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Temperature-dependent emission current–voltage measurements were carried out for nitrogen (N)-doped nanocrystalline diamond (NCD) films grown on n-type Si substrates by microwave plasma-assisted chemical vapor deposition (MP-CVD). Low threshold temperature (~ 260 °C) and low threshold electric field (~ 5 × 10− 5 V/µm) were observed. Both the temperature dependence and the electric field dependence have shown that the obtained emission current was based on electron thermionic emission from N-doped NCD films. We have also studied the relation between nitrogen concentration and the saturation emission current. The saturation current obtained was as high as 1.4 mA at 5.6 × 10− 3 V/µm at 670 °C when the nitrogen concentration was 2.4 × 1020 cm− 3. Low value of effective work function (1.99 eV) and relatively high value of Richardson constant (~ 70) were estimated by well fitting to Richardson–Dushman equation. The results of smaller φ and larger A′ suggest that N-doped NCD has great possibility of being a highly efficient thermionic emitter material.

R&D activities on diamond chemical vapor deposition (CVD) and field emission in the Frontier Carbon Technology Project are presented. The topics are (1) morphology control of diamond films grown by a 60-kW, 915-MHz microwave plasma CVD reactor, (2) growth technology of large single crystal diamond with a low density of defects, (3) heteroepitaxial growth technology of diamond films on Pt, (4) fabrication of sharp emitter tips on single crystal diamond, (5) field emission study from diamond particles, and (6) intense field emission from ion implanted homoepitaxial diamond layer. Research results of field emission obtained by Kyoto University and North Carolina State University are also described.

The present work investigated the possibility of the formation of graphene interconnects and studied the behavior of graphene growth in wiring structure. Graphene nucleated on the facet of catalytic metal, and multi layer graphene grew along the terrace surface of catalytic metal. Selective graphene growth served the stacked interconnects structure of graphene / Ni catalytic metal.

We have succeeded in fabricating ultrafine carbon nanotube (CNT) via interconnects with SiOC interlayer dielectrics. High-quality multiwalled CNTs are grown in via holes with a diameter of 70 nm using pulse-exited remote plasma-enhanced chemical vapor deposition at 450 °C. The resistance of a 70-nm-diameter CNT via is 52 Ω, which is the lowest ever reported for CNT via interconnects. The CNT via interconnect has the capability to sustain current density as high as 1×108 A/cm2.

Multiwalled carbon nanotubes (CNTs) have been grown by remote plasma-enhanced chemical vapor deposition at temperatures as low as 400 °C. In via formation, the selective growth of CNT bundles in via holes at 430 °C and chemical mechanical polishing for planarization have been performed. The electrical evaluation of CNT single vias with various diameters reveals that the via resistance is inversely proportional to the via area. This result indicates that the CNTs are grown with uniform quality and density in the via holes with various diameters and stable contact formations are obtained. Moreover, the resistances of single vias are approximately equivalent to the via resistances estimated from the resistances of via chains, demonstrating the via-to-via uniformity of the CNT vias obtained by the remote plasma-enhanced chemical vapor deposition.

An Hg-sensitized photochemical vapor deposition method has been developed which has enabled the hydrogenated amorphous silicon photoconversion layer to be overlaid on a CCD (charge coupled device) imaging device, without requiring the pixel separation structure. The a-Si:H photoconversion layer prepared by the Hg-sensitized photo-CVD method has several advantages, including high resistivity, coverage conformable to an uneven substrate, few line defects grown between adjacent image pixels, low SiH/sub 2/ bond content without missing the high resistivity, and few dust fragments generated. This CVD method has been used to realize imaging devices with high sensitivity and high resolution for high definition TV. >

Multilayer graphene (MLG) is expected to be a low-resistance and high-reliability interconnect material replacing copper (Cu) in nanoscale interconnects. Chemical vapor deposition (CVD) on catalytic metals is expected as a practical method for MLG deposition. To obtain high-quality MLG films without catalyst agglomeration by CVD, heat-resistant Co–W catalytic metals were investigated. The agglomeration of the Co–W catalytic metals was suppressed by increasing the W composition; however, MLG deposition was suppressed at the same time. The effects of W addition on the MLG growth were discussed from the viewpoints of the crystallographic change of the Co–W catalysts and chemical reactions. It was found that the Co grain size was reduced and the fcc Co formation was suppressed by W addition. In addition, graphite formation was supposed to be suppressed by W addition owing to the formation of phases other than fcc Co according to the Co–W–C phase diagram. With the optimum W concentration, MLG crystallinity was improved by high-temperature CVD using the heat-resistant Co–W catalytic metals (0.7 at. %) without agglomeration, compared with that in the case of using pure-Co catalysts.

