Nobuei Ito

Effect of rare gas dilution on CH3 radical density in RF-discharge CH4 plasma

The behavior of the CH3 radical density in a parallel-plate RF CH4 plasma diluted with rare gases (He, Ne, Ar, Kr, and Xe) was investigated systematically using infrared diode laser absorption spectroscopy. The CH3 radical density increased in CH4/Xe and CH4/Kr plasmas with increasing rare gas dilution. The Xe* atom densities in the lowest metastable state 3P2 and the resonant state 3P1 were measured in CH4/Xe plasma through absorption spectroscopy using a Xe hollow cathode lamp in order to clarify the role of Xe* (3P2 and 3P1) atoms. It was shown that the increase in the CH3 radical density in CH4/Xe plasma was mainly caused by the collision of Xe* atoms with CH4 molecules.

Correlation between CH3 Radical Density and Carbon Thin-Film Formation in RF Discharge CH4 Plasma

The CH3 radical density and the deposition rate of carbon thin film were measured under the same conditions in RF-discharge CH4 and CH4/rare gas plasmas. The behavior of the CH3 radical density showed a similar tendency as the deposition rate of carbon thin film as a function of power and CH4 pressure in CH4 plasma. In CH4/Xe plasma, where a selective formation mechanism increases the CH3 radical density with increasing Xe dilution whereas other CHx radicals are expected to decrease, the carbon deposition rate increased with increasing Xe dilution. These results strongly suggest that the CH3 radical is the dominant precursor in the film formation. The increase of film formation rate in CH4/Xe plasma was slower than that of the CH3 radical density with increasing Xe dilution. This could be attributed to the sputtering of the film by heavy Xe ions. In CH4/He plasma, where the effect of sputtering is expected to be small, the film deposition rate and the CH3 density varied in a much more similar manner.

H 2 Partial Pressure Dependences of CH 3 Radical Density and Effects of H 2 Dilution on Carbon Thin-Film Formation in RF Discharge CH 4 Plasma

Both the CH3 radical density and carbon thin-film formation were investigated in an RF-discharge CH4/H2 plasma. In this plasma, although CH3 radical density was almost constant, the deposition rate decreased markedly with increasing H2 partial pressure. These results suggested that the surface loss of the radicals was decreased due to the change in surface composition of the film, and also the film etching was enhanced with increasing H2 partial pressure. Therefore, the deposition rate of the carbon thin film decreased.

ZnS:Tm grown by metalorganic chemical vapor deposition with Cl codoping

Sm‐doped ZnS thin films were grown by metalorganic chemical vapor deposition using diethyl‐ zinc, H2S, Sm(thd)3 (thd=2,2,6,6‐tetramethyl‐3,5‐heptanedione), Sm(hfa)3 (hfa=1,1,1,5,5,5‐ hexafluoro‐2,4‐pentanedione), SmCl3, and HCl. The following films were prepared: an undoped ZnS, a ZnS:Sm grown with Sm(thd)3 and without HCl, a ZnS:Sm,Cl grown with both Sm(thd)3 and HCl, a ZnS:Cl grown only with HCl, and a ZnS:SmCl3 grown with SmCl3. Very little Sm was incorporated when Sm(hfa)3 was used as the dopant source. In the ZnS:Sm, the Sm was not segregated at grain boundaries, at least at concentrations below 0.2 at. %. In the ZnS:Sm and the ZnS:Sm,Cl, the (200), (220), and (311) reflections of the cubic structure that the undoped ZnS and the ZnS:Cl exhibited were not detected, and preference for the (00⋅1) hexagonal orientation became stronger. The electroluminescence spectrum of the ZnS:Sm,Cl showed three satellite peaks appearing in each of the 7 nm ranges around the three dominant peaks seen in the ZnS:Sm. The...

