To construct low carbon society more and more in the world, it is necessary to develop a high performances new green device such as a solar cell, a lithium battery, a power semiconductor, and light emitting diode (LED) lighting, superconducting device and so on. Metal oxides are expected to be key materials which are used for a new device by controlling metal composition, a crystal structure, orientation or multilayer of the film, a carrier, a spin, etc. In order to fabricate the new devices, their parameters controllable process would be effective. Another important problem is the development of the low cost and power saving process for constructing sustainable society in the world. For these purpose, chemical solution process (CSP) would be suitable because it does not require vacuum and high facility investments and any complicated etching process. In addition, precise metal composition control is possible when the materials are made from the more than 3 or 4 metal components. For the thin film processing, we have developed the photo-induced chemical solution process such as excimer laser-assisted metal organic deposition (ELAMOD) and photo reaction of nano-particle method (PRNP) for the preparation of the patterned metal oxide thin film on organic, glass and single crystalline substrates.
By using the PRNP process, ITO, resistor and phosphor thin films were prepared on glass, PET and PIM substrates at room temperature. The luminescent thin film show higher luminescence compared with commercially available one.
On the other hand, to prepare the epitaxial film, the use of the metal organic compound and single crystal substrate with large optical absorbance was found to be effective. By using the ELAMOD, epitaxial ITO, SnO2, LSMO, PZT films were successfully obtained at low temperature . Also, we have successfully prepared VO2 films with non-hysterisis. The TCR of the VO2 films obtained by ELAMOD exhibit much higher than present uncooled IR sensor. In this presentation, we demonstrate a preparations of ITO, resistor and phosphor thin films on flexible substrates.
Uncooled infrared detectors with 12μm pixel pitch video graphics array (VGA) have been developed. To improve the signal to noise ratio (SNR) for 12μm pixel pitch, a highly sensitive bolometer material, an advanced pixel structure for thermal isolation and a newly designed read-out IC (ROIC) have been also developed. The bolometer material has been improved by using vanadium niobate. Over a wide range of temperature, temperature coefficient of resistance (TCR) is achieved higher level than -3.6%/K, which is 2 times higher than that for the conventional bolometer material. For thermal isolation, thermal conductance (Gth) value for the new pixel structure, fabricated by using triple level sacrificial layer process, is estimated to be 5nW/K, which is 1/5 times lower than that for the conventional pixel structure. On the other hand, since the imaging area is reduced by the pixel pitch, the uniformity of pixel can be improved. This enables to remove the non-uniformity correction (NUC) circuit in the ROIC. Removal of this circuit is effective for low power and low noise. This 12μm pixel pitch VGA detector is packaged in a compact (24 × 24 × 6.5 mm) and lightweight (11g) ceramic package. In addition, it has been incorporated in a newly developed prototype miniature imager. The miniature imager has dimension of 25(H) ×25(W) ×28(L) mm and weight of 30g. This imager is compact and small enough to fit in your hand. Hereafter, this imager is greatly expected to be applied to mobile systems.
The preparation of metal oxide thin films have been developed using the metalorganic (MO) compounds coating photolysis process with ArF excimer laser irradiation at room temperature. The effect of the starting materials and irradiation method on the product films was investigated by FT-IR, UV, XRD and SEM. It was found that metal acetylacetonates or metal 2-ethylhexanoate was effective as the starting materials. When using metal acetylacetonates as the starting materials, crystallized TiO<SUB>2</SUB>, In<SUB>2</SUB>O<SUB>3</SUB> and ZrO<SUB>2</SUB> were obtained with ArF laser irradiation at 50 mJ/cm<SUP>2</SUP> at a repetition rate of 5 Hz for 5 min. When using An-acac, Fe, Sn, or In 2-ethylhexanoate as the starting material, a two-step process consisting of both preliminary weak (10mJ/cm<SUP>2</SUP>) and sufficiently strong irradiation (50mJ/cm<SUP>2</SUP>) was found to be effective for obtaining crystallized ZnO, Fe<SUB>2</SUB>O<SUB>3</SUB>, SnO<SUB>2</SUB> and In<SUB>2</SUB>O<SUB>3</SUB> films. In addition, crystallized complex oxide thin films such as ITO, PbTo<SUB>3</SUB> and PbZrO<SUB>3</SUB> were successfully obtained from the metal acetylacetonates or metal 2-ethylhexanoate using MO coating photolysis process. Patterned metal oxide thin films were also obtained by the ArF laser irradiation through the photomask, followed by leaching with solvents. The crystallization mechanism was discussed from the point of view of the photochemical reaction and photothermal reaction.