Masaharu Terauchi

Preparation and Characterization of CuInSe2 Thin Films by Molecular-Beam Deposition Method

Polycrystalline CuInSe2 films were prepared by coevaporation of the elements under an ultrahigh vacuum by a molecular-beam deposition method. The composition of the film was controlled by changing the In molecular-beam flux intensity while the other elements remained at a constant value. It is shown, at the substrate temperature of 500°C, that there is a critical In molecular-beam flux intensity for the fabrication of stoichiometric films. At the In molecular-beam intensities higher than the critical value, single-phase CuInSe2 films with nearly constant compositions are obtained as a result of the removal effects of excess In. It is shown that the present coevaporation process is suitable for the fabrication of stoichiometric or slightly In-rich composition films. Furthermore, the structural and electrical properties of the films were investigated and discussed in relation to film composition.

Characterization of molecular beam deposited CuInSe2 thin films

We have prepared copper-rich, near-stoichiometric and indium-rich CuInSe2 thin films by using a molecular beam deposition method. The composition of the films was homogeneously distributed. The copper-rich films exhibited low resistivity and p-type conduction. The near-stoichiometric films exhibited intermediate resistivity and n-type conduction. The indium-rich films exhibited high resistivity and n-type conduction. Both the grain size and the relative intensity of the (112) X-ray reflection was larger for the film having larger Cu:In ratio. Kikuchi lines were observed in the electron diffraction pattern within a grain of the copper-rich film. No additional second phase except the copper precipitate at a triple point of the grain boundaries for the copper-rich film was detected.

Preparation of CuInSe2 thin films by selenization of CuInO precursors

Abstract Polycrystalline CuInSe 2 films were prepared by selenization of CuInO films. CuInO precursor were prepared from Cu 2 In 2 O 5 target by rf-magnetron sputtering and pulsed laser deposition. The CuInO films were converted into CuInSe 2 films by annealing in H 2 Se gas atmosphere. The CuInSe 2 films obtained by selenizing CuInO films prepared by a pulsed laser deposition, contained an impurity phase such as In 2 O 3 . But singlephase chalcopyrite CuInSe 2 films were obtained by selenizing the near stoichiometric CuInO film prepared by a rf-magnetron sputtering at a temperature of 450°C.

Homojunction Diode of Cuinse2 Thin-Film Fabricated by Nitrogen Implantation

Rectifying homojunction have been fabricated in polycrystalline CuInSe2 thin film. The p‐n junction diode was obtained by short annealing in nitrogen atmosphere at 450 °C following the ion implantation of nitrogen with the energy and the dose of 50 keV and 1×1015 cm−2, respectively. The properties of the near surface region in the films implanted have been studied by the Raman scattering spectroscopy. The secondary ion mass spectroscopy depth profile of the nitrogens in the CuInSe2 film and the capacitive‐voltage characteristics of the rectifying diode have been measured to characterize the junction properties. The photovoltaic characteristics in AM 1.0, 100 mW/cm2 are shown with the efficiency of 0.35%.

Measurement of Magnesium Oxide Sputtering Yields by He and Ar Ions with a Low-Energy Mass-Selected Ion Beam System

Sputtering yields of magnesium oxide (MgO) by He and Ar ion bombardment were measured at relatively low incident energies with monochromatic ion beams generated by a low-energy mass-selected ion beam system. The measured sputtering yields and their ion incident energy dependence are found to be significantly different from those proposed by an earlier study based on numerical simulations [S. J. Yoon and I. Lee: J. Appl. Phys. 91 (2002) 2487], which seems to be the only source of MgO sputtering yield data widely available in the community for a relatively wide range of ion incident energies. Given the fact that MgO is extensively used as barrier coating of plasma display panel (PDP) cells and the amount of sputtered MgO in PDP cells can affect their discharge characteristics to a large extent, our results indicate that a fundamental revision is urgently needed for the study of MgO sputtering by noble gas ion bombardment.

Fabrication of substrate-type CuInSe2 thin film solar cells

Heterojunctions based on CuInSe 2 films formed by a bilayer process are fabricated and their photovoltaic properties are investigated. The photovoltaic performances are enhanced by post-annealing in air at 200 o C. The fabricated heterojunctions of CdS/CuInSe 2 and ZnO/CuInSe 2 show efficiencies of 10,5% and 6.0%, respectively. The CdS/Cu(In,Ga)Se 2 heterojunction is also fabricated and shows an efficiency of 11.7%.

High-performance MgO thin films for PDPs with a high-rate sputtering-deposition process

— A high-rate sputtering-deposition process for MgO thin films for PDP fabrication was recently developed. The deposition rate of the MgO thin film was about 300 nm/min which shows the possibility of production-line application. The MgO film deposited in this work has a higher density than that of other deposition processes such as electron-beam deposition and shows good discharge characteristics including firing voltage and discharge formation. These were achieved by controlling the stoichiometry and/or the impurity doping during the sputtering process.

Experimental evaluation of CaO, SrO and BaO sputtering yields by Ne+ or Xe+ ions

Barrier coating materials used in plasma display panel (PDP) cells strongly affect the discharge voltages. Although magnesium oxide (MgO) is widely used for barrier coating in the current generation of commercial PDP cells, other alkaline earth oxides have been studied as alternatives and indeed some of them are now known to have lower discharge breakdown voltages for PDP cells, which would increase the energy efficiency of the cells. On the other hand, the resistance against physical sputtering is another critical parameter for barrier coating. In this work, sputtering yields of CaO, SrO and BaO by monochromatic Ne or Xe ion beams are obtained experimentally as functions of beam energy in the range 100–300 eV. Despite the large differences in mass among the targets and incident ions, sputtering yields are found to be similar in magnitude among them for a given incident energy.

Sputtering yields of magnesium hydroxide [Mg(OH)2] by noble-gas ion bombardment

Magnesium oxide (MgO) is widely used for barrier coating of plasma display panel (PDP) cells and its resistance against ion sputtering is a critical issue for the prolongation of lifetime of PDPs. The top surface of an MgO barrier coat may be hydrated to form a thin layer of magnesium hydroxide [Mg(OH)2] due to moisture inadvertently contained in the gas of the PDP cell. In this study, sputtering yields of Mg(OH)2 by low-energy noble-gas ion bombardment have been evaluated experimentally with the use of a mass-selected ion beam system and compared with those of MgO. It has been found that the etched depths of Mg(OH)2 and MgO are nearly equal when they are subject to the same noble-gas ion bombardment conditions.

Surface characterization of MgO:Al,N films with meta‐stable de‐excitation spectroscopy and x‐ray photoelectron spectroscopy

— It is shown that meta-stable de-excitation spectroscopy (MDS) is one of the most useful characterization methods to analyze the interaction between the discharge gas and the surface of the material and is applied to MgO:Al,N films. From the results of the measurement and analysis of helium MDS and the in-situ discharge experiment, it is confirmed that the limited composition films of MgO:Al,N have potentially a larger secondary-electron-emission coefficient (γ) compared with that of MgO. The improvement in γ is caused by the electron-occupied tailing state at around the top of the valence band which is generated by the introduction of Al,N to MgO films. Also, the O1s spectra measured by x-ray photoelectron spectroscopy (XPS) shows that the stable surfaces are formed with the introduction of Al,N to MgO films.