characteristics of DHBTs with buried SiO2 wires were the same as those of DHBTs without buried SiO2 wires on the same substrate. A current gain cutoff frequency (fT) of 213 GHz and a maximum oscillation frequency (fmax) of 100 GHz were obtained at an emitter current density of 725 kA/cm2.

Current collapse phenomenon is a well known obstacle in the AlGaN/GaN HEMTs. In order to improve the surface stability of HEMTs, we have investigated the SiN passivation film deposited by T-CVD, and we found that it improves both gate leakage current and current collapse phenomenon [1]. Moreover, we compared the T-CVD and PE-CVD passivation films, on high electric field DC and RF characteristics. We found that T-CVD SiN passivation film improves BVds-off by 30% because of the reduction of gate leakage current. It also improved ηd in the output power characteristics by load-pull measurement, which indicates the decrease of the current collapse phenomenon. Also we fabricated a multi-fingered 50 W-class AlGaN/GaN HEMT with T-CVD SiN passivation film and achieved 61.2% of high drain efficiency at frequency of 2.14 GHz, which was 3.6 points higher than that with PE-CVD SiN passivation film.

In AlGaN/GaN high electron mobility transistors (HEMTs), drain current reduction by current collapse phenomenon is a big obstacle for a high efficient operation of power amplifier application. In this study, we investigated the effects of SiN passivation film quality on the electrical characteristics of AlGaN/GaN HEMTs. First, we conducted some experiments to investigate the relationship between electrical characteristics of AlGaN/GaN HEMTs and various conditions of SiN passivation film by plasma enhanced chemical vapor deposition (PE-CVD). We found that both gate current leakage and current collapse were improved simultaneously by SiN passivation film deposited by optimized condition of NH3 and SiH4 gas flow. It is found that the critical parameter in the optimization is a IN-H/ ISi-H ratio measured by Fourier transforms infrared spectroscopy (FT-IR) spectra. Next, a thermal CVD SiN was applied to the passivation film to be investigated from the same point of view, because a thermal CVD SiN is well known to have good quality with low hydrogen content and high IN-H/ISi-H ratio. We confirmed that the thermal CVD SiN passivation could improve much further both of the gate leakage current and the current collapse in AlGaN/GaN-HEMTs. Furthermore, we tried to apply the thermal CVD SiN to the gate insulator in MIS (Metal Insulator Semiconductor) structure of AlGaN/GaN HEMTs. The thermal CVD SiN passivation was more suitable for the gate insulator than PE-CVD SiN passivation in a view of reducing current collapse phenomena. It could be believed that the thermal CVD SiN film is superior to the PE-CVD SiN film to achieve good passivation and gate insulator film for AlGaN/GaN HEMTs due to the low hydrogen content and the high IN-H/ISi-H ratio.

This paper presents the selective epitaxial growth (SEG) properties of reduced pressure chemical vapor deposition (RPCVD) at low temperatures (LT) of 675-725 with high aspect ratio mask of dielectric films. The SEG process could be explained in conjunction with the loading effect, the mask pattern shape/size, and the process parameters of RPCVD. The growth rates showed a large non-uniformity up to 40% depending upon the pattern size of the dielectric mask films, but as the SEG film becomes thicker, the growth rate difference converged on 15% between the narrow 2-µm and the wide 100-µm patterns. The evolution of SEG was controlled dominantly by the surface migration control at the initial stage, and converted to the surface topology control. The design of pattern size and distribution with dummy patterns must be useful to accomplish the reliable and uniform LT-SEG.

The historical review of Taiwan's researching activities on the features of PECVD grown SiOx are also included to realize the performance of Si nanocrystal based MOSLED made by such a Si-rich SiOx film with embedded Si nanocrystals on conventional Si substrate. A surface nano-roughened Si substrate with interfacial Si nano-pyramids at SiOx/Si interface are also reviewed, which provide the capabilities of enhancing the surface roughness induced total-internal-reflection relaxation and the Fowler-Nordheim tunneling based carrier injection. These structures enable the light emission and extraction from a metal-SiOx-Si MOSLED.

Effect of the post-growth annealing on the morphology of a Ge mesa selectively grown on Si was studied from the viewpoint of near-infrared photodiode applications. By ultrahigh-vacuum chemical vapor deposition, Ge mesas were selectively grown at 600 on Si (001) substrates partially covered with SiO2 masks. The as-grown Ge mesas showed trapezoidal cross-sections having a top (001) surface and {311} sidewall facets, as similar to previous reports. However, after the subsequent post-growth annealing at ~800 in the ultrahigh-vacuum chamber, the mesas were deformed into rounded shapes having a depression at the center and mounds near the edges. Such a deformation cannot be observed for the samples annealed once after cooled and exposed to the air. The residual hydrogen atoms on the Ge surface from the germane (GeH4) decomposition is regarded as a trigger to the observed morphological instability, while the final mesa shape is determined in order to minimize a sum of the surface and/or strain energies.