SATELLITE PEAK GENERATION IN THE ELECTROLUMINESCENCE SPECTRUM OF ZNS:SM GROWN BY METALORGANIC CHEMICAL VAPOR DEPOSITION WITH CL CODOPING

ZnS:Sm, ZnS:Sm,Cl, and ZnS:Cl thin films were grown by metalorganic chemical vapor deposition using the thd‐chelate (thd=2,2,6,6‐tetramethyl‐3,5‐heptanedione) of Sm and hydrogen chloride. The electroluminescence spectrum of the ZnS:Sm,Cl showed three satellite peaks appearing in each of the 7 nm ranges around the three dominant peaks that the ZnS:Sm has originally. The ZnS:Sm,Cl also showed photoluminescence attributed to the self‐activated centers, but its intensity was less than 10−2 of that of the ZnS:Cl. The effect of the Cl codoping on Sm3+ luminescent properties is discussed on the basis of the Sm‐VZn (zinc vacancy)‐Cl complex formation.

Calculated Three Dimensional Spatial Distribution of CH3 Radical Density in the RF Discharge CH4 Plasma with Parallel-Plate Electrodes

The three-dimensional spatial distribution of the CH3 radical density has been calculated in the model of an RF discharge CH4 plasma-enhanced chemical vapor deposition (P-CVD) chamber with parallel-plate electrodes in both cases with and without the White-type multiple reflection arrangement for absorption spectroscopy. The result showed that the CH3 radical density decreased sharply and was negligible outside the plasma region irrespective of the geometry of the White-type multiple reflection of the glass tube. The deposition of carbon thin film was also measured. The result showed a tendency similar to that of the calculated distribution of the CH3 radical. Therefore, it is concluded that the absorption path length of the laser beam can be defined as the length of the beam which passes through the plasma region in the case of CH3 radical density measurement using infrared laser absorption spectroscopy.

Purification of diamond films by applying current into the plasma stream in the arc discharge plasma jet chemical vapor deposition technique

A synthesis method that provides high‐purity diamond films is proposed employing direct current arc discharge plasma jet chemical vapor deposition. In the method, an electric current was supplied to a plasma jet stream by applying a bias voltage between a cathode and the substrate on which diamond films were deposited. The Raman spectral analysis showed that the purity of the synthetic diamond was remarkably improved by the application of the bias voltage during deposition. The alternating current calorimetric method was employed to measure the thermal diffusion coefficient of the synthesized diamond films. The thermal diffusion coefficient greatly increased for films deposited with biasing. This improved thermal diffusion coefficient suggests higher purity diamond films. Emission spectral analysis revealed that the quantity of the dissociated hydrogen contributing to the plasma emission near the substrate is greater when biasing is used. Thus, the dissociated and excited hydrogen atoms are considered to ...

34.1: Invited Paper: Reduction of Halo in Transparent Electroluminescent (EL) Display

Recently, a variety of information is displayed in automobiles. One of the elements which is expected to be used for display of information is the transparent EL display. However, this display generates a phenomenon called “halo”, which causes the area around the emitter to blur and gleam, resulting in decrease of visibility. In this research, we elucidated the mechanism of how this phenomenon occurs, and reduced the relative halo luminance ratio (i.e. halo luminance of adjacent pixels / luminance of illuminating pixels) from 3.6% to 1.7%. This has made possible the materialization of a dual vision optitron meter, which is a device combining analog meters with digital meters having a transparent EL panel (dual vision optitron meter is a registered trademark).

Gallium‐rich CaGaαSβ:Ce as a new blue electroluminescent phosphor

Ga-rich CaGa α S β :Ce thin films, of which the Ga/Ca ratio was 2.5-4, were grown by metalorganic chemical vapor deposition. After post-annealing at 650°C, a new substance, different from the ordinary CaGa 2 S 4 , grew. This was confirmed by XRD and by a spectral shift of the Ce 3+ emission. This phosphor was found not only to emit a deeper blue, (x, y) = (0.15, 0.16), than CaGa 2 S 4 :Ce, (x, y) = (0.15, 0.19), but also to be electroluminescent. Its luminance was 2 cd/m 2 at 40 V above threshold at a frame frequency of 120 Hz.