Ultrafast optical probing is a widely used method of underdense plasma diagnostic. In relativistic plasma, the motion blur limits spatial resolution in the direction of motion. For many high-power lasers the initial pulse duration of 30–50 fs results in a 10–15 μm motion blur, which can be reduced by probe pulse post-compression. Here we used the compression after compressor approach [Phys.-Usp. 62, 1096 (2019); JINST 17 P07035 (2022)], where spectral broadening is performed in thin optical plates and is followed by reflections from negative-dispersion mirrors. Our initially low-intensity probe beam was down-collimated for a more efficient spectral broadening and higher probe-to-self-emission intensity ratio. The setup is compact, fits in a vacuum chamber and can be implemented within a short experimental time slot. We proved that the compressed pulse retained the high quality necessary for plasma probing.

Thin film Si solar cell has been developed using Via-hole Etching for the Separation of Thin films(VEST) process. The process is based on SOI technology of zone-melting recrystallization (ZMR) followed by chemical vapor deposition (CVD), separation of thin film, and screen printing. Key points for achieving high efficiency are (1)quality of Si films, (2)back surface emitter (BSE), (3)front surface emitter etch-back process, (4)back surface field (BSF) layer thickness and its resistivity, and (5)defect passivation by hydrogen implantation. As a result of experiments, we have achieved 16% efficiency(Voc:0.589V, Jsc:35.6mA/cm2, F.E:0.763) with a cell size of 95.8cm2 and the thickness of 77μm. It is the highest efficiency ever reported for large area thin film Si solar cells.

Maskless dry etching of Mn-Zn ferrite in dich1orodif1uoromethane (CC12F2) by Ar+-ion laser (514.5 nm-line) irradiation has been investigated to obtain high etching rates and aspect-ratios of etched grooves. The etching reaction was found to be thermochemical and caused by Cl radicals thermally decomposed from CCl2F2 gas. High etching rates of up to 360 μm/s, which is about one order of magnitude higher than that in a CCl4 gas and even higher than that in a H3PO4 solution, have been achieved. A high aspect-ratio of up to 12 was obtained. Definite gas pressure and dwell time are necessary to fabricate a smooth groove.

Compositional deviation from the standard stoichiometry of tin-oxide and silicon-oxide lines masklessly deposited by laser-induced thermochemical reaction was investigated by micro Rutherford backscattering (RBS). Micro-RBS spectra of the lines deposited with various laser powers indicated that the stoichiometry of the deposited lines for both tin-oxide and silicon-oxide was improved by the increase in laser power. A tomographic image of the tin-oxide line showed a compositional inhomogeneity across the line.

The change in the behavior of laser—induced etching of Mn—Zn ferrite by MeV ion implantation has been investigated. The etching induced by Ar+ laser irradiation in a H3PO4 solutipn w~s completely suppressed by implanting 3 MeV Au+ to a dose of 1x1016 cm-2 when the laser induced local temperature rise was below the melting point of the ferrite. The etching suppression disappeared when the Au+ implanted sample was thermally annealed at 900 ºC for 30 min. The suppression is found to be related to the crystallinity change induced by ion implantation.

A microbeam line with precisely designed quadrupole magnets has been developed and installed at the Research Center for Extreme Materials, Osaka University. For the purpose of applying the beam line to microbeam RBS/channeling, the damage in <100>Si due to the irradiation of probe beams was studied as a function of incident ion dose from 1015 to 1018 /cm2 with a flux of 8 × 104 nA/cm2. It was found that the dose for channeling measurements should be less than several 1017 /cm2.

Rutherford backscattering (RBS) analysis of small-sized structures, fabricated by laser chemical vapor deposition (LCVD) with a focused laser beam and ion implantation with a focused ion beam (FIB), has been performed by a microprobe with focused 1.5 MeV helium ions. Micro-RBS spectra and RBS-mapping images revealed a local distribution of masklessly deposited Mo layers on GaAs and local doses of masklessly implanted Au atoms in Si.

A nuclear microprobe-forming system for the microscopic RBS/PIXE measurement of micro devices has been developed and installed at the Research Center for Extreme Materials, Osaka University. The use of precision quadrupole magnets and an objective collimator ensures a final spot size of less than 1μm.

Maskless etching of the composite structure of Mn-Zn ferrite and sendust (Fe-Si-Al alloy) was performed by focused argon-ion-laser irradiation in a CCl4 atmosphere and aqueous solutions. Only a mixture of KOH and NaOH aqueous solutions was found to smoothly etch the composite structure by thermochemical reaction using laser irradiation. A maximum etching rate of 14 μm/sec was obtained for sendust-on-ferrite substrates.