Three-dimensional nanostructure fabrication has been demonstrated by 30 keV Ga+ focused-ion-beam chemical-vapor-deposition (FIB-CVD) using a phenanthrene (C14H10) source as a precursor. Microstructure plastic arts is advocated as a new field using micro-beam technology, presenting one example of micro-wine-glass with 2.75 µm external diameter and 12 µm height. The deposition film is a diamondlike amorphous carbon. A large Young's modulus that exceeds 600 GPa seems to present great possibilities for various applications. Producing of three-dimensional nanostructure is discussed. Micro-coil, nanoelectrostatic actuator, and nano-space-wiring with 0.1 µm dimension are demonstrated as parts of nanomechanical system. Furthermore, nanoinjector and nanomanipulator are also fabricated as a novel nano-tool for manipulation and analysis of subcellular organelles.

Carbon nanotubes (CNTs) offer unique properties such as highest current density exceeding 109 A/cm2, ultra-high thermal conductivity as high as that of diamond, ballistic transport along the tube and extremely high mechanical strength with high aspect ratio of more than 1000. Because of these remarkable properties, they have been expected for use as future wiring materials to solve several problems, for examples, stress and electro-migration, heat removal and fabrication of a small-sized via in future LSIs. In this paper, we demonstrate present status of CNT material technologies and the potential of metallic CNT vias. In particular, we report our original catalytic nano-particle technique for controlling the diameter and density of CNTs. We have succeeded in forming a 40-nm via with the CNT density of 91011/cm2, which is the highest density ever reported. The low temperature CVD growth and the electrical properties of CNT vias are also discussed.

This paper describes a dynamic and adaptive scheme for three-dimensional mesh morphing. Using several control maps, the connectivity of intermediate meshes is dynamically changing and the mesh vertices are adaptively modified. The 2D control maps in parametric space that include curvature map, area deformation map and distance map, are used to schedule the inserting and deleting vertices in each frame. Then, the positions of vertices are adaptively moved to better positions using weighted centroidal voronoi diagram (WCVD) and a Delaunay triangulation is finally used to determine the connectivity of mesh. In contrast to most previous work, the intermediate mesh connectivity gradually changes and is much less complicated. We demonstrate several examples of aesthetically pleasing morphs created by the proposed method.

The role of hydrogen in the Si film during excimer laser annealing (ELA) has been successfully studied by using a novel sample structure, which is stacked by a-Si film and SiN film. Hydrogen contents in the Si films during ELA are changed by preparing samples with hydrogen content of 2.3-8.2 at.% in the SiN films with a use of catalytic (Cat)-CVD method. For the low concentration of hydrogens in the Si film, the grain size increases by decreasing hydrogen concentration in the Si film, and the internal stress of the film decreases as increasing the shot number. For the high concentration of hydrogens in the Si film, hydrogen burst was observed at 500 mJ/cm2 and the dependence of the internal stress on the shot number becomes weak even at 318 mJ/cm2. These phenomena can be understood basically using the secondary grain growth mechanism, which we have proposed.

AFM/STM observations were performed on sub nm thick C-Au-S film by co-operation process of plasma CVD and sputtering with using CH4, SF6 and Ar mixture gas and Au plate discharge electrode. From the refractive index values, the conductive granular molecules with a size of 0.4-0.6 nm were expected to exist in the film. For the film at thickness similar to the molecular size, Ra (arithmetic mean departures of roughness profile from the mean line) values were measured to be 0.712/6.10 nm by AFM/STM measurement, respectively. The one order large STM Ra value compared to the AFM Ra value suggests that the film contains conductive granular molecules.

Seeding substrates with diamond nanocrystals has been considered to be a promising nondestructive pretreatment method for growth of diamond films. However, its application is strongly impeded by the segregation of diamond nanocrystals on substrates. In the present study, we suggest a very simple but effective seeding way ("sandwich" (SW) seeding way) to prevent nanocrystals from segregation. By the SW seeding way, the diamond nanocrystals can be nearly uniformly dispersed on Si substrates with the areal density of the order of 108cm-2. On the nano-seeded Si substrates the continuous and homogeneous diamond films can be successfully fabricated using a microwave plasma enhanced chemical-vapor-deposition (MPECVD) equipment. The cross-sectional transmission electron microscopy (TEM) images reveal that compare with the diamond films grown on the Si substrates pretreated by the conventional scratching method, the films deposited on the nano-seeded Si substrates present a much flatter interfacial structure, suggesting that the SW seeding way can effectively reduce the interface coarseness.

