The mechanism of in-source decay (ISD) under matrix-assisted laser desorption/ionization (MALDI) conditions has been described. The ISD characteristic is the formation of c- and (z+2)-ions originated from the N-C_α bond cleavage on the peptide backbone. The ISD processes occurring with 337 nm laser photon irradiation for peptide or protein proceed to form hyper-valent radical species via intermolecular hydrogen transfer between matrix and analyte molecules following the non-ergodic N-C_α bond cleavage. The non-ergodic N-C_α bond cleavage occurs in the MALDI ion source within nanosecond order, as an α-cleavage initiated with unpaired electron at the hydroxyl methyl radical. The ISD is named as hydrogen-attachment dissociation (HAD). Furthermore, the ISD data of three different myoglobins showed a common intense product of c₃₅ ion originated from the cleavage of N-C_α bond at Gly35-His36 or Ser35-His36 residues. It was suggested that the relatively abundant formation of c₃₅ ion was not due to the N-side of His36 residue, but due to a turn region between helices in secondary structure of myoglobins.

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Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) represents a well-accepted and reliable method for the characterization of proteins. The method has great advantages in terms of high through-put, high accuracy, and high sensitivity in measurements, which is well suited for the identification of a wide variety of proteins, such those separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), and for the analysis of post-transnational modifications of a protein, which play important roles in various biological events. Taking advantages of an accumulating sequence databases, the former has been a routine task for overall profiling of proteins expressed in a cell or tissue. The latter, the analysis of post-translational modifications, is one of the most important subjects in post-genome era. We report here on the application of MALDI-MS and Edman chemistry to protein identification. The N-terminal sequence tags as well as the molecular masses of peptides revealed by MALDI-MS could be efficiently used for database searching, which increase the reliability of protein identification.

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This commentary article provides short accounts of matrix-assisted laser desorption/ionization (MALDI) and time of flight mass spectrometry (TOFMS), particularly perspective views of MALDI using an infrared light source (IR-MALDI), and MALDI in conjunction with a tunable infrared free-electron laser (FEL-MALDI) as a state-of-the-art IR-MALDI methodology. The benefits and precautions to use FEL in MALDI are discussed. A novel approach to address the low-sensitivity issue of FEL-MALDI, simultaneous exposure to UV and FEL, is proposed. In the proposed method, each laser can be adjusted to minimize the excess energy under the conditions of rapid heating, which allows analyte molecules to be desorbed and ionized. The current status of the development and preliminary data are reported.

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Time-of-flight mass spectrometers (TOFMS) had once been considered inferior to other types of mass spectrometers in key performance figures such as mass resolving power and mass accuracy. The discovery and development of soft laser desorption method and matrix-assisted laser desorption/ionization (MALDI) prompted the new development of TOFMS. Backed by the new techniques such as delayed extraction and rapid progress in high speed digital electronics, TOFMS is now considered as one of the main streams in mass spectrometry.

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Extremely short period melting and solidification of Si thin film induced by laser annealing is observed by in-situ monitoring techniques of transient reflectance and conductance measurements. The temperature evolution and resulting phase transformation are discussed based on thermodynamic analysis. It was clarified that complete melting of the Si film and following supercooling to 640 K below the melting point induce both microcrystallization and amorphization of the film. The properties of the polycrystalline Si (poly-Si) films formed by the laser annealing are investigated by means of analytical approach and measurement of electrical characteristics. The poly-Si films have high-density defects localized at grain boundary with the concentration of 10¹⁷ to 10¹⁸ cm^-3. Hydrogen or oxygen plasma treatment to the films efficiently terminates the defects and lowers the density below 1 × 10¹⁷ cm^-3. The combined process technology of laser annealing and plasma treatment allows us to apply the film to high-performance poly-Si thin-film transistors (TFTs).

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Laser re-crystallization is being actively investigated to fabricate low temperature, polycrystalline silicon, thin-film transistors (TFTs) onto glass substrate for use in active-matrix liquid crystal displays (LCDs). Some attractive applications of TFTs are peripheral circuits and various sensors on the same glass substrate, which make highly functional active matrix displays. In this paper, an analog driver with operational amplifiers capable of canceling the offset voltage and a low-power consumption TFT-LCD with dynamic memory cells embedded in each pixel, are reviewed. Also an optical sensor array for digitizers and a capacitive fingerprint sensor are demonstrated. To realize a “system on panel” and “smart pixels”, it is necessary to fabricate the TFTs with higher mobility and higher uniformity in their characteristics.

