Akimitsu Nakaue

Selected‐area deposition of diamond films

Selected‐area deposition of diamond film has been accomplished on Si substrates prepared by two different methods: reactive‐ion etching (RIE) and amorphous‐Si masking (ASM). In the RIE method, a Si substrate polished by a diamond paste was patterned with a photoresist mask, and the unprotected areas were etched by RIE, followed by a complete removal of the photoresist films. The diamond deposition was done by electron‐assisted chemical‐vapor deposition (CVD), and diamond films grew only in the areas once covered with the photoresist films and not etched by RIE. In the ASM method, a polished Si substrate was also photolithographically masked with photoresist, followed by a uniform deposition of a hydrogenated amorphous silicon (a‐Si:H) film. The photoresist film was then lifted off together with the overlay of deposited a‐Si:H, leaving the polished Si surface patterned with an a‐Si:H mask. In this case, the diamond deposition was done by microwave plasma CVD, and diamond films grew only in the areas not co...

Studies on the pressure-temperature phase diagram of Nd, Sm, Gd and Dy

Abstract The pressure-temperature phase diagrams of Nd, Sm, Gd and Dy have been studied by energy-dispersive X-ray diffraction at pressures up to 90 kbar and at temperatures up to 700°C, using a cubic anvil-type press. At temperatures above 300°C Gd transforms from an h.c.p. to an Sm-type structure at about 35 kbar and then to a d.h.c.p. structure above 70 kbar. Although transformations due to pressure have previously been reported for Nd, Sm and Dy, the transformation pressures are defined in the present study. The values of dP/dT for the phase boundaries of Nd, Sm and Dy are −0.085, −0.090 and −0.095 kbar °C−1, respectively, whereas the value for Gd is very small (nearly zero). The lattice parameters of Nd, Sm, Gd and Dy have also been measured by energy-dispersive X-ray diffraction at high pressures at 300°C. For these metals, the h.c.p. structure exists below an axial ratio of 1.60, the Sm-type structure at c a ≈ 1.60 and the d.h.c.p. structure at c a ≈ 1.61−1.625 , if the lattice parameter c for the Sm-type or the d.h.c.p. structure is adjusted to correspond with that for a two-layer structure. The relationship between the structural type and the axial ratio found in this high pressure study is similar to that of the rare earth metals at atmospheric pressure.

Microfabrication of diamond films: selective deposition and etching

Abstract For the future application of diamond films to microelectronic devices and sensors, it is necessary to develop methods for making patterns a few micrometers wide of diamond films on substrates. To this end, two different methods of selected-area deposition were developed: reactive-ion etching and amorphous silicon masking of silicon substrates. It was shown that selective nucleation on silicon was achieved by these methods, and selective deposition of new diamonds on diamond film was carried out using the amorphous silicon masking method. The diamond films were etched using electron-beam assisted plasma etching, and consequently, a diamond film pattern of 10 μm wide was formed.

Selected-Area Deposition of Diamond Films

Abstract Diamond film patterns with line/space dimensions of a few μm were accomplished on Si substrates prepared by reactive-ion etching (RIE) and amorphous-Si masking (ASM) methods, both including a photolithography process. For diamond deposition, microwave plasma CVD and electron-assisted CVD were used. Furthermore, a growth of diamond particles at selective sites was attained using the RIE method.

Focused Ion Beam Lithography Using Ladder Silicone Spin-on Glass as a Positive Resist

Focused ion beam lithography using ladder silicone spin-on glass as a positive resist has been demonstrated. This lithographic technique utilizes the structural change of ladder silicone spin-on glass (LS-SOG) to a silicon-dioxide-like structure. A 60-nm-width space pattern and a 90-nm-diameter hole pattern have been fabricated using ion doses of 6.2 x 10 13 /cm 2 and 1.2 x 10 14 /cm 2 , respectively. The development mechanism and the sensitizing effect of post-exposure baking have been investigated using fourier transform infrared spectroscopy (FTIR).

Ultraviolet Irradiation on Hydrogenated Amorphous Carbon Films Deposited by Atmospheric Dielectric Barrier Discharge

Hydrogenated amorphous carbon (a-C:H) films were formed by atmospheric dielectric barrier discharge-chemical vapor deposition (DBD-CVD), and the functional groups substituted at the film surface were characterized. It was found that the CH 3 /(CH + CH 2 ) ratio in the a-C:H films formed by DBD-CVD was higher than in other carbon films formed by different methods, and a high density of carboxyl group was introduced on the film surface due to oxidation and dry etching reactions by ultraviolet irradiation. The result was consistent with the zeta potential measurements as well as the analysis of the surface atomic structures using discrete variational Xα (DV-Xα) calculations.

N channel metal–oxide–semiconductor field-effect transistor with 0.15 μm gate delineated by focused ion beam lithography

An N channel metal–oxide–semiconductor field-effect transistor (MOSFET) with a 0.15 μm gate was fabricated by using focused ion beam lithography for gate level and its electrical characteristics were investigated. The choice of the ion species and the gate structure were designed to avoid contamination and damage due to ion penetration. The MOSFET showed an excellent junction leakage current and subthreshold swing. The impact of the ion irradiation on the thin gate oxide quality was also investigated.

Al Metal Point Contact to B-Doped Diamond Films

The mechanical, thermal, optical, and electrical properties of diamond have been shown to be superior to those of other materials[1,2,3,4]. These properties can be utilized in a wide range of optoelectronic device applications as well as for extreme environmental conditions[5,6]. Chemical vapor deposition(CVD) of diamond offers an attractive solution for obtaining semiconducting diamond thin films. In order to exploit the electronic properties of these polycrystalline films, it is critical to evaluate the properties of electrical contacts to the diamond surface. In particular, reliable ohmic and rectifying contact technologies have been difficult to develop and reproduce. Recently, the formation of Schottky contacts to polycrystalline diamond films have been reported[7,8], but the relationship between the rectifying characteristics and the quantity of B impurities incorporated into the films was not examined.

Pressure induced phases of the BaTixMn1−xO3 system

The phase relation of the perovskite-like structures in the system BaTixMn1−xO3(x=0–1) has been studied at high pressure. The quenched high pressure phases are found to have in order of 2H, 9R, 4H, 6H, and the cubic perovskite structure with increasing pressure. Furthermore, it is proposed that the perovskite-like structures can be represented in terms of the stacking sequence of six compound layers.