We report a synthesis of a closely packed multi-walled carbon nanotube (MWCNT) forest by a multi-step growth method, including a new approach to immobilize catalytic nanoparticles, using plasma-based chemical vapor deposition. The CNT packing density reaches one-half of the theoretical value, where the space of 30–40% is filled with MWCNTs. This value is approximately one order of magnitude larger than that of as-grown CNT forest synthesized using conventional methods. The method is applicable even at a spatially restricted region, for example, in trench or via hole, and is available at the growth temperature as low as 450 °C.

Carbon nanotubes (CNTs) have been grown by surface-wave plasma-enhanced chemical vapor deposition (CVD) using size-classified Co nanoparticles at low temperatures. A mesh grid is used in the remote plasma-enhanced CVD system for the suppression of ion bombardment damage from plasma. The control of the electric field distribution using a mesh grid with a narrower opening is effective for the CNT growth. Multiwalled CNTs are obtained at a low temperature of 400 °C under low ion-density conditions. No significant difference in the microscopic structure of the CNTs grown at temperatures between 400 and 500 °C is observed.

Carbon nanotube (CNT) growth at temperatures below 400 °C by pulse-excited remote plasma chemical vapor deposition was demonstrated. Reduction of plasma power was carried out in order to decrease the amount of all particles, ions, electrons, and radicals. In addition, a biased plate-type screening electrode was introduced to removal of charged particles, ions, and electrons. The negative bias below 50 V was most effective for growth rate. High-quality CNT growth with the growth rate of 98 nm/min was successfully obtained at 400 °C. The results suggest that both removal of charged particles and control of the amount of radicals are important for high-quality CNT growth at temperatures below 400 °C.

The ratio of Si-H2 bonds to hydrogen content in hydrogenated amorphous silicon films, prepared by mercury-sensitized photochemical vapor deposition, depends on the deposition conditions, in particular on the distance between the substrate and the light-transparent window.The ratio is reduced from 20 % to 8 % by decreasing the distance from 30 mm to 8 mm. On the other hand, the hydrogen content remains constant at 15 at.%. Decreasing the distance has been found to be almost equivalent to increasing the light intensity, especially 254 nm-light intensity.

An Hg-sensitized photochemical vapor deposition method has been developed which has enabled a hydrogenated amorphous silicon photoconversion layer to be overlaid on a charge coupled device (CCD) imager, without a pixel separation structure. This chemical vapor deposition (CVD) method has been used to realize imaging devices with high sensitivity and high resolution for high-definition TV.

The relations between the photocurrent transient after the end of steady-state illumination for hydrogenated amorphous silicon photodiodes and the related film properties for undoped hydrogenated amorphous silicon prepared by mercury-sensitized photochemical vapor deposition are investigated. The photocurrent transient characteristic indicates significant correlations with the film properties, such as electron drift mobility ( mu /sub d/), silicon dangling bond density (N/sub s/), a minimum in the density of states near the Fermi level (N/sub min/), and space-charge density (N/sub i/). The photocurrent transient decay decreases with increasing mu /sub d/ and with decreasing N/sub s/, M/sub min/, and N/sub i/. This result was confirmed by a model analysis. >

Hydrogenated amorphous silicon (a-Si:H) films were prepared by mercury photosensitized decomposition of silane using a low-pressure mercury lamp. The deposition rate showed an activation type for substrate temperature (the activation energy: 0.13 eV), because the deposition rate would be determined by the rate of hydrogen elimination from the hydrogen saturated surface. Moreover, the relationship was found between the Si-H2 bond density in a- Si:H films and the gas phase reactions.

The correlation between Si-H2 bond density and electron drift mobility in a-Si:H films has been investigated by using the dependence of the film properties on the silane gas pressure in mercury-sensitized photochemical vapor deposition. It was found that the electron drift mobility decreased with increasing the Si-H2 bond density, when the hydrogen contents were about the same amount.