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Excimer laser based crystallization has become a workhorse in preparing poly-Si films for the manufacture of back plates for active matrix liquid crystal displays. Alternative laser techniques applying cw laser sources provide high quality crystal films however at a very slow rate. Line Beam optics combined with 300 W power excimer lasers to scan large area electronics substrates are achieving fast processing and very homogeneous poly-Si films. Very good laser beam homogeneity is critical for the near complete melt process. Furthermore high resolution diffraction limited optics systems are described for the sequential lateral solidification of amorphous silicon films. High quality films with electron mobility of 100-300 cm²/Vs can be produced. The generation of films for microelectronic circuits is an additional potential of the laser based crystallization process, thus even the application to the formation of shallow junctions for submicron technology is considered.

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Precursor a-Si films are deposited by RF planar magnetron sputtering in argon gas at 200 °C substrate temperature. Properties of the a-Si films have large dependences on sputtering gas pressure. Sheet resistance of polycrystalline Si films which are phosphorus-ion-implanted and crystallized with Ar-laser- irradiation shows low for sputtering gas pressures of from 1.0 to 1.5 Pa. Moreover, the Si films have smaller concentrations of argon and oxygen impurities in film. Polycrystalline Si thin film transistors (poly-Si TFTs) are fabricated using Si films which are sputtered at 1.0 Pa gas pressure and crystallized by Ar-laser irradiation. The polycrystalline Si films feature column structure with near 200 nm grain size. Gate SiO₂ films in the poly-Si TFTs are also deposited through sputtering in oxygen and argon mixed gas. The poly-Si TFTs annealed in hydrogen atmosphere shows excellent characteristics of very high mobility.

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High-performance poly-Si TFTs were created using the diode pumped solid-state (DPSS) continuous-wave (CW) laser lateral crystallization (CLC) method through fabrication processes at no higher than 450 °C. With decreasing Si film thickness, the grain size became finer and the surface orientation of the grains changed from (100) to other orientations. These effects reduced the field-effect mobility as the Si film became thinner, but with the CLC method we can still obtain a high field-effect mobility of over 300 cm²/Vs without applying special processing techniques, even from a Si film as thin as 50 nm. We expect this crystallization method to lead to the fabrication of high-performance Si-LSI circuits on large non-alkaline glass substrates.

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The liquid-solid interface motion and the temperature history of thin Si films during short pulse (< 30 ns) excimer laser annealing are observed by in-situ diagnostics. Substantial supercooling (> 200 K) followed by spontaneous nucleation into fine-grained material is observed. Lateral crystal growth is induced by fluence distribution leading to spatial control of partial/complete melting. However, growth length is limited by the triggering of spontaneous nucleation in supercooled liquid Si and lateral solidification velocity is measured to be about 7.0 m/s. To enhance the lateral growth, the pulse-duration-controlled solid-state laser is utilized. This sequential crystal growth is found to extend over 10 μm in the lateral direction. The validity of the method is confirmed by superior TFT characteristics of high field-effect mobility (n-ch μ > 460 cm²/Vs) with low threshold voltage deviation (V_th: σ < 0.07 V).

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Bamboo is a regenerative resource, which can regenerate within about 3 years. In the architectural field, bamboo materials have been traditionally applied for a wide variety of purposes. However, the use of bamboo has some problems. One of the problems is that it is apt to be damaged by insects. To prevent this, the surface of bamboo has been conventionally treated form carbon layer, using gas burners. In this study, we developed new bamboo material. We tried to carbonize the back surface of bamboo flooring materials by laser. Furthermore, we checked the reduction effect of VOC (Volatile Organic Compounds) of the carbonized bamboo. As a result, we determined the appropriate laser treatment conditions under which carbonization could be come out without warpage of the bamboo flooring. Our attempts revealed that the carbonized materials were effective in reducing the amount of VOC emission.

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We describe the development of a new sodium temperature lidar for probing the upper atmosphere over Antarctica. The laser transmitter consists of two injection-seeded Nd:YAG lasers with wavelengths of 1064 nm and 1319 nm. A narrow-band pulsed laser tuned to the sodium D₂ line (589 nm) is created by sum frequency generation of 1064 nm and 1319 nm laser pulses. The resulting laser pulse has a line width of less than 100 MHz. The two-frequency technique for measuring the temperature profile in the mesospheric sodium layer is evaluated by comparison with the Doppler profile-fitting technique and results show good agreement. Moreover, based on lidar data obtained at Syowa station, Antarctica in 2000, it is shown that the sodium temperature lidar is a powerful tool for probing the temperature profile in the mesosphere and lower thermosphere region as well as the stratosphere.

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