Dissociation species produced by low-energy electron Irradiation of triethylgallium (TEGa) have been used as a carbon doping source during growth of GaAs by chemical beam epitaxy. Mass spectral analysis shows that TEGa dissociates at electron energies greater than 20 eV, and that the fragmentation pattern of TEGa consists of methyl radicals, ethyl radicals, and gallium compounds. In order to study the doping properties of carbon, carbon-doped GaAs films were grown under several conditions and were characterized by Hall measurements, photoluminecence spectrum, secondary Ion mass spectrometry, and double crystal X-ray diffraction. The hole carrier concentration could be varied up to ∼1020 cm−3, and the doping profile of carbon was well-controlled.

Diffusion of arsenic implanted in poly-silicon on insulator structures after furnace and rapid thermal annealing (RTA) has been investigated by Rutherford backscattering (RBS) and Hall effect measurements. The diffusivity for As in poly–Si on insulator is represented by D = 3.12 × 104 exp (− 3.86/kT) cm/sec for the tail region after both RTA and furnace annealing and D = 34.0 exp (− 3.42/kT) cm2/sec for the peak region after RTA. Poly–Si layers after implantation and annealing were found to have tensile stresses of 3.0 – 4.0 kbar.

A high-energy (MeV) helium ion beam has been focused down to 1 μm by a combination of piezo-driven objective slits and a magnetic quadrupole doublet. Rutherford backscattering (RBS) mapping techniques using focused MeV ion beams were, for the first time, applied to multilayered structures of metals, isolated with insulators, representing a test structure for multilayered wiring or interconnections of integrated circuits to nondestructively analyze the imperfection of the structures.

The low-temperature magnetoresistance of PtSi thin wires of varying width, prepared with different mask elements (Cu and Ni) in the reactive ion beam etching, has been studied, to determine the width dependence of the physical parameters in the weak localization. A drastic decrease of the magnetic impurity scattering time τs and that of the superconducting transition temperature Tc have been found for the wires prepared by Ni mask with narrowing width, which suggests that the phase coherence of diffusing electrons responsible for the weak localization and the superconductivity are strongly affected by the presence of a small amount of Ni impurities recoil implanted into the surface region of the sidewalls of wires.

Local variation of photoluminescence (PL) spectra for MBE GaAs grown on an insulating substrate with Ge-islands interface layers, prepared by zone melting recrystallization, has been investigated. The GaAs layers on the single crystalline Ge islands emit PL, the intensity of which was almost comparable to that of the GaAs layers on bulk Ge, while by a factor of 50 lower PL intensity was observed for the GaAs layers on Si02. PL spectra were found to show peak shifts due to the band-gap variation near the interface layer of GaAs, which was in good agreement with the residual strain obtained by microprobe Raman scattering for underlying Ge islands.

Single crystalline germanium islands on SiO2 have been formed by zone melting with graphite strip heaters. Two types of geometrical patterns for islands were successfully used to obtain large single crystalline islands. Most germanium islands were found to be single crystal and the predominant orientation was (100). Electron concentrations of 1016 - 1018/cm3 with Hall mobility of 3 × 103 − 1 × 103 cm2 /Vsec were obtained for single crystalline germanium islands. Gallium Arsenide layers, grown by molecular beam epitaxy, on the germanium islands were found to emit photoluminescence, the intensity of which was almost comparable to that of gallium arsenide layers on bulk germanium crystals.

Pyrolytic local etching of GaAs using focused Ar laser beams in C12 or CCl4 gas atmospheres has been performed to investigate the possibility of maskless etching processes by laser beams. Etching rates from 0.3 to 40 μ/scan with an etched linewidth down to 5 μ were obtained. In the case of CC1 4 , a carbon line buried in GaAs was obtained for a single scan of a laser beam at a pressure above 80 Torr with low scanning speeds or at a pressure above 120 Torr.

Characteristics of maskless patterning of Cr films using focused Sb+ ion implantation have been investigated. Dose and depth dependence of the etching rate of Sb-implanted layers during plasma etching using CCl4 were measured. Sb profiles were also measured by Rutherford backscattering techniques. It was found that a sharp threshold dose exists to form an etch-resistant layer by Sb implantation. It was also found that a latent image of an Sb implanted pattern at a dose ≥3.8×1015/cm2 was developed by the plasma etching, and that Cr patterns with a thickness of a few hundred nanometers were formed by the present maskless patterning technique.

High resistivity silicon single crystals for radiation detectors were grown by the floating-zone (FZ) method with and without one-pass zone refining of ultra pure starting material obtained by the decomposition of monosilane gas. In this method, boron is removed from monosilane during gas generation. The main residual impurity is phosphorus from phosphine which is removed with zeolite A after distillation of monosilane. Photoluminescence analysis and an improved 4-point probe resistivity measuring method were used to evaluate the material.

Time resolved transmission (λ = 1060 nm) and reflectivity (λ = 632.8 nm) during 20 nsec Nd:glass laser annealing in ion implanted Si were measured to study dynamic behaviors of laser annealing. Transmitted laser energy was also measured to complement transient measurements. Transient transmitted light intensity was found to be almost completely quenched as would be expected from absorption by a molten Si layer.