Electron emissions from single-crystalline diamond surfaces by internally exciting electrons from the valence to conduction bands have been investigated. Monte Carlo simulations have been employed to estimate the impact ionization rates of carriers in diamond under high electric fields up to 1107V/cm. The calculations demonstrate substantial impact ionization rates which rapidly increase with increasing electric fields above 8105V/cm. Highly efficient electron emissions with high emission current efficiencies of approximate unity have been attained from a MIS-type diamond layered structure that are composed of heavily ion-implanted buried layer (M), undoped diamond (I) and hydrogenated p-type diamond (S) with an emission surface of a negative electron affinity. The highly efficient emission mechanism is discussed in relation to the field excitation of electrons from the valence band to the conduction band in the undoped diamond layer and the carrier transport to the diamond surface.

In-situ position-controlled lateral deposition of nanometer-size Zn and Al dots on a sapphire substrate was accomplished by dissociating diethylzinc and trimethylaluminum using an optical near field on a sharpened optical fiber probe tip. The minimum diameters of the Zn and Al dots deposited were 37 and 25 nm, respectively, comparable with the apex diameter of the fiber probe. By changing the reactant molecules during deposition, nanometric Zn and Al dots were successively deposited on the same sapphire substrate with high precision. The distance between these dots was as short as 100 nm.

Carbon-gold (C-Au) film was formed by co-operation process of plasma CVD and sputtering with using methane and Ar mixture gas and gold plate discharge electrode. Refractive index of 3.1 for the film was obtained at Au atom content of 5.5 atomic%. The optical transmittance was improved significantly in the visible light wavelength range compared to the C-S-Au film reported previously. Au atom distribution in the C-Au film and the electronic polarizabilities were discussed in the relation to the refractive index.

Optical properties and growth of self-assembled quantum dots (SAQDs) for optoelectronic device applications are discussed. After briefly reviewing the history of research on QD lasers, we discuss growth of InAs SAQDs including the light emission at the wavelength of 1.52-µm with a narrow linewidth (22 meV) and the area-controlled growth which demonstrates formation of SAQDs in selected local areas on a growth plane using a SiO2 mask with MOCVD growth. Then properties of the InGaAs AQDs are investigated by the near-field photoluminescence excitation spectroscopy which reveals gradually increasing continuum absorption connected with the two-dimensional-like (2D-like) wetting layer, resulting in faster relaxation of electrons due to a crossover between 0D and 2D character in the density of states. In the coherent excitation spectroscopy, the decoherence time is determined to be about 15 ps, which is well explained by the phonon induced relaxation mechanism in the SAQDs. Finally, nitride-based SAQDs and perspective of QD optical devices are also discussed.

The long-term reliability of heterojunction bipolar transistor (HBT) continues to be a subject of great interest due to the increased acceptance of this device in a wide range of applications. The most demanding requirements for long-term reliability include high performance microwave instrumentation, X-band radar, and lightwave communication (OC-192). A significant leap in the long-term reliability performance was observed in HBT as the AlGaAs emitter material was replaced with lattice matched InGaP. A dramatic improvement in the long-term reliability was also observed in AlGaAs emitter HBT's as the turn on voltage (Vbe) was lowered. The typical failure mechanism in HBT devices at high current density and high temperature long-term reliability testing was a dramatic increase in the base current at low current densities. One of the limiting factors in obtaining MTTF in InGaP HBT was the long time required to promote failures in the HBT device. Furthermore, a large sample size is necessary to extract a reliable MTTF. Significant increases in the current density as high as 180 kA/cm2 during reliability testing was used to promote failures in order to obtain an MTTF within a reasonable amount of time. The MTTF at a junction temperature of 334C and at a current density of 180 kA/cm2 was 1159 hours. The extrapolated MTTF at a junction temperature of 150C exceeded 106 hours for all of the tested devices. An attempt to predict the MTTF of AlGaAs and InGaP HBT using a simple model based upon the fitting of the initial Gummel plots of large area devices was made. The model was based upon the estimation of the trap defect density at the base/emitter junction, the hole injection component of the base current, and the turn-on Vbe. Degradation of the HBT was assumed to occur at the base/emitter junction and this corresponded to an increase in the trap density at this heterojunction. A factor of 5 improvement in the MTTF of the reliability of AlGaAs HBT with a lower turn on voltage was estimated based upon the above model, which confirmed the experimental results. These results suggested that the emitter material is primarily responsible in determining the long-term reliability characteristics of HBT. The combination of a high effective hole barrier and a low turn-on Vbe are highly desirable for long-term reliability characteristics.

The chemical stability of the constituent elements in polycrystalline Sr-Bi-Ta-O thin film with various Bi content prepared by metalorganic chemical vapor deposition (MOCVD) was investigated by X-ray photoelectron spectroscopy (XPS). Moreover, that of the epitaxial films was also investigated to estimate the effect of the grain boundary in polycrystalline films. Therefore, only the Bi element drastically changed from Bi3+ state to Bi0 one by the Ar sputtering. This change increased with increasing the Ta/Bi mole ratio in the film from 0.64 to 1.67. This result was observed not only for the polycrystalline films but also for the epitaxial films, suggesting that this is the grain character not grain boundary one. The stability and the leakage character of the film strongly depend on the constituent of the film.