Shuzo Hattori

Characterization of epitaxially grown GaAs on Si substrates with III‐V compounds intermediate layers by metalorganic chemical vapor deposition

GaAs grown on Si substrate with AlP, AlGaP, GaP/GaAs0.5P0.5 superlattice, and GaAs0.5P0.5/GaAs superlattice was investigated by varying the structure of the intermediate layers between GaAs and Si by metalorganic chemical vapor deposition. It was found that (1) the insertion of AlP and AlGaP layers makes the crystallinity and the surface morphology better, (2) PL (photoluminescence) intensity with two superlattice layers is about one order of magnitude stronger than that without these layers, (3) the crack formation in the GaAs surface layer can be avoided by the strained superlattice layers, (4) the PL intensity has a maximum at about 20 nm for each layer thickness in the superlattices, and (5) the PL intensity increases and the carrier concentration decreases while increasing the thickness of the surface GaAs and saturates over 3 μm. The PL intensity of GaAs on Si substrates is about 80% of that grown on GaAs substrates.

Plasma polymerized methyl‐methacrylate as an electron‐beam resist

Plasma polymerized methyl‐methacrylate thin film was formed on a glass substrate coated with chromium as a resist for electron‐beam lithography. The polymerizations were conducted at two discharge frequencies of 13.56 MHz and 5 KHz using a capacitively coupled discharge electrode system in a bell‐jar‐type reactor. Delineations were carried out using an electron beam whose diameter and acceleration voltage were 0.5 μm and 20 kV, respectively. As a test pattern, 25 pairs of parallel lines and spaces each having a 10‐μm width were delineated in a rectangular area of 0.5×0.5 mm2. Each line of 10‐μm width was depicted by sweeping over using the electron beam with 20 repetitions. The patterns were developed on the chromium by CCl4 plasma etching.

Epitaxial growth and material properties of GaAs on Si grown by MOCVD

Abstract GaAs grown on Si substrates oriented 2° off (100) with intermediate layers of GaP, GaP/GaAs0.5P0.5 superlattice, and GaAs0.5P0.5/GaAs superlattice is characterized for different thickness of GaAs and different directions of the off angle of the Si substrate. The direction of the off angle is found to be a key factor to obtain a single domain GaAs. The curvature radius of the wafer, the lattice constant perpendicular to the surface and the band gap energy of GaAs decrease with increasing GaAs thickness. These results show the existence of high density of dislocations at the beginning of the growth and its reduction with the growth sequence. No crack appears on the surface even on a 8 μm thick GaAs. The etch pit density decreases with increasing thickness and is about 4000 cm-2 for 8 μm thick GaAs.

Formation of polytetrafluoroethylene thin films by using CO2 laser evaporation and XeCl laser ablation

Laser evaporation and laser ablation methods were applied to the preparation of polytetrafluoroethylene (PTFE) thin films. In the case of the laser evaporation method, PTFE targets were evaporated by a continuous wave (cw) CO2 laser (10.6 μm), and fluorocarbon thin films were formed at a deposition rate of as high as 2 μm/min for a laser power of 10 W. The chemical composition and structure of the deposited film corresponded to those of a PTFE target, which was confirmed by x‐ray photoelectron spectroscopy and Fourier transform infrared absorption spectroscopy analyses. In the laser ablation method, PTFE targets were ablated by a XeCl excimer laser (308 nm). It is found that the deposited films contained a small amount of fluorine atoms on the surface. From these experiments, the successful formation of PTFE thin films was demonstrated for the first time using cw CO2 laser evaporation method.

Photothermoelastic probing for a clamped plate sample

In this paper we report a photothermal probing technique for a clamped thin plate sample that uses thermoelastic bending. Irradiation of the modulated laser light focused on the clamped plate sample generates the flexural vibration caused by thermoelastic bending. By scaning with the focused beam and optically sensing the bending, the irregularity of the plate is detectable nondestructively as changes in amplitude and phase of the flexural vibration. Characteristics of thermoelastic bending are also examined from the viewpoint of bending hot spot theory.

Stress and Strain of GaAs on Si Grown by MOCVD Using Strained Superlattice Intermediate Layers and a Two-Step Growth Method

The stress and strain of GaAs on Si grown by using strained superlattice intermediate layers and a two-step growth method are characterized by the photoluminescence, X-ray diffraction and the curvature radius. The strain of GaAs grown using strained superlattice intermediate layers is smaller than that grown by the two-step growth method.

Deep Levels in GaAs Grown Using Superlattice Intermediate Layers on Si Substrates by MOCVD

Deep levels in MOCVD-grown GaAs using superlattice intermediate layers on Si substrates were investigated by DLTS. Electron traps at 0.44 and 0.73 eV were observed in the undoped n-type GaAs grown on (100)2° off Si substrates while only a 0.73-eV trap was detected in GaAs on a GaAs substrate. The deep-level concentration in GaAs/Si and the capture cross section of a 0.44-eV trap decreased and the half width of the 0.44-eV trap increased with increasing GaAs thickness. The 0.73-eV trap concentration increased upon decreasing the curvature radius of the wafer by polishing the back side of the Si substrate; however, that of 0.44 eV was unchanged. These observations suggest that the 0.44-eV trap is due to Si-defect complexes changing their shapes with the GaAs thickness and that of 0.73 eV is caused by point defects.

Characterization of hard transparent B–C–N–H thin films formed by plasma chemical‐vapor deposition at room temperature

B–C–N–H thin films were deposited by plasma chemical‐vapor deposition with an external capacitively coupled reactor at an rf frequency of 13.56 MHz. The films were formed from a gas mixture of B2H6 (5.25 vol % in N2), methane, and argon or nitrogen as carrier gases. The deposition was carried out at room temperature and without heating the substrate. The films were transparent in the range of 10 000–2000‐A wavelengths. The Knoop microhardnesses were 1825–3324 kg/mm2 and the refractive index was 1.3–1.6. An extensive discussion of the effect of the deposition conditions on both microhardness and film composition is given. In addition, the interrelation between the microhardness and composition is illustrated.

Transparent BCNH thin films formed by plasma chemical vapour deposition

Abstract BCNH thin films transparent at wavelengths of 200–1000 nm were deposited by low temperature plasma chemical vapour deposition using an inductively coupled reactor at a frequency of 13.56 MHz. The films were formed at a discharge power level of 20 W and a pressure of 48.1 Pa from a gas mixture of diborane (4.8 vol.% in nitrogen), ethane and argon. The refractive index was 1.4 and the deposition rate was 20 nm min−1 when it was measured with an ellipsometer at a wavelenght of 632.8 nm.

Lifetimes and transition probabilities in Cu ii

Radiative lifetimes of some of the levels in the Cu ii 3d94p and 3d95s configurations have been measured to accuracies of 10–20% by using a delayed-coincidence technique. Relative line strengths for the 3d94s–3d94p and 3d94p–3d95s arrays have been determined both theoretically and experimentally. The theoretical line strengths are based on intermediate-coupling calculations, and the experimental ones are based on branching-ratio measurements and the J-file sum rule. Good agreement between the two sets of values is obtained; agreement is more satisfactory for the 4s–4p array than for the 4p–5s array. The experimental line strengths are estimated to be accurate to 10% for the 4s–4p array and to 30% for the 4p–5s array. Transition probabilities are determined by normalizing the experimental line strengths to an absolute scale by using the measured lifetimes.